# Fw-190: the roots of the great roll rate?



## tomo pauk (Nov 7, 2012)

The Fw-190 was acclaimed as the plane with a great rate of roll. Why was it able to achieve that?


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## spicmart (Nov 7, 2012)

Sturdier, stiffer wings compared to other contemporaries; rod controlled ailerons that have no fabric but metal cover; small wing area. These are some things that come to mind.


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## Siegfried (Nov 7, 2012)

The Fw 190 had two spars that meant that the wing didn't twist from aileron forces which tended to cause control reversal from aeroelastic twist. The Spitfire with its single main spar suffered somewhat from this.

The wing tips were quite thin which reduced stiffening at high speed.

Friese ailerons reduced aerodynamic forces.


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## drgondog (Nov 7, 2012)

The FW 190 Did suffer twist/aeroelastic torsion in high G/High AoA manuevers. Two features contributed to this.
1. Large effective ailerons
2. Zero washout from 80% semi span to tip. At normal increasing AoA the lift Distribution was primarilt on the inner 40% (like a level wing approach/stall). But under high G/High AoA, the outer panel started to bend/twist and the lift distribution was shifted from inboard to outboard and the wing, then tended to stall completely at the high AoA rather than Inboard ----> Outboard progression .

Gross, P. "Die Entwickland Tragwerkkonstruction Fw 190 -Bericht 176 der Lillenthall-Gesellshaft 2 Tiel, January, 1944"


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## Siegfried (Nov 7, 2012)

Of course all aircraft have aero-elasticity, in the case of the Fw 190 the twin spar wing box ensured relatively high torsional rigidity and therefore a high theoretical reversal speed; this being the speed the aileron imposed forces would roll the aircraft in the opposit direction.

However there was a downside in that under high g the wing would twist so as to increase the angle of attack and therefore induce a premature tip stall with limited warning. Recovery was however immediate as the wing returned to shape. A single spar wing might twist so as to reduce AOA and so did no suffer from this issue.

Ta 152 had a new wing structure, at least in the Ta 152h aileron control might be maintained post stall due to high 3 degree washout. There may have been other issues such as inertia cross coupling since the long nosed version lost roll rate.

Thanks for the citation.

Several US aircraft had good roll rates. P40, the P63, P51B onwards (only at high speed). High P47 roll rate was a myth.

The thick laminar flow wings allowed a stiff structure and internal pressure balancing to reduce pilot forces.


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## GregP (Nov 8, 2012)

I think the Fw 190 also had great aileron gap seals, making the air flow over the aileron, rather than around it, better than other fighters.

Gap seals are a BIG factor in roll rate.


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## CobberKane (Nov 8, 2012)

USN tests found that the Hellcat and Corsair could both roll with the 190, although they noted that the the 190 was more nuetral and easily controlled


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## Siegfried (Nov 8, 2012)

CobberKane said:


> USN tests found that the Hellcat and Corsair could both roll with the 190, although they noted that the the 190 was more nuetral and easily controlled



If it is the test I am thinking of it also noted that during high speed turns that the Fw 190s aileron Flutter was so severe that the vibration started to push the pilot into unconsciousness.

This was in no way normal and indicates improperly rigged ailerons, which were a hard to setup due to the 190s pushrod system. Hence I would argue that the comparisons are not valid.

Late war Corsairs and Hellcats received geared spring tabs that improved high speed roll rate at the expense of low speed.


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## FLYBOYJ (Nov 8, 2012)

Siegfried said:


> If it is the test I am thinking of it also noted that during high speed turns that the Fw 190s aileron Flutter was so severe that *the vibration started to push the pilot into unconsciousness.*This was in no way normal and *indicates improperly rigged ailerons*, which were a hard to setup due to the 190s pushrod system. Hence I would argue that the comparisons are not valid.
> 
> Late war Corsairs and Hellcats received geared spring tabs that improved high speed roll rate at the expense of low speed.



With regards to rigging ailerons (and this is across the board) improperly rigged ailerons (deflection angles) will not flutter, rather give you varied turn rates and may cause the aircraft to fly "one wing low." Aileron flutter is usually associated with improper balance or "play" within in the control circuit (in the case of cables, under tension, in the case of pushrods, loose or worn rod end bearings).

As far as the statement about "pushing the pilot into a state of unconsciousness." I'd like to see that report - if true; I think this statement is a bit exaggerated. If you're flying an aircraft that is experiencing aileron flutter that hard that you're blacking out, chances are other parts of the aircraft already self destructed.


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## Thorlifter (Nov 8, 2012)

Very interesting thread. I only understand about 25% of it, but it's very interesting. I'm not trying to hijack the thread but was just wondering if WWI planes experienced the same effects. My complete guess is yes, but at a reduced effect due to much lower speeds.


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## drgondog (Nov 8, 2012)

Siegfried said:


> Of course all aircraft have aero-elasticity, in the case of the Fw 190 the twin spar wing box ensured relatively high torsional rigidity and therefore a high theoretical reversal speed; this being the speed the aileron imposed forces would roll the aircraft in the opposit direction.
> 
> *No particular design philosophy guarantees high torsional rigidity. True a twin spar box is a sound approach, but depending on the mass distribution, Spar spanwise moment of inertia qualities and the surface skin thikness - such design may not have better torsional rigity of say a single main spar design with reinforced leading edge and aft spar upon which the flap is attched.
> 
> ...



"High P-47 roll rate is a myth" If referring to NACA 868 it only illustrates the P-47C-1. Even so it was superior to all then existant USN and USAAF fighters except for P-63, XP-51 (<320mph) and P-40.

A 'thick wing' in context of max T greater than comparable wing sections for a 'thinner wing' in absolute dimensions does offer some advantages on increased spar section Moment of intertia versus comparable 'shorter' beam with same web and cap material thickness. Note that the 'thinner' Spitfire wing had nearly the same absolute 'thickness' 'tallness', etc as the Mustang but the Spit spar was at ~ 25% chord and the P-51 was closer to 40% - 

The Spit wing was 'thinner' (in ration to T/C) simply because the chord was so much greater than the P-51.


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## drgondog (Nov 8, 2012)

One other note about flutter. Even if properly rigged, resonance may occur at different flight speeds - causing the control surface to flutter.


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## GregP (Nov 8, 2012)

I have never seen any report claiming the Hellcat and Corsair could roll with an Fw 190, but have seen MANY rep[orts claiming the Fw 190 was superior at roll to everything it came against.

Maybe a link to the report in question so we can read it?


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## FLYBOYJ (Nov 8, 2012)

drgondog said:


> One other note about flutter. Even if properly rigged, resonance may occur at different flight speeds - causing the control surface to flutter.


True Bill, but I think for the most case this will be more like a "buzz" at the stick.


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## MikeGazdik (Nov 8, 2012)

Did the FW190 roll well at certain speeds, such as in the Zero only at lower speeds, or was across the board? I understand the Mustang rolled well at speed, and have read the Thunderbolt too. From reading I know the Corsair rolled well, but was it also across the the speed envelope? I knew the P-40 rolled well. Its news to me the P-63 rolled well, but I'm good with that!


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## drgondog (Nov 8, 2012)

MikeGazdik said:


> Did the FW190 roll well at certain speeds, such as in the Zero only at lower speeds, or was across the board? I understand the Mustang rolled well at speed, and have read the Thunderbolt too. From reading I know the Corsair rolled well, but was it also across the the speed envelope? I knew the P-40 rolled well. Its news to me the P-63 rolled well, but I'm good with that!



Google "NACA 868" to get a 1943 persective regarding comparisons..


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## Edgar Brooks (Nov 8, 2012)

Siegfried said:


> The Fw 190 had two spars that meant that the wing didn't twist from aileron forces which tended to cause control reversal from aeroelastic twist. The Spitfire with its single main spar suffered somewhat from this.
> Friese ailerons reduced aerodynamic forces.


How many more times must we refute this nonsense; the Spitfire had a mainspar, attached to frame 5 (the firewall,) and a rear spar (to which the flaps and ailerons were attached) attached to frame 10 (the former under the pilot's seat.) It also had Frise ailerons, and the early Mk.I, with fabric-covered ailerons, had an aileron reversal speed (calculated and corrected in 1942) of Mach .74


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## cimmex (Nov 8, 2012)

Didn’t all WWII planes had a rear spar to attach the flaps and ailerons? Please name a plane with a single spar wing. The Spanish Buchon which is currently going restoration at Meier Motors in Germany had a two spar wing or when you count the rear and front spar also then it is a four spar wing.
Cimmex


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## Tante Ju (Nov 8, 2012)

The rear is only an auxilary spar on both the Spitfire and the 109. It isn't really capable of transversing loads. On the Spitfire the front, relatively thick D-seck of the wing - a legacy of the early evaporative cooling - and the main (centre) spar formed a D-shaped box, which was probably while the design had a tendency for wing flexing under aileron load. The 109 had a box spar design, where the main spar and the thick skin of the wing formed a torsion box.


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## FLYBOYJ (Nov 8, 2012)




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## FLYBOYJ (Nov 8, 2012)

Tante Ju said:


> The rear is only an auxilary spar on both the Spitfire and the 109. *It isn't really capable of transversing loads*. On the Spitfire the front, relatively thick D-seck of the wing - a legacy of the early evaporative cooling - and the main (centre) spar formed a D-shaped box, which was probably while the design had a tendency for wing flexing under aileron load. The 109 had a box spar design, where the main spar and the thick skin of the wing formed a torsion box.



Do you have evidence of that?


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## Tante Ju (Nov 8, 2012)

You may notice that the rear "spar" on this more accurate drawing is hardly more than a very thin aluminium piece, sufficient to attach control surfaces to. Compare it to the actual main spar, which was massive piece of entirely different construction.

That, plus the fact that the aircraft had a rather low aileron revarsal speed due to wing twist, as noted in NACA 868. This indicates lack of stiffness, which is logical if all your main load bearing elements are in/very near to the leading edge of the wing (i.e. the main spar and the D-box) and you have next to nothing in the back. The wing could handle normal accelerations well, but not wing twist.


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## FLYBOYJ (Nov 8, 2012)

Tante Ju said:


> You may notice that the rear "spar" on this more accurate drawing is hardly more than *a very thin aluminium piece*, sufficient to attach control surfaces to. Compare it to the actual main spar, which was massive piece of entirely different construction.
> 
> That, plus the fact that the aircraft had a rather low aileron revarsal speed due to wing twist, as noted in NACA 868. This indicates lack of stiffness, which is logical if all your main load bearing elements are in/very near to the leading edge of the wing (i.e. the main spar and the D-box) and you have next to nothing in the back. The wing could handle normal accelerations well, but not wing twist.



Your basing this on what you see on the drawing. Do you have a size of the rear spar? I know many aircraft whos main spar is no thicker than .030, but when built up into the wing with a spar cap carries a good portion of the load. If there is supporting structure attached to it, it is obvious if carries a load. It is also obvious that it is NOT the primary load carrying structure of the wing, but it does carry a load and by all accounts, it is a "spar" by definition.


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## tomo pauk (Nov 8, 2012)

Roll rate comparison chart:

http://www.wwiiaircraftperformance.org/naca868-rollchart.jpg


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## cimmex (Nov 8, 2012)

FLYBOYJ said:


> Your basing this on what you see on the drawing. Do you have a size of the rear spar? I know many aircraft whos main spar is no thicker than .030, but when built up into the wing with a spar cap carries a good portion of the load. If there is supporting structure attached to it, it is obvious if carries a load. It is also obvious that it is NOT the primary load carrying structure of the wing, but it does carry a load and by all accounts, it is a "spar" by definition.


Definition by whom?-and why were all other wings (eg at German, Bf 109) with the same construction named one spar wing. Being confused now.
Cimmex


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## Tante Ju (Nov 8, 2012)

FLYBOYJ said:


> Your basing this on what you see on the drawing. Do you have a size of the rear spar? I know many aircraft whos main spar is no thicker than .030, but when built up into the wing with a spar cap carries a good portion of the load. If there is supporting structure attached to it, it is obvious if carries a load. It is also obvious that it is NOT the primary load carrying structure of the wing, but it does carry a load and by all accounts, it is a "spar" by definition.



Yes I was going by this drawing. I also think that we basically agree with you - what I meant that it is not a primary load carryinng element in the wing, which is my definition for a two spar design, where both spars contribute to a significant amount to the load carrying. Of course the rear spar also carries some of the load, but my guess that this contribution is not significant, since in these WW2 fighters this is also true to just about any part of the structure. The skin, ribs etc. also carried loads. In short, we seem to argue semantics.


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## FLYBOYJ (Nov 8, 2012)

cimmex said:


> Definition by whom?-and why were all other wings (eg at German, Bf 109) with the same construction named one spar wing. Being confused now.
> Cimmex



I could name at least 2 dozen books such as "Stick and Rudder" (Wolfgang Langewiesche) FAA Advisory Circular AC43.13, Aircraft Structures for Engineering Students (Cutler) that defines a "spar" as (in so many words) *"A structural member of the wing, running spanwise at right angles to the fuselage."* Some German engineers may have thought that because ONE spar carried the main load the wing in question had ONE spar.


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## FLYBOYJ (Nov 8, 2012)

Tante Ju said:


> Yes I was going by this drawing. I also think that we basically agree with you - what I meant that it is not a primary load carryinng element in the wing, which is my definition for a two spar design, where both spars contribute to a significant amount to the load carrying. Of course the rear spar also carries some of the load, but my guess that this contribution is not significant, since in these WW2 fighters this is also true to just about any part of the structure. The skin, ribs etc. also carried loads. In short, we seem to argue semantics.


Agree as well. Bottom line, there is NOT one spar in a Spitfire wing. One spar may carry the majority of the load, but by basic definition, the wing has two spars.


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## cimmex (Nov 8, 2012)

So the conclusion is, there is no one spar wing...
Cimmex


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## FLYBOYJ (Nov 8, 2012)

cimmex said:


> So the conclusion is, there is no one spar wing...
> Cimmex




Not necessarily - I could see a one spar wing with a series of stringers taking up part of the structural load and giving shape to the airfoil. In today's world many gliders have one spar


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## Edgar Brooks (Nov 8, 2012)

Tante Ju said:


> You may notice that the rear "spar" on this more accurate drawing is hardly more than a very thin aluminium piece, sufficient to attach control surfaces to.


It's also substantial enough for the rear of every wing rib to be attached to it, and the wing covering to be rivetted to it, as well. Your "very thin aluminium piece" was strong enough to remain rigid, and hold the flaps and ailerons in place, without bending, or causing them to bind. It helped the wing to retain its integrity so that it could turn inside the 190 109, and still have the gentle stall warning so beloved by Spitfire pilots.


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## Shortround6 (Nov 8, 2012)

Probably not in WW II fighters although some one may find one. Some light planes use a "false" spar to hang ailerons and/or flaps from. The false spar may run across a number of ribs but is not connected to the fuselage or loads are not carried into/through the fuselage.

This may be the dividing point. The main spar may handle 51-99% of the load with the "rear" spar handling 49-1% of the load. Without knowing the designers intent or calculations (wing rib numbers/strength/spacing + wing skin strength + any spanwise stringers + any cross braces it is a little hard to figure out just what the rear spar is doing on most aircraft. If it is connected to a fuselage frame or carried through to the other side you have to assume it is doing something. If it stops at the wing root fillet or before then you can assume it is just a mounting point for movable surfaces although it may help resist twisting a bit. 

Trying to eyeball load carrying ability from a small two dimensional sketch and reach a valid conclusion in 3 dimensional reality is almost impossible.

Which can carry more load or resist twisting better a 1 x 4 X 12 ft piece of wood or a 1 x 6 x 12 ft piece of wood. Both look the same from the top.


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## spicmart (Nov 8, 2012)

Afaik the Ta 152, both short and long wrong versions, had a shortened front wing spar (to accommodate additional fuel tanks? ) afaik. Wonder if with this new wing structure the Tas (short wing) could retain the roll rate.
The late Doras were supposed to have the original fuel tank also, but I've seen an illustration with these tank together with the normal long front spar.


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## tomo pauk (Nov 8, 2012)

Until someone comes up with something better (from Spit XIVE):


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## tomo pauk (Nov 8, 2012)

Take your time to discern the rear spar in the upper picture. In the meantime, the main spar seem like a bulletproof item ,at least the upper lower beams.


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## Edgar Brooks (Nov 8, 2012)

tomo pauk said:


> Take your time to discern the rear spar in the upper picture. In the meantime, the main spar seem like a bulletproof item ,at least the upper lower beams.


Try this photo, instead; you'll find it's the "wafer-thin" item, heading slightly diagonally downwards, to which all the wingribs are attached, at their rears.


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## Juha (Nov 8, 2012)

As I have understood it, at least in late 30s and early 40s single spar design meant a wing which main torsional box was formed by a heavy main/front spar and the skin between it and the leading edge and in a two spar wing the main torsional box was formed by a front and a rear spars and the skins between them. Look Morgan's and Shacklady's or Price's Spitfire books, IIRC in those they say that Spitfire had a single spar wing, and at least here in Finland we say that 109 also had single spar wing even if both had a lighter rear spar.

Juha


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## Juha (Nov 8, 2012)

Hello Edgar
an excellent photo, it also shows the normal situation in the photos on the structure of Spit's wing, one can see the inner structure of the wing behind the main spar but not inside the D shaped torsional box which integrity was weakened only by a few handholes and the holes for the muzzles and barrels of the armament.

Juha


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## CobberKane (Nov 8, 2012)

GregP said:


> I have never seen any report claiming the Hellcat and Corsair could roll with an Fw 190, but have seen MANY rep[orts claiming the Fw 190 was superior at roll to everything it came against.
> 
> Maybe a link to the report in question so we can read it?


 
As is so often the case, I can't find it! But its a fairly well known flight comparison - can anyone else help. 
My recollection is that the 190 was a Fw190A-5 paseed on by the British. It was found to be a bit better than the Hellcat and bout equal to the Corsair, althogh all the pilots said they would refer the American fighters in actual combat. Both outurned the 190 easily and matched it in roll rate though the 190 was praised for the ease whith wich it rolled in either direction. The 190 generally outclimbed and out accellerated the F4F.


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## CobberKane (Nov 8, 2012)

Found it!

http://www.wwiiaircraftperformance.org/fw190/ptr-1107.pdf

an my memeory was off- the Corsair rolled with the Fw190 but the Hellcat could not


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## tomo pauk (Nov 9, 2012)

Photo 1: rear spar (among other items), slightly damaged bent. 
Drawing (Seafire): the spars are within the red ellipses, the item marked with arrow attaches to the main spar's lower beam
Photo 2: attachment point for the rear spar should be somewhere, there...?
Photo 3: attachment point/area for the front spar - looks like it means business.

So maybe it is not a 99:1 between the load ratios of the front and rear spar; 90:10?


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## Edgar Brooks (Nov 9, 2012)

Juha said:


> As I have understood it, at least in late 30s and early 40s single spar design meant a wing which main torsional box was formed by a heavy main/front spar and the skin between it and the leading edge and in a two spar wing the main torsional box was formed by a front and a rear spars and the skins between them. Look Morgan's and Shacklady's or Price's Spitfire books, IIRC in those they say that Spitfire had a single spar wing, and at least here in Finland we say that 109 also had single spar wing even if both had a lighter rear spar.


And therein lies the problem, since (for whatever reason) experts call it a single-spar wing (and I've only ever seen that description in a 1940s "Flight" magazine,) others, less knowledgeable, read it, don't bother to do any research worthy of the name, and trumpet this "The Spitfire only had one spar" stuff, as an explanation for its alleged inferior performance, when we know that there were other factors involved, as well.
During tests, in 1940, RAF pilots found that, when flying the 109, they were capable of withstanding more G than in the Spitfire and Hurricane, and realised that it was due to the straight-out leg position of the 109 cockpit, which delayed the onset of blacking out, since the blood was slower to drain into the lower legs. (Very) late in 1940 this led to the two-bar rudder pedals, in both of our fighters, allowing the pilots to raise their feet for combat, and lower them for normal flight.
Pre-war, the Spitfire was built to withstand 10G, and, even before the war started, work was put in hand to increase it to 12G (the Hurricane was already at that stage, at least once it had all-metal wings,) mainly by increasing the strength of the main spar by use of better quality duralumin.


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## FLYBOYJ (Nov 9, 2012)

Edgar Brooks said:


> And therein lies the problem, since (for whatever reason) experts call it a single-spar wing (and I've only ever seen that description in a 1940s "Flight" magazine,) others, less knowledgeable, read it, don't bother to do any research worthy of the name, and trumpet this "The Spitfire only had one spar" stuff, as an explanation for its alleged inferior performance, when we know that there were other factors involved, as well.



BINGO!

I wonder if there are any stress analysis reports that show how much of the wing load the rear spar actually carries on the Spitfire.


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## drgondog (Nov 9, 2012)

Joe - I would have a hard time believing that a.) the entire wing from aft 'flap spar' to leading edge was Not considered in torque box analysis, and b.) that the first approach in the airframe structures analysis was Not to look at primary spar/cap construction as primary Bending (pure distributed load bending from cantilever support..

The second comment is that airframe structures guys usually take a conservative first pass at stress analysis - 

The wild card for the Spit is that the wheelwell 'interrupts' the torque box integrity aft of the main spar.. From past experience I probably would take a look at the torque box resistance by considering only the 'box section' outboard of the wheel attach point and look hard at the torsion created by the aileron (and some % of lift distribution outboard of wheel well) to determine what the initial deflections could be. I would look at the load paths required to transfer the torque to the inner wing, and thence to the wing attach structure.

As to the flap spar. It has to have significant structural properties because a.) it must act as primary strength member to introduce flap loads to the wing, b.) it is a secondary but important contributor to the 'aft' torque box in which the wheel well is buried, and c.) it is primary bending structure to take out the vertical loads induced by the aileron.


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## FLYBOYJ (Nov 9, 2012)

drgondog said:


> Joe - I would have a hard time believing that a.) the entire wing from aft 'flap spar' to leading edge was Not considered in torque box analysis



Exactly Bill. Somewhere I would think someone considered this in the over-all analysis no matter how less "robust" (for a better description) the rear spar is when compared to the forward spar.

Another interesting angle to look at is within the maintenance manuals - I wonder if in a structural repair manual are there repair limits addressed with regards to the rear spar. If there are limitations on repairs, their size, ect, that would be the smoking gun to show that this component was considered in the torque box analysis. (I'm thinking like a mechanic now)


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## drgondog (Nov 9, 2012)

You're thinking like a structures engineer that took the time to emphasize the "do not poke holes here' instructions to Maintainers.. lol


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## FLYBOYJ (Nov 9, 2012)

drgondog said:


> You're thinking like a structures engineer that took the time to emphasize the "do not poke holes here' instructions to Maintainers.. lol



You're right, LOL!


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## Edgar Brooks (Nov 9, 2012)

Mid-1940 two wings were tested to destruction, and found to resist a factor (G?) of 11-13 (when the design called for 8-10,) tested to an all-up weight of 6,200lbs; the test report is 17 pages, so there's no way that I can put it on here. 
In February 1940, an instruction was issued, with regard to examination for skin wrinkling, after any "abnormal manouevres." Any wrinkling, at all, on the leading edge, forward of the mainspar, would lead to the wing being declared unserviceable, and due for replacement. Aft of the mainspar, between ribs 14-19, any wrinkle less than 1/10" (2.5mm) could be disregarded; any wrinkle deeper than that (or wrinkles of any depth in any other area of the wing) would necessitate examination of the wingroot bolts, and, if they were bent, wing and bolts were to be replaced.
There is a manual, on repairs, patching, etc., but it's umpteen pages long, and I've no idea if the rear spar is mentioned.


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## Juha (Nov 9, 2012)

Edgar Brooks said:


> And therein lies the problem, since (for whatever reason) experts call it a single-spar wing (and I've only ever seen that description in a 1940s "Flight" magazine,) others, less knowledgeable, read it, don't bother to do any research worthy of the name, and trumpet this "The Spitfire only had one spar" stuff, as an explanation for its alleged inferior performance, when we know that there were other factors involved, as well...



I agree but that is a common problem with professional terms. 

Juha


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## Juha (Nov 9, 2012)

An example from 1940 Flight heinkel | 1940 | 0364 | Flight Archive

Juha


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## drgondog (Nov 9, 2012)

Edgar Brooks said:


> Mid-1940 two wings were tested to destruction, and found to resist a factor (G?) of 11-13 (when the design called for 8-10,) tested to an all-up weight of 6,200lbs; the test report is 17 pages, so there's no way that I can put it on here.
> 
> *Edgar - a Destruct Test takes the airplane to Ultimate load to see a.) where the failure occurs, and b.) asks the question "Dit fail where I predicted it would fail". The Design Limit load for those conditions (Pre-yield or 'pre-wrinkling') and should be at 8-8.66 times the weight of the aircraft. Standard airframe structures philosopy was 8G Limit/12 G Ultimate. Plastic conditions exceeding Yield results in permanent deformation - usually resulting in writing off a makor componenet or the entire airframe*
> 
> ...



Note: Destruct tests were performed with lead/sand bag weights distributed to approximate static loads and could not model asymmetric aero loads or any complex condition..


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## cimmex (Nov 10, 2012)

Back to the Fw190 rollrate. Could it be that the general structure construction was responsible for the excellent performance. At all planes I know both wing halves were attached to the side of fuselage. At the Fw190 the wing is one part with one main spar running through the whole wing assembly and was bolted to the fuselage from below. One pic is from FlugWerk and the other a scan from the Wolfgang Wagner’s book “ KURT TANK KONSTRUKTEUR UND TESTPILOT BEI FOCKE WULF .
cimmex


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## Juha (Nov 10, 2012)

I cannot say, but 190 wasn't the only plane with one piece wing, for ex Brewster Buffalo had one and that structure had also its drawbacks, at least that was the opinion of S/L Churchill in his assestment on Brewster Buffalo as a combat plane. He was the leader of the Eagle sqn (RAF 71 Squadron) consisting American volunteer pilots. They were given three Brewsters, which must also have been 339Bs. He filed this report in October 1940.

"It is strongly recommended that this type should on no account be considered as a fighter without considerable modification.

The wings are not bolted to a centre section but appear to have a common main rear spar located through the fuselage. Changing wings in the event of accidents will therefore be uneconomical and slow.

The elevator is actuated by a push-pull tube. While this is a positive method of operation it is feared than an explosive shell or even a bullet . . . may shatter or collapse it. Experience has proved how much punishment the twin cable can stand without breaking down..."

So even the push-pull tube had its downside.

And as has wrote earlier 190 lost its lead in high speed, P-51B rolled better at 360+mph IAS and Tempest V at 365+mph IAS at 10000ft. 

Juha


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## stona (Nov 10, 2012)

I'd like to know how much of the load on the Spitfire's rear,auxiliary or secondary (depending what you are reading) spar is transfered to the main wing spar.
Steve


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## Milosh (Nov 10, 2012)

The Fw190 elevator control. From the stick to the bellcrank at bulkhead 8 was by rod. From there back to the elevator differential unit it was cables. It then switch back to rod. For the rudder it was rods to the rudder differential unit and then cables to the elevator. Only the ailerons were completely rod.


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## Vincenzo (Nov 10, 2012)

Juha said:


> I
> 
> And as has wrote earlier 190 lost its lead in high speed, P-51B rolled better at 360+mph IAS and Tempest V at 365+mph IAS at 10000ft.
> 
> Juha



360 IAS are around 432 TAS at 10k so very uncommon speed


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## Juha (Nov 10, 2012)

Vincenzo said:


> 360 IAS are around 432 TAS at 10k so very uncommon speed



I knew it was a high speed, even if I thought that 360mph IAS at 10 000 ft means 419mph TAS. I used it only to indicate that the wing of 190 wasn't exeptional stiff, but it had a good solid wing and IMHO one important factor to its high roll rate, besides it wing platform and profile, was the use of Frise ailerons, which had the downside of being difficult to rig optimaly, one of complains Quill had with Spitfire's ailerons (also Frise -type) so they slow down acceptance tests.

Juha


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## drgondog (Nov 10, 2012)

stona said:


> I'd like to know how much of the load on the Spitfire's rear,auxiliary or secondary (depending what you are reading) spar is transfered to the main wing spar.
> Steve



Not possible without access to the airframe design/structures analysis - unless you want to start from scratch using the detail design and BOM, the Aero loads as calculated and presented to the structures group.


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## drgondog (Nov 10, 2012)

cimmex said:


> Back to the Fw190 rollrate. Could it be that the general structure construction was responsible for the excellent performance. At all planes I know both wing halves were attached to the side of fuselage. At the Fw190 the wing is one part with one main spar running through the whole wing assembly and was bolted to the fuselage from below. One pic is from FlugWerk and the other a scan from the Wolfgang Wagner’s book “ KURT TANK KONSTRUKTEUR UND TESTPILOT BEI FOCKE WULF .
> cimmex
> View attachment 215551
> View attachment 215552



The Mustang had complete continuity with spar structure (all) via wing (left and right) attaching to each other at the Centerline.


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## drgondog (Nov 10, 2012)

V- you need to be careful about the "rule of thumb" calculations offered to convert from IAS to TAS. The range of those methods will give TAS of 432(high) to 402 (low and very close to my charts) when compared to STP altitude charts. From extrapolation from my handy Vest Pocket Aero Handbook I pick off ~ 403mph TAS. 

The closest "rule of thumb" method of dividing altitude by 1000, multiplying by 3, adding 7kts to the IAS yields:
360 x .869 =312.84kts + 10,000/1000 (=30) + 7 = 349.84kts/.869 = 402.57mph at 10,000 feet


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## riacrato (Nov 10, 2012)

Juha said:


> I cannot say, but 190 wasn't the only plane with one piece wing, for ex Brewster Buffalo had one and that structure had also its drawbacks, at least that was the opinion of S/L Churchill in his assestment on Brewster Buffalo as a combat plane. He was the leader of the Eagle sqn (RAF 71 Squadron) consisting American volunteer pilots. They were given three Brewsters, which must also have been 339Bs. He filed this report in October 1940.
> 
> "It is strongly recommended that this type should on no account be considered as a fighter without considerable modification.
> 
> ...


Not really enough to convince me that this fear really materializes in reality.



> And as has wrote earlier 190 lost its lead in high speed, P-51B rolled better at 360+mph IAS and Tempest V at 365+mph IAS at 10000ft.
> 
> Juha


Which I always thought was due to the fabric covered aileron surfaces. Metal skinned elevators might have enabled the Fw 190 to keep its edge, but the question is if it was worth the trouble (and material).


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## Vincenzo (Nov 10, 2012)

i've used this True Airspeed Calculator


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## drgondog (Nov 10, 2012)

Vincenzo said:


> i've used this True Airspeed Calculator



It uses one of the 5 Rule of Thumb calculations - Calculate your True Airspeed (TAS) [Aviation Rules of Thumb] - Flightsim Aviation Zone

From the same chart (My "Altitude vs True Airspeed" plots) I get 194Kts for the same calc as your link. BTW, the link calc is incorrect in that they used "8.0" for 8500/1000 when he reduced the equation to (.02 x 8) when he should have used (.02x8.5) x 170. The correct calculation would have been 198.9.

All these methods have the drawback of variations depending on Mach number, calibration deviations, surface pressure/temperature. For the Mustang calc, the incompressible flow became compressible at ~ .3M (or for STP at 10,000 feet =218.36 mph) - which is why I try to use the 'Book' Altitude vs True Airspeed - which is corrected for Mach number.


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## rinkol (Nov 10, 2012)

It might be noted that, all other things being equal, that the fighters with wing mounted radiators tended to suffer from the loss in torsional stiffness resulting from the needed cutouts in the wing skin.


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## stona (Nov 10, 2012)

drgondog said:


> Not possible without access to the airframe design/structures analysis - unless you want to start from scratch using the detail design and BOM, the Aero loads as calculated and presented to the structures group.



Yes,but that transference would explain why the rear spar is often referred to as auxiliary or secondary and also why many seem to consider the wing to have been a single spar design.
Steve


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## drgondog (Nov 10, 2012)

stona said:


> Yes,but that transference would explain why the rear spar is often referred to as auxiliary or secondary and also why many seem to consider the wing to have been a single spar design.
> Steve



A 'spar' is a structural member capable of resisting bending loads, a spar integrated with other structure as well as 'skin' is capable of Bending and Shear resistance. While a spar may be primary, and another secondary, they will serve essentially the same purpose although the secondary is by definition the lesser of the two structural systems.

In airframe design, it is rare for an aircraft with training edge control surfaces to Not have a beam we may describe as 'secondary'.


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## Vincenzo (Nov 10, 2012)

drgondog said:


> It uses one of the 5 Rule of Thumb calculations - Calculate your True Airspeed (TAS) [Aviation Rules of Thumb] - Flightsim Aviation Zone
> 
> From the same chart (My "Altitude vs True Airspeed" plots) I get 194Kts for the same calc as your link. BTW, the link calc is incorrect in that they used "8.0" for 8500/1000 when he reduced the equation to (.02 x 8) when he should have used (.02x8.5) x 170. The correct calculation would have been 198.9.
> 
> All these methods have the drawback of variations depending on Mach number, calibration deviations, surface pressure/temperature. For the Mustang calc, the incompressible flow became compressible at ~ .3M (or for STP at 10,000 feet =218.36 mph) - which is why I try to use the 'Book' Altitude vs True Airspeed - which is corrected for Mach number.



the example is incorrect but for us is ok 360+7,2*10 is 432, it's same of number 3 in your link and yes is the highest estimation (n° 1 and 2 give 410)


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## drgondog (Nov 10, 2012)

Vincenzo said:


> the example is incorrect but for us is ok 360+7,2*10 is 432, it's same of number 3 in your link and yes is the highest estimation (n° 1 and 2 give 410)



And it is Wrong by a significant amount.


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## cimmex (Nov 10, 2012)

432mph or 410mph, I doubt that the P-51 or Fw190 could achieve this speed at 10000 feet at all.
cimmex


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## Juha (Nov 10, 2012)

Hello Vincenzo
I used the info from a table tabulated by the Kingston (Hawker) Project Office 1964 which was given to me years ago by an ex-Hawker wing specialist. 

Juha


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## Juha (Nov 10, 2012)

cimmex said:


> 432mph or 410mph, I doubt that the P-51 or Fw190 could achieve this speed at 10000 feet at all.
> cimmex



IMHO in dive or after a dive, so possible in combat but not usual combat speed.

Juha


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## Juha (Nov 10, 2012)

riacrato said:


> Not really enough to convince me that this fear really materializes in reality...



Hello riacrato
I'm not trying to convince anyone, I included that part mostly to hint that S/L Churchill might has been a bit conservative in his opinions on a/c structures and systems and also that a/c design decisions were usually based on compromises. Especially when it is question on mass produced types.

Juha


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## Juha (Nov 10, 2012)

The writer of the Flight article to which I posted link earlier wasn't an average engineer but one of the bright stars of the trade, see: Robert Lickley - Wikipedia, the free encyclopedia or better still Aircraft Designers Engineers and Notables: Sir Robert L.Lickley CBE 1912–1998 , so he probably knew the subject well. If he categorized Spitfire wing as an one spar structure it's enough to me.

Juha


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## tomo pauk (Nov 10, 2012)

Sea Fury - 2 or 3 spars? The photo the the left is from Seafire, another is from Sea Fury.


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## drgondog (Nov 10, 2012)

tomo pauk said:


> Sea Fury - 2 or 3 spars? The photo the the left is from Seafire, another is from Sea Fury.
> 
> View attachment 215568



I could easily argue three.


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## tomo pauk (Nov 10, 2012)

Even better photos of Seafire wing fold; you can easily navigate to another detailed photos (Sea Fury included):

Seafire Mk XV wing fold detail photos


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## stona (Nov 11, 2012)

drgondog said:


> In airframe design, it is rare for an aircraft with training edge control surfaces to Not have a beam we may describe as 'secondary'.



By which definition no aircraft built with trailing edge control surfaces can be a single spar design. I don't believe that to be the case. There are too many references by engineers and designers to single spar wings that do have moveable control surfaces attached to the wing trailing edge. It may just be semantics or a question of degree. If the vast majority (pick a figure  ) of the loads are borne by the mainspar then this might be considered a single spar design.

Cheers

Steve


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## Timppa (Nov 11, 2012)

tomo pauk said:


> Sea Fury - 2 or 3 spars? The photo the the left is from Seafire, another is from Sea Fury.
> 
> View attachment 215568



Seafire 1 spar, Sea Fury 2 spars. All the forces must go through the locking eyes.


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## drgondog (Nov 11, 2012)

stona said:


> By which definition no aircraft built with trailing edge control surfaces can be a single spar design. I don't believe that to be the case. There are too many references by engineers and designers to single spar wings that do have moveable control surfaces attached to the wing trailing edge. It may just be semantics or a question of degree. If the vast majority (pick a figure  ) of the loads are borne by the mainspar then this might be considered a single spar design.
> 
> Cheers
> 
> Steve



Steve, as an airframe structures guy in my youth I can regurgitate the primary approach. First the main spar would be (Should be) close to the aerodynamic center of pressure as possible to be The beam to take all or most of the bending loads due to span and chordwise distributed loads. You may call it what you wish. Other engineers may not parse the phrase the way I do. Having said this I am pretty familiar with the SR-71 and the Bell XV-15 (precursor to V-22) and I can assure you the rear structure, upon which were hung a variety of control surfaces, were essential in both bending and torsion considerations. 
If you wish to consider examples of designing a trailing spar, upon which to hang articulated flap shaft bearings on a wing subjected to EXTREME bending loads and wing deflection on jump take off - look to the Bell XV-15 and V-22 and Vought XC-142 (?CRS).

Net - I choose to parse the phrase and will stick to my considered opinion regarding what 'constitutes', and may be defined as, a beam or a spar. We may agree on the primary load bearing member, and I am happy to agree that it may be called a Single Spar - but I don't agree it is the only 'spar', nor is the trailing edge the Only bending load carring member as leading edges also served that purpose - particularly in torque/torsion deflection calcs.


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## drgondog (Nov 11, 2012)

Timppa said:


> Seafire 1 spar, Sea Fury 2 spars. All the forces must go through the locking eyes.



Timppa - basically true for one flight condition. All the forces outboard of the locking eye rib/wing station must go through the locking eyes. The majority of the symmetrical aero loads will be in the first 50% of the semi span, the outer span will have some aero laods but the primary load transfer should be from the ailerons in high speed asymmetric rolling..


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## FLYBOYJ (Nov 11, 2012)

"Single spar wing" looks great on a marketing brochure...


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## davparlr (Nov 11, 2012)

drgondog said:


> You're thinking like a structures engineer that took the time to emphasize the "do not poke holes here' instructions to Maintainers.. lol



A couple of stories you guys would appreciate. When I first hied on at Northrop there were quite a few "old heads" that I enjoyed talking to. One told me a story about the F-89. He was in charge of installing electrical wiring. On arriving at the aircraft, manufacturing had forgot to provide electrical runs in the bulk head. His solution? Electric drill, which provided the runs. Another story occurred during the early manufacturing of the F-5. The aft fuselage, which contained the vertical and horizontal stabilizers were mounted to the main fuselage by bolts. At that station, there were two experienced assemblers that had been there for years and all went well. One day one was on vacation and one was sick. When the replacement crew started to assemble the next aircraft, the mounting holes did not line up. The manufacturing line stopped. On examining the other fuselage sections in the line, none lined up. When the sick guy returned, they asked him about it. Oh yeah, its been that way for years, we just took a larger drill bit, drilled them out and put in a slightly larger bolts, no problems? After great consternation and analysis, after all quite a few F-5a had been built that way, it was determined that the change they made had no impact on structural integrity.


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## bobbysocks (Nov 11, 2012)

the Polikarpov I-16 had a hellacious fast roll rate iirc. i was trying to find a wing/spar diagram just to compare but seems to be difficult to find...


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## tomo pauk (Nov 11, 2012)

Cutaway:

Polikarpov I-16 - Cutaways

Seems to be 2 main spars + auxiliary spar.


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## bobbysocks (Nov 11, 2012)

Thanks Tomo....


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## jimh (Nov 13, 2012)

FW-190 parts, not Flugwerk. These are part of the White 1 build. The FW-190 has a different construction method than conventional period wings. The top and bottom skins are one piece, while the ribs are riveted in halves to the top and bottom skin. 






flaps




wings skins and a few ribs attached




close up of an original FW wing with the "floating ribs"








unfinished skin




new ribs


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## drgondog (Nov 13, 2012)

Jim - great shots. Beautiful design both for approach and producability. Now if Kurt was still around we could ask him why zero twist on leading edge for last 20% of semi span. Off the top, it may have reduced induced drag a tiny amount, but created the issues with high AoA/asymmetrical stall.


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## Shortround6 (Nov 13, 2012)

We can also now start arguing about the number of "mini-spars" (stringers) in the wing and their effect/s on stiffness


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## drgondog (Nov 13, 2012)

Shortround6 said:


> We can also now start arguing about the number of "mini-spars" (stringers) in the wing and their effect/s on stiffness



They should have a major (positive) effect re: torsion/torque box contribution..


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## bobbysocks (Nov 13, 2012)

Floating Ribs?? someone explain this to me...surely both halves of the rib were rivited together..correct? but i can see where that would be a stiff wing..


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## drgondog (Nov 13, 2012)

bobbysocks said:


> Floating Ribs?? someone explain this to me...surely both halves of the rib were rivited together..correct? but i can see where that would be a stiff wing..



I suspect that the 'z section stringers' running span wise are Not attached to the ribs.


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## bobbysocks (Nov 13, 2012)

ok..i can see that. thanks dr~


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## jimh (Nov 13, 2012)

The ribs are not riveted together, only to the outer skin, which is why we called them "floating ribs". If you look closely at the photograph the ribs are not riveted together. The aluminum sections of wing skins gets progressively thinner from the inboard sections to the tip. There is a lower, for lack of a better term "strap", that is formed to the dihedral of the wing and crosses the center section to about midway out each wing panel. The stringers attached to the skin also vary in thickness and conform to the differences in thickness of the wing skin. It's by no means simple, and from a restoration point of view a nightmare. I watched John build up the skin, then the jig and the ribs. I can't speak for the twist or washout but he was working with all the known available drawings to build the jig. It's a massive undertaking in today's terms, but I am sure that during the war it was a fairly quick way to build a wing. 

Jim


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## Siegfried (Nov 13, 2012)

jimh said:


> FW-190 parts, not Flugwerk. These are part of the White 1 build. The FW-190 has a different construction method than conventional period wings. The top and bottom skins are one piece, while the ribs are riveted in halves to the top and bottom skin.



Precisely,

As your photos show the FW 190 is clearly a *two spar *design with a box like structure formed by relatively heavy upper and lower skins between the two spars. (forward spar and rear spar) 

In the Spitfire the *main spar * is near the quarter chord point with a torsion 'box' like structure formed between the leading edge and the main spar. The leading edge skins purpose is to provide substantial stiffness in the torsional axis. The Center of lift of most traditional wing is at the quarter chord point and this is also where there is the main spar.

A look at an image of the chordwise lift distribution of a wing will show that almost 75% of the lift comes from within +/- 25% of this quarter chord point so the final 66% of the wing aft of the spar needs to transmit little of the lift to the main spar and can be a relatively light structure and thinner guage metal.

In a pure single spar design ribs will be present and it is to these ribs that the airlerons and flaps are attached. Many aircraft of course also receive stringers along the wing and it would seem natural to close of rear of the wing with a small secondary spar which can add some strength. The Spitfire aileron hinges still attached to the ribs and the secondary(rear) spar carried little load and the wings can certainly function if the entire structure rear of the main spar including the skins and rear spar was damaged. The relatively thin non structural leading edge skins of a two spar wing can more easily be cut ot for gun ports, landing lights etc.

Me 109 also had a single spar but it was completely different, more at the 40% of chord point with elaborate detours around objects like the undercarriage and it looks like the upper and lower skins were an important part of the structure. The aircraft had excellent roll rate but this reduced at high speed due to aileron stiffening. The Spitfires roll rate reduced at speed due to wing twist even after all metal Friese airlerons were fitted. Its worth noting that the 109 and 190 retained fabric covered ailerons.
Mk 22 spitfires received a new wing structure and modified planform.

I suppose one could argue that the presence of a much smaller secondary spar at the rear of the wing made the Spitfire a hybrid design though I think this disguises the point that the Spitire roll rate was substantially determined by the wings structure and its aeroelelastic properties ie relatively low torsional stiffness were more that of a single spar design than a two spar design.


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## Edgar Brooks (Nov 14, 2012)

You can twist, turn, (even do handstands) as much as you wish, but the fact remains that the Spitfire had a rear spar which was (as rigidly as possible) bolted to the fuselage frame 10, and went out as far as the wingtip; it had ribs which were fixed to the front and (non-existant) rear spars; it had overlapping skins rivetted (sometimes double-rivetted) to the spars and wing ribs. There are no wing ribs, in the vicinity of the ailerons, aft of the (non-existant) rear spar, since the permissible gap between the aileron nose (before it is covered) and the (non-existant) spar and aileron shroud is .15" - .25", so there's no room for any ribs. Also, the aileron hinges are bolted directly onto the (non-existant) rear spar, not the (definitely non-existant) wing ribs. It seems that all of this concentration on the rate of roll is designed to cover up the fact that the Spitfire could turn inside the 190 the 109, a manouevre which will do more to keep its pilot alive than rolling.


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## cimmex (Nov 14, 2012)

Edgar Brooks said:


> ... fact that the Spitfire could turn inside the 190 the 109, a manouevre which will do more to keep its pilot alive than rolling.


But didn’t help much in 1942 when Mk V were shot down in numbers by Fw190...
cimmex


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## stona (Nov 14, 2012)

This is fun for those of a mathematical disposition!

The Spitfire Wing - A Mathematical Model

And there was me thinking the wing was elliptical 

Steve


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## fastmongrel (Nov 14, 2012)

stona said:


> This is fun for those of a mathematical disposition!
> 
> The Spitfire Wing - A Mathematical Model
> 
> ...



Trying to read that made my brain hurt I need to go and lie down in a dark room with an icepack on my head


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## Edgar Brooks (Nov 14, 2012)

cimmex said:


> But didn’t help much in 1942 when Mk V were shot down in numbers by Fw190...
> cimmex


But it helped a lot, in 1943 onwards, when the Spitfire IX shot down the 190s in droves.


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## riacrato (Nov 14, 2012)

Yeah right, Fw 190 was clearly helpless against Spitfire MkIX in 1943 and shot down "in droves"


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## cimmex (Nov 14, 2012)

Edgar Brooks said:


> But it helped a lot, in 1943 onwards, when the Spitfire IX shot down the 190s in droves.


History and lost list of JG26 tells a different story...
cimmex


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## drgondog (Nov 14, 2012)

stona said:


> This is fun for those of a mathematical disposition!
> 
> The Spitfire Wing - A Mathematical Model
> 
> ...



No. Having said that the lift distribution was theoretically better than a trapezoidal wing plan form. Ditto P-47. The Heinkel 70 was closer to a true elliptical wing.

The article was interesting, particularly in the re-construction process of building a close math model of the wing plan form to approximate closely the extracted Drawing from the remainder of the original representation on a top assembly (presumably) drawing.

The entire reason for 'elliptical' wing is to strive for the least Induced Drag wing plan form. Leading edge Wing Twist and deviations from true elliptical degrade the optimal induced drag wing but are necessary for manufacturability and low speed flying/stall characteristics.

As a comparison, the Spit wing had less induced drag as a function of CL than a Mustang, but much more parasite drag based on wing area... it is all a trade off based on priorities - and we know from the article that armament was a key driver to extend the wing chord to enable necessary height/thikness while keeping the t/c low.


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## Tante Ju (Nov 14, 2012)

Edgar Brooks said:


> It seems that all of this concentration on the rate of roll is designed to cover up the fact that the Spitfire could turn inside the 190 the 109, a manouevre which will do more to keep its pilot alive than rolling.



Sure it preferred to turn since it had definiences in roll and put some limits on the manouvre repertoire.. try scissors vs a 190. Even to initiate a turn will require rolling first, reversing a turn will require rolling first. The pure turn contest was simply won by using a very large wing (compared to the rest of the aircraft) which had the downside that it was also slower (compared to its horsepower). And even Spitfire pilots agreed that turn was not all that important, since success depended mostly on bounces, which is where speed came in. Everyone tried to build faster aircraft, not better turning aircraft.


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## Siegfried (Nov 14, 2012)

Edgar Brooks said:


> You can twist, turn, (even do handstands) as much as you wish, but the fact remains that the Spitfire had a rear spar which was (as rigidly as possible) bolted to the fuselage frame 10, and went out as far as the wingtip; it had ribs which were fixed to the front and (non-existant) rear spars; it had overlapping skins rivetted (sometimes double-rivetted) to the spars and wing ribs. There are no wing ribs, in the vicinity of the ailerons, aft of the (non-existant) rear spar, since the permissible gap between the aileron nose (before it is covered) and the (non-existant) spar and aileron shroud is .15" - .25", so there's no room for any ribs. Also, the aileron hinges are bolted directly onto the (non-existant) rear spar, not the (definitely non-existant) wing ribs. It seems that all of this concentration on the rate of roll is designed to cover up the fact that the Spitfire could turn inside the 190 the 109, a manouevre which will do more to keep its pilot alive than rolling.



Here are *8 references *by different Authors refering to the Spitfire as a *single spar *design including one by the RAF/MOD. Its clear however that the Spitfire had a seldom mentioned minor second spar invariably refered to as an auxiliary or secondary spar to emphasise its lessor significance. Since the wing skining was relatively thin (the thick skin was over the leading edge) it could in anycase not have transfer too much load.

wing | main spar | construction note | 1940 | 0363 | Flight Archive

supermarine spitfire | de havilland | rolls-royce merlin | 1940 | 1142 | Flight Archive

spitfire | supermarine spitfire | rolls-royce merlin | 1942 | 2364 | Flight Archive

Warral » Spitfire

http://spitfiresite.com/2010/04/mr-...spitfire-in-memory-of-a-brilliant-mind.html/2
"It is also interesting to look at another Mitchell’s design that never got into the air – the Supermarine bomber. In designing the Spitfire Mitchell had pioneered a unique method of wing construction, the single spar with a thick metal leading edge. If this leading edge section could be filled with fuel it promised an aircraft with a very thin wing and slim aerodynamic fuselage while still having large fuel capacity. The Supermarine Bomber (project B12/36) would have carried a bomb-load almost as great as the Lancaster at greater heights and at a speed close to that of the Spitfire…"

RAF - The Spitfire
"Construction: Single spar wings, stressed skin covering, flush riveted; tail unit same"

Supermarine Spitfire - Great Britain
"Structurally the Spitfire was a straightforward design with a light alloy monocoque fuselage and a single spar wing, with stressed-skin covering and fabric-covered control surfaces"

Wings Across Canada: An Illustrated History of Canadian Aviation - Peter Pigott - Google Books

***********************

As far as your Spifire turning circle was concerned: in general the Fw 190 had completed its roll and was well into a turn before the Spitifre completed its roll let alone initiated its turn. That kept a lot of Fw 190 pilots alive and it clearly would have cost a lot of Spitfire pilots their lives.

Aileron Hinges sensibly attach at the same span that the ribs are as this transmits the forces to the main spar and leading edge via the ribs.


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## FLYBOYJ (Nov 14, 2012)

Siegfried said:


> Here are *8 references *by different Authors refering to the Spitfire as a *single spar *design including one by the RAF/MOD. Its clear however that the Spitfire had a seldom mentioned minor second spar invariably refered to as an auxiliary or secondary spar to emphasise its lessor significance. Since the wing skining was relatively thin (the thick skin was over the leading edge) it could in anycase not have transfer too much load.
> 
> wing | main spar | construction note | 1940 | 0363 | Flight Archive
> 
> ...



*"SINGLE SPAR WING" looks great in a marketing presentation.*


No matter how you splice it, slice it or dice it, there are TWO spars in that wing. Talk to some who have driven a few rivets into aircraft structures, but then again I'm sure you own a few rivet guns and bucking bars...


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## Juha (Nov 14, 2012)

cimmex said:


> History and lost list of JG26 tells a different story...
> cimmex



Hello cimmex
it depends which part of 43 we are talking, it saeems that during the Autumn 43 Spits IXs at last got upper hand over 190s. After checking July and Nov 43 from Caldwell’s The JG 26 War Diary it seems that during July 43 it was rather even, LW had a slight advance but in Nov 43 Spitfires seemed to have won all the bigger combats. I was a little bit surprised myself on that. Of course only 2 months but I have not more time now.

Juha


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## Juha (Nov 14, 2012)

FLYBOYJ said:


> *"SINGLE SPAR WING" looks great in a marketing presentation.*
> 
> 
> No matter how you splice it, slice it or dice it, there are TWO spars in that wing. Talk to some who have driven a few rivets into aircraft structures, but then again I'm sure you own a few rivet guns and bucking bars...



It's more like a design principle and one spar and 2 spars wings are manufactured differently, see the article I provided a link earlier, the link takes you to the page 2 of the article, so the page before it is the first one.

Juha


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## FLYBOYJ (Nov 14, 2012)

Juha said:


> It's more like a design principle and one spar and 2 spars wings are manufactured differently, see the article I provided a link earlier, the link takes you to the page 2 of the article, so the page before it is the first one.
> 
> Juha



I saw that - it's a matter of what some engineer is attempting to call the structure. Bottom line, in the field "where the rubber hits the pavement" mechanics are going to maintaining and when necessary, repairing two spars, regardless of the way they were manufactured.


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## Vincenzo (Nov 14, 2012)

JG 26
I+II+III+Stab/10/11/UmK/ErK = Total
durch Feindeinw. Anton (Gustav)
01.43 5 + 4(6) + 3 = 12(6)
02.43 4 + 3(1) + 6 = 13(1)
03.43 10+5 + 2 = 17
04.43 0 +12+ 7 = 19
05.43 1 +17+ 2(4) = 20(4)
06.43 3 +18+ 3(1) + 3(2) = 27 (3)
07.43 8 + 7 + 5(4) + 6(6) = 26 (10)
08.43 3 +13 + (14) + 5(1) =21 (15)
09.43 0 +31 + 8(8 ) = 39 (8 )
10.43 10+16+ (5) = 26(5)
11.43 11+ 7 + (8 ) = 18 (8 )
12.43 9 + 7 + (10) = 16 (10)
all year all JG 26 = 254 (70)


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## tomo pauk (Nov 14, 2012)

Could we say it this way: Spitfire's wing featured two spars; the main spar, along with D 'boxes' was the strong part of the wing, carrying the overwhelming part of the loads imposed?

Here are some drawings (from Seafire). Please note that main spar was attached to fuselage with 2 x 4 bolts (to the frame no.5), while the rear spar was attached with a mere 1 bolt (to the frame no. 10). Also note the really strong wing attachment 'section', where the main spar is attached. The rear spar, at the wing fold line, does not have the lock ( unlike the main spar); it's merely hinged.

So even if, from mechanics viewpoint, the wing has two spars, the question is what is the net gain for the pilot, namely, can his wing provide enough rigidity needed for the competitive roll rate.


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## Edgar Brooks (Nov 14, 2012)

Siegfried said:


> Here are *8 references *by different Authors refering to the Spitfire as a *single spar *design including one by the RAF/MOD. Its clear however that the Spitfire had a seldom mentioned minor second spar invariably refered to as an auxiliary or secondary spar to emphasise its lessor significance. Since the wing skining was relatively thin (the thick skin was over the leading edge) it could in anycase not have transfer too much load..


I really don't care how many "references" you throw up; R.J. Mitchell conceived the Spitfire, did the drawings for it, and he drew a rear spar (and not once did he ever refer to it as an "auxiliary" or "secondary" spar, it's always the *rear spar *- nice try, but have another go) in the wing. I (and most others with a even a basic knowledge of the Spitfire) will take the word of the aircraft's designer against any number of "experts," who you dig out, in your increasingly desperate attempts to decry one of the best aircraft this nation has ever had.


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## stona (Nov 14, 2012)

Edgar Brooks said:


> not once did he ever refer to it as an "auxiliary" spar



What did he call it then?

I see it referred to as a rear spar,secondary spar and auxiliary spar in various books. The main spar is called just that,main spar.

I don't know whether the Spitfire is a single or two spar design. It doesn't matter much to me It does seem that most of the load is borne by the front spar and front of the wing.

Steve


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## Edgar Brooks (Nov 14, 2012)

stona said:


> What did he call it then?


Considering that his drawings have "Rear spar" annotated on them, I'm assuming that he called it the rear spar.


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## Tante Ju (Nov 14, 2012)

So what I learned in this thread is that what Mitchell was calling a rear spar was the same thing everybody else called a secondary/auxilarry spar. You are riding on semantics, really. Everything in that thread so far shows that this "rear spar" was unable to carry any significant road. Yes it sounds great in selling brochures..


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## cimmex (Nov 14, 2012)

What is so special on a rear spar, auxiliary or whatever you call it at the Spitfire, every plane with flaps and ailerons had one. 
cimmex


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## FLYBOYJ (Nov 14, 2012)

Tante Ju said:


> So what I learned in this thread is that what Mitchell was calling a rear spar was the same thing everybody else called a secondary/auxilarry spar. You are riding on semantics, really. *Everything in that thread so far shows that this "rear spar" was unable to carry any significant road.* Yes it sounds great in selling brochures..



Don't know about that - as stated earlier, unless someone could come up with factory stress analysis reports on how much of the load that rear spar is carrying, the only other way to determine its structural importance is to examine the repair tolerances on it. If there are repair limitations covering repair size and location, be rest assured it carries a "significant" load.


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## FLYBOYJ (Nov 14, 2012)

cimmex said:


> What is so special on a rear spar, auxiliary or whatever you call it at the Spitfire, every plane with flaps and ailerons had one.
> cimmex


You're correct - there is nothing special, but there are some either to enhance or degrade the design to INCORRECTLY say it has only one spar.


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## fastmongrel (Nov 14, 2012)

If the father of the Spit called it the rear spar then thats good enough for me. If he had called it an auxillary spar that would also be good enough and I would respect R J Mitchells memory and call it an auxillary spar, but he called it a rear spar. So could the Spit haters just give up and call it a rear spar, after all this is getting stunningly boring in a topic on the FW 190.


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## cimmex (Nov 14, 2012)

With that logic the Bf109 wing would be a 3 spar design because it had a rear spar, a front spar where the slats were attached and of course the main spar. Nevertheless the common designation is a single spar wing.
cimmex


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## stona (Nov 14, 2012)

Edgar Brooks said:


> Considering that his drawings have "Rear spar" annotated on them, I'm assuming that he called it the rear spar.



Thanks,then henceforth that is what I will call it too.

Steve


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## riacrato (Nov 14, 2012)

I don't see how you arrive at that conclusion: This has absolutely nothing to do with whether or not you hate the Spitfire. I don't hate the Spitfire or the Bf 109 but they are designs where the majority of the torsional loads are carried by a single spar that is much stronger than the other(s), so they are from that point of view "single spar" wings. And that other designs with "true" multi-spar wings have certain advantages, including sometimes the roll rate, as well as certain disadvantages, is simply a fact.


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## tomo pauk (Nov 14, 2012)

Well put.


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## bobbysocks (Nov 14, 2012)

So with this "floating rib" construction...there is free play between the 2 halves if they are not attached, fixed, rivited together. i assume they are attached to the main spar and at the trailing edge or secondary fixture ( spar, etc ). i can also see how the placement of the "L" type supports on the upper and lower skins would aid in keeping the wing rigid. but with the 2 section rib like that there would have to be some tendancy for either the upper or lower part of the wing to "bow" outwards from the center of the rib to the edges or to slide slightly on each other....especially if one surface of the wing is subjected to negitive "G"s. what would be the advantages of that? and is that design used on any other ac or in use today?


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## Edgar Brooks (Nov 14, 2012)

cimmex said:


> With that logic the Bf109 wing would be a 3 spar design because it had a rear spar, a front spar where the slats were attached and of course the main spar. Nevertheless the common designation is a single spar wing.
> cimmex


If Herr Messerschmitt said that the 109 had a three-spar wing, common courtesy would dictate that so should everybody else, and I would have no quarrel with that, since it was his design. Likewise, when it comes to R.J. Mitchell, I bow to his expertise.
In all this manipulation of the English language, with talk back-and-forth of "single-spar wings," perhaps it's time to remind you all exactly what the person, who started all this, actually said:-


> The Spitfire with its single main spar suffered somewhat from this.


 Not a hint of a secondary, auxiliary, rear, or afterthought spar do I see, there, and anyone who doesn't know the Spitfire would be forgiven for visualising a wing flapping around a single, albeit strong, bar of metal, and there remains a strong suspicion that this was exactly what was intended.


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## CobberKane (Nov 14, 2012)

If I may change the subject by rudely returning to the original point of the thread...
How much of the 190s roll rate was attributable to concerntration of mass along the longitudonal axis? The more weight moves away from the centerline the more mass there is to accellerate in a roll - a real bugbear of twin ingine designs. The 190 mounted most of its firepower in the wing roots and nose, and later models did away with the outboard cannon all together. Where were the fuel tanks? Did Kurt Tank do a better job of mass centralisation than other contemporary desgners? This would seem to my uneducated opinion to be one of the primary determinants of roll-rate.


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## drgondog (Nov 14, 2012)

You need look no further than the relative size of the ailerons


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## CobberKane (Nov 14, 2012)

drgondog said:


> You need look no further than the relative size of the ailerons


 
Really? So the fastest rolling aircraft in the ETO was the B-17?


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## Siegfried (Nov 15, 2012)

CobberKane said:


> If I may change the subject by rudely returning to the original point of the thread...
> How much of the 190s roll rate was attributable to concerntration of mass along the longitudonal axis? The more weight moves away from the centerline the more mass there is to accellerate in a roll - a real bugbear of twin ingine designs. The 190 mounted most of its firepower in the wing roots and nose, and later models did away with the outboard cannon all together. Where were the fuel tanks? Did Kurt Tank do a better job of mass centralisation than other contemporary desgners? This would seem to my uneducated opinion to be one of the primary determinants of roll-rate.



Eric Brown reckoned the roll rate of the long nose versions was less than the radial version. I'm thinking it was caused by a kind of inertia coupling. An aircraft does not roll along its thrust or principle axis which is out of alignment with the flight axis but kind of lollops or nutates a little as it rolls. The longer the aircraft the more mass near the nose will tend to centrifuge out. It's only really supposed to be an issue on jets, a very serious one.

Wing span also an issue, given equal wing tip speed a short span aircraft will roll faster.


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## CobberKane (Nov 15, 2012)

Siegfried said:


> Eric Brown reckoned the roll rate of the long nose versions was less than the radial version. I'm thinking it was caused by a kind of inertia coupling. An aircraft does not roll along its thrust or principle axis which is out of alignment with the flight axis but kind of lollops or nutates a little as it rolls. The longer the aircraft the more mass near the nose will tend to centrifuge out. It's only really supposed to be an issue on jets, a very serious one.
> 
> Wing span also an issue, given equal wing tip speed a short span aircraft will roll faster.


 
Or maybe it was just weight. Increased weight close to the longitudonal axis will not slow down roll as much as displaced weight, but it will still have an effect.


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## bobbysocks (Nov 15, 2012)

Siegfried said:


> . The longer the aircraft the more mass near the nose will tend to centrifuge out. ....
> Wing span also an issue, given equal wing tip speed a short span aircraft will roll faster.



the only way i can see the length of the ac being an issue is weight of the ac vs hp or torgue. equal lengths with different weights will spin on their axis ( roll ) at different speeds due to the torque needed to spin them. so a longer yet lighter span could spin ( roll ) faster than a shorter but heavier one?? next, is it the wing span. if you use equal wing tip speed as a meter, that would bias the shorter wing due to the distance need to be traveled. me and you will have a race...we will both go 60kph. i will go 60 km you go 80...who is gong to get there first? i would think it is more the total area of the wing...cubic displacement vs resistance..that would be the determining factor?? would a longer span roll worse than short a shorter span if the total surface are was less? also for roll rate the ratio of the aileron surface to the surface of the wing might come more into play. hence a long thin wing may have the same roll rate as a stubbier but wider shorter one. i honestly do not know..i am interested to find out .


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## Tante Ju (Nov 15, 2012)

CobberKane said:


> Really? So the fastest rolling aircraft in the ETO was the B-17?



Relative size - aileron area vs wing area. The total size of the aileron was 1,93 sq.m (I believe for one aileron..?), the total wing size was 18,30 sq. m. If I got it right it means the aileron area was no less 21% of the total wing area. Compare that to about 13% on the 109E and 15.5% on the Spitfire I. IIRC La-5 series had also a sizeable aileron area, and they rolled very well.

Also the gearing ratio was very good, the stick travel was the same as the 109's I believe, but the aileron's travelled +/- 17 degrees. That's about twice the gearing advantage for the pilot. 

Ailerons were very well executed, Friese type (which helps stick forces), well sealed on the top.

Radial engine meant that the weight distribution in the rolling axis was even.

The wing structure was also rigid and seems to have resisted twisting forces well, so little reduction due to elasticity.

The wingtips were squared, which again helps the lift distribution to be at the extreme end of the wing for best effect. After all ailerons simply change the lift of both wings, that's why the plane rolls.


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## drgondog (Nov 15, 2012)

CobberKane said:


> Really? So the fastest rolling aircraft in the ETO was the B-17?



No. Tante Ju covered the 'obvious point' very well.


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## tomo pauk (Nov 15, 2012)

Seems like Tante Ju answered the question from the thread's title, too.


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## CobberKane (Nov 15, 2012)

tomo pauk said:


> Seems like Tante Ju answered the question from the thread's title, too.


 
Sounds good to me. It makes sense that aileron and wing design would be the major factor in roll-rate, with weight and mass centralisation also being very important. Doubtless the !() did exceptionally well in both these areas. The Zero would be an interesting counterpoint here, as it was obviously light and also had large ailerons, but apparently rolled poorly at high speeds. I assume this was a function of the gearing of the controls mentioned, as beyond a certain point it would be impossible to move the ailerons against the airflow. Perhaps this was designed into the Zero in recognition that it was not rugged enough to withstand violent manouvers at high speed?


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## cimmex (Nov 16, 2012)

I don’t think that weight and mass centralisation is so important, never heard that the Fw190 rolled better when the outer wing guns were removed.
cimmex


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## Siegfried (Nov 16, 2012)

Edgar Brooks said:


> Mid-1940 two wings were tested to destruction, and found to resist a factor (G?) of 11-13 (when the design called for 8-10,) tested to an all-up weight of 6,200lbs; the test report is 17 pages, so there's no way that I can put it on here.
> In February 1940, an instruction was issued, with regard to examination for skin wrinkling, after any "abnormal manouevres." Any wrinkling, at all, on the leading edge, forward of the mainspar, would lead to the wing being declared unserviceable, and due for replacement. Aft of the mainspar, between ribs 14-19, any wrinkle less than 1/10" (2.5mm) could be disregarded; any wrinkle deeper than that (or wrinkles of any depth in any other area of the wing) would necessitate examination of the wingroot bolts, and, if they were bent, wing and bolts were to be replaced.
> There is a manual, on repairs, patching, etc., but it's umpteen pages long, and I've no idea if the rear spar is mentioned.



The concern for ensuring that overstressed Spitfire wings were wrinkle free on the leading edge but could tolerate with indifference 2.5mm wrinkles aft of the main spar is evidence again that the spitfire in concept is a single spar design.

A two spar aircraft is almost completely indifferent to the state of the leading edge skins and the leading edges can be penetrated by landing lights, pitot tubes, gun ports without any serious engineering.

I believe the Spitfire used no less than 4 bolts to attach the main spar. Evidence not only of the load this spar needed to carry but also of design to resist torsional loads.

Do a thought experiment; take an angle grinder to a spitfire and and cut from the trailing edge at the wing root to the main spar. The wings strength will be minimally effected even with loss of the rest secondary spar and continuity of the skin. Most of the lifting and torsional loads go through the front spar.

Do that to a two spar design and you've likely to loose the wing as you've lost the important rear spar and the thick upper skins that form a torsion box. Likewise cut into the leading edge of the Spitfire and a significant amount of strength has been lost.


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## tomo pauk (Nov 16, 2012)

Siegfried said:


> ...
> 
> I believe the Spitfire used no less than 4 bolts to attach the main spar. Evidence not only of the load this spar needed to carry but also of design to resist torsional loads.
> 
> ...



Main spas: 7 bolts per spar. 4 bolts per lower 'beam' (tube in tube construction; maybe people can remeber biology classes - the tube-in-tub 'construction' is applied by plants and bones); 3 bolts per upper 'beam'.
Here are photos:

http://www.ww2aircraft.net/forum/aviation/fw-190-roots-great-roll-rate-34677-3.html#post954157

For rear spars: 1 bolt.


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## Siegfried (Nov 16, 2012)

CobberKane said:


> Sounds good to me. It makes sense that aileron and wing design would be the major factor in roll-rate, with weight and mass centralisation also being very important. Doubtless the !() did exceptionally well in both these areas. The Zero would be an interesting counterpoint here, as it was obviously light and also had large ailerons, but apparently rolled poorly at high speeds. I assume this was a function of the gearing of the controls mentioned, as beyond a certain point it would be impossible to move the ailerons against the airflow. Perhaps this was designed into the Zero in recognition that it was not rugged enough to withstand violent manouvers at high speed?



Large ailerons are considered a disadvantage to roll rate at high speed due to pilot work load. The zero partially got around this by gearing the ailerons up when the undercarriage was extended. Aileron size and gearing is a complicated trade off it seems.

One obvious thing we've overlooked despite the photographs posted is the Fw 190s use of a carry through spars, there were no bolts and I imagine the lower wing skins were continuous across the fuselage. 

Late war Hellcats and Corsairs received geared spring tabs on the ailerons. At low speed they reduced roll rate since the tabs acted against the ailerons. At high speed their effect in reducing pilot effort dominated and enormously increased aileron deflection and roll rate. Roll rate almost doubled.

The P-51A had a very poor roll rate, however because the laminar wing was relatively thick a sort of concertina bellows was put into the wing of the P-51B onwards that channelled high pressure air from the ailerons deflected side to the bellows and used it to relieve the pilots stick force for greater deflection. This is called internal balancing. A slow P-51B/C/D was easily out rolled by a Me 109 or Fw 190 however above 360mph it matched the Fw 190 and improved relatively from there as shock waves on the lip of the 190s frise ailerons impacted negatively.

That other laminar flow US fighter the P-63 king cobra had the fastest roll of any US fighter, presumably due to pressure balanced ailerons but possibly it had something to do with engine placement.

If hydraulic boost is available the bigger aileron is the better as pilot work load is no longer a factor.


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## drgondog (Nov 16, 2012)

Siegfried said:


> The concern for ensuring that overstressed Spitfire wings were wrinkle free on the leading edge but could tolerate with indifference 2.5mm wrinkles aft of the main spar is evidence again that the spitfire in concept is a single spar design.
> 
> A two spar aircraft is almost completely indifferent to the state of the leading edge skins and the leading edges can be penetrated by landing lights, pitot tubes, gun ports without any serious engineering.
> 
> ...



The leading edge and main spar of a Spitfire Are violated with Cannon and Machine guns. Having said that penetrating a box of H or I section type spar in the center of the shear web is a fault that can be compensated for with suitable doublers to compensate for the loss of shear transfer from top to bottom cap in bending.


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## Milosh (Nov 16, 2012)

> One obvious thing we've overlooked despite the photographs posted is the Fw 190s use of a carry through spars, there were no bolts and I imagine the lower wing skins were continuous across the fuselage.



Nope the wing skins were no continuous from tip to tip. There was a large removable panel to give access to the fuel tanks. The rear spar was not 'carry through', it ended and was bolted to the fuselage.

http://www.albentley-drawings.com/images/FW190A6W.jpg


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## cimmex (Nov 16, 2012)

Siegfried said:


> One obvious thing we've overlooked despite the photographs posted is the Fw 190s use of a carry through spars, there were no bolts and I imagine the lower wing skins were continuous across the fuselage.


Only the main spar went through the fuselage. ( see page 52) the wing skin below the fuselage was the tank bay cover.
cimmex


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## Edgar Brooks (Nov 16, 2012)

Siegfried said:


> The concern for ensuring that overstressed Spitfire wings were wrinkle free on the leading edge but could tolerate with indifference 2.5mm wrinkles aft of the main spar is evidence again that the spitfire in concept is a single spar design.


Do try reading what I wrote; the only part of the Spitfire wing where wrinkles could be ignored, was between ribs 14 - 19, which is the where the aileron hinges attach to the rear spar. Any wrinkles,* anywhere else, forward or aft of the mainspar,* would necessitate bolts and wing inspection, with probable wing replacement.


> A two spar aircraft is almost completely indifferent to the state of the leading edge skins and the leading edges can be penetrated by landing lights, pitot tubes, gun ports without any serious engineering.


Like four .303" Brownings, or cannon, perhaps?


> I believe the Spitfire used no less than 4 bolts to attach the main spar. Evidence not only of the load this spar needed to carry but also of design to resist torsional loads.


As said above, SEVEN bolts + ONE on the rear spar.


> Do a thought experiment; take an angle grinder to a spitfire and and cut from the trailing edge at the wing root to the main spar. The wings strength will be minimally effected even with loss of the rest secondary spar and continuity of the skin. Most of the lifting and torsional loads go through the front spar.


Do a second thought experiment, and think what will happen to the wing, when the ailerons (attached to the rear spar) are operated, and the sliced-through rear spar is free to flap up and down, instead of moving the wing.


> Do that to a two spar design and you've likely to loose the wing as you've lost the important rear spar and the thick upper skins that form a torsion box.


Nice to see that you agree with us.


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## Siegfried (Nov 16, 2012)

tomo pauk said:


> Main spas: 7 bolts per spar. 4 bolts per lower 'beam' (tube in tube construction; maybe people can remeber biology classes - the tube-in-tub 'construction' is applied by plants and bones); 3 bolts per upper 'beam'.
> Here are photos:
> 
> http://www.ww2aircraft.net/forum/aviation/fw-190-roots-great-roll-rate-34677-3.html#post954157
> ...



Thanks, if we use bolts as a unit of strength (assuming they are the same size) we could say 12.5% of the stress goes through the rear spar. I would say that the rear spar however carries mainly twisting forces from the aileron and thus acts only to stiffen the wing torsionally to a considerable degree.

It's intricate engineering. The spitfire doesn't seem to ave a wing box.


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## Siegfried (Nov 16, 2012)

drgondog said:


> The leading edge and main spar of a Spitfire Are violated with Cannon and Machine guns. Having said that penetrating a box of H or I section type spar in the center of the shear web is a fault that can be compensated for with suitable doublers to compensate for the loss of shear transfer from top to bottom cap in bending.



I accept that the rear spar bolt is critical in providing torsional stiffness; however I see the rear spar of almost total insignificance. It could have been eliminated.

Firstly there is almost zero torsional load on the spitfire wing when flying statically since the centre of lift is where the spar is at around 25% of chord.

Minor torsional loads would come from pitching moment as AOA varied; however aileron torsional loads would be more.

How much? 100kg per aileron maybe? That's only about 1000 Newton Meters. Not much really.

The torsional loads from the aileron would be transferred via the ribs at the hinge points to the box formed between the main spar and the leading edge which is part of that same rib. The ribs at the leading edge have elaborate triangular trusses so that leading edge box is much much stiffer than the main spar alone.

Once at the wing root the torsional loads must be transferred from the leading edge box to the rear spar bolt via rib 1. This Rib could have been bolted directly to the fuselage however the load is transferred via the rear spar.

The most significant part of the rear spar are those few inches between rib 1 and fuselage attachment. The trailing edge spar outboard of that area is of little significance I assert.

Supermarine seems to have been cautious in penetrating the leading edge of the spitfire and of course the holes were not that big or had elaborate engineering around them, such as the plug leading edge nacelles that were plugged and left in place when the 0.5 Brownings or Hispano weren't fitted.


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## drgondog (Nov 16, 2012)

Milosh said:


> Nope the wing skins were no continuous from tip to tip. There was a large removable panel to give access to the fuel tanks. The rear spar was not 'carry through', it ended and was bolted to the fuselage.
> 
> http://www.albentley-drawings.com/images/FW190A6W.jpg



You are right about 'discontinuity'. Having said that - if the fasteners were done properly, the removable panel would have served as an effective shear panel.


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## cimmex (Nov 16, 2012)

here is a pic during rebuilt
http://www.white1foundation.org/parts/behalterraumklappe.jpg


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## jimh (Nov 16, 2012)

IMHO, the roll rate of a fighter is a function of aileron size and throw. The Mustang has 3 settings 10 degrees, 12 degrees, and 15 degrees. I want to say that Betty Jane is set at 12 degrees of throw. It is slow getting around, I've flown a couple D models that roll much faster. Speed is also a factor, ailerons will stiffen up as speed is increased, above 240kts it almost takes 2 hands on the stick to do a crisp roll. I can only image how nice an FW rolls with those big ailerons and tons of throw.

JH


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## tomo pauk (Nov 16, 2012)

This is pretty cool:


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## drgondog (Nov 16, 2012)

Siegfried said:


> I accept that the rear spar bolt is critical in providing torsional stiffness; however I see the rear spar of almost total insignificance. It could have been eliminated.
> 
> *If the rear spar bolt is there - and significant in size - then the cross section of the bolt will tell you how much shear stress it was designed to take - as well as some tensile stress. As to insignificant, It would have to match the bolt in load transfer.*
> 
> ...



See prior discussion a couple of posts back


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## FLYBOYJ (Nov 16, 2012)

Let me put this out there - would anyone here want to fly a Spitfire, maybe pull 4 or 5 Gs with it's rear spar damaged or eliminated?

Siegfried - it seems you're making your assumption on a visual observation. Do we even know the exact dimensions, size and material the rear spar was made from?


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## cimmex (Nov 16, 2012)

. Why not- Early WWI aircraft didn’t have a rear spar too...


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## tomo pauk (Nov 16, 2012)

If anybody can shed some light on this: in Seafire, why the rear spar have had the hinge, but not the lock at the wing fold line; in the same time, the main spar was featuring the lock (that was holding the fixed and folding part of the spar's low beam together)?


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## drgondog (Nov 16, 2012)

Siegfried said:


> I accept that the rear spar bolt is critical in providing torsional stiffness; however I see the rear spar of almost total insignificance. It could have been eliminated.
> 
> Firstly there is almost zero torsional load on the spitfire wing when flying statically since the centre of lift is where the spar is at around 25% of chord.
> 
> ...



The latter comment would only be true if a.) the Center of Pressure never changed with AoA (and it always does), and b.) if the primary Normal and Shear loads to wing plane always passed through the Center of Intertia of the Prime Beam/Spar.


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## FLYBOYJ (Nov 16, 2012)

cimmex said:


> . Why not- Early WWI aircraft didn’t have a rear spar too...


They also didn't fly in excess of 300 mph and weren't capable of pulling 4 Gs.....


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## cimmex (Nov 16, 2012)

Max g-load Fokker DR1=8,3


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## Edgar Brooks (Nov 16, 2012)

Siegfried said:


> I accept that the rear spar bolt is critical in providing torsional stiffness; however I see the rear spar of almost total insignificance. It could have been eliminated..


What you see is immaterial, since it wasn't eliminated, therefore it was still there, therefore the Spitfire wing had two spars, not one..


> Supermarine seems to have been cautious in penetrating the leading edge of the spitfire and of course the holes were not that big or had elaborate engineering around them, such as the plug leading edge nacelles that were plugged and left in place when the 0.5 Brownings or Hispano weren't fitted


Obviously your knowledge of the Spitfire falls way below what's needed. The Mk.I/IIa/Va leading edge had tubes fixed to the mainspar and extreme leading edge, through which the .303" Brownings passed, and which stiffened the whole assembly.
For the cannon, there was a substantial casting fitted to the leading edge, which was strong enough for the eccentrics (used for setting the convergence angles of the cannon, and .5" Browning - when fitted) to be fitted inside, and which held the guns rigidly in place.
The casting(s) in question:-


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## FLYBOYJ (Nov 16, 2012)

cimmex said:


> Max g-load Fokker DR1=8,3


On what part of the aircraft? Upper wing? The fabric alone would not be able to take high speed loads and this is like comparing apples and oranges.


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## tomo pauk (Nov 16, 2012)

This one came back:


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## FLYBOYJ (Nov 16, 2012)

tomo pauk said:


> This one came back:
> 
> View attachment 216193



It did! And it would be interesting to see if the damage was repairable and if so, the size of the required repair.


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## Siegfried (Nov 16, 2012)

Edgar Brooks said:


> What you see is immaterial, since it wasn't eliminated, therefore it was still there, therefore the Spitfire wing had two spars, not one..
> 
> Obviously your knowledge of the Spitfire falls way below what's needed. The Mk.I/IIa/Va leading edge had tubes fixed to the mainspar and extreme leading edge, through which the .303" Brownings passed, and which stiffened the whole assembly.
> For the cannon, there was a substantial casting fitted to the leading edge, which was strong enough for the eccentrics (used for setting the convergence angles of the cannon, and .5" Browning - when fitted) to be fitted inside, and which held the guns rigidly in place.
> The casting(s) in question:-



Edgar, thats a little unkind but thankyou you simply prove my point. The image you effortfully provided shows elaborate engineering around the gun penetrations to carry through the loads along the leading edge skins and ribs. Just as I stated. The thought own goal comes to mind but a wonderfully enlightening image. You and tomo have progressed our knowledge.

Just study those "engineered" gun ports. It's probably been pressed or cold drawn in nearly a dozen stamping operations and tooling set ups which would have been followed by quite a lot of drilling at the flanges for bolt attachments. Its a lot more trouble than just wrapping skins around the leading edge and drilling a hole. In a two spar design you would just drill a hole though you would then need to engineer to access magazines in the area between spars.

The rear spar no doubt added some modest but worthwhile amount of stiffness to the trailing edge but it looks like the bulk of the torsional loads were conducted through the torsion box formed between the main spar and substantial leading edge skins. The torsional load would then have been transferred to the wing root rib number 1 and thence to the attachment to the fuselage at the rear of that rib. That first rib would have been extra important.


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## Milosh (Nov 16, 2012)

Siegfried, *substantial casting*.


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## Edgar Brooks (Nov 17, 2012)

Siegfried said:


> Edgar, thats a little unkind but thankyou you simply prove my point. The image you effortfully provided shows elaborate engineering around the gun penetrations to carry through the loads along the leading edge skins and ribs. Just as I stated. The thought own goal comes to mind but a wonderfully enlightening image.


It's only a "little unkind," because, once again, you've manipulated the wording to suit yourself. The Spitfire was not designed with the 20mm cannon in mind, just 8 .303" guns, yet, by the addition of a single machined casting (elaborate engineering? Really?) it was able to take the larger, heavier weapon, and its greater recoil. I think you'll find that the ball has not crossed the line.


> Just study those "engineered" gun ports. It's probably been pressed or cold drawn in nearly a dozen stamping operations and tooling set ups which would have been followed by quite a lot of drilling at the flanges for bolt attachments. Its a lot more trouble than just wrapping skins around the leading edge and drilling a hole. In a two spar design you would just drill a hole though you would then need to engineer to access magazines in the area between spars.


And there we go again; all we get, from you, is "I think," or "probably," while you wait for somebody else to do the research for you, whereupon it's twisted to fit your "German is/was best" agenda. The casting was required to house the eccentric sleeve, which held the 20mm barrel, allowing the cannon's angle to be adjusted to suit the individual pilot's preference. If you remember your mathematics, the longer the distance between the rear and forward mountings, the easier it is to do the adjustments, since the necessarily small movements of the eccentric sleeves have less effect on the guns' angles.


> The rear spar no doubt added some modest but worthwhile amount of stiffness to the trailing edge but it looks like the bulk of the torsional loads were conducted through the torsion box formed between the main spar and substantial leading edge skins.


So, now, instead of being completely pointless, the spar suddenly has some use, after all; if you check, you'll find that nobody has denied that the main spar + "D" box were the most important parts of the wing, so you're arguing with yourself, now.


> The torsional load would then have been transferred to the wing root rib number 1 and thence to the attachment to the fuselage at the rear of that rib. That first rib would have been extra important.


Especially since, together with the rear spar, it was rigidly attached to frame 10 by common brackets.


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## FLYBOYJ (Nov 17, 2012)

Siegfried said:


> Just study those "engineered" gun ports. It's probably been pressed or cold drawn in nearly a dozen stamping operations and tooling set ups which would have been followed by quite a lot of drilling at the flanges for bolt attachments.


There's nothing greatly complicated about that part. From the pic it looks like a machined casting (sand casting) or forging and the holes were probably jig-drilled.


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## Edgar Brooks (Nov 17, 2012)

Siegfried said:


> Just study those "engineered" gun ports. It's probably been pressed or cold drawn in nearly a dozen stamping operations and tooling set ups which would have been followed by quite a lot of drilling at the flanges for bolt attachments. Its a lot more trouble than just wrapping skins around the leading edge and drilling a hole. In a two spar design you would just drill a hole though you would then need to engineer to access magazines in the area between spars.


It's possible you're right, but the irony is that they're brand new 21st. century replacement parts to be used in a modern rebuild of a Spitfire to airworthy status, and manufactured to the wartime drawings, dimensions and tolerances. And, no, it wasn't done to catch you out; I don't work that way, so you did that all by yourself.
If you were to ask for clarification, even help, at times, you might find that those, who take the time to carry out real research in the original archives (and that includes me, to a certain extent,) would offer information quite freely, but you have to come piling in, trying to dazzle everyone with your superior engineering knowhow, when, in fact, you're largely relying on guesswork.


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## FLYBOYJ (Nov 17, 2012)

Edgar Brooks said:


> It's possible you're right, but the irony is that they're brand new 21st. century replacement parts to be used in a modern rebuild of a Spitfire to airworthy status, and manufactured to the wartime drawings, dimensions and tolerances. And, no, it wasn't done to catch you out; I don't work that way, so you did that all by yourself.
> If you were to ask for clarification, even help, at times, you might find that those, who take the time to carry out real research in the original archives (and that includes me, to a certain extent,) would offer information quite freely, but you have to come piling in, trying to dazzle everyone with your superior engineering knowhow, when, in fact, you're largely relying on guesswork.


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## spicmart (Nov 18, 2012)

Do you know how the roll rates of the soviet fighters were compared to the ones mentioned here?


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## mhuxt (Nov 19, 2012)

Found some stuff on Fw 190 wing structure, among other things, in the Flight Global Archive:


View attachment Fw190wings.zip


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## stona (Nov 26, 2012)

cimmex said:


> Only the main spar went through the fuselage. ( see page 52) the wing skin below the fuselage was the tank bay cover.
> cimmex



Exactly. From D.(Luft)T.2190 A-8,the official handbook for that version.

"The main spar is continuous,the rear spar is divided by the fuselage.Wings and fuselage are connected at both the main and rear spars.The main spar forms part of the lower shell,the rear spar part of the upper."

Steve


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## Siegfried (Nov 27, 2012)

Edgar Brooks said:


> It's possible you're right, but the irony is that they're brand new 21st. century replacement parts to be used in a modern rebuild of a Spitfire to airworthy status, and manufactured to the wartime drawings, dimensions and tolerances. And, no, it wasn't done to catch you out; I don't work that way, so you did that all by yourself.
> If you were to ask for clarification, even help, at times, you might find that those, who take the time to carry out real research in the original archives (and that includes me, to a certain extent,) would offer information quite freely, but you have to come piling in, trying to dazzle everyone with your superior engineering knowhow, when, in fact, you're largely relying on guesswork.




It doesn't matter whether the gun bulges were cold drawn, caste, hot forged or machined out of a solid block or whether it is a recreation or original. *They were elaborate constructions by whatever method.* Every piece of literature on the Spitifre wing says it was build around a main-spar with a strong, relatively thick skinned leading edge to form a D section that provided both torsional rigidity and stiffness in the general planes. (Many of British engineers and writers classify it as 'essentially' a single spar design). It's clear these men knew there was a second spar. It's obvious they classified that way because of the way the wing works, structurally, rather than with the absence or presence of other spars. It becomes difficult to rationally argue a point when plain English language words such as 'most' and 'predominantly' are refused.

You and Flyboy are perhaps having a jolly fun time travelling through a pythonesque reality distortion field if you think a "boom headshot" has been achieved because I can't and I don't think anyone else can.

The only reason these gun bulges would have needed to be so eleborate is because they must preserve the strength of the leading edge and D box because that is the strongest part of the wing that can handle manouvering loads such as turning and rolling as well as the recoil forces and it must therefore remain intact On those 'recreations' one can see multiple drill holes on the flanges for screwing presumably on to to a rib.

We've also seen, on this thread, that the seafire wing was hinged near the wing root through the upper part of the rear secondary spar but not latched at the lower half. In other words it could litterally have flapped about were it not for the forward or main spar. This is entirely consistant with the single locating bolt on the rear spar of the spitifre and of course it's secondary nature.

On a two spar design the D section is not particularly important and strong skins are applied between the forward and rear spars so as to form a box like structure and hence one doesn't seem to see such structures on two spar designs since the leading edge skin is not structural.

It's clear the rear spar would have added strength and stiffness, for one it would locate the upper skin and against the lower and prevent them shearing flat against each other (stringers and ribs provide no strength in that regard) as the wing flexed. This is certainly greater than if there was only the main spar.

However at the end of the day the Spitfire wing structure was *different* and worked *different* and it had *different* aeroelastic properties and that lead to lower roll reversal speed than most of its contempories.


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## FLYBOYJ (Nov 27, 2012)

Siegfried said:


> ItYou and Flyboy are perhaps having a jolly fun time travelling through a pythonesque reality distortion field if you think a "boom headshot" has been achieved because I can't and I don't think anyone else can.



Enjoy cyberspace herr Siegfried!


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## drgondog (Nov 27, 2012)

Siegfried said:


> You and Flyboy are perhaps having a jolly fun time travelling through a pythonesque reality distortion field if you think a "boom headshot" has been achieved.
> 
> We've also seen, on this thread, that the seafire wing was hinged near the wing root through the upper part of the rear secondary spar but not latched at the lower half. In other words it could litterally have flapped about were it not for the forward or main spar. This is entirely consistant with the single locating bolt on the rear spar of the spitifre and of course it's secondary nature.
> 
> ...



IIRC the calculated Reversal Speed on the Spit V was ~ 565mph IAS. The P-47 was in the same range ~545 . You may be confused by the statement in the same NACA 868 Report that the Spit aileron was only 1/2 as _effective at 400mph IAS _as the P-47C? Or more precisely the P-47C aileron was 69% effective and the Spit 35% effective due to aeroelastic torsion. So was the pre-clipped wing Spit "less effective" in Roll? Yes. Did it have a Lower Reversal speed than its contemporaries? No.


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## drgondog (Nov 27, 2012)

That would be NACA 868 "Summary of Lateral Control Research by Langley Research Staff- Compiled by Thomas Toll.


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## Edgar Brooks (Nov 27, 2012)

Siegfried said:


> It doesn't matter whether the gun bulges were cold drawn, caste, hot forged or machined out of a solid block or whether it is a recreation or original. *They were elaborate constructions by whatever method.* Every piece of literature on the Spitifre wing says it was build around a main-spar with a strong, relatively thick skinned leading edge to form a D section that provided both torsional rigidity and stiffness in the general planes. (Many of British engineers and writers classify it as 'essentially' a single spar design). It's clear these men knew there was a second spar. It's obvious they classified that way because of the way the wing works, structurally, rather than with the absence or presence of other spars. It becomes difficult to rationally argue a point when plain English language words such as 'most' and 'predominantly' are refused..







Return to the beginning, and see where you made much of the Spitfire having only a single spar, which, as you can see above (in the Air Publication repair manual, for the Spitfire I, issued by the Air Ministry for Air force personnel) is clearly not so. In all of the following, long-winded discussion, you've been basically arguing with yourself.


> You and Flyboy


I've deleted the rest, since it's a clear sign of lack of maturity.


> The only reason these gun bulges would have needed to be so eleborate is because they must preserve the strength of the leading edge and D box because that is the strongest part of the wing that can handle manouvering loads such as turning and rolling as well as the recoil forces and it must therefore remain intact On those 'recreations' one can see multiple drill holes on the flanges for screwing presumably on to to a rib.


Countersunk rivetting, in fact, to ribs and the leading edge skins; you are repeating youself, since it's always been acknowledged that the wing derives its greatest strength from the "D" box. 


> We've also seen, on this thread, that the seafire wing was hinged near the wing root through the upper part of the rear secondary spar but not latched at the lower half. In other words it could litterally have flapped about were it not for the forward or main spar. This is entirely consistant with the single locating bolt on the rear spar of the spitifre and of course it's secondary nature.


Which is a long way away from your initial assertion that the spar didn't exist; incidentally, the Seafire wing hinge is outboard of the wheel well, and nowhere near the wing root, and the wing would "flap about," if it were not secured by the retaining pins.


> It's clear the rear spar would have added strength and stiffness, for one it would locate the upper skin and against the lower and prevent them shearing flat against each other (stringers and ribs provide no strength in that regard) as the wing flexed. This is certainly greater than if there was only the main spar.


So the rear spar had a purpose, then; by heck, it's like drawing teeth, getting an admission from you.


> However at the end of the day the Spitfire wing structure was *different* and worked *different* and it had *different* aeroelastic properties and that lead to lower roll reversal speed than most of its contempories


And also meant that it was able to turn inside enemies like the 109 190, which saved a lot of RAF pilots, and killed quite a few Germans.

For anyone interested in research, rather than one-upmanship, I've found the repair manual, for the Spitfire I, and copied the relevant pages for repairs to the main spar, and the rear spar. For the rear spar, there are 7 pages of instructions and diagrams, and, for the main spar/leading edge, a further 12 (one above,) so far too many to put on here, but if I get an E-mail address, i can send them on. The manual has far too many pages for me to copy, so that's all I can supply, for now.


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## FLYBOYJ (Nov 27, 2012)

Unless there's an overwhelming plea from our members, "Siggy" will float in cyberspace for a while.

My dad had a saying "So smart but yet so stupid."


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## cimmex (Nov 27, 2012)

why???


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## FLYBOYJ (Nov 27, 2012)

cimmex said:


> why???


He has continually said some pretty stupid things on this forum as well as pissing off several members and mods. He has been warned on several occasions, *that's why!!!!*


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## cimmex (Nov 27, 2012)

In my eyes there was nothing wrong in Siegfried’s post 169 but obviously Mr Brook’s unlimited patriotism does not allow any negative comment to his glory Spitfire.
cimmex


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## FLYBOYJ (Nov 27, 2012)

cimmex said:


> In my eyes there was nothing wrong in Siegfried’s post 169 but obviously Mr Brook’s unlimited patriotism does not allow any negative comment to his glory Spitfire.
> cimmex


I have no dog in that fight, I gave this forum's reasons why Siggy is gone. Be advised that the moderators DO speak to each other and monitor what goes on here, but you're entitled to your opinions either way. With that said, this thread WILL get back on topic!!!! I will not repeat myself!!!!!


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## stona (Nov 27, 2012)

Nor do I.
I have disagreed strongly with some of the opinions expressed by Siegfried in the past but he is entitled to his opinion.

Voltaire

"I do not agree with a word that you say, but I will defend to the death your right to say it."

An injunction to mind the way he expresses his opinion is fair enough.

Steve


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## Edgar Brooks (Nov 27, 2012)

cimmex said:


> obviously Mr Brook’s unlimited patriotism does not allow any negative comment to his glory Spitfire.cimmex


1/. You obviously dislike me, but the name is Brooks; at least do me the courtesy of getting that right.
2/. Patriotism is a love of your home country, and, yes, I'm proud of how my mother, father, aunts, uncles and fellow countrymen women fought to stop a most evil regime from subjugating the whole of Europe. Patriotism does not, however, mean a blind love of every inanimate object produced by that country, and that includes aircraft.
3/. Negative comment is fine, but fabricated (downright lies, in other words) negative comment will cause me to fight, tooth and nail, to get it corrected. Show me one instance where I've said that the Spitfire was unbeatable, the best ever, or not capable of being improved.
Perhaps you can point to me making similarly made-up deprecatory remarks about enemy aircraft? Save yourself the bother, because you can't, since I don't know enough about them, and, unlike others with regard to the Spitfire, am perfectly prepared to say so. 
"I think," "I believe," "Presumably" have no place in research, and passing guesswork off as research is an insult to others on this (or any) forum.
I have spent (and am still spending) hours, going through thousands of 70-year-old files, trying to find out the truth about British aircraft of WWII, and it has nothing, whatsoever, to do with my nationality, but simply because that is what the majority of files contain; unfortunately for your belief about my personality, if the file contains material about a fault in the aircraft, I save it into my files, so I do have unflattering papers on the Spitfire, but have spent so much of my time, countering the absolute garbage spouted about the aircraft, that it hasn't been out in the open.
Finally, is the Spitfire my favourite? In WWII, very definitely, but I've had the privilege of seeing it flown by masters like Jeffrey Quill and Ray Hannah, so I consider that I have very good reason, and will never apologise for that.


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## Njaco (Nov 27, 2012)

and that is the end of that.

One more word or comment that is not on-topic will result in a short vacation.


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## spicmart (Dec 18, 2012)

I don't know if this has been covered before but what construction features enabled the P-63 to roll faster at high speed than its contemporaries?


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## drgondog (Dec 18, 2012)

spicmart said:


> I don't know if this has been covered before but what construction features enabled the P-63 to roll faster at high speed than its contemporaries?



The P-63 had slightly larger ailerons than the Mustang (IIRC) but it's 1/2 wingspan was about 7" greater. The difference between the P-39 and P-63 was almost entirely aileron size. 

It's high speed roll was less than either the clipped Spit and Fw 190 and barely above P-51B > 340mph.


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## krieghund (Dec 19, 2012)

Here's how Jane's describes the spitfire's wing arrangement


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## krieghund (Dec 19, 2012)

Not trying to flame the Spitfire...if fact it's one of my favs....however as with all designs compromises are made but this shows the Spitfire Design team were aware and had a remedy in the wings (pardon the pun) I believe the Spitfull/Seafang was the zenith of the Spitfire line only it was over come by events. 

This is from Spitfire: The History


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## stona (Mar 14, 2013)

I've just been reading Beverley Shenstone's account of the bomber that Supermarine designed to specification B12/36.
The wing for this bomber,like the Spitfire wing,was designed by Shenstone. If anyone can describe it accurately then surely he must be that man.

"Wing structure was a D-nose monospar as in the Spitfire........"

That you might say is straight from the horse's mouth and is good enough for me.

Steve


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## riacrato (Mar 14, 2013)

First time I see drawings of the Spiteful radiator setup, though I've often wondered if they were anything like those of the Bf 109 internally. Turns out they kind of are. They also have the boundary layer control bypass the Bf 109 had in the F-version and abandoned then from G onwards. It has always puzzled me and now does so even more since Supermarine apparently found them to be a worthwhile addition. Maybe they only become important at high enough speeds / mach?


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## stona (Mar 14, 2013)

Whilst working in Germany Beverley Shenstone had become very interested in the boundary layer and aircraft skin design. He had studied this with Lippisch and Junkers and had discussed it with Prandtl and von Karman,two of the leading men in the field.

In January 1937 Shenstone published a paper in Aeronautical Engineering entitled "Sucking off the boundary layer,original efforts for boundary layer control."
Shenstone did not apply boundary layer suction via mechanical means to his Spitfire wing,it would be many years before this technology was perfected,but he did sculpt and smooth the airframe to reduce shear layer friction and increase the speed of the boundary layer airflow.

For an example look underneath a Spitfire. At the rear of each wing root are U shaped channels that tune the airflow of the underbody and each wing as it leads back under the fuselage boom.It is an effort to stop the air stagnating or becoming fully turbulent and reduces the wake vortices spilling off the underwing junctions. This was not completely successful as the Spitfires radiators still created fouling of the boundary layer leading to underwing turbulence and boundary layer "bubbling". 

I'm sure Shenstone's boundary layer research would have informed his successors at Supermarine and influenced the radiator set up on the Spiteful,as would the work of his German pre-war colleagues.

Cheers

Steve


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## GregP (Mar 16, 2013)

Went and looked at Reno Racer #232 (finished seciond this year in Unlimited Gold). It started life as a Sea Fury FB 11 and though they have removed the wing fold hydraulics, the locking mechanisms are still there and obviously work or it would never fly.

I believe there was a pic posted where it was speculated that the wing might have been three spars. It isn't; it is a 2-spar wing. The third item in view is merely a pin to transfer the flaps motion to the outer panels ... that is ... the pin locks the outer flap sections to the center flap.


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