The Custer Arc ?

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Pilot-34

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I am suspicious that the gains of the Custer wing mostly come from the center 90°
With that in mind has anyone ever seen only a portion of a Custer wing used ?
It seems like a portion whether it’s 180° arc or perhaps only 90 degrees in place under the propeller arc might add significant benefits.
Seems like this might be the easiest to add to pylon mounted engines due to balance considerations but even regular configuration pusher or tractor engines might be able to benefit.

Has anybody ever experimented with any of this stuff?
 

plncraze

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This is from memory so don't believe it too much. I thought Custer built a small electric model with a cord, this is years ago, and found it would lift off so he built a full scale aircraft which was pretty crude then built a nicer one which is parked outside at the Mid Atlantic Air Museum. My guess is that any gains from the configuration were small.
 

BBerson

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I watched a homebuilt experimental Custer arc wing fly several times. No benefit noted by me. Worse than other bush craft.
 

Pilot-34

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The Custer wing itself seems to have done pretty well.
The biggest downside to them seems to be that if you lose one engine you are in a asymmetrical lift and thrust condition.
Having just one custer wing would solve that problem and be just a supplement too lift.
A single Custer wing what seem to work best with pylon mounted engines.
 

rotax618

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The makers of the SF1 Archon claim that the effect of airflow into the prop through the “duct” increases lift, I think it would be more believable if the “duct” was round and fitted more closely to the prop tips, never the less the prototype had fairly good performance using only a 503 Rotax.
D871FDCB-C8CA-4CA8-8616-9CE302940CB4.jpeg
 

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Dusan

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I am suspicious that the gains of the Custer wing mostly come from the center 90°
With that in mind has anyone ever seen only a portion of a Custer wing used ?
It seems like a portion whether it’s 180° arc or perhaps only 90 degrees in place under the propeller arc might add significant benefits.
Seems like this might be the easiest to add to pylon mounted engines due to balance considerations but even regular configuration pusher or tractor engines might be able to benefit.

Has anybody ever experimented with any of this stuff?
The benefit of the Custer wing comes from the wing top surface exposed to propeller accelerated airflow. This leads to several improvements, as artificially increasing the lift coefficient to very high values, stall practically eliminated at any AoA, and the wing producing lift even at zero aircraft speed. NACA discovered some of the benefits - as increasing the lift coefficient and delaying stall - can be obtained by just exposing a regular wing to propeller slipstream, so they lost interest in the channel wing design. https://cafe.foundation/v2/pdf_tech/High.Lift/NACA.1953.High.Lift.Channel.Wing.pdf

Depending on what do you want to achieve there might be advantages to reduce the wing channel to less than 180 degrees, but the benefits will be drastically reduced. If you don't need producing lift at zero speed, just place a regular wing in the prop slipstream.

The Custer channel wing is not really suitable for a VTOL aircraft. The lift augmentation in hover is relatively small, as the thrust and lift vectors are mostly perpendicular, and also NACA determined regions of flow separation in static conditions. For an improved wing for a VTOL aircraft see the project here: Aliptera
 

Pilot-34

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I noticed a diagram of the airflow through the propeller that greatly deflects the normally horizontally flowing air.

Now I have always thought that the lift vector is perpendicular to the surface of the curved wing.
Because of that I’ve always figured that the lift contributed by the upper surfaces of the channel would be insignificant. Essentially the lift at a 90° Point and the 270° point (the plane of the wing) would be completely horizontal and canceling each other out.
In other words the more vertical any part of the channel is the less lift it would produce.
But the diagram of airflow through the propeller leads me to wonder if those vertical portions might be more important to channelize the airflow than to produce lift.

It’s always seems strange to me how people can look at the same thing and see vastly different results.
What this report seems to say is this configuration Does not have true zero forward speed Hover capability So it is useless as a vertical takeoff machine.
But they didn’t test that!!
Worse yet They missed the point that it might be an extremeSTOL!
I’ve noticed most helicopters takeoff with a little forward speed.
So operationally I’m not sure there would be any difference .
 

Dusan

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What this report seems to say is this configuration Does not have true zero forward speed Hover capability So it is useless as a vertical takeoff machine.
But they didn’t test that!!
They did test the lift at 'hover', see the table at page 10. For a project using channel wings for VTOL see here: https://hopflyt.com/
 

Pilot-34

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Yes but they didn’t test if it could do a vertical takeoff.

There Are some critical differences in the tiny shift from the word hover to vertical.

For example there are some gyrocopters which can not hover But can make both vertical takeoffs and landings.
 

TFF

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Helicopters move forward, if they can, so they don’t have to use max horsepower. It’s called effective translational lift. You are pulling out the wish sandwich. I wish this stuff worked. If it worked , it’s all you would see. The technology was for sale and no one was interested. Not a big enough change in efficiency in the real world to matter with the complexity.
 

Pilot-34

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I think you nailed that on the head.

But if you think about it there are a lot of planes that are being built here where vertical takeoff is not critical but extremely short takeoff would be nearly as good.
Anyone here that watches the STOL competitions like at Valdez knows what I mean.

Sure I’d like a helicopter but if I can reduce price and complexity by an order of magnitude in return for a 25 foot takeoff it seems like a no-brainer.
 

Bill-Higdon

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Helicopters move forward, if they can, so they don’t have to use max horsepower. It’s called effective translational lift. You are pulling out the wish sandwich. I wish this stuff worked. If it worked , it’s all you would see. The technology was for sale and no one was interested. Not a big enough change in efficiency in the real world to matter with the complexity.
Some of the Russian Helios can't hover under load
 
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