F4U inverted gull wings

On Sun, 4 Jul 2004 21:46:07 +0000 (UTC), hobo wrote:

This website was my sole source for the claim that the Corsair had a 3
blade prop. Perhaps a 4 blade was later added, but it seems odd that a 3
blade was ever used if ground clearance was so pivotal to the whole
design.

Prop design is extraordinarily complicated. The Corsair, like several
of the high powered, high speed fighters of WWII had a high enough
performance to reach the boundaries of propeller powered design.

The problem was how to harness all that power. You can use a multi
blade prop with a smaller diameter, but acceleration and climb may be
compromised.

The people who designed the Corsair understood that you loose whatever
thrust was being developed by the inner diameter of the prop because
the thrust is masked by the cowling housing the engine. One way of
getting around the large cowling is to make a large prop. The large
prop allows good takeoff and climb performance. The ability of the
Corsair to haul large loads into the air was likely one of the reasons
it was still flying for the Navy by the time of the Korean war, even
though it had been designed in 1938.

There were actually several reasons for the inverted gull wing design:
This was to be a Navy carrier fighter. Carrier fighters have to land
on board aircraft carriers and this landing is often so harsh that
it's been likened to a barely controlled crash. The landing gear had
to be very very sturdy to take the severe G forces when the airplane
smacked down on the deck.

The design of the fuselage, as was typical for the day, involved a
round cross section. Mating a wing to a round cross section required
a large fairing to reduce drag at the wing to fuselage intersection.
The fairing was not necessary if the wing could be mated at a 90
degree angle to the fuselage.

Finally, the prop being proposed was the biggest ever attached at the
time to a fighter, because the design was to use the Pratt and Whitney
R-2800 engine which at the time was one of the most powerfull ever
developed.

The elegant solution to all three problems was to use the inverted
gull wing. This kept the landing gear short, or at least shorter than
it would have been with a straight wing, made the wing to fuselage
intersection possible without a fairing, and gave the necessary
clearance for that huge prop.

It was not without it's problems however.

Corky Scott