F4U inverted gull wings

In article ,
Orval Fairbairn wrote:

They wanted to keep the main landing gear as short as possible, to
simplify structural loads. The Hellcat had a relatively long main gear
leg.

A four-bladed prop for the same power output should be shorter than the
three-bladed equivalent.
--

In article ,
Steve Hix writes:
In article ,
Orval Fairbairn wrote:

They wanted to keep the main landing gear as short as possible, to
simplify structural loads. The Hellcat had a relatively long main gear
leg.

A four-bladed prop for the same power output should be shorter than the
three-bladed equivalent.

But somewhat less efficient. Each blade added to a propeller knocks
the efficiency down. Later model Corsairs with the more powerful
R2800 'C' series engines had a 4 blade prop, but the diameter is
essentially the same - 13 ' 2".

You also have to tune 'J', the Advance Ratio of the propeller (A
product of propeller rotational speed, propeller diameter, and the
forward velocity of the propeller (and the airplane it's attached
to.) in order to get teh best performance. reducing the diameter for
a given horsepower may have beneficial effects at high speed, but
severely affect the propeller's performance below, say, about 350 mph.

It's all a balancing act - but in ggeneral, you're best off going with
the largest diameter propeller with the fewest number of blades that
you can practically manage.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster
--

hobo wrote:

In article ,
"Geoffrey Sinclair" wrote:

Corsair propeller diameter 13 feet 4 inches, ground clearance
9.1 inches, engine R-2800-8.

The corsair used a 3-blade prop. Why didn't they use a smaller 4-blade
prop if ground clearance was such an issue?

Check again, please: http://www.warbirdalley.com/f4u.htm

| George Ruch
| "Is there life in Clovis after Clovis Man?"

In article ,
George Ruch wrote:

hobo wrote:

The corsair used a 3-blade prop. Why didn't they use a smaller 4-blade
prop if ground clearance was such an issue?

Check again, please: http://www.warbirdalley.com/f4u.htm

The F4U-4 had a four-blade prop, but earlier versions had three blades,
and include a large part of what saw combat in WW2.
--

In article ,
George Ruch wrote:

hobo wrote:

In article ,
"Geoffrey Sinclair" wrote:

Corsair propeller diameter 13 feet 4 inches, ground clearance
9.1 inches, engine R-2800-8.

The corsair used a 3-blade prop. Why didn't they use a smaller 4-blade
prop if ground clearance was such an issue?

Check again, please: http://www.warbirdalley.com/f4u.htm

The link you provided has no textual information regarding the prop, but
there is a picture, dated 2001, of a surviving Corsair with a 4 blade
prop. This prop may not be the original factory issue.

When this question was first posted the first website on the Corsair I
found was this:
http://www.nasm.si.edu/research/aero...t/voughtf4.htm

This is the Smithsonian's website and has a photo of a Corsair with a 3
bladed prop and this text: "The R-2800 radial air-cooled engine
developed 1,850 horsepower and it turned a three-blade Hamilton Standard
Hydromatic propeller with solid aluminum blades spanning 13 feet 1 inch."

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.
--

In article ,
hobo writes:
The link you provided has no textual information regarding the prop, but
there is a picture, dated 2001, of a surviving Corsair with a 4 blade
prop. This prop may not be the original factory issue.

When this question was first posted the first website on the Corsair I
found was this:
http://www.nasm.si.edu/research/aero...t/voughtf4.htm

This is the Smithsonian's website and has a photo of a Corsair with a 3
bladed prop and this text: "The R-2800 radial air-cooled engine
developed 1,850 horsepower and it turned a three-blade Hamilton Standard
Hydromatic propeller with solid aluminum blades spanning 13 feet 1 inch."

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.

Hobo,
All the F4U-1 models had 3-blade propellers, with a 13'1" diameter.
The later production models, the F4U-4 and F4U-5, with higher-powered
engines, had 4 blade props with a 13'2" diameter, to absorb the extra
power. (More than 800 HP in some versions.)

So, its fair to say that they didn't go to a 4-blade prop to decrease
ground clearance.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster
--

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

"hobo" wrote in message
...

The corsair used a 3-blade prop. Why didn't they use a smaller 4-blade
prop if ground clearance was such an issue?


A 3-blade prop was used on the XF4U-1 through F4U-2 and equivalent Corsairs.
A 4-blade prop was used on the XF4U-3 and subsequent Corsairs.

"Bob M." wrote in message
...

I recently visited the Udvar-Hazy facility and received the usual
story about how the Corsair got its inverted gull wings, i.e. to
accomodate the 13 ft. prop which, in turn, was necesitated by the
engines power. However, the Hellcat used essentially the same engine,
and IIRC also used a 13 ft. prop. Yet it did not need those wings.
In fact it was mid winged, not low winged. So what is the true story?
Were the gull wings just one solution. How did the Hellcat
accomodate the prop? Longer landing gear? Or am I wrong? Was the
Hellcat prop 13 ft.?


The F6F-5 propeller was 13' 1" in diameter.

In article , "Steven P. McNicoll"
wrote:

The F6F-5 propeller was 13' 1" in diameter.

When new;-)
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