F4U Corsair

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The Royal Navy operated Corsairs at sea successfully - by reducing the inflation pressure on the oleo struts sufficiently to reduce bounce.

Back to the pros-cons of Gull Wings - Corsair wings are inverted Gull for the various reasons described at the top of this thread. Non inverted Gull wings were used on aircraft like German flying boats to raise the engines props higher from the water. In both cases, clearance and strength seem to be the number one factor in the design.

MM
 
Hello Folks,

I believe the claimed advantage of the inverted gull wing on the Corsair was that the join between the wing and fuselage was the smallest area that it could be because the joint was at a 90 degree angle. I believe that the lack of a need for a fillet was incorrect. Observe that the heavily modified Corsairs that are currently used in Unlimited Class air racing DO have fillets at the wing root.

There is no question that the landing gear struts could be shorter with the inverted gull wing. Because of the design, the length of the strut and wheel was limited by wing chord.

I believe the other aerodynamic issues are the following:
The Corsair has very low lateral stability because the center of lift is VERY low in relation to the center of gravity.
The wing center section is a major contributor to lift because the wing bends act as fences to prevent the high pressure air from spilling out to the wingtips. Modern jet fighters use the center fuselage section between widely spaced engines for the same effect.

Let me know what you all think.
- Ivan.
 
Ivan1GFP said:
...the join between the wing and fuselage was the smallest area that it could be because the joint was at a 90 degree angle
Click to expand...
Hi Ivan
I know I'm being a bit slow here
so if I drew an imaginary line back through the bent section of the wing (looking at the a/c from head-on) and continued the line back into the cylindrical fuselage, it would - in 2D - pass through the centre of the circle created by the frontal aspect of the fuselage (the longeron datum line)?

I'm trying to get a fix on what this wing angle is at 90 degrees to, mating as it does to a cylindrical (fuselage) section.
 
Hi Colin1,
The wing root meets the fuselage at 90 degrees to the surface of the fuselage (surface of your cylinder). Consider that in most low wing monoplanes, the wing meets the fuselage almost at a tangent to the surface of the fuselage (cylinder). (The lower wing surface typically IS tangent to fuselage.) Because it meets at nearly a tangent, the intersection between wing root and fuselage is very large.

I am not an aerodynamics person. I just read a fair amount, so I don't know my opinions have a whole lot of validity.

- Ivan.
 

That's what I was trying to say, but you put it in much better words than I. I didn't do so hot in trig...
 
As far as the wing to fuselage goes, it is like a mid mounted wing. Like the F4f Wildcat. But a mid mount would create extremely long landing gear if it extends from the wing rather than the fuselage like a Wildcat. So you rotate the wing down to the "bottom" of the fuselage while still keeping a 90 deg. connection, and then bend the wing up towards an area around the lower or mid point of the fuselage.

I am no aerodynamcist myself, but I can easily see that this makes for a far less area of wing attachment to the body of the airplane.

And once again, I am not sure this was on purpose, but incidental. I think Vought first did this to simply shorten and strenghten the landing gear.

If you look at a few threads back, I had a question about the aerodynamics of the Corsair. Drgondog and several others also contributed greatly to that question. The Corsair seems to be a study in questionable or unique aerodynamics. Starting at the wing and ending at the tail design. Truely a very unique fighter no doubt!

I read once, that anytime you see cranked wings, or twisted tails, you are seeing aerodynamic "fixes" for a less than perfect design. This was talking about the F4 Phantom jet fighter, but it may also apply in this instance.

And I am not slamming the F4U Corsair, I like them!
 

That's how I understand it Colin...

 


Based on Vought's V-326 (above) they trialled a R-4360 Wasp Major in a Corsair which became the F4U-1 WM, the predecessor to the F2G, but I don't know what year it was. No prop clearance problems here...



...and there was an Aero Products contraprop trialled on a Corsair, but I don't know the diameter or when they did it...

 
Colin1 said:
If that's a standard workbench to the right with the toolbox on top and that's a normal engine crane to the left, that leg's got to be touching 7ft
Click to expand...

Excellent logic! Thanks Colin. I'd figure around the same, based on halving the "extended" dimension of this drawing. Either way it's a very long leg for a carrier plane. The Pirate and Cutlass didn't work out well for Vought.



Maybe the F-7D would have been the solution...



Sought-After Models... [Archive] - The Great Planes and warbirds Community
 

The thing about the F4U's crank though was that it was basically designed in from the get-go, it wasn't put in as a fix.
 
Way back someone was discussing the propeller diameter. The Corsair came with two different diameter 3 blade props. The first was 13'4" diameter. Its tips would go supersonic at full rpm and in fact was slower at full throttle than at part throttle (as tested by the British). The later prop was 13'2" and generally was better for performance. Regarding the contra-prop, the issue with it was that it added several hundred pounds to the weight of the aircraft and actually decreased performance over the 4 blade prop.

I believe that most aircraft need some kinds of refinement between prototype and production versions. F-104's anhedral, Fin fillet on the TBF Avenger, etc. It doesn't necessarily indicate that the basic design was faulty (though I do believe the F-104's basic design wasn't very good).

- Ivan the opinionated.
 
I'm curious to know what aerodynamic benifits were realized from the 90 degree wing/fuselage mounting on the Corsair? The F4F Wildcat (mid-wing, also 90 degree?) wasn't known as a speed demon, so I'm guessing speed increase wasn't it?

I do see lots of daylight between the "v" of the gull wing and the horizontal stabilizer (in the image Graeme posted), and that should be a good thing as far as elevator control and stability I would think.
 
claidemore said:
I'm curious to know what aerodynamic benifits were realized from the 90 degree wing/fuselage mounting on the Corsair? The F4F Wildcat (mid-wing, also 90 degree?) wasn't known as a speed demon, so I'm guessing speed increase wasn't it?
.
Click to expand...

Or.. how much slower would it have been with a low mounted wing?
 
There is no question that the intersection of the Corsair wing root with the fuselage was cleaner than the intersection of the wing and fuselage of the Hellcat with the fairing that was needed. That was a part of the reason that the Corsair had better performance than the Hellcat with essentially the same engine. The design philosophy of the Corsair was to have the smallest and cleanest air frame possible married to the most powerful radial engine available. The R2800 was chosen not only because of it's power but because it was a twin row engine which gave it a relatively small cross section and the fuselage of the Corsair was round like the engine and therefore had a small cross section. The wing intersection was a side effect of the effort to make the landing gear shorter and therefore stronger. It was fortunate that the amount of propellor clearance created was generous because the later Corsairs needed a taller tail wheel strut for aerodynamic and visibility effects. The prototype Corsair had all fuel in the wings and the guns in the nose. The desire to relocate the guns into the wings and most of the fuel into the fuselage and keep the fuselage slender resulted in moving the cockpit aft about three feet in order to create room for the fuselage fuel tank in production models. The moving of the cockpit created visibility problems, especially at high AOAs. The Corsair, as with all AC, was a series of compromises. The resulting AC, considering it's time frame, was an engineering tour de force.
 
I once calculated Cd's of various WW2 radial engined fighters. I was expecting fighters like the La-7 and Fw190A having the lowest figures. But F4U-1 came on top.
 
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