# Whats the deal with Soviet Wing design?



## Ottobon (Oct 3, 2015)

Just looking at some soviet aircraft of wwii the most distinctive feature is the diamond wings, which basically all of their fighters seemed to feature. 

Any idea why the soviets were so obsessed with this tapered design? and any idea what the big benefits and disadvantages of it were? 


I don't know anything about it but it would _seem_ to be a good design for helping with roll rate, and from the very basic i have read on aerodynamics i would assume that it would be one of the better designs for reducing induced drag (during turns), if not as good as a pure elliptical design, but these are simple guesses and i'd love to know more from somebody who has studied aerodynamics a bit more.


Just for reference:

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## fastmongrel (Oct 4, 2015)

What I know about aerodynamics could be written on the back of a stamp with a Sharpie pen. Is it possible the Soviet Air Ministry or even Stalin just liked wings with that plan and coming up with something different could mean a knock on the door at midnight.


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## drgondog (Oct 4, 2015)

That planform has advantages - first the taper ratio is empirically near enough to an elliptical planform that the Induced drag is only slightly higher. Typically fighters had between .3 and .5 Tip to Root Chord Ratio. Second, it is nearly ideal when planning for structural integrity, requiring a thick root chord but easy to design spar combinations to reduce weight. It also has a tendency to 'pull' the lift distribution inboard - another desirable feature for structural design to reduce bending moments due to lift distribution.

It is also very easy to plan for and execute manufacturing process

However, the more you taper the more susceptible to tip stall which requires either wash out wing twist or LE devices to decrease safe landing speeds.

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## fastmongrel (Oct 4, 2015)

drgondog said:


> However, the more you taper the more susceptible to tip stall which requires either wash out wing twist or *lE devices* to decrease safe landing speeds.



IE devices ? drgondog can you tell me what that means thanks


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## drgondog (Oct 4, 2015)

meant to write LE for leading edge devices (such as slats)


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## Koopernic (Oct 4, 2015)

fastmongrel said:


> What I know about aerodynamics could be written on the back of a stamp with a Sharpie pen. Is it possible the Soviet Air Ministry or even Stalin just liked wings with that plan and coming up with something different could mean a knock on the door at midnight.



That is quite possible. The totalitarian ideology present at the time interfered directly with scientific ideas (For instance, Darwinism represented a potential threat to Communist ideas in that it might mediate that human nature was somewhat a matter of nature rather than a pure product of socialisation so the Lamarckian ideas of Lysenko were promoted and Darwinists who didn't believe that 1+1=4 knew they would end up in the Gulag). I know of one incidence of communist interference in engineering and manufacturing: in Eastern Germany one reason they kept producing 3 cylinder 2 stroke cars known as Trabants is because any radical improvements (such as 4 cylinder 4 strokes) would suggest that the original planners had made bad choices and such revolutionary improvements might be, well, counter revolutionary. It sounds absurd but these people had kindergarden teachers pass on notes to the Stassi about what TV shows had been watched by the children and thus in the household. It's worth noting we still have this problem with Darwinism in western polities as well. 

More likely the proponents of these tapered plan form had more political clout and those with alternative ideas simply backed away. One can imagine a well connected proponent in the TsAGI as even bombers were effected by this fashion.

The highly tapered wing planforms used by the Soviet fighters would have had the following characteristics:
1 Highly tapered planforms stall at the tips first and so need a high degree of twist to avoid premature tip stall near the ailerons and the resultant poor spin stall. 

It's worth noting that the Soviet fighters such as the MiG 1 and MiG 3 had problems in this area. The La and LaGG series seem to have overcome it only with the use of automatic slats.

For the record the stall characteristic of basic planforms are
a/ rectangular, excellent: stall develops at the roots and progresses out to the tips. Wing twist may not be needed.
b/ tapered, stalls first at the tips, wing twist or slats definitely needed
c/ elliptical, stalls simultaneously at all points of the wing, moderate wing twist needed.

2 These highly tapered wing planforms might have been easier to produce given the thickness of the spar at the roots and the space for fuel and undercarriage it might provide.

The Spitfire's elliptical plan form had less need of aerodynamic twist than the tapered plan form of most other fighters yet it in fact had as much if not more (Approx 2.25-2.5 degrees compared to the 2 degrees common in other aircraft)


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## GrauGeist (Oct 4, 2015)

fastmongrel said:


> Is it possible the Soviet Air Ministry or even Stalin just liked wings with that plan and coming up with something different could mean a knock on the door at midnight.


You're pretty close with that.

The Soviets were caught up short at the start of the war, so there was a rapid succession of changes to the airframes, trying to not only keep the Germans at bay, but almost as important: keeping Uncle Joe happy.

When Kalinin's designs failed (and crashed, killing several), Stalin was unhappy. Therefore, Kalinin was "removed" - permanently.

The difficulties with the LaGG-1 and LaGG-3 caused great displeasure with Uncle Joe, nearly costing Lavichkin more than his aircraft facilities (which were handed over the Yakovlev). Lavochkin, now working in a tiny hut on the edge of an airfield, managed to save himself by taking a LaGG-3 and placing the nose of a Su-2 (ASh-82 radial and all) onto the LaGG's frame. The result was a game-changer, the La-5. Not much else was changed, so there's no surprise that the La-5 looks a great deal like a LaGG-3 (wings and all). Of course, now that Lavochkin saved his hide and got Uncle Joe smiling again (it is good when Uncle Joe is happy), he was able to go on to take the La-5 to the next level: the La-7, which did go through several changes to improve on the La-5.

So if a large number of the early war Soviet aircraft looked similar, it's because in many cases, they were directly related.


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## Koopernic (Oct 5, 2015)

One thing to note about Soviet aircraft production is that the organisations that designed the aircraft did not also produce it. There were design burro and there were factories that were quite independent.


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## Timppa (Oct 5, 2015)

Wooden wings were heavier than all metal -ones. I guess that lower taper ratio was chosen just to save weight. 
De Havilland aircraft (DH. 88 , Mosquito, Hornet) also have low taper ratio.


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## Milosh (Oct 5, 2015)

Koopernic said:


> One thing to note about Soviet aircraft production is that the organisations that designed the aircraft did not also produce it. There were design burro and there were factories that were quite independent.


I like the play on words. A burro is a small donkey.

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## gumbyk (Oct 5, 2015)

These wings would have been much easier to produce than spitfire wings. Each spitfire wing skin is a compound curve, rather than a simple flat sheet bent around the leading edge.

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## GregP (Oct 5, 2015)

Good point.

A lot of the design aspects of Soviet aircraft were done to adapt for harsh climate conditions and the use of unskilled labor being for maintenance.

I daresay the wings could easily have been designed for ease of manufacture by unskilled labor, too.

Actually, when I say "unskilled," I mean rural farmers, not completely inept people. Most rural farmers are pretty good at fabricating and inventing things because there is nobody to help them. They either figure it out or do without. A guy like that can easily get you into trouble by being inventive on an aircraft structure. Most aspects of the aircraft must be as designed or the strength calculations are out the window.

A number of Soviet prototypes crashed under strange circumstances, sometimes by inflight breakup, and I have often wondered if that might be due to deviation from plans by inventive-but-untrained rural farmer-type labor used for construiction of prototypes.

I've never seen a Soviet book or article that addressed the many strange crashes with any indications they might have actually looked into the crashes. Of course, information was government property in the former Soviet Union, so maybe the information was simply never dissiminated.

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## gumbyk (Oct 5, 2015)

Yeah, particularly when you think that original spitfire wings would have required an English wheel to manufacture. Having tried an English wheel - I've got a real appreciation of the skills involved with the manufacture of the aircraft. There isn't a straight line on a spitfire wing.


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## GregP (Oct 5, 2015)

I own one and would not want to try to make 2 identical parts on it, either. Great for one-off prototypes. Lousy for production work.

English wheeling might get better if you become expert at it, but it isn't going to go fast no matter what you do. I'm sort of OK at it, but clearly no expert. At least I can remove dents and things with it, and do planishing without work-hardening the Aluminum ... most of the time. Sometimes it DOES work-harden the Aluminum. When that happens, I start again and hope for better results.

I've never tried wheeling with -O Aluminum because there's much too great a chance of ruining the soft stuff in big pieces before it gets into a big oven. Our heat-treat oven is small, so I mostly only do small parts I can heat-treat myself.

I watched one of Steve Hinton's guys wheel new landing gear doors for a Tigercat and it was a thing of beauty to watch. They looked factory new! His guys are pretty good at Aluminum work! I'm OK for most normal things, but have a lot to learn about forming strange new shapes in Aluminum without generating some new baby scrap pieces.

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## tyrodtom (Oct 5, 2015)

Koopernic said:


> That is quite possible. The totalitarian ideology present at the time interfered directly with scientific ideas (For instance, Darwinism represented a potential threat to Communist ideas in that it might mediate that human nature was somewhat a matter of nature rather than a pure product of socialisation so the Lamarckian ideas of Lysenko were promoted and Darwinists who didn't believe that 1+1=4 knew they would end up in the Gulag). I know of one incidence of communist interference in engineering and manufacturing: in Eastern Germany one reason they kept producing 3 cylinder 2 stroke cars known as Trabants is because any radical improvements (such as 4 cylinder 4 strokes) would suggest that the original planners had made bad choices and such revolutionary improvements might be, well, counter revolutionary. It sounds absurd but these people had kindergarden teachers pass on notes to the Stassi about what TV shows had been watched by the children and thus in the household. It's worth noting we still have this problem with Darwinism in western polities as well.
> 
> More likely the proponents of these tapered plan form had more political clout and those with alternative ideas simply backed away. One can imagine a well connected proponent in the TsAGI as even bombers were effected by this fashion.
> 
> ...


 One thing wrong with your theory, the Trabant was a TWO CYLINDER 2 stroke, not 3 cylinder, the very late production models, 89 and up, had 4 cylinder VW Polo engines.
Several car companies made 3 cylinder 2 strokes, Saab, DKW, just to name two, and many motorcycle makers come out with 3 cylinder 2 strokes.


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## Koopernic (Oct 6, 2015)

tyrodtom said:


> One thing wrong with your theory, the Trabant was a TWO CYLINDER 2 stroke, not 3 cylinder, the very late production models, 89 and up, had 4 cylinder VW Polo engines.
> Several car companies made 3 cylinder 2 strokes, Saab, DKW, just to name two, and many motorcycle makers come out with 3 cylinder 2 strokes.



The "Berlin Wall" fell just after August 1989 and production of Polo engine versions started well after this in 1990 making it German rather than East German production. 

Admittedly it was the result of trade agreements developed in 1989; it was late in the piece as Eastern European communism was a rotting carcass clutching at straws. I've ridden in a Trabant, picked up from a train station, when Eastern Germany was still under communist domination. I recall the machine gun toting guards confiscating packets of coffee people were carrying to relatives. No, I don't think the cylinder count is substantive to the story. Ideological and political interference hamstrung any progress on the basic design.

The factory where they were produced once belonged to the "Auto Union" which became Audi. One of the directors and founding partners of Auto-Union, Horche, stayed on in communist East Germany out of parochial loyalty but the regime just kept restricting him in many ways, for instance in the number of employees he could have etc. till it folded. West Germany ended up with a monster like Audi, East Germany with a sick little Trabant which showed little improvement in 30 years.


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## Koopernic (Oct 6, 2015)

gumbyk said:


> Yeah, particularly when you think that original spitfire wings would have required an English wheel to manufacture. Having tried an English wheel - I've got a real appreciation of the skills involved with the manufacture of the aircraft. There isn't a straight line on a spitfire wing.



I think the Spitfire wing ended up being rather easy to produce once large stamping presses were established, there may have been some issue with modifying them after that since the Mk IX was mainly produced at Castle Brownwich but I doubt it was much of a problem. Somewhat ironically the Me 109E wing was rather hard to mass produce as it had been designed to be manufactured by multiple small scale subcontractors and then placed in to final assembly. Ease of mass production was one reason the Me 109F series was developed.

Comprmising aerodynamics and handling for the sake of mass production seldom works out.


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## GregP (Oct 6, 2015)

Elliptical wings are NEVER easy to produce.

They can get easier than one-off prototypes, but are labor intensive under the best of circumstances.

Good jigs help a lot, but it still isn't easy.


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## drgondog (Oct 6, 2015)

Koopernic said:


> The Spitfire's elliptical plan form had less need of aerodynamic twist than the tapered plan form of most other fighters yet it in fact had as much if not more (Approx 2.25-2.5 degrees compared to the 2 degrees common in other aircraft)



The elliptical plan form is the guarantor of minimum Spanwise Induced Drag due to the spanwise circulation. However it does not eliminate stall at the tip due to the upwash from spanwise circulation/lift vortices. Ergo - washout as you noted or LE devices.

As you know, introducing twist results in a Delta Induced drag so they wanted additional low speed roll control more than they wanted to further reduce induced drag.

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## tyrodtom (Oct 6, 2015)

Koopernic said:


> The "Berlin Wall" fell just after August 1989 and production of Polo engine versions started well after this in 1990 making it German rather than East German production.
> 
> Admittedly it was the result of trade agreements developed in 1989; it was late in the piece as Eastern European communism was a rotting carcass clutching at straws. I've ridden in a Trabant, picked up from a train station, when Eastern Germany was still under communist domination. I recall the machine gun toting guards confiscating packets of coffee people were carrying to relatives. No, I don't think the cylinder count is substantive to the story. Ideological and political interference hamstrung any progress on the basic design.
> 
> The factory where they were produced once belonged to the "Auto Union" which became Audi. One of the directors and founding partners of Auto-Union, Horche, stayed on in communist East Germany out of parochial loyalty but the regime just kept restricting him in many ways, for instance in the number of employees he could have etc. till it folded. West Germany ended up with a monster like Audi, East Germany with a sick little Trabant which showed little improvement in 30 years.



I'm sorry I'm just a simple mechanic and bodyman, when someone can't be bothered to even get the correct cylinder count on a engine, I wonder what other details might be too unimportant for him to get right.

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## pbehn (Oct 6, 2015)

tyrodtom said:


> I'm sorry I'm just a simple mechanic and bodyman, when someone can't be bothered to even get the correct cylinder count on a engine, I wonder what other details might be too unimportant for him to get right.



The Warburg Knight was an East German 3 cylinder two stroke, they sold a few in UK, eventually killed off by emission regs.


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## gumbyk (Oct 6, 2015)

Koopernic said:


> I think the Spitfire wing ended up being rather easy to produce once large stamping presses were established, there may have been some issue with modifying them after that since the Mk IX was mainly produced at Castle Brownwich but I doubt it was much of a problem. Somewhat ironically the Me 109E wing was rather hard to mass produce as it had been designed to be manufactured by multiple small scale subcontractors and then placed in to final assembly. Ease of mass production was one reason the Me 109F series was developed.
> 
> Comprmising aerodynamics and handling for the sake of mass production seldom works out.



Have you seen how a spitfire wing is constructed?


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## FLYBOYJ (Oct 6, 2015)

Koopernic said:


> I think the Spitfire wing ended up being rather easy to produce once large stamping presses were established, there may have been some issue with modifying them after that since the Mk IX was mainly produced at Castle Brownwich but I doubt it was much of a problem. Somewhat ironically the Me 109E wing was rather hard to mass produce as it had been designed to be manufactured by multiple small scale subcontractors and then placed in to final assembly. Ease of mass production was one reason the Me 109F series was developed.
> 
> Comprmising aerodynamics and handling for the sake of mass production seldom works out.



How do you think stampings helped or are you guessing? Unless you're building an aircraft by hand, each have their difficulties in assembling. Assembly jigs help greatly but one must develop a process to fit all the pieces in the jig and assemble them in an order to you could shoot all the rivets and get all components to match engineering drawings.

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## KiwiBiggles (Oct 7, 2015)

Oh no, we've moved on to Spitfire wings. I fear the dreaded one-spar two-spar argument is not far away.

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## GregP (Oct 7, 2015)

Everyone knows it's really a spar and a half!


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## GrauGeist (Oct 7, 2015)

KiwiBiggles said:


> Oh no, we've moved on to Spitfire wings. I fear the dreaded one-spar two-spar argument is not far away.


We could always toss in a random comment about the Bf109's box spar for good measure.

Wait...I just did!


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## Koopernic (Oct 7, 2015)

FLYBOYJ said:


> How do you think stampings helped or are you guessing? Unless you're building an aircraft by hand, each have their difficulties in assembling. Assembly jigs help greatly but one must develop a process to fit all the pieces in the jig and assemble them in an order to you could shoot all the rivets and get all components to match engineering drawings.



Over the years [decades really  ] I've read of the use of presses in spitfire production a number of times, so no, I'm not guessing though I have little direct detail. If you have simple two dimensional shapes and relatively thin aluminium sheet it could be simply wrapped around the stringers/ribs or jig, held on by temporary rivet "Cleveland" pegs and riveted.

For the more difficult compound shape a press could be used for mass production rather than a craftsmen beating them or rolling them to shape on something like an "English Whee". These are likely to be 'stretch forming presses' whereby the sheet was gripped and pulled over a male die. A more conventional press such as where a male die forces a sheet into a female die could also have been used, I've seen that process used to produce DC-3 nose cones. In that case the male dies was simply blocks to rubber cut and layed up to approximate the shape of the nose cap. The stretch forming press was the more common process.

One a press is involved the spitfire wing is no longer harder to produce than an ordinary wing, in fact it is easier to produce. The only cost was the initial tooling cost: you need to first of all order a press, develop a die, then experiment and modify a little. Then you are able to make large sections of thick skinned material that is of consistent dimensions and likely more rivet and fabrication free.

I suspect this is the actual stretch forming press (machine) used to make Spitfire wing leading edges at Castle Bromwich, it looks long enough:

_View: https://www.youtube.com/watch?v=Tp6age-sn2c_
Of the cowling of a CFM-56 (boeing 737)

_View: https://www.youtube.com/watch?v=Kh4MBHyHAtg_
This is the hard labour intense craftsmens way of doing it:

_View: https://www.youtube.com/watch?v=IGElSHzm0q8_

As aircraft skinds become thicker and more 'monocoque' presses became more and more important. I've read in a "Wings" article on the B-26 Marauder that the skin over the wing box that interconnected to two wings was about a 72 inch or so long single piece that was stretch pressed. It kept cracking until an 'old hand' recognised the problem and added a little grease to let the metal move a little as it stretched.

The B-29 Super fortress had rather thick skins and they had to be formed with presses.



KiwiBiggles said:


> Oh no, we've moved on to Spitfire wings. I fear the dreaded one-spar two-spar argument is not far away.


They fabricated ((pressed) the D section leading edge and likely mated it with the main spar first.





http://spitfiresite.com/wp-content/uploads/2012/07/39-39-7558001446_ec9e89b851_k.jpg
http://spitfiresite.com/wp-content/uploads/2012/07/41-41-7558010984_37d4748325_k.jpg

The construction techniques used on the leading edge of the Spitfire wings were very advanced, they involved techniques that became normal only 8-10 years latter at the dawn of the jet age.

The point is, once you've set up the tooling and presses it likely cost no more to produce than an more ordinary wing. The only production excuse for not doing this is that you can't get presses or are scared they'll get bombed.

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## GregP (Oct 7, 2015)

Spitfire wings were not stretch-formed. They were done the old fashioned way.

I don't believe stretch-forming tools were available in WWII ... but I also haven't absolutely verified that timeframe. 

Quenching was not in vogue until Aluminum was well along in the 1950s, as far as I know. Basically you form the 2024-O ALuminum, heat it to about 900°F for 25 minutes (varies with thickness and volume of Aluminum), and quench it in water within 10 seconds of removal from the oven. If you don't, you have to do it all over again in order to get 2024-T3. You cannot handle it with cloth gloves or they just flame away instantly and burn the crap out of you. I use duckbill pliers and just drop them into the water with the Aluminum.

900°F is nothing to trifle with.

If I am not mistaken, Spitfire wings were formed with O Aluminum and, when formed, were heat treated and then final-shaped

By the way ... GREAT videos! I love 'em.

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## Koopernic (Oct 7, 2015)

pbehn said:


> The Warburg Knight was an East German 3 cylinder two stroke, they sold a few in UK, eventually killed off by emission regs.



I've had my nose under the bonnet of both a Trabant and a Wartburg around 1993 when visiting sister in law relatives. To be frank I didn't take much of an interest in the cylinder count as they were already on the way out, almost immediately replaced by second hand German and French cars (car yards on every corner, personnel mobillity a freedom we don't even notice) but remember now that it was the Wartburg that had the 3rd cylinder. The Wartburg had received greater engineering effort but was still primitive. People had to wait years to get one. At the time, with the expose of STASSI files it had been revealed to the German villagers that two 'boys' had gained their apprenticeships as refrigeration mechanics by betraying some other boys who had made mild sarcastic jokes about competence of the political authorities. The betrayal was recorded, created a black mark for others but earned points for the scabs. When it came to good jobs or university access the file was pulled and consulted. That's what communism leads to. You have little freedom or choice to decide what to buy, you can't choose who to work for in your chosen field. Political intrigue rather than work, competency or meting demand is the way to advance. They could do reasonably well in some areas when there was a clear goal, such as making a better tank or fighter plane or creating a spectacular programme to say launch a satellite.

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## FLYBOYJ (Oct 7, 2015)

Koopernic said:


> Over the years [decades really  ] I've read of the use of presses in spitfire production a number of times, so no, I'm not guessing. If you have simple two dimensional shapes and relatively thin aluminium sheet it could be simply wrapped around the stringers/ribs or jig, held on by temporary rivet "Cleveland" pegs and riveted.


 So you read this - did you also read that the component has to be held in place with a jig?!?!? Cleveland peg?!?! Don't you mean a* Cleco*???


Koopernic said:


> For the more difficult compound shape a press could be used for mass production rather than a craftsmen beating them or rolling them to shape on something like an "English Whee". These are likely to be 'stretch forming presses' whereby the sheet was gripped and pulled over a male die. A more conventional press such as where a male die forces a sheet into a female die could also have been used, I've seen that process used to produce DC-3 nose cones. In that case the male dies was simply blocks to rubber cut and layed up to approximate the shape of the nose cap. The stretch forming press was the more common process.



OK - what you describe fabricates one component - it has to be attached to the rest of the assembly. How you supposed that done?!?!? 


Koopernic said:


> One a press is involved the spitfire wing is no longer harder to produce than an ordinary wing, in fact it is easier to produce. The only cost was the initial tooling cost: you need to first of all order a press, develop a die, then experiment and modify a little. Then you are able to make large sections of thick skinned material that is of consistent dimensions and likely more rivet and fabrication free.


 "likely more rivet and fabrication free" are you sure about this?!?!


Koopernic said:


> *I suspect *this is the actual stretch forming press (machine) used to make Spitfire wing leading edges at Castle Bromwich, it looks long enough:


You "SUSPECT? 

Again, youre giving a great narrative of single component *fabrication*and nothing about *ASSEMBLY.*


Koopernic said:


> The point is, once you've set up the tooling and presses it likely cost no more to produce than an more ordinary wing. The only production excuse for not doing this is that you can't get presses or are scared they'll get bombed.


I could agree with that statement but again you have totally missed the point - weather individual components are stretched formed or formed with an English wheel they have to be assembled in a jig, end of story. You keep saying "ordinary wing," please tell us what you mean by that? If you were assembling a swept wing with compound curves, is that an "ordinary wing? Is an F4U or Stuka's wing ordinary? You're putting out information here based on what you're reading in books not realizing that some of us ACTUALLY built a few aircraft over the years [decades really  ], so please spare us the tutorials unless you've been there your self and really know how to use a rivet gun!!!!


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## The Basket (Oct 8, 2015)

Didn't TsAGI design the wings?


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## tomo pauk (Oct 8, 2015)

The Lavotchkin's fighters used NACA 230 series profile (until switch to the laminar flow wing from La-9 on), the MiG used the Clak YH. Planform was probably a design choice of the design bureau.


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## Koopernic (Oct 8, 2015)

GregP said:


> Spitfire wings were not stretch-formed. They were done the old fashioned way.
> 
> By the way ... GREAT videos! I love 'em.



I've given a link with a picture of a stretching machine above, here is the link again:
http://spitfiresite.com/2012/07/cas...ory-photos.html/37-37-7557991922_b5a00aa490_k
The caption to this photo says:
*"Castle Bromwich Aeroplane Factory. 150-ton stretching machine at Block 'F'. "* So clearly they were using the process 
(and on the B-26) though it was considered an advanced technique.
*Block F *is shown in the picture below:





It has both a "press room" and 24 "Wheeling machines" next to the tool room so that doesn't clear anything up at all except that there was a 150 ton pulling machine and also wheeling machines which by one account made the wing fillets?

" F Block - At the West end of the block was another steel stores whilst at the East end was another Tool Room and Pattern Shop. The Tool Room was actually on the North side with the Pattern Shop on the South Side. In the middle on the North side was the Press section, and on the South side of the centre were 24 "wheeling" machines that produced the "Hockey Sticks" used to seal the wings to the fuselage. These machines had to work 24 hours a day, 7 days a week. "



It could have made Lancaster parts, or perhaps parts of the fuselage. The wing fillet was also a compound curve. Perhaps both systems of production were used. With the Spitfire having a wing span of 36 feet I think that pulling press, which looks about 3 man lengths long could handle an entire leading edge. Having said that, the photographs of wings in my previous post seem to be of universal "C" type wings since they have openings for up to 2 x Hispano guns and the openings were separately fabricated. The C type was in part developed to simplify mass production.





FLYBOYJ said:


> So you read this - did you also read that the component has to be held in place with a jig?!?!? Cleveland peg?!?! Don't you mean a* Cleco*???
> 
> 
> OK - what you describe fabricates one component - it has to be attached to the rest of the assembly. How you supposed that done?!?!?
> ...



The reason I use the word suspect is that although there is definitely a 150 ton stretching press at Castle Bromwich there is no caption to indicate what it was used for. Also although I recall reading the comment about parts of the elliptical wing being pressed the Author may have been wrong and I can't at present recollect the book/author to confirm, I'll get there. Heinkel also had problems with his metal built elliptical wings and the He 112 prototypes were of a lumpy appearance as they had no dies to use.

By "ordinary wing" I mean a standard tapered wing which lacks significant compound curve. My argument is that with a press the labour content used on subsequent assembly would be no worse than for a straight wings while the pressing operation is not labour intensive in itself. Thicker wings skins with fewer stringers and stiffeners members may need less rivets or make it easier to countersink. (and I'm repeating something I read) was pretty good from a mass production point of view.

Yes I did mean Cleco, I've seen them called Cleveland Clamps in a very old book.


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## GregP (Oct 8, 2015)

Central Louisian Electric COmpany makes a very neat "Cleco" brand name, doesn't it.

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## FLYBOYJ (Oct 8, 2015)

Koopernic said:


> By "ordinary wing" I mean a standard tapered wing which lacks significant compound curve. My argument is that with a press the labour content used on subsequent assembly would be no worse than for a straight wings while the pressing operation is not labour intensive in itself. *Thicker wings skins with fewer stringers and stiffeners members may need less rivets or make it easier to countersink.* (and I'm repeating something I read) was pretty good from a mass production point of view.


And again that's you're opinion - it's quite obvious you're making these assumption on what you read or by looking at pictures. The amount of rivets used or number of stringers have NOTHING to do with wing thickness!!! What type of wing structure are you talking about? Will it be conventionally built or feature corrugation sub skin? How long will it be? Will it be made from milled wing planks and held in place with hi locks? Is the wing for a fighter, bomber or transport aircraft???? 

I've built aircraft as well as sub assemblies and worked at Lockheed, Boeing and BAE to name a few and I could tell you don't have a clue what you're talking so please don't try to school us with what you read in books, some of us have actually "been there/ done that."

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## fastmongrel (Oct 8, 2015)

I am surprised everyone still believes the Factory cover story for Spitfire construction. Spitfires were actually carved from a single Oak Tree that had been blessed by a Druid, a Bishop and a Virgin riding a Unicorn (Virgins are always in very short supply but luckily the Govt Unicorn breeding programme was coming along nicely by 1939). When a pilot got his wings he went to Saville Row and was measured for his Spitfire the Tailor would ask "Which side does Sir dress his Oxygen Tube" then a group of woodland Elves would carve the aircraft to suit. When it was finished the Elven Queen would tell the new pilot "This Plane is to rule them all you must fly it to Mordor but you only have 5 minutes of fuel for combat before you must return or the Orc 109s will shoot you down"

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## fastmongrel (Oct 8, 2015)

GregP said:


> Central Louisian Electric COmpany makes a very neat "Cleco" brand name, doesn't it.



*CLE*veland pnuematic tool *CO*mpany

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## tyrodtom (Oct 8, 2015)

Why all this talk about metal forming when all three aircraft in the original question had wooden wing construction, or a combination of wood and metal ?

Two of the 3 could hardly be termed substandard aircraft by anyone's yardstick, so they can hardly be held up as good examples of the failures of the communist system.


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## FLYBOYJ (Oct 8, 2015)

Koopernic said:


> It could have made Lancaster parts, or perhaps parts of the fuselage.



Again you're guessing!!!!

Most if not all WW2 aircraft wings were assembled in some kind of jig - if they weren't when you started riveting everything together you would get structure that twisted and warped. Very simple wings like the Spit and -109 were built in jigs that allowed the placement of a front and rear spar. Jig "details" aligned ribs to their proper location in reference to engineering drawings. Once attached the skin is installed in such a manner so you don't rivet yourself in a corner. Blind rivets were used in inaccessible areas but their application was limited because they for the most part cannot take high tension loads. Explosive rivets were also used for inaccessible areas as well. 






In the case with a P-38 wing being assembled, the L/E is facing down and the structure is assembled vertically. The jig will "build in" any twist or compound curve. Wings are still built this way, here's a link to a Seversky product, possibly a P-35 being assembled.

SeverskyWingBuild.jpg Photo by VNSPEC22 | Photobucket

This is a Spitfire Repair Jig






And a B-24 wing being assembled






Some wings were assembled with a corrugated skin attached to the ribs then an outer skin riveted to the "hats" of the corrugations. This provided great strength to the wings.






A later process involved taking very rigid slabs of aluminum (7075) and milling down the slabs so the inside of the skin had a series of uniformed "risers" that attached to ribs. For the most part many modern aircraft wings are built this way and are held together with hi-loks. This is a link that shows a P-3 wing.

http://www.navair.navy.mil/img/uploads/11_12F.jpg

Stretch forming was done during the fabrication state and was limited during WW2 because aluminum alloying and heat treatment techniques were being developed on the fly. Annealed aluminum could be formed quickly but had to be heat treated after the forming process unless the stretching of the aluminum allowed it to be "cold worked" to the point where it carried enough strength for its intended purpose. English wheels were used for hand fabrication but required a lot of time and skill to turn out a good product. Drop hammers were the easiest way to form parts with compound curves but were limited in as dies did wear out and could be expensive to make (let alone the cost of the press).






This isn't everything but explains the basic process WITHOUT GUESSING or assuming things while sitting at your lounge chair!!!! So when you hear someone say that one wing is easier to build than another (or perhaps maybe, assuming, it could have, possibly) have them state the facts!!!!!

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## GrauGeist (Oct 8, 2015)

fastmongrel said:


> I am surprised everyone still believes the Factory cover story for Spitfire construction. Spitfires were actually carved from a single Oak Tree that had been blessed by a Druid, a Bishop and a Virgin riding a Unicorn (Virgins are always in very short supply but luckily the Govt Unicorn breeding programme was coming along nicely by 1939). When a pilot got his wings he went to Saville Row and was measured for his Spitfire the Tailor would ask "Which side does Sir dress his Oxygen Tube" then a group of woodland Elves would carve the aircraft to suit. When it was finished the Elven Queen would tell the new pilot "This Plane is to rule them all you must fly it to Mordor but you only have 5 minutes of fuel for combat before you must return or the Orc 109s will shoot you down"


I believe you forgot two very important details:
First, at the village workshop, each new Spitfire being fashioned required a fresh supply of dirt from Hastings cast on the floor.

Secondly, before each pilot was led through the doors to receive his Spitfire, he was required to kiss the pommel of Excalibur and exclaim "For King and Country!"

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## GregP (Oct 8, 2015)

About the Central Louisiana Electric Company ... I was referring to the always reliable Wikipeida: https://en.wikipedia.org/wiki/CLECO fiasco.

Don't tell me they are WRONG? What? Again?

Oh the humanity of it ... it's like watching the Hindenberg crash all over again ... only it keeps happening over and over and ... you get the idea. What's a poor criminal supposed to do with information this good?

About the stretcher, that's VERY interesting to hear. I have several references that talk about Spitfire manufacturing in general, but ... and here's the catch ... they never mention Castle Bromwich specifically when discussing manufacturing, only that Spitifires were built at the various locations, of which Castle Bromwhich was one. So I knew Castle Bromwich made Spitfires, but not that they had and used a stretcher, especially on Spitfire wings.

It would make forming the leading edge a lot easier, to be sure. I'm not so sure it would make fabrication any easier since you still have to rivet everything, either on a jig or predrilled ... and they didn't have any CNC mill-drills. So, I am again assuming the wings were jigged and had a very specific fabrication sequence.

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## FLYBOYJ (Oct 8, 2015)

GregP said:


> So, I am again assuming the wings were jigged and had a very specific fabrication sequence.


 Exactly!


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## gumbyk (Oct 8, 2015)

FLYBOYJ said:


> Exactly!



Which is why it takes so much longer to build on now - a lot of that sequencing has been lost.

150 tonne press - possibly used to put the bend in the main spar upper and lower caps. I know that it is a pretty precise piece of work to do, and requires some pretty heavy machinery to do.

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## GregP (Oct 8, 2015)

Hi Joe,

We're in the middle of restoring a North American O-47 wing right now and must replace some skins. The problems is ... the assembly sequence has been lost and we're having a very difficult time deciding how to sequence the work so we can get solid rivets in all the holes. It wouldn't be so bad is we were completely disassembling the wings, but we need to replace a skin roughly in the center of the wing ... and no matter which way you go ... you lose access at some point unless ALL the skins are removed. It's gonna' be interesting to see how it finally works out. I think complete disasembly is the only practical solution, but ... I'll wait for some of Steve Hinton's guys to weigh in with their thoughts before diving in without a wing jig. A few Cherry Maxes are better than a crooked wing ... maybe ... depends on how many would be required.

They built jigs for the F-86 right and left wings and slats ... I doubt they're too interested in building 2 more ...


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## Koopernic (Oct 8, 2015)

Stretch forming was not unknown in the industry at the beginning of WW2. The 150 ton stretch press at Castle Browmwich is surely for sheet stock. The 20 or so cylindrical sized caps I believe are the hydraulic cylinder heads, probably for the clamping jaws to hold the sheet but possibly to raise the forming die.


The Me 109:
EzineArticles Submission - Submit Your Best Quality Original Articles For Massive Exposure, Ezine Publishers Get 25 Free Article Reprints

"_The rear section of the fuselage (the section immediately behind the pilot' seat and extending to the front of the tail) was also unique. To explain, first visualise a stack of cups. The rear section or in German, the "Rumpf" is made up of parts that nestle together like a stack of cups. Each section including what would normally be the former or main structural part forming the shape is made of a single sheet of aluminium. Each section was formed on a stretch press with the former being created out of some clever folds to provide strength. To be precise every second section was formed on a stretch press. So, to visualise, keep every second cup and replace every alternate one with a sheet wrapped around the bottom of each cup - that is what the back end of the Bf 109 is like. It was innovative, strong and it greatly simplified production by removing a lot of fiddly framework._"

Martin B-26 Marauder:
LiTOT: The Martin Marauder B-26

"_The general production setup called for extensive use of spotwelding in secondary structure to eliminate, where possible, the more costly and time-consuming process of riveting. The *stretch press*, used by the automobile industry at the time of World War I to form fenders, was reintroduced to shape convex-curved pieces of aluminum skin, four times the average size in other aircraft. These large sheets of skin were employed in the fuselage and cowling to eliminate the multiplicity of stringers, rivets and other small detail parts normally associated with a fuselage of this size and length. Hundreds of castings, forgings and plastic parts were used to simplify mass production methods and eliminate the use of critical materials. Thus, the B-26 uses more castings, forgings and other miscellaneous parts adapted to intensive production methods, fewer rivets and detail parts, than any comparable airplane. Some of the new design elements in the Marauder follow: 

WING ARRANGEMENT — It was decided to depart from the usual procedure of keeping wings integral from nacelle to nacelle by breaking the wing panels at the sides of the fuselage. This entailed the eventual design of the "dumbbell" lower spar chord forging to eliminate the use of heavy and costly fittings. Manufacture of this forging, the largest aluminum type ever made, required five sets of dies, each weighing more than two tons. Thus the wing and its engine and nacelle is an entire assembly. The center section was eliminated. Each wing is attached to the dural forgings at the wing roots, which serve as anchors for the attaching bolts. This arrangement facilitates assembly and replacement. 

FUSELAGE — Its construction around a very strong keel made for almost perfect streamlining, and extra strength in crash landings. B-26 crews nearly, always walk away from a forced landing. This same keel was also excellent as an anchor for the external torpedo rack. There are no stringers, just skin and forming frames — five compartments in three major sections._"

The Pe-2 also had this kind of structure but was regarded as a little weak.

*The below is from "Martin B-26 Marauder" by Martyn Chorlton (Osprey Publishing)*

The Marauder was designed and built from the outset to be a mass- 
produced aircraft. Martin engineers confidently pre-empted a large order 
being received from the USAAF as the world situation continued to 
deteriorate. Martin also accurately predicted that the workforce required 
to build the bomber would have no, or very little, experience of building 
aircraft. 

To help achieve the task of building a complex flying machine, the 
B-26 was put together from approximately 650 minor sub-assemblies, 
which were then joined to create 32 major sub-assemblies, and the final 
aircraft. All of the Marauder's frames and stringers were pre-drilled in 
their jigs and, once these components were delivered to the shop floor, 
the task of riveting was made all the easier. 

The Marauder's fuselage was covered in 63 pieces of metal skin, each 
with its own compound curvature. Each piece of skin *was produced on a 
stretch press* with a high degree of accuracy and consistency that made 
the job of producing the B-26's streamlined fuselage quicker than be- 
spoke panel beating. 

Wing parts were also produced with the same degree of accuracy and 
consistency thanks to Martin working closely with a milling machine 
manufacturer to develop a machine with a travelling head and a 30ft bed. 
Every part of the wing was produced to be foolproof, basically meaning 
that the parts could only be fitted in one way — the correct one!

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## GregP (Oct 9, 2015)

The Pe-2 was weak? Really?

The Petlyakov Pe-2 (Russian: Петляков Пе-2) was regarded as one of the best ground attack aircraft of the war and it was extremely successful in the roles of heavy fighter, reconnaissance and night fighter. It was one of the most important aircraft of World War II, similar in many respects to the British de Havilland Mosquito. Pe-2s were manufactured in greater numbers (11,427 built) during the war than any other twin-engined combat aircraft except for the German Junkers Ju 88 and British Vickers Wellington. The Pe-2 was fast, maneuverable and *durable*. Several Communist nations flew the type after the war, known by the NATO reporting name Buck. Six captured Pe-2s were also transferred from the Germans to the Finnish Air Force during the Continuation War, with the serial code PE- and the unofficial nickname Pekka-Eemeli.


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## Juha (Oct 9, 2015)

Pe-2 wasn't so good as a ground attack version, the fighter version, Pe-3 was even worse and suffered heavy losses when forced to ground attack work in late 41. And IMHO it wasn't a great success as a heavy fighter. But Pe-2 series did good work as light bomber and recon machine. But as a bomber suffered from light bomb load.

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## FLYBOYJ (Oct 9, 2015)

GregP said:


> Hi Joe,
> 
> We're in the middle of restoring a North American O-47 wing right now and must replace some skins. The problems is ... the assembly sequence has been lost and we're having a very difficult time deciding how to sequence the work so we cna get solid rivets in all the holes. It wouldn't be so bad is we were completely disassembling teh wings, but we need to replace a skin roughly in the ecenter of the wing ... and no matter which way you go ... you lose access at some point unless ALL the skins are removed. It's gonna' be interesting to see how iot finally works out. I think complete disasembly is the only practical solution, but ... I'll wait for some of Steve Hinton's guys to weigh in with their thoughts before diving in without a wing jig. A few Cherry Maxes are better than a crooked wing ... maybe ... depends on how many would be required.
> 
> They built jigs for the F-86 right and left wings and slats ... I doubt they're too interested in building 2 more ...



I dealt with Westpac Aviation a few years ago - they moved here from SoCal when Rialto airport closed. they are in the final throws of restoring a P-38F (White 33) I believe flown by several aces. They had the same issue and had to make bucking bars to fit inside the wing corrugations. Westpac Restoration - P-38 White 33

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## FLYBOYJ (Oct 9, 2015)

Koopernic said:


> Stretch forming was not unknown in the industry at the beginning of WW2. The 150 ton stretch press at Castle Browmwich is surely for sheet stock. The 20 or so cylindrical sized caps *I believe* are the hydraulic cylinder heads,* probably *for the clamping jaws to hold the sheet but possibly to raise the forming die.





Koopernic said:


> The Pe 2 also didn't have stringers in the fuselage and was regarded as rather week, *possibly* because it was made differently to Magruder's Marauder.





GregP said:


> The Pe-2 was weak? Really?
> 
> The Petlyakov Pe-2 (Russian: Петляков Пе-2) was regarded as one of the best ground attack aircraft of the war and it was extremely successful in the roles of heavy fighter, reconnaissance and night fighter. It was one of the most important aircraft of World War II, similar in many respects to the British de Havilland Mosquito. Pe-2s were manufactured in greater numbers (11,427 built) during the war than any other twin-engined combat aircraft except for the German Junkers Ju 88 and British Vickers Wellington. The Pe-2 was fast, maneuverable and *durable*. Several Communist nations flew the type after the war, known by the NATO reporting name Buck. Six captured Pe-2s were also transferred from the Germans to the Finnish Air Force during the Continuation War, with the serial code PE- and the unofficial nickname Pekka-Eemeli.



Koopernic - why do you keep guessing?!?!?


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## Juha (Oct 9, 2015)

To the original question. Not knowing but my guess is that it was a result of TsAGI research.


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## Juha (Oct 9, 2015)

Hello Koopernic
thanks for the Spitfiresite link, many interesting photos there.

Juha


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## Wurger (Oct 9, 2015)

Koopernic said:


> The Pe 2 also didn't have stringers in the fuselage and was regarded as rather week, possibly because it was made differently to Magruder's Marauder.




So.. what kind of structure was the Pe-2 fuselage ?


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## Juha (Oct 9, 2015)

Pe-2 was used also as dive-bomber, so it should not be too fragile.


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## GregP (Oct 9, 2015)

Sure LOOKS like it has stringers:







Look at all the little stringer-type-thingies in the fuselage around the tailwheel area.


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## Elmas (Oct 10, 2015)

What does it mean "fragile" by a techical point of view?
A6M was certainly not fragile structurally, but was extramely fragile in a combat environment, were it is possible to receive a shower of bullets...


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## drgondog (Oct 10, 2015)

Koopernic said:


> FUSELAGE — Its construction around a very strong keel made for almost perfect streamlining, and extra strength in crash landings. B-26 crews nearly, always walk away from a forced landing. This same keel was also excellent as an anchor for the external torpedo rack. There are no stringers, just skin and forming frames — five compartments in three major sections.[/I]"
> 
> The Pe 2 also didn't have stringers in the fuselage and was regarded as rather week, possibly because it was made differently to Magruder's Marauder.



I immediately wonder how applied loads to the empennage in all three axes were taken to withstand bending - A 'shell' without fore and aft longerons, to intersect with bulkheads and connect all with shear panels will not work - except in case of Mosquito type construction where the 'shell' acts a cylindrical Plate with inherent bending load absorption capability.

Stringers are nothing more or less than smaller (than Longerons) beams upon which thin sheet metal shear panels are riveted fore and aft, and vertically at the bulkheads.

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## Juha (Oct 10, 2015)

Elmas said:


> What does it mean "fragile" by a techical point of view?
> A6M was certainly not fragile structurally, but was extramely fragile in a combat environment, were it is possible to receive a shower of bullets...



I meant from structural viewpoint, the optimal pull-up for Pe-2 was 3G and there was a warning system if the pilot pulled over 4G. Not much for a fighter but not bad for a bomber which pe-2 was. It wasn't a Zero, it had some armour and inert gas could be pumped into the fuel cells. But sometimes they blew up when hit by MG 151/20 shells.

But Koopernic might well be right that there was no stringers, only the longerons. Difficult to say anything definite, I have only a handbook drawning of the front part of the fuselage and some photos of the cockpit and of the area front of the cockpit.


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## Koopernic (Oct 10, 2015)

GregP said:


> Sure LOOKS like it has stringers:
> 
> Look at all the little stringer-type-thingies in the fuselage around the tailwheel area.




The following link:
Pe-2 family by V.M.Petlyakov, A.M.Izakson, A.I.Putilov, V.M.Myasichev

"Fuselage (designed by A.I.Putilov) was *close to monocoque *of circular cross-section. Sparsely placed ribs (each 0.5m) supported thick (1.5 to 2.0mm) aluminum alloy skin *without stringers*, only windows, cockpit and turret openings had enforcing frame."

While I am very much inclined to believe your drawing (one can trust a draftsman more than an author) I have read of the claim that the Pe-2 lacked stringers several times and these drawings are after all often reconstructions for a magazine and not manufacturing general assembly drawings. Of course through the wonders of Google one can always verify incorrect information by putting in the search string to get what one wants.

Looking at some of the detail images in the above link I do notice a distinct lack of rivet lines over where there could be stringers on the mid rear section of fuselage. In other words there were stringers up to the trailing edge area, then most of thr stringers cut off, then near the tail section they restarted. This tends to conform the stringer free statement, A picture of the fuselage inside would clear things up here.






I admit the Pe-2 didn't have a weak structure, that comes from the Germans sources as they regarded it as vulnerable to canon fire as the structure could collapse during attack, as Elmass suggested. I would not regard this as a serious criticism given the immense destructive power of 4 canon armament that was showing up in the Fw 190A (and Typhoon/Tempest/Mosquito/Beuafighter) under which German aircraft or any aircraft would not survive long.

The Pe-2 rather conforms to the original abandoned German Zerstoerer concept which envisaged a 3 man crew. Petlokov along with Tupolev were both sent to a Soviet concentration camp (Gulag) for allegedly forming counter revolutionary groups. It took 4 days to break the men down to the point they signed confessions of all sorts. Petlokov was supposed to have sold the Pe-2 to the Germans who turned it into the Me 110, supposedly. Petlokov did have German contacts, he learned the art of aluminium aircraft construction at Junkers in the 1920's. He was the Soviet expert in this field.

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## drgondog (Oct 10, 2015)

I'm inclined to agree - no stringers aft - all bending/torsion taken out by longerons, bulkheads and shear panels just aft of trailing edge of wing.

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## Koopernic (Oct 10, 2015)

drgondog said:


> I immediately wonder how applied loads to the empennage in all three axes were taken to withstand bending - A 'shell' without fore and aft longerons, to intersect with bulkheads and connect all with shear panels will not work - except in case of Mosquito type construction where the 'shell' acts a cylindrical Plate with inherent bending load absorption capability.
> 
> Stringers are nothing more or less than smaller (than Longerons) beams upon which thin sheet metal shear panels are riveted fore and aft, and vertically at the bulkheads.



There is a subtle difference between the longeron and stringer which may have escaped some authors. The following is from Wikipedia, it does cite an engineering textbook.

"Sometimes the terms "longeron" and "stringer" are used interchangeably. Historically, though, there is a subtle difference between the two terms. If the longitudinal members in a fuselage are few in number and run all along the fuselage length (usually 4 to 8.), then they are called "longerons". The longeron system also requires that the fuselage frames be closely spaced (about every 4 to 6 in or 10 to 15 cm). If the longitudinal members are numerous (usually 50 to 100) and are placed just between two formers/frames, then they are called "stringers". In the stringer system the longitudinal members are smaller and the frames are spaced farther apart (about 15 to 20 in or 38 to 51 cm). Generally, longerons are of larger cross-section when compared to stringers. On large modern aircraft the stringer system is more common because it is more weight-efficient, despite being more complex to construct and analyze. Some aircraft use a combination of both stringers and longerons.[2]"

My previous post #45 added the fact that all of the B-26 63 fuselage panels were stretch pressed. The design was stringer free but it supposedly had a "keel" from which the torpedo could be hung. I'm sure it had longerons though the source says there were forming frames. The B-26 was known for strength.

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## Wurger (Oct 11, 2015)

Here is a couple of images of the the rear interior I found via the net. Not of too good quality but it can be noticed that there were two stringers at least. These two running back can be seen at the top of the compartment. According to the diagram there these run up to the tail whiil section. The diagram dosn't show it clearly but there were two more running at the floor level, also the floor there was the reinforcement of the section too. All of the stringers were becoming thinner going farther back what is a correct way of getting tappered stringers for the proper structural strength. The side "longerons" were a kind of stringers in fact that made the structural strength of the tail section with a couple of additional stiffeners and longerons. So it seems that the diagram posted by Koopernic is a little bit inaccurate with the riveting layout.

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## Juha (Oct 11, 2015)

Very interesting photos, thanks a lot, Wurger!
I’d say that there are the normal 4 longerons that formed the box girder to assure longitural stiffness of the fuselage by taking at least part of the bending loads. The basic structure that had been used since the first planes, of course in semi-monocoque the other part of the strength comes from the external skin. But practically no stringers as Koopernic said, so the fuselage skin seems to took greater part of the loads than usual at that time.

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## Wurger (Oct 11, 2015)

And here a couple of diagrams I found via the net additionally.

The Pe-2 ...












The Pe-3...


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## FLYBOYJ (Oct 11, 2015)

Thanks for the pics Wurger...

Juha started to mention the one thing that everyone is missing here...

With all this talk about lack of stringers vs. longerons, has anyone considered the thickness of skin, and the thickness *and construction *of the longerons? To really determine if this design was "weak' one would have to determine the alloys used in construction, and a stress analysis to determine how strong this really is.

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## Elmas (Oct 11, 2015)

Stringers are needed to prevent buckling: with a thicker aluminium sheet less stringers are needed, and viceversa.






The same in a wing D-box, were stresses are due not only to bending but also to torsion, less important in a fuselage. 






Exact calculation, before computers, was not an easy task, as all the theories about bending and stretching of plates were in those days quite recent, as they went out about 1920. Not that today, even with computers, calculation can be a kid's play.

Modellers probably will find this site interesting:

Antrvm Ratvs - Reproducing stressed skin effect in aircraft models

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## FLYBOYJ (Oct 11, 2015)

Elmas said:


> Stringers are needed to prevent buckling:* with a thicker aluminium sheet less stringers are needed, and viceversa.*
> View attachment 303474
> 
> 
> ...



That's only part of it. You have to consider the alloying of the components which will determine strength and what kinds of loads they could actually take. You could have a thick skinned structure made from 2024-T3 skins held in place with 6 or 7 7075-T6 longerons and it may have the same structural properties as a thinner skinned structure with thinner longerons and a series of stringers made from 2024 T-6. Mind you this is only an examples that there are dozens of considerations that could effect this.


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## Elmas (Oct 11, 2015)

FLYBOYJ said:


> That's only part of it. You have to consider the alloying of the components which will determine strength and what kinds of loads they could actually take. You could have a thick skinned structure made from 2024-T3 skins held in place with 6 or 7 7075-T6 longerons and it may have the same structural properties as a thinner skinned structure with thinner longerons and a series of stringers made from 2024 T-6. Mind you this is only an examples that there are dozens of considerations that could effect this.



Certainly. But, if the plates are "thin", buckling can arise well before yeld strenght is reached, so using a material with a superior yeld strenght, if the structure is not very carefully studied and tested, is irrelevant.
It is the "mix" of plate thickness, number and size of stringers and yeld strenght of materials that make a rigid and light structure or not,
and this is why some airplanes are "hawks" and some others "turkeys"..... to design an airplane structure must be considered a sort of an "art".

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## FLYBOYJ (Oct 11, 2015)

Elmas said:


> Certainly. But, if the plates are "thin", buckling arises well before yeld strenght is reached, so using a material with a superior yeld strenght, if the structure is not very carefully studied and tested, is irrelevant.
> It is the "mix" of plate thickness, number and size of stringers and yeld strenght of materials that make a rigid and light structure or not,
> and this is why some airplanes are "hawks" and some others "turkeys"..... to design an airplane structure must be considered a sort of an "art".



Exactly!

- so it's silly to try to determine the strength or durability of an aircraft just by visually observing how many rivet rows it has!


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## GrauGeist (Oct 11, 2015)

FLYBOYJ said:


> Exactly!
> 
> - so it's silly to try to determine the strength or durability of an aircraft just by visually observing how many rivet rows it has!


Also considering that there's virtually no mention of structural failure under severe flight conditions and the Pe-2's max. T/O weight was rated well over 18,000 pounds (amplified by less than desirable airfields), it would seem the tail's construction was sturdy enough.

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## Wurger (Oct 12, 2015)

I haven't found the exactly thickness of the covering plates so far. But russian sources say that it was a little bit more than the standard one used for a such structure. And it was enough fully to keep the tail's construction very sturdy.


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## Koopernic (Oct 12, 2015)

in regards to the use of stretch presses in Spitfire Production at Clastle Bromwhich.
https://www.flightglobal.com/FlightPDFArchive/1941/1941 - 0847.PDF

Lord Nuffield, (William Morris), the genius that set up this factory to run using automotive style mass production deserves credit rather than the shoddy treatment he received at the hand of Beaverbrook. Setting up mass production is a difficult matter.


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## FLYBOYJ (Oct 12, 2015)

Koopernic said:


> in regards to the use of stretch presses in Spitfire Production at Clastle Bromwhich.
> 
> 
> Lord Nuffield, (William Morris), the genius that set up this factory to run using automotive style mas production deserves credit rather than the shoddy treatment he received at the hand of Beaverbrook.
> Setting up mass production is a difficult matter.



What is being shown there are presses that more form than stretch, although there is stretching involved. That's usually done with annealed aluminum (2024-0 or back in ww2 24-0). The forming and stretching would work harden the component depending on the "amount of forming and stretching". There many be post forming heat treating involved depending on the component and what type of loads it may face. This is a *fabrication process of individual components and not reflective in the ease or difficulty of the actual assembly of a major sub structure such as a wing.*


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## Balljoint (Oct 12, 2015)

FLYBOYJ said:


> Thanks for the pics Wurger...
> 
> Juha started to mention the one thing that everyone is missing here...
> 
> With all this talk about lack of stringers vs. longerons, has anyone considered the thickness of skin, and the thickness *and construction *of the longerons? To really determine if this design was "weak' one would have to determine the alloys used in construction, and a stress analysis to determine how strong this really is.





I’ve thought of stringers as working in tension and not much in compression, while longerons have enough “depth” to provide compression (bending) strength. Similarly, a thin stressed skin is primarily a tension member while a thicker skin has significant compressive strength.


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## FLYBOYJ (Oct 12, 2015)

Balljoint said:


> I’ve thought of stringers as working in tension and not much in compression, while longerons have enough “depth” to provide compression (bending) strength. Similarly, a thin stressed skin is primarily a tension member while a thicker skin has significant compressive strength.


Again this will be dependent on what the material you're working with as well. 7075 aluminum is strong but not flexible, it could probably take shear loads good but not bending. 2024 T-3 will take bending but depending on application could eventually work harden and fatigue. In a high heat area one could use stainless steel but now you're looking at a weight factor as well as possible dissimilar metal issues (corrosion). It's all a balancing act.


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## pbehn (Oct 12, 2015)

Elmas said:


> Certainly. But, if the plates are "thin", buckling can arise well before yeld strenght is reached, so using a material with a superior yeld strenght, if the structure is not very carefully studied and tested, is irrelevant.
> It is the "mix" of plate thickness, number and size of stringers and yeld strenght of materials that make a rigid and light structure or not,
> and this is why some airplanes are "hawks" and some others "turkeys"..... to design an airplane structure must be considered a sort of an "art".



Guys, be careful when comparing properties, the top of a wing buckles when under compression. Compressive yield is similar to tensile yield but not exactly the same. Resistance to torsional loads is related to yield strength but is not exactly the same.

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## Balljoint (Oct 12, 2015)

FLYBOYJ said:


> Again this will be dependent on what the material you're working with as well. 7075 aluminum is strong but not flexible, it could probably take shear loads good but not bending. 2024 T-3 will take bending but depending on application could eventually work harden and fatigue. In a high heat area one could use stainless steel but now you're looking at a weight factor as well as possible dissimilar metal issues (corrosion). It's all a balancing act.



Maybe beam loading would be a better term than bending since the material doesn't have to bend to take such loading. If it's in tension on the outer loading and tension at the inner loadingit's loaded "in bending" even though the material is tough rather than compliant,


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## FLYBOYJ (Oct 12, 2015)

Balljoint said:


> Maybe beam loading would be a better term than bending since the material doesn't have to bend to take such loading. If it's in tension on the outer loading and tension at the inner loadingit's loaded "in bending" even though the material is tough rather than compliant,



Again you're going to have to be specific on where you're talking about. I'm not a structural engineer but have done structural repairs based on data developed by an engineer. In laymen's term I've always dealt with engineers dealing with bending, twisting, shear and compression loads.


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## parsifal (Oct 12, 2015)

Interesting discussion guys. Id really like to know about the Zeke wing. ive read it was exceptionally lightly constructed, with about half the fasteners of a spitfire, made of a new alloy material, with something called a single spar construction (whatever the hell that is) that made its fabrication difficult. the Zeke was generally regarded as a difficult aircraft to construct. I was hoping someone like greg might illuminate me........


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## tyrodtom (Oct 12, 2015)

I'm certainly not Greg, but i'll attempt to tackle it.

I've seen it called a one piece wing spar, but that doesn't mean it's a one spar wing. There's plenty of cutaways online showing two distinct wings spars front and rear, even the rivet pattern on the wing points them out.
But the wing spar going under the fuselage is continuous, and integrates with the fuselage so completely, that once constructed by the factory could not easily be taken apart without almost completely disassembling the whole central structure of the aircraft. The fuselage came apart behind and in front of the cockpit, and the wings appear to have a joint about half span. No wing strong points bolted to fuselage strong points, it was all one riveted piece, and lighter because of that.

It's construction caused problems when the Zero damaged in the Dutch Harbor attack was found at Attu island. The crew sent to recover it couldn't disassemble it the way most aircraft they were probably used to.

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## GregP (Oct 13, 2015)

Hi Parsifal,

Our Zero is intact and complete ... but undergoing overhaul. If you are interested I can get some pics, but there is no access to the wing interior.

Perhaps the attachment might help you out.

- Greg

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## GrauGeist (Oct 13, 2015)

Greg, isn't there any photos of the PoF Zero that was disassembled and shipped to Japan a few years back?

There might be some shots of the wing detail


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## Elmas (Oct 13, 2015)

GregP said:


> Hi Parsifal,
> 
> Our Zero is intact and complete ... but undergoing overhaul. If you are interested I can get some pics, but there is no access to the wing interior.
> 
> ...



The hand made drawings in this article are really a masterpiece.....


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## tomo pauk (Oct 13, 2015)

Don't know whether people are familiar with this gold mine:
LiTOT: Content

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## Juha (Oct 13, 2015)

Hello Greg
re your post #80
Wow!

Juha


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## FLYBOYJ (Oct 13, 2015)

parsifal said:


> Interesting discussion guys. Id really like to know about the Zeke wing. ive read it was exceptionally lightly constructed, with about half the fasteners of a spitfire,*made of a new alloy material,* with something called a single spar construction (whatever the hell that is) that made its fabrication difficult. the Zeke was generally regarded as a difficult aircraft to construct. I was hoping someone like greg might illuminate me........



I didn't read all the way through Greg's *excellent* download but I do know that the Japanese were instrumental in developing 7075 aluminum and I know i read somewhere the Zero had a lot of 7075 in it's construction. As far as it being "difficult" to construct, one would actually have to examine how it was assembled in the jig because once a jig assembly process is established it's really a repetitive process unless there's a situation with getting detail parts to fit correctly - I do know the Japanese has issues with interchangeable parts so that might have played into this.


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## GregP (Oct 13, 2015)

I have some pre-overhaul pics and will get more this coming Saturday so I can post a before and after. The Zero is coming along well and should be flying again in December.

What happened was we sent it over to Japan for 110 months in 2012-2013 and when it came back, it was time for an overhaul. We restored it originally in 1976, so we flew it for 37 years and it was time. Then the airshow season hit together with some critical things to a couple of other warbirds and, before we knew it, the Zero was down for a year. So it is being worked on as you read this and I'll post pics this weekend.

I came across that file on the design analysis of the Hamp about 15 years ago and thought everyone who was interested had it or I'd have posted it much sooner. Attached is another one that some may find interesting. It isn't AC-43-13, but is quite good anyway.

The second one is a Hellcat versus J2M Raiden comparison. We have a J2M-3 at the museum.

View attachment Aircraft_Metal_Structure_Repair.pdf


View attachment F6F-5 vs J2M3-b_opt.pdf

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## tyrodtom (Oct 13, 2015)

I've seen figures on how many man-hours it took to make a Bf-109 in 1940, 42, etc.
Does anyone have such information on the Zero ?

Because my impression is that it would be high.


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## GregP (Oct 13, 2015)

Here's a few Zero pics before the overhaul when it was disassembled:

1. Here's looking into the rear fuselage of the Zero before overhaul. This is an A6M5 Model 52.







Naturally the cables are loose because the rear fuselage is detached from the center section.

2. Here is looking into the cockpit center section when the entire front and rear have been removed. This is before overhaul got to the interior, but you can see we replaced the skin over one the wheel well and a few other places where you can see fresh green primer. The shaft on the left side (actually right side, but backwards) about mid fuselage controls the cowl flaps and there is a small crank that the pilot turns to open or close them.

After this was taken, the entire interior was stripped, repaired as necesssary, primed, and painted. The they started fitting the controls and fixtures back in.






I'll get some more this weekend and you can see the difference between that time and now. These pics were taken in May 2015.

3. Here is a shot of our Nakajima Sakae 31 radial. This aircraft was captured on Saipan in 1944 and was returned to the US for some study. It was placed back in flyable status and was one of the aircraft used at the 1944 Fighter Conference at Pax River, Mayrland. It was the only aircraft of the entire group, as far as I know, that never broke the entire time. The Sakae 31 is running great! It could use some cosmetic spruce-up, but runs quite nicely. Our other Sakae 31 is complete but in parts. That way, we can fix the flying engine if it breaks. So far, it hasn't.






For some reason, it won't let me add any more, even in a new post. Perhaps a bit later. I already uploaded quite a few Mb in 2 threads today and it looks like there is a limit.

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## BiffF15 (Oct 13, 2015)

Greg,
Thanks again for sharing!
Biff

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## Hiromachi (Oct 13, 2015)

FLYBOYJ said:


> I didn't read all the way through Greg's *excellent* download but I do know that the Japanese were instrumental in developing 7075 aluminum and I know i read somewhere the Zero had a lot of 7075 in it's construction.


Peter C. Smith in his latest book Mitsubishi Zero - Japan's Legendary Fighter said it was T-7178 zinc aluminium alloy. Generally speaking I found book quite accurate, so its possible with this author was correct as well. But the best option is looking on the Japanese side of the internet.


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## GrauGeist (Oct 13, 2015)

Not sure how 7178 was used in the A6M, as that particular alloy was developed in the early 1950's, where as 7075 was developed in the mid 1930's specifically for Mitsubishi by Sumitomo...

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## GregP (Oct 13, 2015)

I can say this about Japanese WWII aluminum from personal experience.

When you find it today on a Pacific Island, if it has started to corrode ... the alloying metal has corroded completely away, leaving flaky pure Aluminum that peels away like mica. It has no strength left. We see some of the same with US Aluminum, but it is clearly intergrannular corrosion and usually still has some strength left.

I hear Japanese WWII Aluminum was alloyed with Zinc and ours was with Copper. This doesn't mean Japanese metalurgy was not as good as US metalurgy .... all it means, if the assumption is true, is that Zinc corrodes quicker than Copper does in salt air. Once intergrannular sets in, it will happen eventually ... there is no "rescue" possible for either alloy.

Surprisingly, most of the Aluminum on our A6M5 Mode 52 Zero is original, not all, and has not even come close to starting to corrode yet. We did see SOME corrosion and that metal was replaced in 1976. We also replaced a few things this year so far, but not much in the total aircraft ... a small skin here and there and a few brackets. 

We see the same in Corsairs, Hellcats, Spirfires, etc. Some of the original metal is good and some needs to be replaced. More is OK than not OK. Sometimes we make a new panel not because of corrosion, but becaause the panel was creased or bent and making a new one is easier than trying to straighten it. Plus, you KNOW the metal is OK if you make it new. 

Sometimes we make a new piece from the next thicker gauge of metal. An example would be the formers in a T-6 cowling. The stock ones are made from 0.040" 2024-T3 ... and people tend to stand on them when they do maintenance. Not surprisingly, the formers tend to bend when "Bubba" is wrenching. We make new formers from 0.050" 2024-T3 and they don't bend anymore with Bubba or without him. They aren't structural, and so arn't "changing the design" ... they just hold the cowling metal pieces on the plane.

We got a Bf 109Erecovered from the bottomn of a lake in Russia some years back. It had been underwater (fresh water) for 48 years. Surprisingly, some of the metal looks like it still might be OK. It might NOT be OK when looked at closely, but some looks like it would clean up and have no corrosion on it. I consider that to be extraordinary. Of course, the Magnesium was gone away completely. But some Aluminum looks pretty decent. Believe it or not, the engine was rebuildable and is being rebuilt at this time.

I'll get some pics of the Bf 109E this weekend, too.

Interesting you should mention Sumitomo, Graugeist. The propeller on our Zero is generally called a Mitsubishi, but was really made by Sumitomo.

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## parsifal (Oct 13, 2015)

greg, remind me never to argue with you about aircraft mechanicals......


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## FLYBOYJ (Oct 13, 2015)

Hiromachi said:


> Peter C. Smith in his latest book Mitsubishi Zero - Japan's Legendary Fighter said it was T-7178 zinc aluminium alloy. Generally speaking I found book quite accurate, so its possible with this author was correct as well. But the best option is looking on the Japanese side of the internet.



As mentioned 7178 wasn't around in the late 1930s/ early 1940s IIRC. I think zero construction material is mentioned here.

How To Build a Zero (1945) | From The Archives

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## gumbyk (Oct 13, 2015)

GregP said:


> I hear Japanese WWII Aluminum was alloyed with Zinc and ours was with Copper. This doesn't mean Japanese metalurgy was not as good as US metalurgy .... all it means, if the assumption is true, is that Zinc corrodes quicker than Copper does in salt air. Once intergrannular sets in, it will happen eventually ... there is no "rescue" possible for either alloy.



That ties in with the alloy number - 7XXX series alloys are zinc and 2XXX are copper. Interestingly, the Zinc provides a harder alloy than copper.

http://www.esab.ca/ca/en/education/blog/understanding-the-aluminum-alloy-designation-system.cfm


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## FLYBOYJ (Oct 13, 2015)

GregP said:


> I can say this about Japanese WWII aluminum from personal experience.
> 
> When you find it today on a Pacific Island, if it has started to corrode ... the alloying metal has corroded completely away, leaving flaky pure Aluminum that peels away like mica. It has no strength left. We see some of the same with US Aluminum, but it is clearly intergrannular corrosion and usually still has some strength left.
> 
> I hear Japanese WWII Aluminum was alloyed with Zinc and ours was with Copper. This doesn't mean Japanese metalurgy was not as good as US metalurgy .... all it means, if the assumption is true, is that Zinc corrodes quicker than Copper does in salt air. Once intergrannular sets in, it will happen eventually ... there is no "rescue" possible for either alloy.


Greg, you nailed this on the head. 7075's major alloying elements are Zinc and magnesium. It's strong stuff but will turn to dust in the right humid conditions. 2024 (or 24T in WW2 days) has more copper in it, one of the reasons its so malleable, especially in the "O" condition.

I've worked on GA aircraft out of Florida, the Texas gulf coast and Camarillo and seen corrosion attack parts of them and virtually turn them to powder!

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## GregP (Oct 14, 2015)

Hi Joe,

I've seen that, too. When we redstored our Yokosuka D4Y, I saved a piece of longeron that is a graduate study in corrosion.

Makes me angry when we come across an Allison or a Merlin that was left to rot in a field ... and they didn't even leave the spark plugs in and plug the coolant openings. What it means is the inside is junk, needlessly so ... but there may be a few good pieces on it.

Hey Parsifal,

If you don't want to argue about it with anyone, make it FlyboyJ. He does it for a living and I'm a volunteer. Somewhat of a difference there, but I appreciate it anyway. Hope you can get to the Planes of Fame sometime and can see it and maybe take a flight in a warbird. Plenty of aircraft-related things around the area from our museum (Planes of Fame) to Yanks, to Palm Springs, the Lyon museum, San Diego Air and Space museum, Reuben Fleet museum, and lots of warbird operations happening ... most of the time.

All the best. - Greg

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## Hiromachi (Oct 14, 2015)

FLYBOYJ said:


> As mentioned 7178 wasn't around in the late 1930s/ early 1940s IIRC. I think zero construction material is mentioned here.
> 
> How To Build a Zero (1945) | From The Archives


Alright, than it seems the author was wrong. I have original Jiro Horikoshi book, Eagles of the Mitsubishi but its only mentioned there that they used ESD, not indicating a specific digit.



GregP said:


> Interesting you should mention Sumitomo, Graugeist. The propeller on our Zero is generally called a Mitsubishi, but was really made by Sumitomo.


Sumitomo Metals was biggest manufacturer of the propellers in Japan. It's hard not to find an aircraft that used the Sumitomo propeller Greg.

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## drgondog (Oct 14, 2015)

FLYBOYJ said:


> Again you're going to have to be specific on where you're talking about. I'm not a structural engineer but have done structural repairs based on data developed by an engineer. In laymen's term I've always dealt with engineers dealing with bending, twisting, shear and compression loads.



And Tension...

Sheet metal panels have primary function to transfer loads via shear. Rivets carry the loads individually in shear and the allowable shear load is balanced between the shear stress of the rivet and the point of failure applied to the cross section of the hole in the sheet.

Bending loads and torsion that we have been talking about for the Pe-2 in the empennage are transferred to the Longerons (for bending in the Y and Z axis) as axial tension and compression, the torsional loads are transferred to the Bulkhead - all via the riveted panels.

To visualize placing a vertical load in 'bending' on an "I" beam with upper and lower caps connected by a web ('spar'). One cap is in tension, one is in compression and the loads are transferred via the 'web' in shear.

Stringers, if connected to say bulkheads, can perform as mini-longerons but the primary purpose is to prevent buckling of the shear panels they are riveted to, when bending/torsion is applied to the 'box' or 'cylinder'

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## parsifal (Oct 14, 2015)

> Makes me angry when we come across an Allison or a Merlin that was left to rot in a field ... and they didn't even leave the spark plugs in and plug the coolant openings. What it means is the inside is junk, needlessly so ... but there may be a few good pieces on it.



Here i go, but what the heck. I would have thought if you could get the pistons out, you could rebore and re-sleeve the cylinders. New caps in the crank housing, crankshaft re- machined (well a big maybe there) and the valve and seats, should be recoverable if they have carbonisation....and require a reseat, or are they so far gone that nothing remains inside?




> Hope you can get to the Planes of Fame sometime and can see it and maybe take a flight in a warbird. Plenty of aircraft-related things around the area from our museum (Planes of Fame) to Yanks, to Palm Springs, the Lyon museum, San Diego Air and Space museum, Reuben Fleet museum, and lots of warbird operations happening ... most of the time.



Something like that would be a dream for me. Maybe in two or three years when i retire......I would love to just sit in something like a P-51 and soak up the smell of gasoline.


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## GregP (Oct 14, 2015)

Want to sit in a P-51? I can help you do that, and maybe get a flight. They smell like fighers ... not necessarily gasoline. The cockpits are full of the smell of old leather, warm electronics, sun-baked paint and bakelite, etc, plus maybe some pilot sweat ... hard to describe but, once you sit in one, you can't mistake the smell of an old warbird. They are all similar with the radials smelling a bit more oily.

About the old engines corroding, I can give you an example. Joe Yancey came across some old Allisons that were formerly used in Hydroplanes. The owner was the wife of a late racer (20 years ago). She had left the Allisons sit out in a field, no plugs in them, unclosed coolant openings, in the weather. They had gone through at least two floods where they were under water for a month or more.

None would turn over when a 10-foot long pipe was attached to prop wrench, even when we put oil for 2 days into each cylinder. That has a few connotations ...

The only pistons approved for aircraft use in a V-1710 by the factory manual are nominal, 0.10" over, and .020" over. The rings will compensate for up to 0.010" of egg-shape. So that means if any of the cylinders are pitted deeper than .027" or so, the liners are shot. The water jacket had water in it for 20 years and had rusted through in a couple of places on 3 of the 4 Allisons, so the blocks weren't any good and the 4th one was probably very close to coming through, too. A pressure test probably would have burst it, maybe not. The cams and were rusted enough to be useless. We never saw the crankshafts, but you can bet they were bad, too, along with the rods.

That means we could probably hydraulic the pistons out once the cams were off (maybe not if we couldn't get the valves closed with a dead-blow hammer against the srpings), but the pistons, liners, rods, and probably the wrist pins were going to be pretty much not usable except for maybe a museum cutaway ($10,000 easily). A cutaway doesn't fly. The cases were shot.

The nose case might have been OK, but the very necessary nosecase bearings probably were too far gone to be recoverable ... you'd have to disassemble it to find out. I do not know the condition of the accessory case and the supercharger. Two of the engines had fallen over and had broken the carburetor and carb mount off the accessoriy cases, so the cases were no good either. The carbs looked like the surface of the moon from Earth.

So maybe we could use assorted nuts and bolts, the valves, valve guides, maybe 1/3 of the valve springs, the valve spring washers retainers, some nuts and bolts but not all, the intake manifolds, probably all the studs, MAYBE the intake rubber pieces (maybe not), the gaskets that seal the valve covers and maybe a few more, perhaps the cam towers and tachometer drive, and accessory plates. That ain't much when you consider a V-1710 has about 7,000 parts. OK, we could probably use all the crankshaft plugs and oil galleys and a few minor but necessary pieces, too. Maybe the mags were overhaulable, maybe not.

The woman wanted $20,000 each and was quite distressed to hear that we pay very much less than that for an engine that turns over, and $200 - $1000 for one that doesn't turn depending on condition. Hers were so bad that Joe wouldn't offer even $500 each. There were that many parts ruined.

Here's the thing ... there are only about 4 - 5 shops in the world that can do a GOOD rebuild of these old Allisons. I'm not too sure about Merlins, but the good Merlin shops in the U.S.A are few and we probably mostly know them in this forum. Only these guys know what to do with old parts to make them serviceable, if possible. To anybody else, the engines are scrap metal. You can't buy a core that turns over from ANY of the shop owners for $5,000 because they are worth $90,000 - $250,000 (depending on mfg model scarceness) or more when overhauled and sold after break-in to an aircraft owner. So why in the name of heaven would anyone sell you one for pennies on the dollar unless he was desperate? None of the owners of the Allison / Merlin overhaul shops are desperate. If he saves it, perhaps it can be overhauled and sold at a later date.

If you are smart,and if there's nothing else going on in the shop, you take the old cruddy engines apart in slack time, recondition the parts to where they are suitable for overhaul, and put them into "overhaulable stock." When you can't make money, it's time to at least stock up on things that will sell when someone wants an engines built from parts. It happens, and usually on SHORT notice, and you either react or lose the money. If you can't react and if you have a pile of old, disassembled engines ... it's YOUR fault. The parts are only sellable when the condition can be seen.

The amount of oil and crud on the engine has nothing to do with it ... it's the internal condition that counts. In fact, the more old, dirty oil and grease on it, the better the condition will be when it is cleaned up and refurbished.

Perhaps you will get an idea when I get some Zero pics this wekend. You can compare the before and after.

These aren't engine parts, but you can see a very noticeable difference between the pics, and it should be obvious why the overhaul was needed.

It is much the same with engines. I'll get a shot of an old Japanese engine recovered from a beach on Yap and post that, too. You should be able to see the issues with overhaul easily.

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## pbehn (Oct 14, 2015)

GregP said:


> It is much the same with engines. I'll get a shot of an old Japanese engine recovered from a beach on Yap and post that, too. You should be able to see the issues with overhaul easily.



Great post Greg, in principle aluminium resists corrosion to most things however salt water attacks it as any owner of a motorbike knows. For old engines, they are full of many types of metals, normally these are separated by oil, once allowed to dry and water to get in they set up corrosion cells and start to eat each other on the galvanic scale. I havnt seen it in an old Aero engine but have seen a couple of triumph bikes with exhausts off in a field, just junk really.


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## GrauGeist (Oct 14, 2015)

I know that when Chevrolet revamped their L-6 engines (194, 230) and introduced the L-4 (153) in 1960, they were using a cast aluminum thermostat housing that bolted to a cast iron base, which in turn was bolted to the cast iron head.

Over time, the coolant passing through the brass radiator, cast iron components, cast iron waterpump (with steel vanes) and then through the brass and copper thermostat would eventually "pit" the interior of the thermostat housing by way of electrolysis to the point of failure. In some cases, these housings failed in about 5 years, most started failing before 10.


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## gumbyk (Oct 14, 2015)

GregP said:


> Want to sit in a P-51? I can help you do that, and maybe get a flight. They smell like fighers ... not necessarily gasoline. The cockpits are full of the smell of old leather, warm electronics, sun-baked paint and bekelite, etc, plus maybe some pilot sweat ... hard to describe but, once you sit in one, you can't mistake teh smell of an old warbird. They are all similar with the radials smelling a bit more oily.



I've always thought it strange that even newly-restored WW2 aircraft have that smell.



> If you are smart,and if there's nothing else going on in the shop, you take the old cruddy engines apart in slack time, recondition the parts to where they are suitable for overhaul, and put them into "overhaulable stock." When you can't make money, it's time to at least stock up on things that will sell when someone wants an engines built from parts. It happens, and usually on SHORT notice, and you either react or lose the money. If you can't react and if you have a pile of old, disassembled engines ... it's YOUR fault. The parts are only sellable when the condition can be seen.



And we've bene on the receiving end of this stocking up. Less than 24 hours after locating a Griffon magneto, we had it down here, and the aircraft flying and delivered to the customer.

Couldn't agree more with the external vs. internal condition statement. Some of the best internal condition of engines that I've seen in storage have been from engines that have looked pretty horrible on the outside. I think that oil-soaked dirt and dust must act like a preservative.


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## GregP (Oct 14, 2015)

That's why outboard motors have the dissimilar trim tab that looks like a small rudder just above the prp. It is supposed to corrode instead of the Aluminum outboard engine and transmission and lower unit. Maybe some of you have had to change these, even in fresh water?

One of the interesting things in ownership happens when they put a few pieces of steel into an otherwise-Aluminum airplane that YOU own with Aluminum rivets (or steel rivets). That is dissimilar metal and unless it is carefully prepped painted/sealed, will eventually corrode both the rivet and the hole in the steel ... and bleed over into the Aluminum-to-Aluminum part, too. The hope is you get enough use out of the aircraft structure before that happens. Landing a seaplane in salt water greatly accelerates this corrosion process and, once you DO land one in salt water, the process of complete destruction of the aircraft starts and you WILL lose your airplane sooner or later. How well you control it will determine how much "later" that is.

You can imagine the crud control procedures that have been accomplished by the operators of the last Martin Mars that started life in WWII and that have gone on since it was launched. It's probably as bad or worse than engine maintenance. I'd guess worse.

Probably FlyboyJ knows for sure.

Hi gumbyk,

After being around it a bit, I think you are right ... oil-soaked dirt IS a great preservative. So it's probably against the law somehow. But it happens anyway when you let an old, oil-soaked engine sit around in the elements.

Here is a WWII pulsejet as we found it in the Planes of Fame junkyard atfer sitting around since 1957:







Here are close-up:






and here the cowling we metal-spun for it:

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## GregP (Oct 15, 2015)

And here is a pic of the same engine setup taken earlier this year:






You can see the discoloration from running it (ordinary paint), but the condition should hopefully apparent from the pics above. The control panel and gas tank, as well as all OTHER parts except the rubber diaphragm in the fuel controller, are exactly the same units as above when we found it ... we just restored them.

We made a mold and molded the rubber diaphragm. It took a year and maybe 8 tries to get it to start. After that it was much easier.

All it needs to run again is an overhaul of the fuel pump motor. When we quit running it the pressure was fluctuating to the point of slightly erratic running.

In practice in WWII, the pressure didn't fluctuate as it was delivered by shperical tanks of compressed air.

Here it is pushing my truck down the runway in our 2009 airshow:


_View: https://www.youtube.com/watch?v=KTv7dfs_Mlc_

First we started it at idle power, then transitioned to full pwoer, then released the brakes. I had my friend Bob,who was driving, keep it under 35 mph because I didn't want anybody to either get hurt or buy a new truck. It ran about one minute and 15 seconds before the temperature got to 1,100°F and we shut it down to save the reed valves. By that time we had passed the entire airshow crowd. You can't tell from the video, but you could hear it for 10 miles around.

The team was Robin Scott, Bob Velker, and Me, Greg Pascal. Robin was the major contributor to the overhaul and Bob and I did a bit of restoration, helped figure out how to start and run it, and helped with the cowling and trailer restoration. Robin had maybe 3 years in it. Bob and I had maybe 1.5.

Unfortunately, Robin recently passed away. We miss him.

Bob and I are thinking about overhauling the fuel pump and running it again ... sort of a tribute to Robin, when we get the time.

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## GregP (Oct 15, 2015)

If you Google "Chino pulsejet" you can see some videos as we progressed. We took a video of one night run and it is somewhat interesting, but the files show up in here as the wrong file-type. They run fine on my PC screen.


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## gumbyk (Oct 15, 2015)

That was you guys?!?!

I've got a bit of a soft spot for these engines - I want to build one down here - preferably around 75% to go with our scale model. Get the idea? 

Would it be easier to run it on compressed gas? AFAIK these will run on anything, and using a pressurised fuel would eliminate the fuel pump issue.


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## GrauGeist (Oct 15, 2015)

gumbyk said:


> That was you guys?!?!
> 
> I've got a bit of a soft spot for these engines - I want to build one down here - preferably around 75% to go with our scale model. Get the idea?
> 
> Would it be easier to run it on compressed gas? AFAIK these will run on anything, and using a pressurised fuel would eliminate the fuel pump issue.


I've always wanted to fool around with a pulsejet, too...

Anyway, here's a couple sites I've been checking on, great info and some really cool applications (especially the jet-cart in the first link)!
Pulse Jet Engine and then a page that's Argus specific: Argus V1 Pulsejet

Pulse Jet Engines | How To Make A Pulse Jet


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## Lucky13 (Oct 15, 2015)

What is it that makes it sound like it does?


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## GrauGeist (Oct 15, 2015)

Lucky13 said:


> What is it that makes it sound like it does?


The combustion process which basically is a series of explosions, one right after the other in a resonant chamber that controls the amount of combustion per cycle. As the exhaust gases expand and thrust out the back, the next portion of feul entering is ignited by the exiting gases and ignites, starting the cycle over again.


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## GregP (Oct 15, 2015)

The pulsejet would be easy to make except for a few items. The critical part is the reed petals. Our engine is from a US Navy JB-2 Loon, which was a US copy of the V-1. Our engine is about 3/4 the size of the German engine and still makes good thrust.

It sounds the way it does because, as ably said above, it is a series of explosions. First, assume the engine is running. OK ... you get one explosion. The shock wave extends forward and aft. When the forward wave hits the reeds, they snap shut, cutting off the shock wave and reflecting it backwards. When it does, a negative pressure is created and it draws in more air and fuel mixture behind the shock wave. Meanwhile the other shock wave heads out the exhaust end and, when it hits the end of the expansion chanber (tapering part of the pipe), there is a discontinuity since the pipe tapering stops, and some of the shock wave is reflected back in the forward direction, just like in a tuned exhaust on a 2-stroke motorcyle. When it hits the incoming reflected wave from the closed reeds with the accompanying air-fuel mxture just behind it, that mixture is ignited and the process begins all over again.

We checked our pulsetjet by recording the sound and anlyzing the resulting sound waves. Ours resonates right about 43 Hz. That is down in the low-frequency range and that type sound travles a LONG way before dissipating. It is above the hearing threshold of 20 Hz, but not by much. Believe me, when you are close to it, it resonates in your chest cavity (even if you happen to be Dolly Parton). If you have ever been to an American NHRA Top Fuel drag race, you KNOW about sound that resonates in your body ... it's the main reason people go who aren't driving. Top Fuel anything is kick-butt.

Anyway, we installed a calibrated spring against a screw stop and put the other end against a force cylinder that we had around. The engine runs at two levels of power. When you start it, it is in idle mode. When you get it into full power mode, the sounds almost doubles in intensity.

Before we installed the cowling we spun from Aluminum, the thrust came in at about 380 pounds while the engine was at a standstill. The cowling smoothes the airflow into the intake and we never expected it, but simply installing the cowl changed the thrust at full power while still at a standstill to 440 - 450 pounds. We figure it must be due to the airflow having a smooth surface to follow into the reeds instead of a square opening with no smoothing ... les turbulence at the intake.

Anyway, when we ran the engine down the runway, my friend Bob was driving and I was operating the engine control box. Robin worked the controls on the engine itself to help it start when I made the right moves on the control box. Once it started in idle mode, Robin pushed the fuel controller down to get it into full power mode, locked it down with a screw knob stop, switched off the 90 psi airflow, and sat down on the trailer. After we made it up to about only 35 mph (I had Bob use the brakes to keep us from going any faster), the thrust showed at about 550 pounds!

I don't know if traveling at 350 mph would increase it much more, but I'd imagine so. I decline to predict the end thrust at 350 mph based on only 2 runs at 35 mph. 

On Saturday they made us run down the main runway. When we didn't die from explosions, they let us run it down the taxiway on Sunday. That was about half as far away from the spectators as the runway was. We heard later that everyone could feel the vibrations in their bodies. Some were outright shocked and some a bit panicked, never having experienced it before.

Steve Hinton was in the cockpit of a fighter (Tigercat at the time) that was only about 30 feet from the taxiway and he said it felt like nothing he'd exerpienced before. We think that may be due to the frequency ... 43 Hz being lower than normal jet engines or drag race Top Fuel engines ... or any other engines we know of.

So the real issue is to make some steel reed valve petals that will bend when required while still being hard enough to withstand the heat. We only have a 3.3 US gallon gas tank and the engine at full power burns about 3.5 gallons a minute (2.2 gallons per minute at idle). So our run timne was only 1 minute and 10 - 20 seconds depending on the fuel level and how long we were at idle before going to full power. We set a self-imposed limit of 1,100°F to try to keep the reeds from "going away" quite as quickly as they otherwise might. In real life the reeds were wearing out just about as the V-1's went over London or very slightly farther. After that the steel reeds would fail one at a time until the engine no longer could function. That's how we captured some V-1s nearly intact ... the vane anemometer system on the front (little propeller-looking thing) probably failed somehow and the V-1 just flew until the reeds failed and it glided in without ever triggering the fatal dive or arming the warhead. Alternately, maybe it ran out of fuel before triggering the dive.


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## GregP (Oct 15, 2015)

You can see the tapering of the expansion chamber type cone in the pic below. We managed to capture ONE frame of a pulse coming from the pipe:






You can see that one pulse is just about to dissipate and the next one is JUST coming out of the exhaust. We don't know if that is as long as the first pulse got because we only have this ONE frame of the event. But the length is very close to twice the distance from the spark plug (used only at startup) to the reed assembly.

That's Robin in the picture (someone had to take the pic, and that was Bob ... I'm off the right side of the pic at the end of the white control cable that goes to the control box). Robin's boat and Yak-52 are in the background.

As you can see, this was when we were learning how to run it. We had not yet made the cowling or restored the trailer, and were not going to put much more effort into it unless we were successful in getting it to run ... which we managed to do after over a year and a half of trying to re-invent the WWII pulsejet without the advantage of a manual of any sort.

We DID have some "manuals" for hobby-type pulsejets, but they mostly mnake noise, are poorly designed, and are usually about 10% the size of this one ... and ostly run on propane. This one makes useful thrust on 87-Octane unleaded gasoline and was fairly optimized for the type engine it is. I'm sure they could improve it today ... if anyone were really interested in pulsejets, but they certainly wouldn't pass any airport noise regulations! Just ONE of these could wake the dead some miles away. I shudder to think of an airliner with 8+ of them ... bigger units. The crew probably wouldn't survive the noise and the entire town would think the dreaded Russian hordes were attacking enmasse.

I said "Russian hordes" because the aircraft in the background above is a Russian Yak-52 ... so don't be offended if you happen to be Russian. Send Vodka and we'll be your friend. We'll trade you some Levi's jeans and maybe a belt.

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## gumbyk (Oct 15, 2015)

GrauGeist said:


> I've always wanted to fool around with a pulsejet, too...
> 
> Anyway, here's a couple sites I've been checking on, great info and some really cool applications (especially the jet-cart in the first link)!
> Pulse Jet Engine and then a page that's Argus specific: Argus V1 Pulsejet
> ...



The guy in the first link has come into a bit of close scrutiny from national security organisations. He claimed that he could build a cruise missile for under $5k, and was planning on a proof of concept to demonstrate it.


Making petal valves (the ones shaped lie a flower) isn't really too much of a problem - you can electro-etch them out of thin spring steel. but the array system on the Argus looks quite a bit more work to perfect.


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## parsifal (Oct 15, 2015)

> I said "Russian hordes" because the aircraft in the background above is a Russian Yak-52 ... so don't be offended if you happen to be Russian. Send Vodka and we'll be your friend. We'll trade you some Levi's jeans and maybe a belt.




LMAO on that one


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## GregP (Oct 15, 2015)

The issue comes with how thin and of what exact material to make the steel petals. Just any old thin sheet steel won't necessarily work. It has to allow bending at just the right pressure and flow. It is possible that the right combination would be easy to find ... and it is possible it would take years.

There are any number of guys who can make pulsejets. We found one guy in Oregon (at the time) who claimed to be the world's expert on them. He wanted decent money to help us, so we just did it ourselves. He told us we'd NEVER get it running without his help. I'll admit it took more than one case of beer and one large Pizza to make the thing run, but it wasn't insurmountable.

The thing is to have a test plan that methodically goes through the variables until you get a pop. Then you know you're close. Once you get the first pop, you're usually not more than 10 - 15 tries away from a start. Our big issue was NO pop until we tied compressed air at 90 psig. Then we puzzled for about a month on how to get it up to full power from idle and not blow out the rubber diaphragm with the 90 psig airflow, since WE were paying for new diaphragms ourselves. When nothing else worked (and we were just about out of beer), I suggested that Robin walk up and push on the fuel controller's solenid shaft with his thumb. It went rapidly to full power and quit. It SOUNDED like it quit because it went lean rather than rich. Anyone who flies radio control models will know the difference or buy a LOT of engines. After a restart, he pushed much softer and could hold it there for about 10 seconds before the radiant heat from the jet tube started to burn a bit too much. It singed me once or twice, too. So, we added a spring-loaded set of washers that clamped the solenoid shaft with a screw-knob. You push it down to where you want it and clamp it there and jump away from the heat.

We next turned off the 90 psig airflow and then opened the air blocking valve and loosened the screw-knob ... and the old German fuel controller kept it running! It took maybe another 3 - 4 runs to perfect the process and we could get consistent runs.

Then we added another solenoid controlled by a 10-turn potentiomenter that adjusted the second solenoid current. Now we could push down the first solenoid shaft from the remote box by turning a knob! That made things a bit cooler during runs.

Right when we got it figured out, the 2009 Chino airshow was coming up and they let us into the lineup, but were concerned it might blow up. So they made us run down the main runway on Saturday. Of course, you cannot blow up a pulsejet from within the jet tube under ANY cicumstances because there can be no explosion without containment (so no pressure buildup). One end of the jet tube is always open.

The only place you could get an explosion was the fuel pump area, and we were running an aircraft type fuel pump. So Steve said we could run down the taxiway on Sunday (if we survived Saturday). I'm not too sure most people appreciated the act, but we DID get a comment from several older gentlemen in the audience that the last time they had heard that sound was in London in 1944.

If nobody else did, WE had a good time with it. We were with the Planes of Fame, so we called ourselves the "Pains of Flame" Demo Team. Here is a pic of the license plate I made for the engine bed trailer. I got the V-1 picture from Romatic Technofreak of this forum.






The pic is from a video game and the girl losing her panties is the result of too many beers, or not enough ... I still haven't figured out which. We put that on the back of our polo shirts, too, and all wore them during the airshow runs. We still have the shirts ... but they're a bit faded today. Silkscreening isn't what it used to be ...

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## FLYBOYJ (Oct 16, 2015)

GregP said:


> That's why outboard motors have the dissimilar trim tab that looks like a small rudder just above the prp. It is supposed to corrode instead of the Aluminum outboard engine and transmission and lower unit. Maybe some of you have had to change these, even in fresh water?
> 
> One of the interesting things in ownership happens when they put a few pieces of steel into an otherwise-Aluminum airplane that YOU own with Aluminum rivets (or steel rivets). That is dissimilar metal and unless it is carefully prepped painted/sealed, will eventually corrode both the rivet and the hole in the steel ... and bleed over into the Aluminum-to-Aluminum part, too. The hope is you get enough use out of the aircraft structure before that happens. Landing a seaplane in salt water greatly accelerates this corrosion process and, once you DO land one in salt water, the process of complete destruction of the aircraft starts and you WILL lose your airplane sooner or later. How well you control it will determine how much "later" that is.
> 
> ...




Hi Greg;

Great stuff here!!! Don't know much about how the Mars was taken care of but I did work with a PBY owner and I could tell you that corrosion control was like plugging holes in a leaky dam with your fingers, it's a never ending process especially if the aircraft is landed on salt water. We would treat and if necessary repair anything that seemed to really get into the parent material. The PBY I worked on came from Spain and despite it's age was well taken care of. IIRC we spent more time plugging leaks in the hull, it seemed like the green fuel tank sealant worked the best.

Sand, zinc chromate, prime, seal or paint, repeat.

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## GregP (Oct 16, 2015)

Hi Joe,

Somehow I figured you would have worked on flying boats.

The only sea-dwelling aviation constructs I have worked on were much the same ... as much or more work on corrosion than on the rest of the aircraft. I know a couple of guys up in Alaska who have floatplanes. They stay firmly in fresh water except in an emergency and STILL have to do very regular looks at the airframes and pontoons to keep up with it.

I'm glad most military fighters days are land planes. That way, when we restore them, most of the metal is still there.


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## Elmas (Oct 16, 2015)

Why do not use sacrificial anodes in float planes?


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## FLYBOYJ (Oct 16, 2015)

Elmas said:


> Why do not use sacrificial anodes in float planes?



that's a question for the manufacturer or the person responsible for the maintenance program.


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## GregP (Oct 16, 2015)

Just don't sacrifice a virgin. It won't change the corrosion rate at all ...


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## GrauGeist (Oct 16, 2015)

Elmas said:


> Why do not use sacrificial anodes in float planes?


The Mars Hawaii has "zincs" attached to the hull...I have photos I took of a couple of them when I went aboard the Mars several years ago, somewhere in my archives.

All the aluminum boats manufactured in this area also has "zincs" attached to the hull and interestingly enough, when I purchased a new fuel tank from Ford for my 1966 Mustang years ago, it came with zinc buttons that were loose in the tank.

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## Elmas (Oct 16, 2015)

Galvanic protection is essential in any boat...

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## Balljoint (Oct 16, 2015)

GregP said:


> Just don't sacrifice a virgin. It won't change the corrosion rate at all ...



Are you sure? It seemed to work.


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## GregP (Oct 16, 2015)

Don't tell me you wasted a perfectly good virgin, thou infectious fen-sucking malt-worm! 

And it wasn't her. It was all that sanding, priming, and sealing.


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## pbehn (Oct 16, 2015)

Why do not use sacrificial anodes in float planes?




FLYBOYJ said:


> that's a question for the manufacturer or the person responsible for the maintenance program.



Nothing to do with aircraft but on pipeline cathodic protection (with sacrificial anodes) they use an induced current. If you have anything further up the galvanic scale than zinc it becomes sacrificial, I suspect many aircraft alloys with magnesium would become very expensive anodes, as Flyboy says refer to the manufacturer and the approved maintenance programme.


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## GregP (Oct 16, 2015)

I could be wrong here, but I think most floatplanes (as opposed to flying boats) flying today are mostly made of 2024-T3 Aluminum allowed with Copper.

Unless I'm way off base, Edo and most other float makers ... at least those that aren't fiberglass, are Aluminum. I'm sure someone in Europe and Asia makes float, but virtually all the floats I've seen are either of US or Canadian manufacture and made with 2024-T3. Some have some very nice heavy spray bars to help keep spray out of the prop arc, such as the spray bars on a Canadair CL-125, but I believe they are 2024-T3, too.

You can see the spray bars hanging down along the outer edge up around the cockpit area in this shot to keep spray away from the cockpit.


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## Elmas (Oct 17, 2015)

I think in the pre-WWII era and immediately afterwards nobody really cared for long-term aluminium corrosion. First, because aluminium use in aircrafts was relatively new and corrosion problems not well known, but I suspect that the main factor was that designers and Air staff were aware that the life span of an aircraft was to be no more than three or four years at maximum before becoming obsolescent, and that of course just in the case the airplane surviving enemy bullets or bubba pilots.
I think that if someone would have said to Boeing designers that the flyable lifespan of a B52 could have been of ninety years they would have been quite astonished: so it is a miracle that airplanes built seventy years ago are still flyable today.

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## GregP (Oct 17, 2015)

I finally realized I was hijacking this thread to discuss corrosion, and then the pulsejet and Zero, so I revived the "Planes of Fame Update" thread and started at post # 8 there.

Meanwhile, I like Russian wing design, corrosion or not these days. Their planes, while maybe not quite up to the best of standards in good weather, were flying in conditions that grounded German, British, and American planes. And if the Russians (actually Soviets) were flying while nobody else was, then the performance of their planes mattered very little. All that mattered was the performance of the flak guns and crews under attack, assuming they could get ready and fire at anything in a snowstorm that was frightful to the Germans and old hat to the Soviet pilots.


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## GrauGeist (Oct 18, 2015)

GregP said:


> I finally realized I was hijacking this thread to discuss corrosion, and then the pulsejet and Zero, so I revived the "Planes of Fame Update" thread and started at post # 8 there.


Well, it was actually a good side-track, as the construction materials usually discussed at depth, are the wooden composites (DH Mosquito, He219, Ho229, et. al.).

Rarely is the different types of aluminum alloys used or developed during the war, as well as the forming process for various portions of the aircraft, discussed in detail...this subject would actually would make for a great and informative thread


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## GregP (Oct 18, 2015)

I'll participate, and over in the Planes of Fame Update thread, I posted a pic of an extreme intergrannular corrosion example on an Aluminum spar from a Zero fighter. Some of my pics are showing up and some are links to the photo ... I don't know why. I have a 12 Mpixel camera and these are just standard photos from a digital camera.

The detail is pretty good though ...

Now, after two or three hours, I got a no-response from one of the links. Maybe my files are too big ... I don't know. I tried to show some progress and a museum update.


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## Milosh (Oct 18, 2015)

GrauGeist said:


> Well, it was actually a good side-track, as the construction materials usually discussed at depth, are the wooden composites (DH Mosquito, He219, Ho229, et. al.).
> 
> Rarely is the different types of aluminum alloys used or developed during the war, as well as the forming process for various portions of the aircraft, discussed in detail...this subject would actually would make for a great and informative thread



The He219 used wood? The Ta154 did.


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## GrauGeist (Oct 18, 2015)

Milosh said:


> The He219 used wood? The Ta154 did.


Yes, yes, I meant the Ta154...was a long, rough day yesterday


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## GregP (Oct 18, 2015)

Hey, I've never done that, Graugeist! 

Only, maybe ... half-dozen times ...

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## fastmongrel (Oct 18, 2015)

> I think that if someone would have said to Boeing designers that the flyable lifespan of a B52 could have been of ninety years they would have been quite astonished: so it is a miracle that airplanes built seventy years ago are still flyable today.



How much of the Buffs are the original plane though. I imagine over the years virtually all the major parts will have been renewed iirc the main spar was replaced or strengthened.


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## FLYBOYJ (Oct 18, 2015)

fastmongrel said:


> How much of the Buffs are the original plane though. I imagine over the years virtually all the major parts will have been renewed iirc the main spar was replaced or strengthened.



The B-52 (lake many aircraft in the USAF) go though a major rebuild (PDM) every several years. Tinker AFB is the B-52 is done.

Workers in B-52 PDM get a lift, new platforms


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## Elmas (Oct 19, 2015)

FLYBOYJ said:


> The B-52 (lake many aircraft in the USAF) go though a major rebuild (PDM) every several years.
> ..................



Of course: planes






need a rebuild after several years, included a litlle bit of "lifting", just like ladies


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## Elmas (Oct 19, 2015)

double post


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## fastmongrel (Oct 19, 2015)

Holy Crap who is that did she sit too close to the fire and melted


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## Elmas (Oct 19, 2015)

Donatella Versace, the world famous fashion stylist......


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## FLYBOYJ (Oct 19, 2015)

Elmas said:


> Of course: planes
> 
> View attachment 304017
> 
> ...



Actually that wrinkling of the b-52 skin is normal - SHE ISN'T


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## GregP (Oct 19, 2015)

I understand the wingtips of the B-52 normally flex up and down some ± 12 - 15 feet in flight, and that produces skin wrinkles. They are all gone when a fresh set of wings is installed.

I really hadn't intended this thread as a Halloween mask thread, but the lady sure turns it into one, huh?

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## fastmongrel (Oct 19, 2015)

Elmas said:


> Donatella Versace, the world famous fashion stylist......



I would rather wake up next to a Horses Head

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## parsifal (Oct 19, 2015)

you would be if you woke up to her, though I think also she would scare any horses she came close to........

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## GrauGeist (Oct 20, 2015)

Elmas said:


> Donatella Versace, the world famous fashion stylist......


So that's where Star Trek got the inspiration for the Borg Queen!

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## BiffF15 (Oct 20, 2015)

GrauGeist said:


> So that's where Star Trek got the inspiration for the Borg Queen!



Ouch!

8)


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## gjs238 (Oct 20, 2015)

I wonder if that is Gianni Versace, after a sex change.


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