Forward swept wings...

[First time Juke]

I am really interested about this now.

They seem to not tip stall..and can be used in order to make small plane.

I once represented the small R-2800 powered forward swept wing new GeeBee kinda thing....remember it still..anyone ?

Ju-287 was a test bed for this kinda innovation during WW II. Proved to be very successfull.

[AirDOGGe]

Re: Forward swept wings...

Forward swept wings have their own problems, and probably wouldn't help a Reno Unlimited go faster or handle any better. Not at current race velocities.

I believe for the type of flying unlimiteds have to excel at (low, tight turns at high subsonic speeds), you can't do much better than the P-51's planform. Maybe a thinner version of the 'Stang wing...

If and when the big racers ever start approaching 550-600 mph, THEN I'd say start looking hard at swept wings...

[G. van Dyk]

Re: Forward swept wings...

I suspect something like an embiggened NXT with that NLF414 airfoil would be the hot ticket. Get it up around the wing area of a Bearcat or Sea Fury with a Bear / S.Fury-like R-3350 and you'd have something unbeatable for years to come. (IMHO) I've always thought the Yak sized bird with the monster engine ala Mr. Awesome would just be too small and highly loaded to carry the speed through the turns efficiently, but thats based on no calculations whatsoever.

Now lets see... Quarter mil for an NXT, square the size, cube the volume, dollars to the fourth power... those pennies in the coffee can ain't gonna cut it.

Cheers
Gerry

[First time Juke]

Re: Forward swept wings...

Forward swept wings have their own problems, and probably wouldn't help a Reno Unlimited go faster or handle any better. Not at current race velocities.

If and when the big racers ever start approaching 550-600 mph, THEN I'd say start looking hard at swept wings...

Do you mean forward swept wing can only deliver edge at really high speeds ?

How come hundreds of planes have forward sweep then ?

[PropFan]

Re: Forward swept wings...

Flying fast is all about managing Mach numbers, right up to our old friend the "sound barrier" at Mach 1.0. At Reno on a nice warm day, 500 mph translates into about M 0.65. Modern biz jets with straight wings are flying around efficiently at M 0.72 - 0.75, (560 - 580 mph at Reno conditions) so you really don't need wing sweep until the speed get above these.
The real limit to speeds at Reno is the prop technology. Just listen to the planes when they pass, and you can hear who has good prop efficiency. (hint: its not the T-6 class) The NASA "propfan" research in the 80's started out by showing all the WWII props were limited to about M 0.60 due to the blade designs, and then systematically designed solutions to the Mach problems to get efficient props to work at speeds up to M 0.80, mostly by sweeping the blade tip. The Hartzell racing prop used by all the Sport Gold class winners over the past several years is based heavily on the NASA research, and works efficiently even with prop tip speeds over M 1.0. But no one has invested the resources to incorporate that swept design technology up to the unlimited power levels. Some of the modern 5000 shp - 10000 shp turboprops are using swept prop blades, but I have no idea if any of those blades would fit on a WWII piston engine.
So then next performance level in Reno Unlimiteds does not need swept wing (forward or aft), but swept props.

PropFan

[Skyracer]

Re: Forward swept wings...

Amen!

[David E. Wells]

Re: Forward swept wings...

Amen!

Howard Pardue tried one of those Scimitar props at Phoenix '94, I believe his Quote was... "Lost 20mph with that thing"...D.

[dvddude]

Re: Forward swept wings...

Howard Pardue tried one of those Scimitar props at Phoenix '94, I believe his Quote was... "Lost 20mph with that thing"...D.

I hadn't heard of that. Do you have a picture of this? Which airplane was it on?

[Bill Marsh]

Re: Forward swept wings...

Wierd Prop on the ORACLE promo aircraft (red and gas turbine powered) back in the late 90's

Questioin.......what is the deal on that prop efficiency ( ?? 750 hp power)


thanks BMarsh

[PropFan]

Re: Forward swept wings...

Bill,
The wide chord prop on Wayne Handley's Turboprop Raven was originally designed for the Cessna Caravan. So it has lots of low speed pull. I saw Wayne do his "stop and go" maneuver at Reno. Amazing, sitting in a hover and then accelerating to 60 kts straight up!

THere are some more details and a picture on Hartzell's website http://www.hartzellprop.com/pressroom/index_press.htm

scroll down to the June 1999 and Jan 2000 press releases.

PropFan

[AirDOGGe]

Re: Forward swept wings...

Flying fast is all about managing Mach numbers, right up to our old friend the "sound barrier" at Mach 1.0. At Reno on a nice warm day, 500 mph translates into about M 0.65. Modern biz jets with straight wings are flying around efficiently at M 0.72 - 0.75, (560 - 580 mph at Reno conditions) so you really don't need wing sweep until the speed get above these.

PropFan

That's it in a nutshell. Wing sweep has no real benefit at Reno speeds, as the main purpose of sweeping them back (or forward) is to reduce the drag of the shockwaves that form as you approach transsonic velocities.

The only subsonic production aircraft I know of that use forward sweep do so for CG or compartment space reasons (the Ju 287 light bomber had such wings so that the main spar could pass behind the bomb bay, and the HFB-320 business jet uses them to place the spar behind the passenger cabin instead of below, for more stand-upright space for the passengers).

According to tests run with the X-29, "the forward-swept wing design produced a 15 percent better ratio of lift to drag in the transonic speed region". Unlimiteds still have a ways to go before they enter that region, if they ever get that fast with recips.


and...


"After the war (WWII), the National Advisory Committee for Aeronautics (NACA) in the United States conducted wind tunnel tests of forward swept wings. NACA engineers even mounted a model of the Bell X-1 with forward-swept wings in a wind tunnel. But they found little inherent aerodynamic advantages to such a design. Even the Russians conducted full-scale model flights of forward-swept-wing gliders but abandoned the concept."

...and finally...

"Wind tunnel tests made it clear that there were many problems with forward-swept wings and few aerodynamic advantages. One major problem was that the wingtips tended to bend upwards and cause the plane to stall—inevitable for metal wings."




Forward swept wings look neat-o, but useless for unlimited air racing. They are difficult to make for high speed usage too, due to wingtip divergence. You either have to make then stronger than straight wings using standard metal-fab methods, or use exotic materials and specific computer-designed tape-laydown patterns to control the bending loads, directions and stresses when building with newer materials like carbon fiber.

The former contruction method leads to heavier wings, and the latter is a lot to ask for from the typical Unlimited racing team.

.

[ebutner]

Re: Forward swept wings...

I understand all that, and apreciate all the input.... but it would look sooooo cool!

[rmudbugs]

Re: Forward swept wings...

Just a question some of you smart guys can answer.

Why not an offset wing? If most of the race is in a turn then would it be any advantage to do some kind of offset wing? I know the old "twisted sister" cars NASCAR ran were offset to one side to make them turn better. Would any of this apply to air racing?

[First time Juke]

Re: Forward swept wings...

That's it in a nutshell. Wing sweep has no real benefit at Reno speeds, as the main purpose of sweeping them back (or forward) is to reduce the drag of the shockwaves that form as you approach transsonic velocities.

The only subsonic production aircraft I know of that use forward sweep do so for CG or compartment space reasons (the Ju 287 light bomber had such wings so that the main spar could pass behind the bomb bay, and the HFB-320 business jet uses them to place the spar behind the passenger cabin instead of below, for more stand-upright space for the passengers).

According to tests run with the X-29, "the forward-swept wing design produced a 15 percent better ratio of lift to drag in the transonic speed region". Unlimiteds still have a ways to go before they enter that region, if they ever get that fast with recips.


and...


"After the war (WWII), the National Advisory Committee for Aeronautics (NACA) in the United States conducted wind tunnel tests of forward swept wings. NACA engineers even mounted a model of the Bell X-1 with forward-swept wings in a wind tunnel. But they found little inherent aerodynamic advantages to such a design. Even the Russians conducted full-scale model flights of forward-swept-wing gliders but abandoned the concept."

...and finally...

"Wind tunnel tests made it clear that there were many problems with forward-swept wings and few aerodynamic advantages. One major problem was that the wingtips tended to bend upwards and cause the plane to stall—inevitable for metal wings."




Forward swept wings look neat-o, but useless for unlimited air racing. They are difficult to make for high speed usage too, due to wingtip divergence. You either have to make then stronger than straight wings using standard metal-fab methods, or use exotic materials and specific computer-designed tape-laydown patterns to control the bending loads, directions and stresses when building with newer materials like carbon fiber.

The former contruction method leads to heavier wings, and the latter is a lot to ask for from the typical Unlimited racing team.

.

This is 100 % correct..well researched Airdogge !

It also reduces the drag at wing fuse juncture says Martin Hollmann of Monterey California.

The plane that I am working on at the moment is small and thus needs forward sweep to handle the CG, but since it also uses the lifting body (sorta like Facetmobile/YF-117 ) it only needs very small wings and those can be made strong without becoming/getting excessively heavy.

And indeed looks really cool ! At least to me it does.