F4U inverted gull wings

[Bob M.]

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.?
--

[MLenoch]

>From: (Bob M.)

wrote:(The Hellcat)> was mid winged, not low winged.

The Hellcat was actually low wing.
Otherwise good historical question.
VL

[Steven P. McNicoll]

"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.?
>

Propeller diameter on the F6F-5 was 13' 1".
--

[Air Force Jayhawk]

On Wed, 30 Jun 2004 15:38:25 +0000 (UTC), (Bob M.)
wrote:

>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.?

First off, the F6F was a low wing aircraft...

Roscoe
--

[Ken Duffey]

Bob M. wrote:
> 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.?

I'm not sure if it is the answer - but fitting gull wings (whether
inverted or not) means that the wing root joins the fuselage at approx
90 deg - therebye eliminating the need for a large, drag-producing
wing-to-fuselage fillet.

Having said that, the F4F Wildcat had mid-wings without any fillets.

You only need fillets on high or low-winged a/c

Is the Hellcat mid-winged - I can't remember ?

ken

[Stephen FPilot Bierce]

Air Force Jayhawk > wrote:

>First off, the F6F was a low wing aircraft...

Okay...

1) Shorter rear fuselage and tail landing gear struts, so the nose points higher
when the plane is parked,

2) engine is set higher, with the air ducting set under the engine rather than
the wings; the fuselage, while the about the same thickness side-to-side, was
thicker top-to-bottom.

Stephen "FPilot" Bierce/IPMS #35922
{Sig Quotes Removed on Request}
--

[George Z. Bush]

"Ken Duffey" > wrote in message
...
> I'm not sure if it is the answer - but fitting gull wings (whether
> inverted or not) means that the wing root joins the fuselage at approx
> 90 deg - therebye eliminating the need for a large, drag-producing
> wing-to-fuselage fillet.
>
> Having said that, the F4F Wildcat had mid-wings without any fillets.
>
> You only need fillets on high or low-winged a/c
>
> Is the Hellcat mid-winged - I can't remember ?

Take a look at the picture.....looks like a low wing to me.

http://www.warbirdalley.com/f6f.htm

George Z.

--

[Geoffrey Sinclair]

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.?

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

Hellcat propeller diameter 13 feet 1 inch, ground clearance
7.3 inches, engine R-2800-10.

The gull wing was one solution to the trade offs between wing
placement relative to the fuselage, propeller diameter and landing
gear size.

I would suggest looking at cut away drawings to see the differences
between the two types. The Corsair went for a smaller fuselage
size, putting the fuel in front of the cockpit and putting the air intakes
in the wing roots. The Hellcat had the fuel located effectively under
the cockpit, with the bonus that the deeper fuselage raised the cockpit
giving better forward view, very useful for carrier operations, it also had
the air intakes mounted under the engine, hence a larger frontal area
than the Corsair with the inevitable performance penalties but mounting
the engine higher in the fuselage to help propeller clearance. It looks
like the Hellcat's wing was slightly broader than the Cosairs, so more
room for the landing gear and the Hellcat had a smaller landing gear
tread 11 feet versus 12 feet 1 inch so the gear was mounted closer
to the fuselage where the wing was broadest.

Geoffrey Sinclair
Remove the nb for email.

--

[Steven P. McNicoll]

"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.

[W. D. Allen Sr.]

The Navy Wildcat F4F was midwing. The Hellcat F6F was low wing.

WDA

end

"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.?
> --
>

[hobo]

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?
--

[Orval Fairbairn]

In article >, 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?

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.
--

[George Ruch]

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?"

[B2431]

>From: Orval Fairbairn
>Date: 7/2/2004 10:30 AM Central Daylight Time
>Message-id: >
>
>In article >, 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?
>
>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.
>--

Corsair had a 4 bladed prop. A 3 bladed prop may have been big enough to
irritate the Seabees who had no sense of humour when it came to prop blades
chewing up their runways.

Dan, U.S. Air Force, retired

[Steven P. McNicoll]

"B2431" > wrote in message
...
>
> Corsair had a 4 bladed prop.
>

It also had a 3 bladed prop. It all depends on the specific model.

[Dale]

In article >,
(B2431) wrote:



> Corsair had a 4 bladed prop. A 3 bladed prop may have been big enough to
> irritate the Seabees who had no sense of humour when it came to prop blades
> chewing up their runways.


The early Corsairs used a 3-blade prop, later versions had a 4-blade
prop.

--
Dale L. Falk

There is nothing - absolutely nothing - half so much worth doing
as simply messing around with airplanes.

http://home.gci.net/~sncdfalk/flying.html

[Steven P. McNicoll]

"Orval Fairbairn" > 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?
>
> 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.
>

You appear to be answering a question other than the one asked.
--

[Steve Hix]

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.
--

[Bill]

In article >, "Steven P. McNicoll"
> wrote:

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

When new;-)
--

[Steve Hix]

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.
--

[Steve Hix]

In article >,
(B2431) wrote:

> Corsair had a 4 bladed prop. A 3 bladed prop may have been big enough to
> irritate the Seabees who had no sense of humour when it came to prop blades
> chewing up their runways.

The F4U had a three-blade prop from the XF4U-1. The F4U-4 introduced the
four-blade prop on production Corsairs. (The XF4U-3 had a four-blade
prop, but didn't go into production, and the prototypes were returned to
their F4U-1 initial state.)

[Krztalizer]

>The F4U had a three-blade prop from the XF4U-1. The F4U-4 introduced the
>four-blade prop on production Corsairs. (The XF4U-3 had a four-blade
>prop, but didn't go into production, and the prototypes were returned to
>their F4U-1 initial state.)

I have a formerly classified file of a Vought tech-reps final tour report from
1943. The guy traveled everywhere in the South West Pacific theater, checking
on the servicability and operational needs of all US units that used Corsairs
at that point in the war. He hit every island that supported Corsair
operations, recording every nit pick and shortage among each unit, at times
under direct enemy attack. Planes crashed in front of him, he occasionally
landed at forward airstrips in the middle of battles and airraids.

The only serial problem that the report contains is a repeated cry for tires -
since the F6F-3, F4U-1, and TBFs all used the same 32x8 tire, they were in
critically short supply. Other problem areas include the cartridge starters
and nagging issues with the voltage regulators. The report has comments about
every aspect of Corsair operations - surprising to me is that nearly every unit
he visited requested a modification for a locked-wing Corsair, with the wing
fold mechanism removed for weight saving and increased roll rate.

As to props - this is old Jack's only comments:


TOUR OF INSPECTION OF THE SOUTH AND CENTRAL PACIFIC AREAS COVERING F4U-1
OPERATIONS, MAINTENANCE, AND SPARES. 30 DEC 1943 LT JOHN J. HOSPERS, USNR

Page 32 Material and Equipment

56. All Squadrons have been informed that the F6F-3 propellor is
interchangeable with the F4U-1 and that this paddle blade design will improve
the performance of the F4U-1.

v/r
Gordon

<====(A+C====>
USN SAR

Its always better to lose -an- engine, not -the- engine.

[Greg Hennessy]

On 03 Jul 2004 04:42:25 GMT, (Krztalizer) wrote:


>56. All Squadrons have been informed that the F6F-3 propellor is
>interchangeable with the F4U-1 and that this paddle blade design will improve
>the performance of the F4U-1.

Improved by how much I wonder ?


greg

--
Konnt ihr mich horen?
Konnt ihr mich sehen?
Konnt ihr mich fuhlen?
Ich versteh euch nicht

[Peter Stickney]

In article >,
Greg Hennessy > writes:
> On 03 Jul 2004 04:42:25 GMT, (Krztalizer) wrote:
>
>
>>56. All Squadrons have been informed that the F6F-3 propellor is
>>interchangeable with the F4U-1 and that this paddle blade design will improve
>>the performance of the F4U-1.
>
> Improved by how much I wonder ?

I _thought_ I'd posted to this thread yesterday, with a few fidbits on
propellers, but the record shows that it didn't make it, for some
reason.

Anyway - The amount of power that a propeller can absorb (and turn
into thrust) is goverened more htna anything else by the total blade
area, and its Activity Factor (Essentially its Solidity - the ratio of
the area of the ptopeller blades to the total area of the propeller
disk.) The higher the solidity, the more power you can absorb.

The Efficiency of the propeller, (The amount of Shaft Horsepower that
it turns into Thrust) is driven by the Advance Ratio (A product of the
propeller's rotational speed vs. the airplane's forward speed), and
the blade angle. With a Constant Speed propeller, the blade angle
factor is removed, within the limits of the propeller's pitch stops,
because the propeller governor will always select the most efficient
blade angle to absorb the shaft horsepower. The propeller's pitch
range is such that, for any power level normally encountered in
flight, the propeller blades are not on the stops, and we can safely
ignore it for the purposes of this post, and only consider Advance
Ratio. Efficiency drops off at both low and high Advance Ratios, so
you can't just shoot for the highest one you can reach. (And, in the
WW 2 fighter case, with geared propeller drives, you start to run into
efficiency losses at high speed as the propeller blades start going
transonic. Other airplanes can get the propeller tips transonic at
lower airspeeds. One of the big reasons for a T-6/SNJ's irritating
snarl is that, with its ungeared R1340, the prop tips are transonic.)

Also, there are purely mechanical considerations - the propeller had
to be able to stay together while its working. Propeller blades are
thin, but they aren't light, and the forces both along their length
(ccentrifugal), and across the propeller disk (Thrust) are high. All
the force is concentrated at the blade root at the hub, so not only
are there high forces, but they've got long lever arms to work with.

You can add blade area in 3 ways - you can increase the propeller
diameter, you can increase the area per prop blade, or you can
increase the number of prop blades. There are tradeoffs for all three
options. Increasing the diameter of the propeller works well
aerodynamically at most Advance Ratios, but the tip speeds are high.
since most of the thrust of a propeller is generated at the tips, it
also puts huge loads on the propeller blade & hub. (And it has to fit
on the airplane).
Increasing the blade area of each propeller blade ("Paddle Blades")
will increase the efficiency at low Advance Ratios, giving better
takeoff and climb performance, but at a cost in high Advance Ratio
performance, and with added problems with structural strength.
It also allows the diamter to be more carefully controlled, with some
benefits at high speed.
Increasing the number of propeller blades also allows the diameter to
be controlled, and doesn't requires as much structural strength per
blade as the other two options. It does decrease overall efficiency.
(A good rule of thumb is 2-3% per blade) This is due to interference
effects of a propeller blade tip running into the vortices of the
blade ahead of it.
So, in general, the order of merit of the three options is this:
1) Increase the propeller diameter, if practicable.
2) Increase teh propeller blade area without increasing the diameter
(Paddle blade)
3) Increase the number of propeller blades.

As to the Hellcat propeller being fitted to the Corsair - it was
certainly done - for example, the tests performed by the USN of a
P-51B vs 2 hotted up Corsairs used Hellcat propellers for both
aircraft. (The preort can be found online at:
http://www.geocities.com/slakergmb/id95.htm

As to how much it would affect performance - The Hellcat propeller
would mose likely by about 2% more efficient at the F4U's climb speed,
and about the same efficency at maximum speed. At climb speed, the 2%
greater efficency would give 40 more Thrust Horsepower at Sea Level
(2000 SHP), and about 34 more Thrust HP at high altitudes. (This is
because the Corsair's geared supercharger delivered less Shaft
Horepower at high altitudes, since more power was diverted to the
supercharger). At teh Corsair's best climb speed of 135 Kts at Sea
Level, that's 95# more excess thrust. it doesn't sound like much, but
since it's all excess, it gives about 108 ft/min more climb. At
22,000', the excess thrust would be about 58#, giving a improved rate
of climb of 95 ft/minute. It doesn't seem like much, but it makes a
difference.

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

[Steven P. McNicoll]

"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.

[John R Weiss]

Very interesting! The only part I question is:

"Peter Stickney" > wrote...
>
> Increasing the diameter of the propeller works well
> aerodynamically at most Advance Ratios, but the tip speeds are high.
> since most of the thrust of a propeller is generated at the tips, it
> also puts huge loads on the propeller blade & hub.

How can "most of the thrust" be generated at the tips -- given the
combination of shorter chord, lower AOA, and [vortex] airflow around the
tips -- compared with the midspan of the blade?

[Greg Hennessy]

On Sat, 3 Jul 2004 11:15:02 -0400, (Peter Stickney)
wrote:

[snip excellent detail]

>It doesn't seem like much, but it makes a
>difference.

ISTR something about a paddle bladed P-38 being ~40 mph faster than the
stock model.

But it wasnt possible to schedule the production changes to implement it.


I suppose the US war dept had more important things to do like waste money
on the Fisher P75.



greg

--
Konnt ihr mich horen?
Konnt ihr mich sehen?
Konnt ihr mich fuhlen?
Ich versteh euch nicht

[Peter Stickney]

In article <PyBFc.18031$%_6.5403@attbi_s01>,
"John R Weiss" > writes:
> Very interesting! The only part I question is:
>
> "Peter Stickney" > wrote...
>>
>> Increasing the diameter of the propeller works well
>> aerodynamically at most Advance Ratios, but the tip speeds are high.
>> since most of the thrust of a propeller is generated at the tips, it
>> also puts huge loads on the propeller blade & hub.
>
> How can "most of the thrust" be generated at the tips -- given the
> combination of shorter chord, lower AOA, and [vortex] airflow around the
> tips -- compared with the midspan of the blade?

Ah, you caught me oversimplifying/underexplaining. Thanks.

Because the airspeed of the propeller is much higher at the tips,
most of the thrust produced by the propeller is higher there. A
simple rectangular prop with a constant chord would, all other things
being equal, be developing a tremendouds amount of force at the tips,
and hardly any near the hub. This sets up a severe structural problem
- a simple propeller shape will have a tremendous bending moment both
at the point where the blade joins the hub, and along the length of
the blade. (As an aside, you also don't want the propeller blades to
be too heavy - a WW 2 fighter propeller blade typically weighed about
100#/45 Kilos). Building strong, lightweight blades that could take
these forces and not have, say, problems with resonance, was a
difficult and involved process, fraught with danger - It wasn't
unusual for a disintegrating propeller to destroy the test cells at
Hamilton Standard and Wright Pat, let alone be something that could be
trusted in the air - so propeller shapes, before WW 2, were tweaked to
provide a fairly constant (at some particular design point wrt prop
pitch and airspeed) distribution of forces. This included reducing
the area at the tips (Which also decreased the strucural issues),
changing the propeller pitch across the propeller blade's length, to
keep the lift coefficient the same, and making the shank of the blade
completely round. (For greater strength, and for making the
pitch-change mechanisms easier to design & build.)
using a progressive pitch ditribution (propeller twist) allows for
more thrust at low speeds.

A typical early WW 2 propeller, with a relatvely narrow propeller
blade chord and a fiarly pointed tip produced its maximum thrust in a
region between 80 and 90% or the propeller radius.
(Ref: NACA Report No. 712, "Propeller Analysis From Experimental
Data", Stickles & Crigler, 1940.)
As structural techniqes improved during the war, it became possible to
make wider chord propeller tips, moving the point of maximum thrust
further out along the blade radius. It still doesn't peak at the
tips, though, because of the tip vortices. It's still a serious load
on the propeller shank.
Compare, for example, the early and later CUrtiss Electric propellers
used on P-47s - the early propeller blades are "toothpicks", while the
later "paddle" blades are nearly rectangular, with the same maximum
chord, but held for a much longer section of the blade radius.
Or the propeller of a P-40 or P-51A to that of a P-51B.


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

[Grantland]

GREAT POST Sticky! Much better! Keep it up!

Grantland

(Peter Stickney) wrote:

>In article >,
> Greg Hennessy > writes:
>> On 03 Jul 2004 04:42:25 GMT, (Krztalizer) wrote:
>>
>>
>>>56. All Squadrons have been informed that the F6F-3 propellor is
>>>interchangeable with the F4U-1 and that this paddle blade design will improve
>>>the performance of the F4U-1.
>>
>> Improved by how much I wonder ?
>
>I _thought_ I'd posted to this thread yesterday, with a few fidbits on
>propellers, but the record shows that it didn't make it, for some
>reason.
>
>Anyway - The amount of power that a propeller can absorb (and turn
>into thrust) is goverened more htna anything else by the total blade
>area, and its Activity Factor (Essentially its Solidity - the ratio of
>the area of the ptopeller blades to the total area of the propeller
>disk.) The higher the solidity, the more power you can absorb.
>
>The Efficiency of the propeller, (The amount of Shaft Horsepower that
>it turns into Thrust) is driven by the Advance Ratio (A product of the
>propeller's rotational speed vs. the airplane's forward speed), and
>the blade angle. With a Constant Speed propeller, the blade angle
>factor is removed, within the limits of the propeller's pitch stops,
>because the propeller governor will always select the most efficient
>blade angle to absorb the shaft horsepower. The propeller's pitch
>range is such that, for any power level normally encountered in
>flight, the propeller blades are not on the stops, and we can safely
>ignore it for the purposes of this post, and only consider Advance
>Ratio. Efficiency drops off at both low and high Advance Ratios, so
>you can't just shoot for the highest one you can reach. (And, in the
>WW 2 fighter case, with geared propeller drives, you start to run into
>efficiency losses at high speed as the propeller blades start going
>transonic. Other airplanes can get the propeller tips transonic at
>lower airspeeds. One of the big reasons for a T-6/SNJ's irritating
>snarl is that, with its ungeared R1340, the prop tips are transonic.)
>
>Also, there are purely mechanical considerations - the propeller had
>to be able to stay together while its working. Propeller blades are
>thin, but they aren't light, and the forces both along their length
>(ccentrifugal), and across the propeller disk (Thrust) are high. All
>the force is concentrated at the blade root at the hub, so not only
>are there high forces, but they've got long lever arms to work with.
>
>You can add blade area in 3 ways - you can increase the propeller
>diameter, you can increase the area per prop blade, or you can
>increase the number of prop blades. There are tradeoffs for all three
>options. Increasing the diameter of the propeller works well
>aerodynamically at most Advance Ratios, but the tip speeds are high.
>since most of the thrust of a propeller is generated at the tips, it
>also puts huge loads on the propeller blade & hub. (And it has to fit
>on the airplane).
>Increasing the blade area of each propeller blade ("Paddle Blades")
>will increase the efficiency at low Advance Ratios, giving better
>takeoff and climb performance, but at a cost in high Advance Ratio
>performance, and with added problems with structural strength.
>It also allows the diamter to be more carefully controlled, with some
>benefits at high speed.
>Increasing the number of propeller blades also allows the diameter to
>be controlled, and doesn't requires as much structural strength per
>blade as the other two options. It does decrease overall efficiency.
>(A good rule of thumb is 2-3% per blade) This is due to interference
>effects of a propeller blade tip running into the vortices of the
>blade ahead of it.
>So, in general, the order of merit of the three options is this:
>1) Increase the propeller diameter, if practicable.
>2) Increase teh propeller blade area without increasing the diameter
>(Paddle blade)
>3) Increase the number of propeller blades.
>
>As to the Hellcat propeller being fitted to the Corsair - it was
>certainly done - for example, the tests performed by the USN of a
>P-51B vs 2 hotted up Corsairs used Hellcat propellers for both
>aircraft. (The preort can be found online at:
>http://www.geocities.com/slakergmb/id95.htm
>
>As to how much it would affect performance - The Hellcat propeller
>would mose likely by about 2% more efficient at the F4U's climb speed,
>and about the same efficency at maximum speed. At climb speed, the 2%
>greater efficency would give 40 more Thrust Horsepower at Sea Level
>(2000 SHP), and about 34 more Thrust HP at high altitudes. (This is
>because the Corsair's geared supercharger delivered less Shaft
>Horepower at high altitudes, since more power was diverted to the
>supercharger). At teh Corsair's best climb speed of 135 Kts at Sea
>Level, that's 95# more excess thrust. it doesn't sound like much, but
>since it's all excess, it gives about 108 ft/min more climb. At
>22,000', the excess thrust would be about 58#, giving a improved rate
>of climb of 95 ft/minute. It doesn't seem like much, but it makes a
>difference.
>
>--
>Pete Stickney
> A strong conviction that something must be done is the parent of many
> bad measures. -- Daniel Webster

[Peter Stickney]

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]

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/aircraft/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.
--

[Alan Dicey]

Peter Stickney wrote:

>
> 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.
>

i) I'm sure I remember seeing, years ago, a picture of a Noorduyn
Norseman with a single-bladed prop. Since you seem to know what you are
talking about (more than I do, anyway), what factors would drive a
manufacturer to adopt such a radical solution?

ii) Radical solutions such as the Unducted Fan proposals mooted a few
years ago, had many curved blades - any idea what gain they were seeking
that justified the loss in efficiency?

iii) How does this work with contraprops? On the face of it they must
interfere with each other horribly, but they seem to fly quite well.
Can you point me in the direction of some clues?

[John Lansford]

hobo > wrote:

>Why were 2 and 3 blade props used anyway? Is there some engineering
>tradeoff favoring fewer blades in certain situations?

A two or 3 bladed prop was easier to balance than a four bladed one
was. They could also be built faster than the more bladed props.

John Lansford
--
The unofficial I-26 Construction Webpage:
http://users.vnet.net/lansford/a10/

[John Lansford]

hobo > wrote:

>Why were 2 and 3 blade props used anyway? Is there some engineering
>tradeoff favoring fewer blades in certain situations?

A two or 3 bladed prop was easier to balance than a four bladed one
was. They could also be built faster than the more bladed props.

John Lansford
--
The unofficial I-26 Construction Webpage:
http://users.vnet.net/lansford/a10/

[Peter Stickney]

In article >,
Alan Dicey > writes:
> Peter Stickney wrote:
>
>>
>> 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.
>>
>
> i) I'm sure I remember seeing, years ago, a picture of a Noorduyn
> Norseman with a single-bladed prop. Since you seem to know what you are
> talking about (more than I do, anyway), what factors would drive a
> manufacturer to adopt such a radical solution?

In a word, efficiency. Note that many of the model airplanes used in
free-flight competitions, (Escpecially the rubber powered ones, where
the judges issue you your engine (So many strands of Pirelli rubber,
of some particular length) and "fuel" it up for you (So many turns of
the rubber bands)) where getting the absolute most out of the limited
omount of energy you've got means the difference between winning and
losing, use very wide chord single-bladed propellers. The downside is
that you need a fairly large diameter. That's not much of a problem
in a hand-launched model airplane, but it doesn't work so well in Full
Scale stuff.

>
> ii) Radical solutions such as the Unducted Fan proposals mooted a few
> years ago, had many curved blades - any idea what gain they were seeking
> that justified the loss in efficiency?

In tha case, what they're trying to do is reduce the effects of the
shockwaves that form on the propeller blades as they fly further and
firther into the transonic region. It's not unlike sweeping a wing
back to delay the Mach Number that the drag rise occurs at, and the
magnitude of the drag rise. Above about Mach 0.65, the efficiency of
a straight propeller drops off alarmingly. At typical airliner cruise
speeds, (Mach 0.78-0.85) efficiency would be down around 60% at teh
low end of the speed range, and 50% at the high end. That's not very
useful at all - there are some measures that you can do to cut the tip
speed down - for example, the Tu-95 Bear (Russian turboprop transonic
bomber) uses a very high step-down gearing from the engines to the
propellers - the props rotate at 750 RPM, vs, say, 1500 or so for that
of a P-51, and a very clever variable pressure ratio compressor system
in its engines that essentially "supercharges" them to deliver sea
level power at 40,000'. (About 3 times what you'd get from a typical
turboprop). The swept propeller blades supply efficiencies in the
Mach 0.78-0.85 range of between 75% and 70%. Using many blades allows
the diameter to be cut down from, say, 22 ft for our notional
conventional propeller to 13 ft. This gives a lower airspeed at the
propeller tip than a large diameter propeller, thus delaying the
transonic effects.
(Note that the entire propeller doesn't go transonic - the airspeed at
the propeller blade is a product of the propeller's rotational speed,
and teh forward speed of the airplane. The rotational speed of the
propeller in ft/sec or m/sec increases as you move outward along the
propeller blade. So, a propeller will start having supersonic flow
appear at the tips, with the supersonic flow field moving inward as
speed increases. A smaller diameter and a slower rotational speed are
helpful in delaying the formation of these shock waves.
(transonic/supersonic flow). You do lose efficiency in the lower
speed ranges, but you get big gains at what your desired cruise speeds
are.

>
> iii) How does this work with contraprops? On the face of it they must
> interfere with each other horribly, but they seem to fly quite well.
> Can you point me in the direction of some clues?

A contraprop does lose some efficiency by placing one propeller behind
the other, and it requires a more complex drive system. (Which gave
fits on several early U.S. contraprop-equipped aircraft, most notably
the XB-35 Flying Wing, where they never got the contraprops doped out,
and the Hughes XF-11 recon machine (looked like a hyperthyroid
P-38). which was lost on its first flight becasue the aft bladeset in
one of the contraprops went into reverse pitch at low altitude. (This
is the crash that nearly killed Howard Hughes, and led to his drug
addiction (painkillers) and fear of infection.)

What you gain is a greater ability for a propeller of a particular
diameter to absorb power, adn the elimination of torque and P-factor
(destabilization of the airframe due to the rotating airflow from the
propeller affecting the airframe). P-Factor is a Big Deal, with a
high-powered airplane. For example, with a P-51 or a Corsair, you
have to be careful with throttle movement at low speeds, or on
takeoff. If you jam the throttle to it too fast, you'll either swing
off the runway or roll the airplane inverted.

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

[Alan Dicey]

Peter Stickney wrote:
> In article >,
> Alan Dicey > writes:
>
>>Peter Stickney wrote:
>>
>>
>>>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.
>>>
>>
>>a Noorduyn Norseman with a single-bladed prop: what factors would drive a
>>manufacturer to adopt such a radical solution?

> In a word, efficiency.

Hmm. Efficiency in the sense of translating engine power to thrust? I
can't see it being aimed at top speed, so I guess it would give more
range for a given fuel load?

>
>>ii) Radical solutions such as the Unducted Fan proposals mooted a few
>>years ago, had many curved blades - any idea what gain they were seeking
>>that justified the loss in efficiency?
>
>
> In tha case, what they're trying to do is reduce the effects of the
> shockwaves that form on the propeller blades as they fly further and
> firther into the transonic region. It's not unlike sweeping a wing
> back to delay the Mach Number that the drag rise occurs at, and the
> magnitude of the drag rise. [...] You do lose efficiency in the lower
> speed ranges, but you get big gains at what your desired cruise speeds
> are.

Of course - tip speed and transonic drag rise. To get more airscrew in
the airflow /and/ keep the tip speed suitably subsonic,the only answer
is more blades - with sweepback to delay the drag rise. I should have
remebered that from the discussions at the time. None of the Unducted
Fan experiments seem to have made it into a production implementation. I
guess the aim was a cheaper powerplant - propellors being cheaper than
ducted fans - but the loss of efficiency was too great.

>
>>iii) How does this work with contraprops? On the face of it they must
>>interfere with each other horribly, but they seem to fly quite well.
>
>
> What you gain is a greater ability for a propeller of a particular
> diameter to absorb power, adn the elimination of torque and P-factor
> (destabilization of the airframe due to the rotating airflow from the
> propeller affecting the airframe).
>

So, for an increase in power turned into thrust there's an improvement
in flyability and the ability to make the airframe lighter because it
doesn't have to absorb the stresses - they're balanced out at the
source. That explains to me how the Fairey Gannet was able to shut off
one half of the Double Mamba powerplant, feather one half of the
contraprop and achieve better endurance at patrol speed.

Thanks very much for taking the time to give me some pointers.

Do you do this for a living? :-)

[Peter Stickney]

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/aircraft/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
--

[Tracy White]

> I'm not sure if it is the answer - but fitting gull wings (whether
> inverted or not) means that the wing root joins the fuselage at approx
> 90 deg - therebye eliminating the need for a large, drag-producing
> wing-to-fuselage fillet.

Uhhh no. The fillets were there to DECREASE drag.

> You only need fillets on high or low-winged a/c

Fillets are used to smooth out airflow and thus decrease drag. The air
over a wing is moving at a higher velocity than the air over the
fuselage, and when the streams mix you get turbulence and drag. The
fillets work to counteract this interaction and the drag it causes.

[no useful info]

In article >,
John Lansford > wrote:


> A two or 3 bladed prop was easier to balance than a four bladed one
> was. They could also be built faster than the more bladed props.
>


Considering the few inches of ground clearance any of those props
provided, does anyone have a good idea of how often the propeller was
damaged by (bad) landings?

[Peter Stickney]

In article >,
Alan Dicey > writes:
> Peter Stickney wrote:
>> In article >,
>> Alan Dicey > writes:
>>
>>>Peter Stickney wrote:

>>>a Noorduyn Norseman with a single-bladed prop: what factors would drive a
>>>manufacturer to adopt such a radical solution?
>
>> In a word, efficiency.
>
> Hmm. Efficiency in the sense of translating engine power to thrust? I
> can't see it being aimed at top speed, so I guess it would give more
> range for a given fuel load?

Efficiency in the sense of power to thrust. You're right - it won't
work so well at higher speeds.

>>>ii) Radical solutions such as the Unducted Fan proposals mooted a few
>>>years ago, had many curved blades - any idea what gain they were seeking
>>>that justified the loss in efficiency?
>>
>>
>> In tha case, what they're trying to do is reduce the effects of the
>> shockwaves that form on the propeller blades as they fly further and
>> firther into the transonic region. It's not unlike sweeping a wing
>> back to delay the Mach Number that the drag rise occurs at, and the
>> magnitude of the drag rise. [...] You do lose efficiency in the lower
>> speed ranges, but you get big gains at what your desired cruise speeds
>> are.
>
> Of course - tip speed and transonic drag rise. To get more airscrew in
> the airflow /and/ keep the tip speed suitably subsonic,the only answer
> is more blades - with sweepback to delay the drag rise. I should have
> remebered that from the discussions at the time. None of the Unducted
> Fan experiments seem to have made it into a production implementation. I
> guess the aim was a cheaper powerplant - propellors being cheaper than
> ducted fans - but the loss of efficiency was too great.

They're also complicated and heavy. UDFs, like propellers on
high-powered aircraft, have to be variable pitch to operate halfway
decently across their speed & altitude range. The pitch change
mechanism and, for that matter, the structure of the blade itself
aren't simple problems. For teh lower end of teh airliner cruise
range they may be somewhat more efficient - but they'll also have a
shorter Time Between Overhauls, and overhaul costs aren't going to be
cheap. Fuel prices would have to go up a _lot_ more than they have to
make it worth the extra overall cost.


>>>iii) How does this work with contraprops? On the face of it they must
>>>interfere with each other horribly, but they seem to fly quite well.
>>
>>
>> What you gain is a greater ability for a propeller of a particular
>> diameter to absorb power, adn the elimination of torque and P-factor
>> (destabilization of the airframe due to the rotating airflow from the
>> propeller affecting the airframe).
>>
>
> So, for an increase in power turned into thrust there's an improvement
> in flyability and the ability to make the airframe lighter because it
> doesn't have to absorb the stresses - they're balanced out at the
> source. That explains to me how the Fairey Gannet was able to shut off
> one half of the Double Mamba powerplant, feather one half of the
> contraprop and achieve better endurance at patrol speed.

Right. Another example would be the Griffon engined Seafires. With a
single rotation prop, the Griffon Seafires had 5-bladed single
rotation propellers, and were limited to roughly 66% power on takeoff.
This was becasue of 2 reasons - the Torque/P-Factor would drag the
airplane right into the carrier's island. (A bad idea), and trying to
hold it straight was overstressing the tire sidewalls, forcing tire
changes after only a couple of flights. It's tough when you've got to
explain that you need to pull your ship out of the battle becasue you
ran out of tires, rather than gas, bullets, or bombs. The contraprop
used on the later Seafire 47s (6 blades, 3 per bank) allowed more
power to be used without the swing, and better propeller clearance.

The same basic engine allowed the development of teh Avro Lincoln into
teh Shackleton - you could hang Griffons with contraprops in the same
wing center section without changing the location of the engine
mounts. That's basically a Lancaster wing, so they got a lot of
stretch out of it.

> Thanks very much for taking the time to give me some pointers.
>
> Do you do this for a living? :-)

Sometimes. I'm an Engineering Mathemetician/Computer Scientist type,
and a Certified Wing Nut and Gearhead.

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

[Cub Driver]

On Wed, 7 Jul 2004 01:48:52 -0400, (Peter Stickney)
wrote:

(about the one-bladed prop:)

>Efficiency in the sense of power to thrust. You're right - it won't
>work so well at higher speeds.

It's a hovering prop--is that the idea?

You see many-bladed props on turbo-prop commuter planes. That's to get
max efficiency out of a very powerful engine (compared to recips).
There are only two things you can do to use up engine power: increase
the length of the prop or increase the number of props. Length is
restricted by practical reasons: you don't want to strike the ground
or cause the landing gear to be extra long; and you don't want the
tips to go supersonic. So that leaves multiple props.

Working backwards, a single prop would use the least possible power.
So the plane could travel very slowly for a very long time?

(Then there's the factor that the plane came out of the Northrop shop,
which sometimes seemed like a Skunk Works mirror image: wild ideas
that didn't quite pan out.)

all the best -- Dan Ford
email: (put Cubdriver in subject line)

The Warbird's Forum www.warbirdforum.com
The Piper Cub Forum www.pipercubforum.com
Viva Bush! weblog www.vivabush.org

[hobo]

In article >,
no useful info > wrote:

>
> Considering the few inches of ground clearance any of those props
> provided, does anyone have a good idea of how often the propeller was
> damaged by (bad) landings?

I would speculate that after the first negative result the props ground
clearance would increase by several inches.
--

[no useful info]

In article >, hobo >
wrote:


> I would speculate that after the first negative result the props ground
> clearance would increase by several inches.

no doubt, the question is, how frequently did this first negative result
happen.
--

[Peter Stickney]

In article >,
(Tracy White) writes:
>
>> I'm not sure if it is the answer - but fitting gull wings (whether
>> inverted or not) means that the wing root joins the fuselage at approx
>> 90 deg - therebye eliminating the need for a large, drag-producing
>> wing-to-fuselage fillet.
>
> Uhhh no. The fillets were there to DECREASE drag.

That's only true up to a point - A wing/fuselage joint that isn't at
right angles produces quite a bit of Interference Drag, as the
differing airflows try to sort themselves out. Filleting can ease
that transition.

>> You only need fillets on high or low-winged a/c
>
> Fillets are used to smooth out airflow and thus decrease drag. The air
> over a wing is moving at a higher velocity than the air over the
> fuselage, and when the streams mix you get turbulence and drag. The
> fillets work to counteract this interaction and the drag it causes.

True as far as it goes, but fillets also add wetted area, and increase
Parasite Drag. They're only drag reduction tools when they are
required, and only if used in moderation. It's all a balancing act,
after all - the designer is balancing out the drag increase casued by
the fillet itself, vs. the reduction in interference drag. The
decision made with the Corsair was to reduce the Interference Drag by
acheiving, as much as possible, a wing-fuselage joint perpendicular to
the fuselage, (The inverted gull wing) with a minimum of filleting,
thus reducing Parasite Drag.

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

[DJFawcett26]

>The
>decision made with the Corsair was to reduce the Interference Drag by
>acheiving, as much as possible, a wing-fuselage joint perpendicular to
>the fuselage, (The inverted gull wing) with a minimum of filleting,
>thus reducing Parasite Drag.

Actually, the major driver for the inverted gull was finding a way to make
clearance for the HUGE prop so runways and carrier decks didn't get chopped up.
All the drag reduction trades and benefits were a natural fall out of the
design.

Keep in mind, the wings could have been put have been put at the 90 and 270
position and achieved the same benefit. But the prop would have went chop,
chop. Also, the inverted gull was not the best actor in stability and control.
I am not saying that ultimately it was not good, but even then the spins and
the recoveries were an occurence to behold.

[Steven P. McNicoll]

"DJFawcett26" > wrote in message
...
>
> Actually, the major driver for the inverted gull was finding a way to make
> clearance for the HUGE prop so runways and carrier decks didn't get
chopped up.
> All the drag reduction trades and benefits were a natural fall out of the
> design.
>
> Keep in mind, the wings could have been put have been put at the 90 and
270
> position and achieved the same benefit. But the prop would have went
chop,
> chop.
>

The F6F had the same engine and similar propeller but didn't go chop chop
without the inverted gull wing.

[Peter Stickney]

In article >,
(DJFawcett26) writes:
>>The
>>decision made with the Corsair was to reduce the Interference Drag by
>>acheiving, as much as possible, a wing-fuselage joint perpendicular to
>>the fuselage, (The inverted gull wing) with a minimum of filleting,
>>thus reducing Parasite Drag.
>
> Actually, the major driver for the inverted gull was finding a way to make
> clearance for the HUGE prop so runways and carrier decks didn't get chopped up.

Sorry, but the evidence points in the other direction. There was
nothing particularly outstanfing wrt teh Corsair's propeller diamter -
13'1" for the 3-blade prop, and 13'2" for teh 4-blade - the F6F
Hellcat - no inverted gull wing - low mid-wing, in fact, had no
problems operating in the same environment. - in fact, around the
boat, it was a much better airplane than the Corsair.

The Vought TBU Seawolf, intended to be the successor of the TBF/TBM
Torpedo Bomber, had a mid-wing, and a 13'3" diameter prop.
The low-winged Martin AM-1 attack airplane had a 14'8" diameter
propeller.

The mid-wing P-47 had a 13'2" prop. (And in fact, was flown off of,
but not landed on, carriers in the Pacific, during several of teh
Island-hopping invasions.)

The low-wing Hawker Typhoon & Tempest had a 14' diameter propeller.

The fact is, given the expected speed range of the airplanes, and the
propeller RPM (_Not_ Engine RPM - these are geared engines, all with
a of between 1200 - 1500, a 13' propeller diameter gives the best
advance ratio range for efficiency.

As demonstrated by the small selection of examples above, it was
certainly possible to design an airplane to fit the Corsair's
requirements without resorting to in inverted gull wing to make it
work.

> All the drag reduction trades and benefits were a natural fall out of the
> design.
>
> Keep in mind, the wings could have been put have been put at the 90 and 270
> position and achieved the same benefit. But the prop would have went chop,
> chop. Also, the inverted gull was not the best actor in stability and control.

And in fact, it was, on larger aircraft (The TBU, which, interestingly
emough, was the Vought project that followed the Corsair), without any
problems. Stbility wasn't a problem for the Corsair - the objective
numbers Cnalpa, Cnbeta - the Stability deriviatices show that it was
in the middle range for contemprary fighters. Teh stall behavior was
worse than that of the Wildcat & Hellcat, but better than the SBD
Dauntless, the Fw 190, or the P-51. Much of the of Corsair's Torque
Roll tencency at low speeds was corrected by a cuff on the leading
edge of the inboard right wing.

> I am not saying that ultimately it was not good, but even then the spins and
> the recoveries were an occurence to behold.

From contemporary reports, and objectively obtained data by the NACA,
not any more so than otehr WW 2 fighters, and much less than some.
(You do _not_ want to spin a P-51 with a full fuselage tank, for
example, or a Spitfire with the drop tank in place.)

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

[DJFawcett26]

>Sorry, but the evidence points in the other direction.

I understand exactly what you are saying, the evidence is somewhat in support.
But this is not an issue of evidence, it is an issue of knowing several of the
guys that were on the test program. Witnesses are far better than
circumstantial evidence. Also, you have to take into account the geometry of
the aircraft you specify. There is a significant difference in configuration.

Just remember, what appears obvious may not at all be the obvious.

[DJFawcett26]

Look at the geometry, that in itself is the telling tale.

[ANDREW ROBERT BREEN]

In article >,
Peter Stickney > wrote:
>In article >,
> (DJFawcett26) writes:
>>>The
>>>decision made with the Corsair was to reduce the Interference Drag by
>>>acheiving, as much as possible, a wing-fuselage joint perpendicular to
>>>the fuselage, (The inverted gull wing) with a minimum of filleting,
>>>thus reducing Parasite Drag.
>>
>> Actually, the major driver for the inverted gull was finding a way to make
>> clearance for the HUGE prop so runways and carrier decks didn't get chopped up.
>
>Sorry, but the evidence points in the other direction. There was
>nothing particularly outstanfing wrt teh Corsair's propeller diamter -
>13'1" for the 3-blade prop, and 13'2" for teh 4-blade - the F6F
>Hellcat - no inverted gull wing - low mid-wing, in fact, had no
>problems operating in the same environment. - in fact, around the
>boat, it was a much better airplane than the Corsair.

It's a story which has been around a long time, though - pretty much
as long as the Corsair itself. Norman Hanson was given that as the
reason for the "bent-wing" when he visited Voights in 1943 prior
to picking up the RN's first back of Corsair Is*, so someone at the
factory obviously thought that was the reason. It's possible that the
bent wing was needed to get the big prop. /and/ some other bit of
configuration that Voights thought desirable (which Grumman didn't
adopt for the Gannet/Hellcat or Hawker for the Tiffie).

* source is originally direct - Hans was a family friend - but is
included in his (regrettably out of press) book, "Carrier Pilot".

--
Andy Breen ~ Interplanetary Scintillation Research Group
http://users.aber.ac.uk/azb/
"Time has stopped, says the Black Lion clock
and eternity has begun" (Dylan Thomas)

[ANDREW ROBERT BREEN]

In article >,
hobo > wrote:
>In article >,
> (ANDREW ROBERT BREEN) wrote:
>
>> It's a story which has been around a long time, though
>
>I read something about the Corsair having the first fully retracted and
>enclosed landing gear in order to reduce drag. The same article said the

Maybe for Voight.. but plenty of aeroplanes had fully retracting 'carts
long long before. I'd guess the first would probabllt have been the
I-16, kicking on fofr a good 10 years before, but even such latecomers
as Hawker's Hurricane and Willi Messerschmidt's Bf109 had fully-retracting
undercarriages in 1934-ish.
Given that Voight were a clearly competant outfit - the Corsair being one
of the best aerial weapons* of WW2 - I doubt if they'd missed this one.

>shorter gear resulting from the gull wing was necessary for the gear to
>fully retract. The article said that if long gear was retracted sideways
>it would reach into outer parts of the wing that were too narrow and if

Hmm. Not sure about that. Grumman managed the dame tricj with a deeper
fuselage. Hawker offered a navalised Typhoon at one point (a lovely
thought, given the rep. of the early Sabres :(, so they obviously figured
that it was possible to combine a 14' prop and folding wings without
bending the latter (come to that, what was the diameter of the prop on the
Sea Fury?).

My suspicion is that the truth lies in the rather slim fuselage of the
Corsair, plus a degree of (laudable) coservatism on Voight's behalf
- the blow-down gear for the undercart must have eaten into wing depth,
but it undoubtedly saved lives. OTOH the original hood design was /not/
a good one, nor was the undercart valveing..

*Weapon as distinct from aeroplane. Hans was always insistent on that
point. The Gladiator and the Fulmar were aeroplanes. The Corsair was a
weapon. The Tiger Moth was an abomination.

--
Andy Breen ~ Interplanetary Scintillation Research Group
http://users.aber.ac.uk/azb/
"Who dies with the most toys wins" (Gary Barnes)

[Guy Alcala]

ANDREW ROBERT BREEN wrote:

> In article >,
> hobo > wrote:
> >In article >,
> > (ANDREW ROBERT BREEN) wrote:
> >
> >> It's a story which has been around a long time, though
> >
> >I read something about the Corsair having the first fully retracted and
> >enclosed landing gear in order to reduce drag. The same article said the
>
> Maybe for Voight.. but plenty of aeroplanes had fully retracting 'carts
> long long before. I'd guess the first would probabllt have been the
> I-16, kicking on fofr a good 10 years before, but even such latecomers
> as Hawker's Hurricane and Willi Messerschmidt's Bf109 had fully-retracting
> undercarriages in 1934-ish.

Even if you restrict it to fully retracting AND enclosed, the Spit prototype
had both. They removed the outboard cover doors when it was found that the
extra drag was minimal, and the Spits didn't get fully-enclosed wheels back
until the Mk. 21 or even later Marks (which were about 100 mph faster than the
Mk.I), IIRR.

> Given that Voight were a clearly competant outfit - the Corsair being one
> of the best aerial weapons* of WW2 - I doubt if they'd missed this one.

<snip>

Not only were they technically competent, they also knew the name was spelled
"Vought" ;-)

Guy

[[email protected]]

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