# Messerschmitt 109 Improvements



## Ivan1GFP (Aug 26, 2013)

My apologies if this is seen as provoking a discussion that digressed and degenerated a bit, but I believe the original topic had a lot more life.

The subject of Toe-In versus Toe-Out was brought up but I believe it didn't get proper coverage.
It IS a geometry problem but not quite what folks were discussing:
The big problem is the NEGATIVE CAMBER of the wheels because of the angle of the struts from the fuselage.
The Spitfire and Wildcat also have very narrow track landing gear but this isn't as much of a problem because their wheels have POSITIVE camber when unloaded and closer to Zero camber when loaded.

With Negative camber, the wheels may have neutral toe when the fuselage is level but in a 3 point attitude, there is unavoidable severe Toe Out.

If I were selecting bad features of the 109F to correct, it would be the following:
1. Correct the camber of the landing gear. It was corrected to some extent in later models but ended up putting bulges in the wings. Perhaps the camber could be changed with a link of some kind as the wheel retracts.
2. Make the Ailerons internally balanced and add tabs to lighten them a bit at high speed. An external mass balance just isn't right on a high performance aircraft.
3. Add more aerodynamic balance on the elevators to lighten forces at high speed.
4. Install an improved canopy similar to the Erla-haube. (Or go to a sliding canopy which is a bit more redesign.)
5. Add a cockpit adjustable Rudder Trim and increase the height of the fin for less swing at take-off.
6. Add a bit more wing area perhaps with extended tips or a less extreme take on the carrier versions.
7. Clean up the armour glass installation on the windscreen. The bolt on stuff is just bad.

This would be the most extreme change and I have no idea of the engineering changes required but:
Lower tail by reshaping the aft fuselage. This would correct the ground angle that the elongated tail gear was meant to correct.

I do not believe enlarging the fuel tank rearward would be a good idea because it is already way aft of the CoG of the aircraft. If possible, the fuel should all be located as close as possible to the CoG so that trim changes as little as possible.
The German drop tank system already has some pretty good advantages over the Allied systems.

Opinions?
- Ivan.


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## Mangrove (Aug 26, 2013)

Ivan1GFP said:


> Opinions?


 
Finnish VL Pyörremyrsky was basically a project to try to include all of the good factors of the BF 109, use the same engine, but with some of the faults of the Messerschmitt fixed.


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## GregP (Aug 26, 2013)

I am leaning towrd having stub wings permanently attached to the fuselage and bolting the existing wings onto the stubs. The stub wings need only be about 1.5 - 2.5 feet wide and the gear would be moved ourward as well. You could put self-sealing fuel tanks in the stub wings.

I like the idea of adjusting the wheel angle with links but would prefer moving the gear outward and retracting inward as on the Me 209.

Not quite sure why the controls got so heavy at speed, but correcting this should have been a poriority and it COULD have been been corrected or at least made much better. Had the Luftwaffe insisted on fixing this early-on, it would have been a non-issue later. Ditto the lack of rudder and aileron trim ... there is simply no decent excuse for not having it.

Improving the windscreen would seem to be easy on the surface. Every WWII fighter I have sat in has a better windscreen than the Bf 109, so improvement wouldn't seem to be too big of an issue.

If you lower the horizontal tail you create another issue ... susceptibility to FOD damage. These planes operated from farmer's fields and rocks can easily render a plane unserviceable by causing damage to the leading edge of the horizontal tail. When I was at Reno in 2011, Rare Bear managed to poke a hole in the starboard horizontal tail leading sdge on a paved runway. The repair wasn't too tough, but wartime planes maybe could have had a thick leading edge specifically to avoid this situation ... or leave the tail high.

Since we're talking improvements anyway, I would investigate eliminating the slats. They almost never opened at the same time and induced yaw when they opened asymmetrically. Once open, they were fine. The question is why have slats at all? The fighters that didn't have slats didn't seem to suffer from the lack thereof. Maybe all that was needed was some washout and slightly more wing area. Whatever, it could be examined in a wind tunnel and/or on one or two individual airframes. Seems like an unneeded gimmick that, while it worked after a fashon, was not anything close to optimal.

I'm glad you started the topic again and hope it stays on track. I would reitterate, the Bf 109 wasn't a bad fighter at all. We're just talking about improvements that could have been made, not running it down as a warplane. It well might be that these changes would be extensive but, if they had been made early-on, they could have made quite a difference.


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## Milosh (Aug 26, 2013)

> They almost never opened at the same time and induced yaw when they opened asymmetrically.



The first part is a bit of a myth Greg. Mtt investigated wing fences which would have been an easy 'fix' but the slats were the better option.


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## GregP (Aug 26, 2013)

Might have been a myth on the German Bf 109's, but the same slats on the Hispanos definitely opened asymmetrically if the ball wasn't centered. In the heat of battle, keeping the ball centered might have taken a back seat to other considerations such as keeping your head on a swivel.


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## Shortround6 (Aug 26, 2013)

The slats help a lot with landing, at least in theory, they start to add lift when the angle of attack exceeds 13-14 degrees? Nose up attitude for 3 point landing plus glide slope? Helping maintain aileron control at low speed is probably as important as actual lift. Max lift not occurring until over 20 degrees. A number of English aircraft started with slats and dropped them but then a Halifax shouldn't be operating at 16-24 degree angle of attack anyway  

Mid 30s say a lot of new things being tried but it took a few years and a LOT of experiments and experience to sort out what really worked in the real world and what didn't. Some plane designs had new "high lift" features added just to see what happened and some were dropped when they found they didn't help in many of the planes fight regimes, even though a different type plane (with different missions, flight characteristics) might benefit from the same device.


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## bobbysocks (Aug 26, 2013)

what about swaping the slats for standard adjustable flaps?


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## cimmex (Aug 26, 2013)

Why nowadays people always want to improve the Bf 109? The RLM was the only authority who could request improvements. But they never did. There must be a reason.
cimmex


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## stona (Aug 26, 2013)

cimmex said:


> Why nowadays people always want to improve the Bf 109? The RLM was the only authority who could request improvements. But they never did. There must be a reason.
> cimmex



Because there was a war on 

Lowering the tail might cause all sorts of aerodynamic problem, masking the rudders or elevators for a start. It's a non starter. For example, the only way to get an early tail dragging Me 262 off the ground was to apply the brakes to raise the tail as the elevators had no authority, being masked by the fuselage. 
The rest seem to me at least feasible.
Cheers
Steve


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## Shortround6 (Aug 26, 2013)

bobbysocks said:


> what about swaping the slats for standard adjustable flaps?



They don't do quite the same thing. The Flaps _may_ improve lift at lower angles of attack but they do nothing for maintaining aileron effectiveness at low speeds.


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## stona (Aug 26, 2013)

The Bf 109 already had adjustable flaps, just over 50% of the wing span and 42,5 degrees maximum deflection. An interesting feature was that they were linked to the ailerons which also drroped progressively with the flaps. With flaps fully down the ailerons drooped by 11 degrees.
The slats served a different purpose, not only at low speed but also high angles of attack, by increasing lift and preventing the wing from stalling. The mechanism by which they work was not properly understood in the 1920/30s and is rather complicated. Pre-war designers just knew that they worked.
How do the slats improve aileron effectiveness at low speed? 
Cheers
Steve


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## Shortround6 (Aug 26, 2013)

Slats (and fixed slots) keep the air on the top surface from separating (stalling). An Aileron trying to operated in a stalled or partially stalled (disturbed) air-stream looses effectiveness. The slats/slots do not "improve" aileron effectiveness over what it would be at low speed with the wing un-stalled, but they help maintain the effectiveness at high angles of attack right before the stall or even a bit during it. Many wings do not stall all at once but progressively from the wing root out or from the tip in. The slats/slots keep the area of the wing they affect (pretty much the area behind them) from stalling, at least up to a point. The root/ mid wing area may be stalled and the plane loosing lift and mushing but if the outer wings are NOT stalled the ailerons allow some lateral control.


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## davebender (Aug 26, 2013)

Me-109 was the most successful fighter aircraft in history. 

Why not improve the rest so they become as successful as the Me-109 series?


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## Tante Ju (Aug 26, 2013)

GregP said:


> Since we're talking improvements anyway, I would investigate eliminating the slats. They almost never opened at the same time and induced yaw when they opened asymmetrically. Once open, they were fine.



I have never read about yaw. The 109 had low directional stability, but this was perhaps due to the tail design. As for the slats, the British noticed some aileron buffeting and stick floating while the slats were opening (which may well only last a fraction of a second) and somewhat disturbing aim, but this may well have been a peculiarity of the single example they were testing. Mark Hanna flew the 109G and noticed there was no disturbance around any axis when they deployed. Either the kinematic design improved or it was just that 109E that had badly set up slats.



> The question is why have slats at all? The fighters that didn't have slats didn't seem to suffer from the lack thereof. Maybe all that was needed was some washout and slightly more wing area.



Because they had positive stabilizing influence at high angle of attack, that's why subsequent fighters, even jets had them. The 109 was known to be an extremely well controllable plane in stall and devoid of any nasty stall characteristics. That's how it actually beat the Heinkel design in stall tests. The rest is history. Most planes today have some sort of slat-like high lift device in the leading edge, it cannot be such a bad idea.. WW2 fighters without slats sure did not suffer from the lack of, but sure as hell did not benefit from that either. More wing area means more drag, all the time, and less top speed. A slat is practical since it only adds drag when its needed. And that's basically throwing the baby out with the bathwater - all of the great performance characteristics essentially came down to its extremely high power to weight/drag ratio, following Willy's idea of an air frame with the lowest possible weight and drag with a very powerful engine.



> Whatever, it could be examined in a wind tunnel and/or on one or two individual airframes. Seems like an unneeded gimmick that, while it worked after a fashon, was not anything close to optimal.



Messerschmitt did investigate boundary layer fences on the 109 and decided against it. They weren't fanatic about slats, the Me 210 did not have them initially, they added them later on, when landing characteristics were found to be too challenging.

People also seem to start out from what was actually mass produced and assume that no background research was done. Its a false presumption, a lot of things were tried and tested - there were even 109s with butterfly tail units, the Me 209 which was found to be a bit faster but less maneuverable, 109H with larger wings etc - but the ones that weren't introduced were simply dropped because they simply did not worth it.


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## Ivan1GFP (Aug 26, 2013)

The idea of moving the entire tail down probably would not cause any blanking at take-off because the tail would be at the same relative position to the wing. The only difference would be the angle of attack of the wing and the horizontal stabiliser. The idea is just to change the ground angle a bit with a fuselage shaped more like a Heinkel 100 but without the goofy long tail gear strut. Perhaps the payoff would be too little.
The reason I believe this would be a fairly simple change is because the 109's structure in the tail is VERY simple. The improved ground angle should also help with directional stability.

Slats seem like a better idea than washout. The problem with washout is that it generally increases drag because if one section of the wing is at an optimal angle of attack, other parts would not be. The uneven opening of the slats was a known problem with the 109E which is why the bearings were changed for the 109F and later. If they are operating properly, they should deploy because of their own weight and be retracted by air pressure against the leading edge.

I am also not convinced the idea of a single radiator under the fuselage is a good one. It would absolutely require that the wings be redesigned for bomb racks and drop tanks and might need quite a lot more engineering. Also, keep in mind that this is where all the spent shell casings end up.

I am generally not a big fan of asymmetry, but how about mounting a 13 mm MG only on the starboard side but set back enough to be in line with the supercharger? I don't happen to remember what other equipment is located there other than the engine mounts.

- Ivan.


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## DerAdlerIstGelandet (Aug 26, 2013)

davebender said:


> Me-109 was the most successful fighter aircraft in history.
> 
> Why not improve the rest so they become as successful as the Me-109 series?



I am a 109 freak, my favorite acft all time, but I question whether it was successful by design or simply because of the situation it was forced in.


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## Milosh (Aug 26, 2013)

davebender said:


> Me-109 was the most successful fighter aircraft in history.
> 
> Why not improve the rest so they become as successful as the Me-109 series?



When there is 30,000+ built, and the only other option is a Fw190, it is not hard to be successful.


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## DerAdlerIstGelandet (Aug 26, 2013)

Milosh said:


> When there is 30,000+ built, and the only other option is a Fw190, it is not hard to be successful.



My point exactly.


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## GregP (Aug 26, 2013)

Hey guys,

I tried my best to state this at the start. I am not running down the Bf 109. What I was saying is that changes should have been explored. It well might be they WERE explored and discarded ... but it also well might be nobody tried for major improvement in multiple areas. I don't know and don't care a great deal.

The changes I suggested were just that, suggested areas for investigation ... except for the lousy windscreen, controls that stiffened up at combat speeds, and the lack of trim. These were major. The rest were areas to LOOK at, not areas that would make a major difference.


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## Tante Ju (Aug 27, 2013)

Whats so lousy about the windscreen, being too steep, too small or...?


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## GregP (Aug 27, 2013)

Can't see crap out of it except forward or to the side. Forward and left or right is problematic. Lots of sky blocked out or distorted compared with other fighters.

Go sit in one. Bad and easily correctable with very little effort.


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## stona (Aug 27, 2013)

Shortround6 said:


> Slats (and fixed slots) keep the air on the top surface from separating (stalling). An Aileron trying to operated in a stalled or partially stalled (disturbed) air-stream looses effectiveness. The slats/slots do not "improve" aileron effectiveness over what it would be at low speed with the wing un-stalled, but they help maintain the effectiveness at high angles of attack right before the stall or even a bit during it. Many wings do not stall all at once but progressively from the wing root out or from the tip in. The slats/slots keep the area of the wing they affect (pretty much the area behind them) from stalling, at least up to a point. The root/ mid wing area may be stalled and the plane loosing lift and mushing but if the outer wings are NOT stalled the ailerons allow some lateral control.



Yes, the slats prevent the wing from stalling, the fact that the ailerons still work is due to the unstalled condition of the wing. Keeping the wing flying at high angles of attack is the function of the slats, continued aileron effectiveness is a function of the unstalled wing, not the slats. It's a bit pedantic but its a chain of functions, one dependent on another. The designers did not install slats to keep the ailerons working, they installed them to stop the wing stalling, and the aircraft from stopping flying.
The Spitfire wing stalled from the inboard area outwards which meant it could still fly, with aileron control, even when partially stalled. Experienced pilots could make the famously tight turns in this condition. Lesser mortals would not. It didn't need slats to do this, but it was a much more sophisticated shape.
Cheers
Steve


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## stona (Aug 27, 2013)

GregP said:


> Can't see crap out of it except forward or to the side.



You certainly can't, the view is appallingly bad. It's also not exactly the most aerodynamically slick piece of armour. 

Designing a new canopy with better vision ultimately falls back on the Bf 109's biggest shortcoming. It was just too small.

Cheers

Steve


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## cimmex (Aug 27, 2013)

GregP said:


> Can't see crap out of it except forward or to the side. Forward and left or right is problematic. Lots of sky blocked out or distorted compared with other fighters.
> 
> Go sit in one. Bad and easily correctable with very little effort.


After the war Avia designed a new hood for their S99/199 series but kept the windshield, Spain also used the old design even Switzerland as a foreign customer didn’t request a new one and there was no pressure of war. I would like to see your proposal without altering the slim fuselage and still have an armored screen in front.
cimmex


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## Tante Ju (Aug 27, 2013)

stona said:


> The Spitfire wing stalled from the inboard area outwards which meant it could still fly, with aileron control, even when partially stalled.Experienced pilots could make the famously tight turns in this condition. Lesser mortals would not.



Yes, its doable with a washout, even though that washout was fairly commonplace so I do not see why to invoke another baseless spitfire fetish outburst in a 109 advancement thread... its silly, especially given that the Spit was half a generation behind in aerodynamic solutions - virtually all high lift devices were absent from it. Yes you can provide huge chunk of wing which may give you still enough lift when the roots stall, the 'only' downside is that you are 30-40 mph slower that way.



stona said:


> Designing a new canopy with better vision ultimately falls back on the Bf 109's biggest shortcoming. It was just too small.



The canopy may have been better designed though I do not see how and compared to what. The idea was to semi-sink windshield (and the pilot) into the fuselage, as in case of the Fw 190 and P-51 for example (the "German school" of some North American designers is notable). This limits 11-2 o clock vision of course, its a price you pay for more speed. A Fw 190 style canopy and windshield could be adopted without much ado, I am not sure why it wasn't (one probability is the requirement for pressurized cocpit on G series which is a huge factor for high altitude pilot efficiency). The oft and erroneously claimed "size issue" was certainly not among the reasons.


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## stona (Aug 27, 2013)

Tante Ju said:


> Yes, its doable with a washout, even though that washout was fairly commonplace so I do not see why to invoke another baseless spitfire fetish outburst in a 109 advancement thread... its silly, especially given that the Spit was half a generation behind in aerodynamic solutions - virtually all high lift devices were absent from it.



It's not silly and I resent the implication.
If you bother to read the post to which I was replying to you will see that it was not I who raised the issue of progressive stalling along a wing. My response was entirely relevant to that post. I used the Spitfire as an example, there are plenty of others. The Bf 109s use of slats was one solution to a problem, but there were others that did not use your "high lift devices". Leading edge slats were hardly cutting edge in the mid 1930s! They can be a fix for a wing which misbehaves at low speed or high angles of attack (or both), as seen on the Me 210/410.

Cheers

Steve


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## stona (Aug 27, 2013)

Tante Ju said:


> A Fw 190 style canopy and windshield could be adopted without much ado, I am not sure why it wasn't



Because the Bf 109 has a very slim fuselage and you would need to make a "low back" version like later versions of P-47s, P-51s, Spitfires and others. I don't believe that could be done "without much ado" and I'm guessing that the designers didn't either.

Cheers

Steve


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## Shortround6 (Aug 27, 2013)

stona said:


> Yes, the slats prevent the wing from stalling, the fact that the ailerons still work is due to the unstalled condition of the wing. Keeping the wing flying at high angles of attack is the function of the slats, continued aileron effectiveness is a function of the unstalled wing, not the slats. It's a bit pedantic but its a chain of functions, one dependent on another. The designers did not install slats to keep the ailerons working, they installed them to stop the wing stalling, and the aircraft from stopping flying.



A bit pedantic to be sure, many aircraft had the spats/slots pretty much in line with ailerons and not over the majority of the wing or the entire wing. Planes like the Fiesler Storch, the Westland Lysander had full length slats. Even the Swordfish had slats but only on the upper wing in front of the ailerons (no ailerons on the lower wing). Lockheed used fixed slots on the Electra airliners and Hudson bombers, again just in the aileron area (of course they used wacking big Fowler flaps just inboard of the ailerons for lift).
You are correct on the chain of function but if they were truly looking for more lift to keep flying the slats/slots would have covered a greater area of the wing like the STOL aircraft. The slats kept the outer wing from stalling, not the inner, just like the Spitfire's washout.


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## razor1uk (Aug 27, 2013)

Most aircraft I think, if they do have washout (measured at the tip), it's usually between -0.5 and less than -5 degrees; 5 degrees downwards/negative (hence the '-',) perhaps ignoring the wing designs angle of incidence.

On jets, the higher speeds, to me, less washout might generally be needed so as to not restrict higher speeds or controllability (unless they want it more unstable - look at the tips(-/tiprails) of a F-18C the F-18G) via aerodynamic induced and parasitic drag caused by the washout; all that is also dependant upon the wings shapes, its various loadings and the aircrafts envisaged usual flight profile etc.


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## spicmart (Aug 27, 2013)

stona said:


> Designing a new canopy with better vision ultimately falls back on the Bf 109's biggest shortcoming. It was just too small.



Yak-3?


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## stona (Aug 27, 2013)

FYI the Spitfire's inflight loaded wing has a washout of +2 degrees at the root and -0.5 degrees at the tip, thus creating a twist axis of 2.5 degrees along the wing.

Since this is a Bf 109 thread I will elaborate no further, except to say that for this, and a variety of other aerodynamic reasons, this wing did not require the addition of drag inducing lift devices to enable it to fly safely at low speeds and high angles of attack. 

Cheers

Steve


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## stona (Aug 27, 2013)

spicmart said:


> Yak-3?



I know nothing about Soviet aircraft I'm afraid! I'm guessing that it was designed from the get go with the bubble canopy and flat back and not modified as such?
Cheers
Steve


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## Milosh (Aug 27, 2013)

How wide was the 109's, the Spitfire's and the P-51's fuselage at the cockpit?


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## Tante Ju (Aug 27, 2013)

stona said:


> I know nothing about Soviet aircraft I'm afraid! I'm guessing that it was designed from the get go with the bubble canopy and flat back and not modified as such?
> 
> Cheers
> Steve


 
Yak 1, the immediate predecessor of Yak 3...







Lagg 3, the immediate predecessor of ...






.... La 5/7 series.






Also looking on the Spitfire, which is at least as slim in the fuselage, and could successfully adopt a bubble canopy with a "cut" fuselage, I do not see why it cannot be done in the 109. A lot of aircraft successfully done (P-51, P-47, Yak, La series etc.), for some reason Mtt did not want. IMHO it was certainly doable. Perhaps they were satisfied with the rear view after the installation of the Erla cockpit, or there were other reasons like pressurization, which was in effect until 1944 with variants... the last version, the K was largely redesigned in 1943, when this was a concern. It is very difficult to obtain proper pressure maintain with a canopy with neccessary gaps for sliding action.


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## spicmart (Aug 27, 2013)

Milosh said:


> How wide was the 109's, the Spitfire's and the P-51's fuselage at the cockpit?



The Yak-3 seems to have a wider cockpit section than the 109 even if the Yak being even a smaller airframe though.
Yet it seems it had not the vices that plagued the 109 design.


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## Milosh (Aug 27, 2013)

Didn't the PR Spitfire have a pressure cockpit? Iirc so did the Ta152H.


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## stona (Aug 27, 2013)

Not sure what the point of those Soviet aircraft is. If you build a Yak 3 with a bubble type canopy, then it's not a Yak 1. I have never suggested that a version of the Bf 109 could not be made with a better canopy. I simply said that the idea that it would be a simple thing to do is not supported by the evidence. There may well have been "much ado."
Who knows what structural changes were required between the two Soviet aeroplanes? There may also be problems of longitudinal stability (as on the P-51). This wasn't one of the Bf 109's, or Spitfire's, strongest points to start with.
A lot depends on how the fuselage is constructed. On a Spitfire it was_ relatively _ simple to alter frames 11 to 18 and the relevant skins. The Bf 109 fuselage which is effectively built in two halves might not be so easy. Each halves skin plates are made in one piece with alternate plates formed with Z-section flanges which constitute the frames or formers to which plain intermediate plates are riveted. It is a very production sympathetic method of construction, but not so easily modified.
Cheers
Steve


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## razor1uk (Aug 27, 2013)

Once the design of those fuz halfed sections was finalised and distributed to the 'shadow workshops'/fabricatiors amongst the wider population, getting all of them to swap the old former for the new one once the new changes bugs have been worked out would have been more difficult than writing it suggests - include that to the loss of production and or wastage of meterials during the change-over, and you can envisage why they kept to the design, assuming it wasn't all just Willy's fastidiousness to science and his demon, the risk to losses in production.

That's not to say they perhaps with hindsight could not have done something equivalent earlier or better etc - like the Erla Canopy(../ies) Galland Glass, but just producing and changing to those two designs is at least 1/8 easier and quicker than altering the rear cockpit, storage/pilots locker, the rear fuz sections the fuz halfs, the possible airflow effects affecting the tailplane fin + rudder behaviours that'd need 'checking rechecking prior to calibrating', and then the likely conversion training of pilots should it handle too differently.


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## stona (Aug 27, 2013)

As a matter of interest some of todays Spitfire war birds are low backs converted to high backs. This is done by adding "quarter frames" on to the frames I mentioned, above the top (datum) longeron. Again, _relatively _simple.

This is actually a Seafire 47, but it will serve.






There's absolutely no way a similar modification could be made to a Bf 109 fuselage without effectively re-making a good proportion of it, if not everything behind the cockpit.

Cheers
Steve


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## Tante Ju (Aug 27, 2013)

stona said:


> There's absolutely no way a similar modification could be made to a Bf 109 fuselage without effectively re-making a good proportion of it, if not everything behind the cockpit.



I still struggle to see why, perhaps you can explain and highlight the major differences in construction? To me the fuselage construction of the Me 109 and the Spitfire are quite similar. I do not see how the joining method for the two plates effects this - in the 109 the sections slided into each other, giving a smoother transition - but the shape was decided by the ribs and the longerons provided stiffness on both planes.


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## razor1uk (Aug 27, 2013)

AFAIK the 109's rear fuz was built up in quite a different manner indeed, the skin lateral edges were folded and forged/forced into the interlocking J section shapes that correspond to the webs/frames of the Spirfire - the tail of the 109 ended up a monococque construction that the longerons were then it'd appear were inserted in-thorough holes in the 'webs' to finalise lock the structure, where as in the Spit, it had a structural skeleton of ribs and longerons to which the skin was then applied to.


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## cimmex (Aug 27, 2013)

Tante Ju said:


> I still struggle to see why, perhaps you can explain and highlight the major differences in construction? To me the fuselage construction of the Me 109 and the Spitfire are quite similar. I do not see how the joining method for the two plates effects this - in the 109 the sections slided into each other, giving a smoother transition - but the shape was decided by the ribs and the longerons provided stiffness on both planes.


The fuselage construction of a Bf 109 is totally different. There are no particular formers. The formers are part of the relevant skin segment. See link Metallflugzeugbau Metallbau Flugzeugteile spare parts Me Bf 109 - Hartmair Leichtbau Freising


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## stona (Aug 27, 2013)

As above. Thanks gentlemen. What something looks like and how it is constructed are two entirely different things.
Cheers
Steve


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## Tante Ju (Aug 27, 2013)

I still don't see your evidence stona... So again, why would it be structurally so difficult to use a smaller volume 109 fuselage past the cocpit? Separate or built in former, not having holes in the ribs and other minuscule details have absolutely nothing to do with it! Yes the British choose a rather more tedious way of building a very similar load bearing structure that presented less smooth finish but that's that. Please don't tell me that producing different sized former is actually easier than pre-fabbing sheet metal at a different angle...

Mtt apparently managed to do it for the sake of a single prototype, and I absolutely doubt that they put much energy into "totally redesigning" the fuselage or that there was any major difference. I suppose there was another reason - either yaw stability would be compromised, or, even more so, satisfactory pressurized cockpits could not be build this way! Assuming that it would extremely difficult to do something that even a minimal design crew of a mock-up could do or that it just escaped the attention of some of the brightest minds in the aviation industry is not making any sense to me.


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## razor1uk (Aug 27, 2013)

I think that t on the radial engines prototype model, the cockpit is higher (for similar visibility over the engine, nose sides) as the radial would be taller than the inline so..., and so when the altered forward to mid fuz is smoothed into the tail fuz, that it might be for all intent purposes, a normal tail, the open canopy is resting slightly over and rearwards of where the jettisonalbe aft glazing would've been in my mind, but /I may be quite wrong.


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## stona (Aug 27, 2013)

The point is that to make a low back Bf 109 you would have to redesign every single skin-sheet (both types) that make up the fuselage monocoque behind the cockpit. All those skins are a full half fuselage profile, (at the relevant place) and have other integral structural elements built into them. The stringers pass through what engineers would call the "integral formers". The two stringers running along the joins between the two halves (top and bottom) were wider and could take two rows of rivets, effectively holding the two halves together. I think that's what the worker wedged inside the fuselage is doing above.
This is not the case for the Spitfire where the skins are riveted to an easily modified framework comprising all the structural parts attached to the frames. The low back modification is to eight frames and some skins. It is a much simpler modification to carry out mid production. It's the reason that both high and low backed versions of some Marks could be built.
The two construction methods are quite different and that of the Bf 109 does not lend itself to easy modification.
A one off prototype is hardly relevant to re-engineering the fuselage of an extant type already in full production.

Here you can see the "top hat" stringers (so called due to their cross section) passing through the formers _which are part of the skin plate_





Here you can see that this is not the case on a Spitfire. The stringers are riveted to the frames and the skin plates are entirely separate.






Cheers
Steve


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## nuuumannn (Aug 28, 2013)

> Designing a new canopy with better vision ultimately falls back on the Bf 109's biggest shortcoming. It was just too small.



I hate to say it, but you are right, Steve. The Bf 109 was a brilliant design and arguably the most advanced fighter in the world when it first flew, combining modern features such as landing flaps, all metal stressed skin construction, enclosed cockpit, retracting undercarriage, high lift slats etc in one airframe, as well as practicalities inherent in its design, which made it susceptible to mass production and ease of maintenance. Like many objects of its time, the Bf 109 was also suceptible to fashion, which was among single-seat fighters for a high back rear fuselage that the cockpit faired into; almost all designs of the time were the same.

The fact that enabled such high numbers of the type to be built was the basic design, but like Adler suggests, was subject as much to environment as it was because of its design. My thoughts on a low backed Bf 109 are as follows bearing this in mind; to redesign the rear fuselage in such a fashion would take up time and require new jigs on the production line and retraining of staff, all of which takes time. If such a measure was to be undertaken, would it be worth interrupting production to do this? The Bf 109 underwent many significant changes in its lifespan, but not structurally aft of the firewall. This was the secret to its success and its longevity as much as it was the aircraft's most limiting factor (its size). Besides, other than improving the pilots' view, was it entirely necessary with a better, more modern design under development and production in the Fw 190?

The reason I ask this is that toward the end of the war the Bf 109 was showing its age and design limitations and advanced fighters, both German and Allied were proving superior to it in terms of technology and performance. Besides, despite the poor view form the cockpit (I too have had the priviledge of sitting in a Bf 109 - very hard for me since I'm six foot two), German aces did not shy away from the type toward the end of the war.

Was it necessary to carry out such a modification to its basic design, taking all things into consideration? Also, since it could be done, albeit not without considerable redesign, why was it not done? Messershmitt and Co were aware of its shortcomings and its not like they didn't have the rersources to do it early on. Is it because there were better, more advanced designs waiting on the drawing board? Probably.


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## stona (Aug 28, 2013)

Well done getting into a Bf 109 at 6'2". I'm 5'9" and barely fitted. I'm also rather broad in the shoulders (think front row in amateur days!) and that was a bigger problem, I am wider than the cockpit opening meaning I was effectively hunched all the time. This also makes it almost impossible to rotate to see behind, or as much behind as is actually possible, which isn't a lot. It's definitely not for more heavily built pilots.
I don't think photographs and drawings can show just how tight it is.
Only last year I sat in a Spitfire and thought it was a bit tight, until I remembered the Bf 109 
Cheers
Steve


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## GregP (Aug 28, 2013)

It isn;t that tough to redesign the fuselage to cut it down for a bubble. The parts are different, to be sure, but the new parts are just Aluminum assemblies lke the old ones.

It does take some effort, but nothing extraordinary.


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## cimmex (Aug 28, 2013)

Messerschmitt was a private company with the goal to earn money. Of course, nearly everything could be done if there is someone who requested this and was willing to pay for it.
cimmex


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## razor1uk (Aug 28, 2013)

Paying for the 100's/1000's of new... moulds, formers, shaping and press tools, shape checking gauges, and the collection and redistribution of old and new such items to the production untis, factories, workshops and sheds etc. And that's assuming the prototyped new tail fuz section passed trials. 
Achieving all the same strengths and good attributes as the old design, while bringing other extra benefits to the overall package as well as natural affect of the new desing, reduced material wastage, slightly less structural weight for no-less or more structural strength, improved or same aerodynamical figures etc The sectional halves would at least all need reshaping/new compound radii so they couldn't be used to repair 'early design sections' as they wouldn't match.

If that could be done, I'd say the cut down wouldn't be as much as the Spitfire or Mustang or Thunderbolt, perhaps a tapering/progressive cutdown to handle the flight structural loadings. where there is more lost at the cockpit end and almost none by the tail attatchment end - perhaps a fin fillet would be ahhed later around the equivalent of the late smoother G10-AS...

Guesstimating say 10cm height reduction at the cockpit and 2cm at the other tail end with the contours redone and the pilots/started-handle locker also having to be reduced reshaped to merge the 'new' tail fuz. The merging of the cockpit glazing/perspex towards the rear might look a little Yak like in the rear aero glazing, perhaps a Earla canopy if this was happening semi late war?


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## stona (Aug 28, 2013)

GregP said:


> It isn;t that tough to redesign the fuselage to cut it down for a bubble. The parts are different, to be sure, but the new parts are just Aluminum assemblies lke the old ones.
> 
> It does take some effort, but nothing extraordinary.



Of course it could be done. The problem is that unlike most other types, and due to the way the fuselage is constructed it involves re-engineering 100% of the structure behind the cockpit. That's been my point all along. 
It would be an expensive and time consuming exercise. It cost Messerschmitt AG 38,000,000 RM to sort out the Me 210, not the RLM. It cost Messerschmitt his job. It also cost considerable production of the Bf 109 for reasons I don't have time to type here. Suffice to say that between October and December 1941, just as production was switching from the E to the F not one Bf 109 left the Regensburg assembly lines.
I don't think that the Ministry had a great deal of confidence in the company mid war. Just about all they needed was another fiasco involving one of the two single engine fighters they had which actually worked.
Cheers
Steve


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## Shortround6 (Aug 28, 2013)

Germany had some advantages and some disadvantages with 109 production I believe. I am not a 109 expert so would welcome correction on this. 

How many factories or plants built 109s? 

If you are going to do something like the cut down fuselage do ALL plants/factories get the new tooling or just some and some 109s keep getting built with the high back? 

I believe that NA had just two factories building P-51s ( could be wrong and I don't know how the sub-contractors fit into it) 

Many Allied fighters came from 2 or 3 factories, granted they may have been larger than the German factories and may have required more tooling _per_ factory. 

Anyway, just an Idea I am throwing out.


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## stona (Aug 28, 2013)

Shortround6 said:


> How many factories or plants built 109s?



If we're talking about a realistic time frame for this modification we are probably talking mid G production. By early 1943, around the time that the G-6 started arriving at operational units, the Bf 109 was essentially coming out of three plants, Regensburg, Erla and Wiener Neustadt. A few were licence built at Gyor in Hungary.

If a low backed version was shown to be viable I would expect that initial production of the type would come from Regensburg as this seems to have been the way the company operated, followed by the others. Whatever happens production will be lost, and that's assuming there is no repeat of the numerous fiascos that dogged the production of various Messerschmitt types throughout the war.

Cheers
Steve


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## Tante Ju (Aug 28, 2013)

stona said:


> Of course it could be done. The problem is that unlike most other types, and due to the way the fuselage is constructed it involves re-engineering 100% of the structure behind the cockpit. That's been my point all along. It would be an expensive and time consuming exercise.



You make a lot about it. The original Bf 109 was designed in about _six _months from scratch, using the previous Bf 108 experience as a rough basis. In twelve months the prototype was ready. That puts into perspective how much design work would be needed to reshape a couple of very simple structural element. Another example - the 109K for example incorporated over 1500 minor changes in construction, some effecting the fuselage (rearranging access doors and internal equipment, so somewhat similar components are effected). Again the design work from proto lasted about six months.

The Germans (and I am sure pretty much everybody else) used general machining tools - cutting sheet aluminium to size, bending them to shape etc. - otherwise resetting production would have taken a lot more than it actually did, and would be largely impractical to invest in, given that most companies produced a good number of aircraft types, not just one. These would need to be re-set but its hardly big issue either. Even small sub contractors built parts.

I believe there were three major factories in the mid/late war engaged in Bf 109 production/assembly, these would be Messerschmitts Regensburg plant (Bavaria), Erla (in Leipzig, Saxony) and WNF in Austria (the latter was pretty much the equivalent of Castle Bromwhich, being a large, automatized state owned factory, and probably more demading to set up, as it also had conveyor line production).

BTW thank you for your description, very good indeed. But I failto see what makes to design fundamentally different - construction method was, sure. the formers did not just grow onto the skin of the fuselage on the 109, I assume it was simply designed that way because it was probably easier to bend an aluminium plate to form the skin, and then attach the former to it on a bench, and then assemble (rivet) the whole thing together from two halfs than trying to do a lot of riveting inside the fuselage in very restricted space. But the components are essentially the same, the assembly sequence is different. There is simply no reason as to assume one is more easily modified than the other. You still need to produce a new set of nearly identical components (which doesnt strike me as terribly demanding, especially looking at how much simpler the 109 former is - a simple bent shape instead of of tediously holed one).


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## stona (Aug 28, 2013)

The Bf 109 (and other Messerschmitt fuselages) were built that way because it was a very efficient production system. The entire Bf 109 design was sympathetic to the rigours of series production.
Whether you like it or not, to make a low back Bf 109 you have to re-engineer the entire fuselage behind the cockpit. Every single skin plate and integral former will have to be redesigned and re-tooled on the production line. This was never done throughout the entire series production, right up to the K, and there is a reason for that.
Cheers
Steve


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## Tante Ju (Aug 28, 2013)

stona said:


> Whether you like it or not, to make a low back Bf 109 you have to re-engineer the entire fuselage behind the cockpit. Every single skin plate and integral former will have to be redesigned and re-tooled on the production line.



Right, just like on any other plane, including the Spitfire. You can't get around it, you need to design (not too terrific task) and produce new components for the fuselage. It may cause some production loss, and the RLM just like the British Air Ministry decided it just does not worth the fuss. Only a handful of low back Spitfires ever saw service at the end of the war, and there's a reason for that, even though the RAF was anything but hard-pressed in 1944.


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## bobbysocks (Aug 28, 2013)

those cockpits werent designed for 30 year old or 40+ year old men. the guys that flew them were late teens...early 20s for the most part. if i tried to slide into the cockpit of any of them now it would be a way tighter fit than it would have been 37 years ago when i was 20. back then i weighed a buck 35 with wet hair. you look at pictures ( from both sides ) most of the pilots are fit and trim. and those cockpits were still large enough for the occasional romantic moment with a fraulein....


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## nuuumannn (Aug 28, 2013)

> you need to design (not too terrific task) and produce new components for the fuselage.



You also need to compensate for the reduced surface area of the fuselage by increasing the size of the fin/rudder assembly - as it was, the Bf 109's fin/rudder was very small.

I'm still not convinced by the need to do this at all, to be honest. Yes, the pilot would have a better view, but as I stated earlier, the Bf 109 was a product of its time and had the war not intervened would probably have been replaced by something more advanced, like a jet fighter, rather than the extent of the modifications that were actually carried out on it. The requirement for a single-seat turbojet fighter was issued to Messerschmitt/BFW in January 1939, with the P 1065 design appearing on paper in October of that year. At that time, the future of the Bf 109 was to be different to what it became in the eyes of its designers. This is because the war brought about many of the modifications incorporated into the design and arguably led to its longevity. Besides, the Fw 190 proved a better fighter, despite everything done to improve the 109.


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## FLYBOYJ (Aug 28, 2013)

bobbysocks said:


> those cockpits werent designed for 30 year old or 40+ year old men. the guys that flew them were late teens...early 20s for the most part. if i tried to slide into the cockpit of any of them now it would be a way tighter fit than it would have been 37 years ago when i was 20. back then i weighed a buck 35 with wet hair. you look at pictures ( from both sides ) most of the pilots are fit and trim. and those cockpits were still large enough for the occasional romantic moment with a fraulein....



Also remember people in general were a lot shorter (and thinner) in the late 1930s than today.


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## stona (Aug 28, 2013)

Tante Ju said:


> Right, just like on any other plane, including the Spitfire.



That is simply not true. For the Spitfire you have to alter 8 of the frames and a few skins. All the rest of the structure, longerons etc remains the same.
For the Bf 109 you have to alter every single major component of the fuselage which are the skin plates and integral formers. The only things that would not need substantial alteration would be the stringers.
If you refuse to see the evidence presented by myself and others above then you will not be open to persuasion, and I give up.

The view out of a standard Spitfire is a lot better than the Bf 109, I've sat in both. The Spitfires had blown hoods which were adopted early on in the war. The thread was about improvements to the latter. I don't think it was any kind of issue for the Spitfire.

Cheers
Steve


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## stona (Aug 28, 2013)

FLYBOYJ said:


> Also remember people in general were a lot shorter (and thinner) in the late 1930s than today.



They were slightly shorter but I agree, a lot less likely to be overweight.
When I sat in a Bf 109 I was still a fit and relatively young man, certainly not overweight. A heavy build is I'm afraid a genetic advantage to a rugby player (a necessity playing where I did) though not to a WW2 pilot 
Cheers
Steve


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## Tante Ju (Aug 28, 2013)

stona said:


> That is simply not true. For the Spitfire you have to alter 8 of the frames and a few skins. All the rest of the structure, longerons etc remains the same.
> For the Bf 109 you have to alter every single major component of the fuselage which are the skin plates and integral formers.
> 
> Cheers
> Steve


 
So you have to "redesign" 8 frames and 8 skins on the Spitfire. For the 109 lets assume you are right you have to alter every single major component of the fuselage which are the skin plates and integral formers.

Now please count the fuselage sections of the 109, between frame 2 and 9 thank you. 







But you see the fact is - none of us know the exact amount of work involved, you just jump to the conclusion that intergral formers somehow make redesign incomparable harder than redesignning seperate formers, and that skin on the Spitfire is incomparably easier to redesign than skin on the 109. It just doesn't make any sense to me...


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## Tante Ju (Aug 28, 2013)

FLYBOYJ said:


> Also remember people in general were a lot shorter (and thinner) in the late 1930s than today.



True. Height is very much of a factor of nutrition at very young age. Now, in the 1920s when these young guys flying in that devastating war were anything but well fed... the Great War devasted economies and agriculture, and especially in Germany post-war entente blockade lead to famine...


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## stona (Aug 28, 2013)

Tante Ju said:


> But you see the fact is - none of us know the exact amount of work involved, you just jump to the conclusion that intergral formers somehow make redesign incomparable harder than redesignning seperate formers, and that skin on the Spitfire is incomparably easier to redesign than skin on the 109. It just doesn't make any sense to me...



I do know exactly how much work it takes to convert a low back to a standard Spitfire.......thank you.
You couldn't do it to a Bf 109 and the other way around would be just as difficult due to the engineering required on the Bf 109's structure. You can pop a few new frames and the altered skins (I can't remember how many, but relatively few, most remain unchanged) into a production line with virtually no disruption at all. How do I know? Because it was done.
That's me done too.
Cheers
Steve


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## bobbysocks (Aug 28, 2013)

Tante Ju said:


> True. Height is very much of a factor of nutrition at very young age. Now, in the 1920s when these young guys flying in that devastating war were anything but well fed... the Great War devasted economies and agriculture, and especially in Germany post-war entente blockade lead to famine...



and both the americans and the germans had recently come out of a depression economy....also to a factor to not being well fed.


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## nuuumannn (Aug 28, 2013)

> They were slightly shorter but I agree, a lot less likely to be overweight



I looked in the cockpit of a P-47 once, the Michelin Man would call it spacious in there!  I remember reading somehere about how British pilots commented favourably about how big American fighter cockpits were.


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## GregP (Aug 28, 2013)

We DO modifications to aircraft at the Planes of Fame and it just ins't that difficult. Someone is making mountains out of molehills.

You don't have redesign the entire rear fuselage ... you have to make the top curve shorter and redesign 5 - 6 bulkheads to have an abbreviated top curve, change the length of a few stingers (VERY simple), maybe a couple of longerons and maybe not, and resahpe the upper part of the skins.

The fin and rudder always could have been made a bit bigger and had trim added to the rudder.

From someone who does restorations and modifications, it isn't all that big a deal. The ONLY reason I would not do it today is becasue any Messerschmitt Bf 109 I work on should be a s stock as possible. Back in the war, it would have been a VERY different story.

They didn;t seem to have much trouble doing it to the P-051 Mustang, the Li-61 / Ki-100, the Spitfire, the P-47, or the P-40 (think P-40Q). Since EVERY ONE of tehse had the same thing done, how tough is it?

Answer, not very. The first trial example could be done by 3- 4 guys in 2 weeks or so with some plans (fuselage changes only ... someone else would have to make the canpoy and slide pieces. 

A friend and I made a piece of trailing edge about 4 feet wide for a North American O-47 last weekend (port stub sing) from nothing but Aluminum sheets. We cut the 3 ribs, formed them, cut the top and bottom skins, made the stiffeners and a few braces, and drilled enough holes to hold them together in 8 hours on a Saturday. We took our time and will have this piece of trailing edge done in about a total of 3 Saturdays with 2 guys who are working at this for fun and not as a job. We shoot the bull while working and keep moving, but not at a breakneck pace ... it IS for fun, after all. The main issues are having the material, tools, and plans. We traced the original parts and went from there.

This just is NOT all that difficult as is being touted in here. Ask FlyboyJ ... he works on real planes, too and can do sheet metal.

When they punched a hole in the horizontal stab on Rare Bear at Reno on 2011, they had it pactched in 12 minutes. Applying the bondo, fethaering it in, wiping it with a tack rag, and painting it took longer.

Modifying an existing fuselage would take longer ... making a new one from scracth would be WAY faster and easier, and might or might not save time from the existing design.

It's sort of like turning a right hand Allison engine intoa left turn engine. It is a major change if you have an existing right-turning engine. But if you are building one up from parts, it is trivial to make a left-turning engine instead. There is a difference of 3 - 4 gears, a different wire harness for the spark plugs, and an opposite-turning starter. If you are assembling it from parts ... the difference is miniscule. 

If you want to CHANGE it, you have to pull the engine, remove the accessory case, the nose case, change the starter, and change the wiring harness ... and, of course, the propeller. Time-consuming. But build it from scracth and the difference can be neasured in minutes ... the length of time to read the changed instructions for sequenced assembly.


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## cimmex (Aug 29, 2013)

@ GregP obviously you haven’t understood how the rear fuselage of a 109 is constructed. Several times you stated that you have access to a Buchon at the museum so I suggest to have a look inside and you will see that your proposals will not work. Thanks Matthias Dorst who made a detailed documentation of the restoration of an original E-1 and the reconverting of a Buchon to G-2 standard at meiermotors with hundreds of photos on his website. I have posted the links earlier in this thread already so everybody who is interested can make his own opinion.
Sorry, I’m out now and will not post again in this thread.
cimmex


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## FLYBOYJ (Aug 29, 2013)

GregP said:


> We DO modifications to aircraft at the Planes of Fame and it just ins't that difficult. Someone is making mountins out of molehills.





GregP said:


> This just is NOT all that difficult as is being touted in here. Ask FlyboyJ ... he works on real planes, too and can do sheet metal.



Greg is right (thanks for the plug). Although original assembly considerations are taken into effect (example: _"The fuselage construction of a Bf 109 is totally different. There are no particular formers. The formers are part of the relevant skin segment."_)Many times it doesn't make any difference once the aircraft is assembled.

Folks, Greg and I (as well as a few other forum members) have worked on MANY aircraft, we are by far not god's gift to aircraft maintenance or aviation (as a matter of fact I consider every day I work a learning process and will never be too cocky or confident to continue to say "I know it all"). Unless you've driven some rivets, worked structural repairs or modifications, or restored aircraft to include war birds, please don't try to patronize us by your impressions taken from a book unless you've been there yourselves.


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## stona (Aug 29, 2013)

GregP said:


> You don;t have redesign the entire rear fuselage ... you have to make the top curve shorter and redseign 5 + 6 buylkhead to have an abbreviated top curve, change the length of a few stingers (VERY simple), maybe a couple of longerons and maybe not, and resahpe the upper part of the skins.
> This just is NOT all that difficult as is being touted in here.



I can't believe what I'm reading 

That is precisely what is involved to change the rear fuselage of a Spitfire or an aircraft constructed in a similar way. This is NOT what is involved to alter the rear fuselage of a Bf 109. I'm not going to go over it all again, but I have explained above.

Re-forming all the skin plates c/w integral formers for the Bf 109 is not a difficult engineering job, I don't believe it has ever been suggested that it could not be done. It is a difficult thing to do, mid production, in an aircraft series in the middle of a war. We are not talking metal bashing a prototype or museum example, we are talking re-tooling at least three major production facilities to produce an _entirely new rear fuselage_.

Cheers

Steve


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## FLYBOYJ (Aug 29, 2013)

stona said:


> Re-forming all the skin plates c/w integral formers for the Bf 109 is not a difficult engineering job, I don't believe it has ever been suggested that it could not be done. *It is a difficult thing to do, mid production, in an aircraft series in the middle of a war.* We are not talking metal bashing a prototype or museum example, *we are talking re-tooling at least three major production facilities to produce an entirely new rear fuselage*.



(while getting bombed around the clock)

BINGO!!!


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## Tante Ju (Aug 29, 2013)

Looking at the pressing machines I have seen, all it takes is a new etalon shape, really. Then the machine presses the sheets of aluminium to proper shape.


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## Milosh (Aug 29, 2013)

One factory could have been converted to construct the new fuselages. When all the wrinkles were worked out there, the next factory could have been converted and then finally the third factory.


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## FLYBOYJ (Aug 29, 2013)

Milosh said:


> One factory could have been converted to construct the new fuselages. When all the wrinkles were worked out there, the next factory could have been converted and then finally the third factory.


Easier said then done especially after the round the clock bombing campaign began. For the improvement in the aircraft IMO it wasn't worth disrupting the production line considering Germany's situation.


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## nuuumannn (Aug 29, 2013)

> Then the machine presses the sheets of aluminium to proper shape.



The skin sheets would have been rolled by hand in a roller then drilled to a pattern before fitting together on a jig, not necessarily machine pressed. Many of the components used to build these aircraft were made by hand using benders, folders etc then assembled by hand.

Redesigning an existing type, producing drawings for the new design, jigs etc and assembling a prototype using specialised engineers and staff is one thing, modifying an existing production line by retraining manufacturing staff, re-equipping jigs and facilities is another, not to mention the delay caused by the disruption of production to introduce the new changes. During wartime, with the stress of long working hours for the work force, the threat and sometimes reality of Allied air attacks that disrupted output and destroyed facilities, introducing changes was often extremely detrimental to the flow of production. 

Wartime production staff were not 'aircraft engineers' as we know them, they were generally 'drones' (for want of a better expression) that followed processes and carried out single repetitive tasks. They were not necessarily highly skilled thinkers and had to be retrained in order to do tasks other than the ones they were employed to do. A rivetter working on final assembly would not necessarily have any experience on the folding line or forming line - it wasn't like today where as trainees and apprentices you go through different shops to learn different skills, wartime production staff were often women who had never worked before and people from all walks of life roped into doing single tasks on the line, and that's often all they did.


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## GregP (Aug 29, 2013)

Just to set the record straight, I DO understand the Buchon fuselage, having been inside it. It would NOT be that tough, and major changes to aircraft were made all the time.

I find it difficult to belive that it would be that big a task for people who take raw Aliminum and make airplanes from it. That's why they have all those special tools.


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## Milosh (Aug 29, 2013)

FLYBOYJ said:


> Easier said then done especially after the round the clock bombing campaign began. For the improvement in the aircraft IMO it wasn't worth disrupting the production line considering Germany's situation.



There wasn't much bombing in 1942 when the Bf109G was first produced. The German situation was not that great at that time.


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## swampyankee (Aug 30, 2013)

Automatic leading edge slats are used to maintain aileron authority into stall; most aircraft do without them by a combination of taper, washout, and local airfoil modification. Properly done, this does not increase cruise drag any more than retractable slats (and a lot less than fixed slots). Also note that no other fighters needed LE slats; this is definitely not because all the other designers were stupid clods and was absolutely certainly not because none of the other designers knew about them: take a look at a Dehavilland Tiger Moth. 

Most other aircraft designers were able to get acceptable -- for various values of "acceptable" -- stall characteristics without Handley-Page-type (or, if you prefer, Lachmann; the idea was developed independently and roughly simultaneously) slats on their fighters.

Back to Bf109 improvements: a canopy with better vision out. When the Luftwaffe was doing all the bouncing on people, poor rearward vision wasn't a big concern. As the amount of bouncing by Allied air forces increased, being able to see behind became increasingly important. Also, the struts supporting the tail are likely to be significant sources of drag: they are on the suction side of the airfoil. Braces on aircraft like the Cessna 172 are on the pressure side of the airfoil, and disturb the flow much less. Getting rid of them would require a completely new horizontal tail (and maybe more; since the stabilizer is mounted on the fin, it's possible that the fin isn't stiff enough, and the braces are to compensate for that, too).

As an aside, I've read that the Bf109 had one of the highest zero-lift drag coefficients of any WW2 piston-engined monoplane fighter, with reported values as high as 0.029 (the Corsair was about 0.023,he Mustang was about 0.017; most other monoplane, piston fighters were between about 0.022 and 0.025). If that's the case (I have my doubts, but even if it's 10% high, it's still on the high side), the plane could use a good aerodynamic cleanup.


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## Shortround6 (Aug 30, 2013)

swampyankee said:


> ..... stall characteristics without Handley-Page-type (or, if you prefer, Lachmann; the idea was developed independently and roughly simultaneously)



The two men became partners and life long friends. A much better approach than long patent suit battles.


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## swampyankee (Aug 30, 2013)

Shortround6 said:


> The two men became partners and life long friends. A much better approach than long patent suit battles.



Certainly, much better, and also, I think, something of an indication of how much interchange went on in the world of aerodynamics: Max Munk emigrated from Germany, coming to the US in 1920, von Karman came to the US in 1930, Santos-Dumont migrated from Brazil to France, von Mises, from Germany to Turkey(1933) to the US (1939). I'm sure there were others.


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## nuuumannn (Aug 30, 2013)

> I'm sure there were others.



Wsiewolod Jakimiuk from Poland - worked with Sigmund Pulawski with PZL on the P-11 gull winged fighter - went to Canada and became Chief Engineer with De Havilland Canada. The Chipmunk was his first design with the Canadian company. German Carl Clemens Bucker of the German firm of the same name, which produced the Jungmann and Jungmeister biplanes and the Bestmann trainer started Svenska Aero AB after WW1 (actually a subsidiary of Heinkel and not a strictly Swedish firm); the two biplane trainers that he lent his name to were designed by a Swede, A.J. Andersson... Many more, I suspect.


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## FLYBOYJ (Aug 30, 2013)

Milosh said:


> There wasn't much bombing in 1942 when the Bf109G was first produced. The German situation was not that great at that time.



But there was money spent to get the "frozen" basic design into production. As stated, there would be the need for re-design, stress analysis, tool design and manufacture and last the facility set up. Fact is German industry WAS getting bombed (the first bombs fell on the Ruhr in May 1940) and although this hypothetical mod wouldn't be that difficult I find it impractical during that period, resources "would have" been better spent developing turbine technology.


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## stona (Aug 30, 2013)

Alexander Lippisch nearly came to Vickers Supermarine _in 1938_ according to Beverly Shenstone. The offer was made after the two men attended a lecture at the Royal Aeronautical Society. Those two also remained life long friends, despite having been on different sides during the war.
Shenstone had some influence on the American decision to take Lippisch to the US post war.
Cheers
Steve


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## Milosh (Aug 30, 2013)

FLYBOYJ said:


> But there was money spent to get the "frozen" basic design into production. As stated, there would be the need for re-design, stress analysis, tool design and manufacture and last the facility set up. Fact is German industry WAS getting bombed (the first bombs fell on the Ruhr in May 1940) and although this hypothetical mod wouldn't be that difficult I find it impractical during that period, resources "would have" been better spent developing turbine technology.



In 1940 the Bf09 went thro a major redesign > 109E to 109F. A little more effort and the rear vision on the Bf109 could have been improved at that time.

How many bombs fell on Regensburg and Augsburg in 1940?


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## rank amateur (Aug 30, 2013)

In 1940 most people in Germany figured the war was almost won and the bf 109 the hottest bird in the air anyway.


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## davebender (Aug 30, 2013)

DB603 engine mass production projected for 1941.

Now 1937 RLM can announce a 1939 fighter competition for an aircraft that will succeed or supplement Me-109 in production. 
.....Powered by DB603 engine. Prototype engines will be provided for testing.
.....MG151/20 hub cannon. Prototype weapons will be provided for testing.
.....Bubble canopy. RLM will consider different canopy variants as long as visibility is considerably better then Me-109.
.....Internal fuel at least 600 liters (i.e. 50% more then Me-109). Must be in fuselage tank to facilitate roll rate and increase protection.
.....250kg fuselage hard point. Prototypes will be tested with 300 liter drop tank and 250kg bomb.
.....Wide track landing gear.
.....Estimated airframe production cost no greater then Me-109 production cost +25%.

1939. Luftwaffe single engine fighter competition.
.....Let the chips fall where they may. I am certain at least one contestant will be entered by Messerschmitt.


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## FLYBOYJ (Aug 30, 2013)

Milosh said:


> In 1940 the Bf09 went thro a major redesign > 109E to 109F. A little more effort and the rear vision on the Bf109 could have been improved at that time.


Again easily done, but would have it been worth it. I don't think you realize what it takes to re-tool and set up production lines for a major mod. In any event by 1943 the Messerschmitt factory was flattened, I doubt this effort would have prevented this.


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## silence (Aug 31, 2013)

davebender said:


> DB603 engine mass production projected for 1941.
> 
> Now 1937 RLM can announce a 1939 fighter competition for an aircraft that will succeed or supplement Me-109 in production.
> .....Powered by DB603 engine. Prototype engines will be provided for testing.
> ...



Sounds suspiciously like a Dora-14 or -15!


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## stona (Aug 31, 2013)

Milosh said:


> In 1940 the Bf09 went thro a major redesign > 109E to 109F. A little more effort and the rear vision on the Bf109 could have been improved at that time.
> 
> How many bombs fell on Regensburg and Augsburg in 1940?



They didn't change the rear fuselage apart from, after a few broke, strengthening it, and then by simply riveting some reinforcement strips in place (initially on the outside as a quick fix). I've argued all along that the rear vision could have been improved, but not easily. Lowering the fuselage would need considerably more than "a little more effort" and, importantly, the will to do it.

The F series suffered some serious teething problems. The empennage ripping off at frame 9 wasn't the only problem. There were problems with the tail plane and elevators, skin wrinkling on the wings and at least some cases of the wings separating from the fuselage. Fastening bolts for the wing tips also became loose and the aileron fabric covering had problems. In other words there were issues with just about every single air frame component that was altered. There were other problems with various "new" features. The feed for the MG 151/15 ammunition, positioned in the port wing jammed in flight. This was partially solved in the field by inserting small wooden chocks, but not solved completely until the MG 151/20 became available in mid '41. Pilots liked the centre line cannon, but only when it actually worked. There were also problems with the throttle control which had been redesigned.
Changing anything is a risky business. There is a tendency to assume that any changes (as seen in various armaments threads) are much simpler than they actually were.

Bf 109 F production was held up considerably by the first phase of the Me 210 debacle at Regensburg. Messerschmitt didn't need RAF bombers to slow them down!

Cheers

Steve


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## Milosh (Aug 31, 2013)

FLYBOYJ said:


> Again easily done, but would have it been worth it. I don't think you realize what it takes to re-tool and set up production lines for a major mod. In any event by 1943 the Messerschmitt factory was flattened, I doubt this effort would have prevented this.



Actually I do know what it takes.

The bombing of Augsburg in World War II included one British RAF and two USAAF bombing raids against the German city of Augsburg on 17 April *1942* and 25/26 February *1944*. What are the other dates when the Mtt factories were bombed?


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## FLYBOYJ (Aug 31, 2013)

Milosh said:


> Actually I do know what it takes.
> 
> The bombing of Augsburg in World War II included one British RAF and two USAAF bombing raids against the German city of Augsburg on 17 April *1942* and 25/26 February *1944*. What are the other dates when the Mtt factories were bombed?



Wiener Neustadt - August (2x), October, November 1943

There's more and some by the RAF, I'll have to look them up


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## stona (Aug 31, 2013)

I have just read another example of where a really minor change in specification had severe ramifications for a production aircraft. 
The Westland Whirlwind was originally designed with a shelf for the TR9 radio behind the pilot and under the cockpit canopy. Other equipment in the fuselage would be accessed by removing the upholstered cover from the tubular frame of the pilot's seat. This access was denied when armour behind the seat was introduced. A new rack to hold the TR1133 VHF radio and desert ration packs were introduced in the fuselage and required a large access door to be fitted in the starboard side of the fuselage. You can NOT just cut a hole and fit a door in a stressed skin constructed monocoque! Substantial strengthening of the fuselage structure was required and this had a knock on effect on the first production run. The first twenty five airframes effectively became non-standard prototypes. 
Seemingly minor modifications are nearly always much more difficult than the might appear. We are talking about fitting one access panel/door.
Cheers
Steve


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## davebender (Aug 31, 2013)

Fw-190C (i.e. DB603 variant) would certainly be a contender but there will be others too. 

I would expect something similar to DB603 powered Me-309 in competition. Probably also a larger DB603 powered version of He-100 that looks a lot like the historical Ki-61 (with conventional cooling system). Both would be tough competition for Dr. Tank's design.


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## Milosh (Aug 31, 2013)

FLYBOYJ said:


> In any event by 1943 the Messerschmitt factory was flattened, I doubt this effort would have prevented this.



Wiener-Neustaedter certainly wasn't flattened in 1943 for it went from producing 2200 in 1943 to 3177 in 1944. ERLA went from 2012 to 4472 and MTT Regensburg went from 2164 to 6329.
Volume 14 - Wiener Neustaedter Flugzeugwerke Wiener Neustadt Austria - Page 9 - WWII Archives


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## stona (Aug 31, 2013)

The complex at Regensburg was attacked surprisingly infrequently.
The 8th AF dropped about 7% of its ordnance on ALL aircraft industry targets in Europe. The RAF and 15th AF somewhat less, about 3%. Overall about 4% of total munitions dropped were dropped on the German aircraft industry, about 20,000 tons. 
Nonetheless, according to German sources about 75% of aircraft plants were destroyed or seriously damaged by the 1944 bombing aimed at the industry.
Cheers
Steve


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## swampyankee (Sep 3, 2013)

In addition to the physical damage to the plants, the bombing must have had some detrimental effects on worker productivity because of lack of sleep, worry about coming home to a bomb crater instead of an apartment, having to detour around roads blocked because of building damage, etc.


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## davebender (Sep 3, 2013)

If that were me I'd be outraged the enemy attacked my family in violation of Hague Conventions. Which would make me fight or work even harder to defeat them.


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## Ivan1GFP (Sep 4, 2013)

Pardon me for changing the subject slightly, but it seems like we have a few folks here that are quite knowledgeable about the 109.
Does anyone here have good dimensional drawings for a 109F-109K? I have been looking for locations of frames, widths and height at each station, etc.

Thanks.
- Ivan.


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## stona (Sep 4, 2013)

davebender said:


> If that were me I'd be outraged the enemy attacked my family in violation of Hague Conventions.



Precisely which article of which set of conventions? 

If you defend a town or anything else it becomes a legitimate target. Now you have a ridiculous chicken and egg argument which is futile. 

Cheers

Steve


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## Tante Ju (Sep 4, 2013)

stona said:


> If you defend a town or anything else it becomes a legitimate target.



Precisely which article of which set of conventions?


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## stona (Sep 4, 2013)

In 1907 they were just about anticipating bombers. The 1907 Convention covering Laws and Customs of War on Land, Article 25 states:

"The attack or bombardment, by whatever means, of towns, villages, dwellings, or buildings which are undefended is prohibited."

There was a failure to get ratification of a clause about "the prohibition of the discharge of any kind of projectile or explosive from balloons or by similar means", which was suggested in 1898, extended to include aircraft in 1907. This was because the major powers were not going to sign away their right to try out the new method of bombardment.
It is therefore the article considered legally relevant to bombardment from the air. 

The problem is that as soon as you place an anti aircraft gun or build a flak tower to defend your factories (which are legitimate targets) you are also defending other dwellings and buildings.

It is notable that nobody was ever charged with any war crime related to the bombing of cities at Nuremberg precisely because everyone had done it (including of course the victorious, prosecuting, powers) and the defence would refer to this clause.

Cheers

Steve


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## nuuumannn (Sep 6, 2013)

> If that were me I'd be outraged the enemy attacked my family in violation of Hague Conventions.



The Germans, of course had the right to take the moral high ground over the needless and senseless unprovoked attacking of their sovereign territory....


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## silence (Sep 6, 2013)

nuuumannn said:


> The Germans, of course had the right to take the moral high ground over the needless and senseless unprovoked attacking of their sovereign territory....



Yep


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## Tante Ju (Sep 6, 2013)

stona said:


> In 1907 they were just about anticipating bombers. The 1907 Convention covering Laws and Customs of War on Land, Article 25 states:
> 
> "The attack or bombardment, by whatever means, of towns, villages, dwellings, or buildings which are undefended is prohibited."
> 
> ...


 
There is also Article 27.

_Art. 27. In sieges and bombardments* all necessary steps must be taken to spare, as far as possible, buildings dedicated to religion, art, science, or charitable purposes, historic monuments, hospitals, and places where the sick and wounded are collected, provided they are not being used at the time for military purposes.*
It is the duty of the besieged to indicate the presence of such buildings or places by distinctive and visible signs, which shall be notified to the enemy beforehand.
_


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## stona (Sep 6, 2013)

Tante Ju said:


> There is also Article 27.
> 
> _Art. 27. In sieges and bombardments* all necessary steps must be taken to spare, as far as possible, buildings dedicated to religion, art, science, or charitable purposes, historic monuments, hospitals, and places where the sick and wounded are collected, provided they are not being used at the time for military purposes.*
> It is the duty of the besieged to indicate the presence of such buildings or places by distinctive and visible signs, which shall be notified to the enemy beforehand.
> _



Yes, and that went out the window in WWI as well. Not even hospitals were marked by "distinctive and visible signs" as a rule. Bombing was never accurate enough to specifically avoid such buildings. The 1940 Blitz on London destroyed 16 of the churches built by Sir Christopher Wren after the great fire. Only nine were rebuilt, of three the towers survive, the others are gone forever. It very nearly got the greatest of all his churches (St Paul's Cathedral) too.

Here's a nice picture of Hallsville Junior School in London.







77 bodies were recovered but the number killed in this one school was much higher. Recent estimates suggest that up to 600 people, many children waiting for evacuation, were sheltering in the basement.

I notice that a lot of comments about bombing in WW2 come from people who live in countries that were never subjected to it.

The reasons why area bombing was developed (as opposed to the sort of bombing inflicted on Rotterdam which was purely to intimidate the population) has been done to death both here and elsewhere.

Cheers

Steve


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## Tante Ju (Sep 6, 2013)

stona said:


> The reasons why area bombing was developed (as opposed to the sort of bombing inflicted on Rotterdam which was purely to intimidate the population) has been done to death both here and elsewhere.



You see things upside down but thats not the topic of the thread.


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## stona (Sep 6, 2013)

Tante Ju said:


> You see things upside down but thats not the topic of the thread.



Why do you think that the Luftwaffe attacked Rotterdam ? They dropped less than 100 tons of bombs but managed to kill nearly 900 civilians and destroy 24,978 homes, 24 churches and 62 schools. So much for Article 27. 
It worked, the Dutch surrendered, they were trying to before the bombs fell.

It's not a question of who did what first. I couldn't care less. This was the way that aerial bombing was going to go. The Germans reaped the whirlwind.

War really is hell. It's a lesson that we all seem incapable of learning.

Cheers

Steve


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## Tante Ju (Sep 6, 2013)

stona said:


> Why do you think that the Luftwaffe attacked Rotterdam ?



The city was under siege and the Luftwaffe provided close support bombardment for the impeding German Army attack after the garrison refused to surrender.

Just like RAF Bomber Command did at Caen etc.

Again not the subject of the thread.


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## nuuumannn (Sep 6, 2013)

> The city was under siege and the Luftwaffe provided close support bombardment for the impeding German Army attack after the garrison refused to surrender.



No, the correct answer is that the German armed forces invaded the Netherlands, and yes, not the subject of the thread. Probably a good idea to get back on topic. 

So, the Bf 109; small, potent fighter that lived far longer than its designers envisaged and proved an enormously successful design, long after it had reached obsolescence. Not being an expert on the '109, but an interested party, when looking over the different variations and modifications, I find it interesting to note the actual modifications that were carried out in comparison to what we have discussed here. They weren't as substantial as we might have done (obviously). Yes, there were recontoured nose, revised armament and modified wings between the first production examples and the last, but the big changes that were made were to armament and of course to powerplant throughout its career and latterly the tail section in later models as a result of wartime expediency - in German hands that is. Obviously the Czech and Spanish derivatives had more alteration outside of what Messerschmitt could have done - again out of expediency compared to the original Gustav, but even then the changes were not structural and only the Czechs saw to substantial changes to the canopy.


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## stona (Sep 6, 2013)

Tante Ju said:


> The city was under siege and the Luftwaffe provided close support bombardment for the impeding German Army attack after the garrison refused to surrender.



Close bombardment of the city centre, almost, they just missed. Schmidt threatened the destruction of the city centre in an attempt to convince the Dutch to surrender, he did not specify how he would do this. I'm sure those 900 Dutch people would have appreciated the niceties of having their city centre flattened in support of an assault rather than to force a surrender.

Caen was more than four years later, we were living in a different world.

Cheers

Steve


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## Tante Ju (Sep 6, 2013)

stona said:


> Close bombardment of the city centre, almost, they just missed.



Exactly. Rotterdam city centre is actually about _500 _meters from where the Dutch and German troops were fighting over a bridge and a couple of hundred meters perhaps from the river bank. The Dutch held the area north of the river, the Germans planned an assault with paratroopers flanking somewhere around that bridge.

The centre burned out as a result of the fires ignited by the something like 50 bombers that performed the bombing from as low a 700 meter altitude, severing gas lines and igniting large vegetable oil tanks in the docksides.


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## stona (Sep 6, 2013)

I'm sure those Dutch civilians would appreciate the explanation 
Steve


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## Tante Ju (Sep 6, 2013)

Well the discussion on that started with you arguing that the Germans could happily bomb and/or machinegun/barrage them to bits, since the town was defended, so... 

I am sure Dutch civillians did not give a _neuken _ about wheter it was the German, Dutch, British or American Army or Air force wrecking their homes to bits.


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## stona (Sep 7, 2013)

To return to the original topic, sort of, I think the saga of the Hawker Typhoon canopy illustrates just how hard it can be to modify an aircraft for a different canopy and better rear vision.
The prototype Typhoon (and early production) looked like this.






The rear vision was terrible and was quickly flagged as a problem. An initial solution was some rear quarter lights. Due to the structure of the air frame, which I have no intention of explaining here, the skins in the area behind the cockpit were stressed. It was thought that a small quarter light might be an adequate solution in the short term.






On 9th May 1940 the prototype suffered a serious structural faiiure of the rear fuselage. Whilst not a definitive cause the quarter lights were considered as possibly having contributed to this. 






As a result the entire rear fuselage was redesigned to allow a better clear view canopy. It was NINE MONTHS before this appeared in production aircraft.






In the mean time a thicker and stronger quarter light was fitted as a temporary measure.

It was January 1943 before the single piece sliding hood was introduced as the ultimate refinement.

I keep saying that there is a tendency for many here to underestimate the consequences of modifications to aircraft, particularly those already in production. Even the smallest changes can have serious ramifications, both for the aircraft and production schedules.

You can't "just" do anything to a production WW2 fighter 

Cheers

Steve


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## Milosh (Sep 7, 2013)

P-47, P-51 and Spitfire afaik had no structural problems when the bubble canopy was fitted.


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## stona (Sep 7, 2013)

Milosh said:


> P-47, P-51 and Spitfire afaik had no structural problems when the bubble canopy was fitted.



The Spitfire was a relatively simple alteration structurally. I don't know enough about the P-51's construction to make an informed comment. For many aircraft it was not a simple matter, the argument I made regarding the Bf 109 previously.
It all depends how the airframe is constructed and stressed. I know why it was such a problem for the Typhoon, but really don't have the time or will to explain it here. The facts are that it entailed major structural alterations and took nine months to reach production aircraft.
The Typhoon also illustrates that such changes CAN be made, even when they entail considerable modifications. The problem for the Germans and the Bf 109 was that they didn't have the time to even explore, never mind undertake, such a task.
Cheers
Steve


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## swampyankee (Sep 7, 2013)

Milosh said:


> P-47, P-51 and Spitfire afaik had no structural problems when the bubble canopy was fitted.



Perhaps, but the P-51 did have stability issues, due to reduced keel area aft of the c/g, after the bubble canopy was installed.


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## spicmart (Sep 7, 2013)

The Germans tried to make a wooden wing that could house the MK 108 plus ammo. This was a failure.
Why didn't they do it with the normal metal wings?


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## Milosh (Sep 7, 2013)

swampyankee said:


> Perhaps, but the P-51 did have stability issues, due to reduced keel area aft of the c/g, after the bubble canopy was installed.



That would be the P-51D/K but the razor back P-51B/C also had the same problem.


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## wuzak (Sep 7, 2013)

swampyankee said:


> Perhaps, but the P-51 did have stability issues, due to reduced keel area aft of the c/g, after the bubble canopy was installed.


 


Milosh said:


> That would be the P-51D/K but the razor back P-51B/C also had the same problem.



It seems that the stability issues stemmed from the more powerful engine (Merlin 60-series vs Allison single stage) and the 4 blade prop. Teh stability issue wasn't solved until the -H, which had a larger fin and rudder.


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## Milosh (Sep 7, 2013)

wuzak said:


> It seems that the stability issues stemmed from the more powerful engine (Merlin 60-series vs Allison single stage) and the 4 blade prop. Teh stability issue wasn't solved until the -H, which had a larger fin and rudder.



The H also had the rear fuselage lengthened.


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## Aozora (Sep 7, 2013)

swampyankee said:


> Perhaps, but the P-51 did have stability issues, due to reduced keel area aft of the c/g, after the bubble canopy was installed.



Much of the reduced stability was due to the introduction of the fuselage fuel tank, rather than a reduction in keel area. If anything the removal of the "razorback" structure probably meant that the total structural weight aft of the cg was reduced, and the structure itself made stronger because it became more of an oval monocoque.


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## swampyankee (Sep 7, 2013)

The P-51D had yaw stability issues, which were worsened, of course, in aft c/g conditions.


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## nuuumannn (Sep 7, 2013)

This is why the dorsal fin was fitted to the 'D; the earliest production ones didn't have it. in relation to the Bf 109, it'd be wise to enlarge the fin, rudder assy and if necessary fit a dorsal fin.


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## GregP (Sep 8, 2013)

Wasn't necessary. It was only necessary to get there. Then the P-51 was more than capable of dealing with a Bf 109 since any aft CG condition was gone by the time it got there.


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## stona (Sep 8, 2013)

GregP said:


> Wasn't necessary. It was only necessary to get there. Then the P-51 was more than capable of dealing with a Bf 109 since any aft CG condition was gone by the time it got there.



This was true in the tactical situation that existed in the ETO at the time. Elsewhere, or at a different time, it might have been a serious problem.

It is hardly a desirable feature in any aircraft.

Cheers
Steve


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## nuuumannn (Sep 8, 2013)

> It is hardly a desirable feature in any aircraft.



Yep, otherwise, if the fin fillet wasn't necessary, why did NAA add it, then go to the lengths of changing the P-51H's fin area?

I wrote


> in relation to the Bf 109, it'd be wise to enlarge the fin, rudder assy and if necessary fit a dorsal fin.



and I meant that the Bf 109 would need increased fin area; as it was its fin and rudder was too small and this was altered on later variants.


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## GregP (Sep 8, 2013)

What I meant to say was enlargement of the tail wasns't necessary, not the presence of the dorsal fin. That "fix" was added even to razorback P-51's. A larger tail wasn't necessary once the fuselage tank was burned off. The P-51 with the dorsal fin flies just fine.

As for not being desireable, you get a choice ... shorter range and good flying characteristics or longer range with some lateral instability until the fuel burns off. If you need the range, the choice isn't there and you go with it. In the real war, there wasn't any better escort fighter anywhere in the world. Wanting the aft CG condition to magically "go away" wasn't possible, so I don't get what is being said.

Ensuring the condition gets addressed as quickly as possible by burining the fuselage tank first seems to be quite a reasonable tradeoff. If combat is anticipated right after takeoff, then you'll be fighting a much shorter war and you simply don't fill the fuselage tanks.


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## drgondog (Sep 8, 2013)

NAA was aware of the yaw stability issues with the B/C. The also experimented with "H" style tall vertical stabilizer but it wasn't sufficient improvement. This was clarified when the D-5 was on the production line and the dorsal fin mod was designed as field kit for B/C and installed on the D-10.

It did improve (slightly) the high speed yaw but no discernible improvement to aft cg problem. Only lengthening the fuselage of the H by ~13 inches and reducing the fuselage tank from 85 to 50 gallons solved the problem. Much focus has been placed on the reduction of the turtleback when the D was designed but subsequent experience showed that was not the issue.

The root of the issue was the increased HP and torque of the Merlin with insufficient Vert stab and horizontal stab authority to compensate - which led to subtle design changes to horizontal stab incidence as well as the taller tail and lengthened fuselage for the H.


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## GregP (Sep 8, 2013)

Just to make sure this is clear, some pics below of the P-51 models with and without the small dorsal fin just at the front of the vertical tail. Here's a pic of the B/C without the dorsal fin.







Here's a pic of the P-51B with the dorsal fin.






Here's a P-51D without the dorsal fin.






And, finally, the P-51D with the dorsal fin.


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## stona (Sep 8, 2013)

Didn't the P-47 get a fillet as well as some point?
Cheers
Steve


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## drgondog (Sep 8, 2013)

stona said:


> Didn't the P-47 get a fillet as well as some point?
> Cheers
> Steve



Yes P-47D as well as P-47N


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## Ivan1GFP (Sep 9, 2013)

I think there is a bit of confusion here. The P-51 always had a directional (yaw) stability issue at least as far back as the B model. The problem became worse with the reduced keel area on the bubbletop (D/K) models. The solution to DIRECTIONAL stability was the fin fillet. This improved things but didn't really completely solve the problem.

The fuselage fuel tank didn't really add to the directional stability problem. The aft CoG condition resulted in a LONGITUDINAL stability issue. In other words, with even a partially filled fuselage tank, the aircraft would tend to wander a bit vertically.

These are two separate problems.

- Ivan.


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## Ivan1GFP (Sep 9, 2013)

drgondog said:


> Yes P-47D as well as P-47N



I believe the P-47D-30 was the first to come from the factory with a fin fillet. They were also retrofitted to earlier aircraft though.

- Ivan.


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## GregP (Sep 9, 2013)

CG too far aft is ALWAYS a pitch issue, but can turn into a yaw issue if it starts spinning after the departure!


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## Aozora (Sep 10, 2013)

One other change associated with the dorsal fin fillet was that the rudder trim tabs had a reverse boost linkage installed, although I don't know what effect that had.

I'm also pretty sure that the incidence on the P-51B/C/D/K tailplanes was increased and the elevators reskinned in duralumin to help alleviate the problem with longitudinal instability with the full fuselage tank, but I'll have to check Gruenhagen to be sure of the facts.


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## drgondog (Sep 10, 2013)

Ivan1GFP said:


> I think there is a bit of confusion here. The P-51 always had a directional (yaw) stability issue at least as far back as the B model. The problem became worse with the reduced keel area on the bubbletop (D/K) models.
> 
> *It was originally believed that the loss of the turtledeck on the P-51D-5 was the problem. It was not. The first dorsal fin was installed on 44-13902 in the last stage of the P-51D-5 block, running through end of production for all Mustangs - but the kits were developed and installed on all operational P-51B/C's in the field to assist with reducing yaw issues at high speed... and did as you say, help but not solve*
> 
> ...



The instability arising from aft cg contribution, coupled with increased torque of the merlin engine, coupled with control responses necessary to fly the airplane increased Both pith And yaw issues contributing to a.) loss of control (i.e. Snap roll and subsequent departures and b.) subsequent structural failure of the empennage.

The were several fatal accidents traced back to pitch and yaw coupling due to the aft cg - but slow rolls and snap rolls with full control authority also caused similar structural failures.


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## bobbysocks (Sep 10, 2013)

i have read the structural failures of the empennage but have never seen it exactly described as to what the failure was. was it a bend, break, twist, loss of structure ... the like rudder, elevator, trim tab, etc. ??


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## drgondog (Sep 11, 2013)

Bending/torsion failure for the slow roll issue. The 51 had excellent rudder response with average pedal force - easy to really crank it, so unexpected results when trying to reduce the yaw in a near terminal dive resulted in too large forces on rudder and hence to the aft fuselage/empennage. That is why the reverse boost on trim tab was installed - to make it harder to overpower the rudder.

I a slow roll, you have rudder and elevator forces controlling the airplane for asymmetric flight loads - again creating additional torsion in the aft fuselage.


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