Washout/wing twist F4U

mad_max · Apr 25, 2018

I've looked everywhere I can think of, but can't find a source that tells me. I've seen talk about no washout, but nothing definitive. Any help out there?

Thanks

tomo pauk · Apr 25, 2018

Seems like there was no washout, the 'America's hundred thousand' says that wing incindence was 2 deg both at root and tip.

Edit: picture

mad_max · Apr 25, 2018

Thanks. I've seen this before, but wanted to make sure I understood it properly.

drgondog · Apr 26, 2018

tomo pauk said:
Seems like there was no washout, the 'America's hundred thousand' says that wing incindence was 2 deg both at root and tip.

Edit: picture

Tomo - not sure that is the 'final answer'. Recall that the wing root incidence spanwise has a termination point at the Gull Wing interaction with outer wing..I would believe that the spanwise distribution from there to tip is Zero to -2 degrees. It is hard to believe no washout given the requirement for roll authority at low speed for carrier landing.

tomo pauk · Apr 26, 2018

drgondog said:
Tomo - not sure that is the 'final answer'. Recall that the wing root incidence spanwise has a termination point at the Gull Wing interaction with outer wing..I would believe that the spanwise distribution from there to tip is Zero to -2 degrees. It is hard to believe no washout given the requirement for roll authority at low speed for carrier landing.

We know that F4U have had a problem with low-speed handling, in particual with a tendency to 'drop a wing' - IIRC a 'whole' wing on one side will drop in the same instant, vs. eg. Spitfire that will produce enough of stall warning due to having a washout (meaning that root will start to stall, but the ooutboard-ish section of a said wing will still produce lift).
FWIW, I've cropped te part of the picture linked from above, it depicts 2 deg incindence at root, at the 'kink' and at theoretical tip:

MIflyer · Apr 27, 2018

The F4U was unusual in that it was a big, fast, powerful, heavy airplane with fabric covered outer wings and wooden fabric covered ailerons. Also, washout at the tip is required less if you use differential ailerons. The Ercoupe has no washout at the outer tip but has a stall strip at the root and highly differential ailerons; spin resistance was a primary objective.

drgondog · Apr 29, 2018

tomo pauk said:
We know that F4U have had a problem with low-speed handling, in particual with a tendency to 'drop a wing' - IIRC a 'whole' wing on one side will drop in the same instant, vs. eg. Spitfire that will produce enough of stall warning due to having a washout (meaning that root will start to stall, but the ooutboard-ish section of a said wing will still produce lift).
FWIW, I've cropped te part of the picture linked from above, it depicts 2 deg incindence at root, at the 'kink' and at theoretical tip:

View attachment 491041

Interesting and informative. The two advantages I can think of are 1.) no incremental induced drag introduced with twist/washout, and b.) simpler jig/tooling for constant incidence.

Vought introduced a spoiler on one lower wing (right?) to initiate 'common' stall speed at high angle of attack due to upwash/downwash created by prop vortex.

pbehn · Apr 29, 2018

If the idea of washout is for the inner wing to stall before the outer wing does, wouldn't the bend in the wing achieve that? Although the wing profile and angle of incidence may be uniform there is obviously a bigger surface area underneath the wing than above it?

Washout/wing twist F4U

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