Slotted wing for propeller ?

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Bigshu

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That is a very good question, I had not thought of that!

I have not seen any material about it before either.

It will be interesting to see if anyone has some information, especially on how to build one.

Cheers
K
There are lots of RC designs that feature a pusher prop in a slot in the wing, FWIW.
 

Bigshu

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That configuration works well on several small model airplanes.
A disadvantage is that prop blades are exposed to gravel thrown up by wheels.
The prettiest version of that is the Aerosports Archon SF-1 ultralight that resembles a stealthy, fifth generation, jet fighter from a distance. It has a slot in the wing and the top of the fuselage where the prop turns. The prop is near the trailing edge of the wing, but the lower half rotates in a hollowed out fuselage. The fuselage belly skin deflects gravel away from the propeller.

This configuration also offers the option of mounting the propeller ahead of the rear spar ... if needed for balance.
I like the Archon design. Fisher Flying products is a distributer, so you could talk to them about it.
 

cluttonfred

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Stark AS.37?

CB9882C9-D606-49E9-86C2-8F8EAEC5F330.png

 

WINGITIS

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Stark AS.37?

View attachment 115988

Checkout those Ruddervators between the wings, I wonder if he tested them with the rear rudder and elevator disengaged?

STARCK-PRIVE-MN66-80-238.jpg
 

WINGITIS

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They are not ruddervators, just canted ailerons that happen to be attached to the interplane struts. They may look odd but are apparently completely unremarkable in practice.

View attachment 116004
They have an effect in both planes, they must do!

The same as a V-TAIL.


ANDRE STARK.jpg

This one below appears to show it linked to the RUDDER AND OR ELEVATOR, as it is out of plane with the strut.

Either way even if its connected as an Aileron it still has a V-TAIL effect.

RUDDERVATOR AND ELEVATOR MOVEMENT AND LEFT HAND RUDDERVATOR OUT OF PLANE WITH STRUT.png
 
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cluttonfred

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No, not really. Look at the bottom view drawing and note how far forward the surfaces are relative to the CG location a little forward of the main wheels. Those interplane structures are actually panels, not struts, so they are flying surfaces and the deflection of the ailerons turns them into little wings with their aerodynamic centers at about 25% chord. That moves the effective location of the force input due to aileron deflection even closer to the CG. There just isn't enough lever arm in a fore-and-aft sense to have much rudder effect, maybe a tiny bit of adverse yaw but probably not enough to notice. They do have plenty of lever arm for aileron effect. It's really no different than a Jodel wing in practice

They have an effect in both planes, they must do!
 

WINGITIS

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No, not really. Look at the bottom view drawing and note how far forward the surfaces are relative to the CG location a little forward of the main wheels. Those interplane structures are actually panels, not struts, so they are flying surfaces and the deflection of the ailerons turns them into little wings with their aerodynamic centers at about 25% chord. That moves the effective location of the force input due to aileron deflection even closer to the CG. There just isn't enough lever arm in a fore-and-aft sense to have much rudder effect, maybe a tiny bit of adverse yaw but probably not enough to notice. They do have plenty of lever arm for aileron effect. It's really no different than a Jodel wing in practice
They are BIG surfaces for just small YAW adjustments, and are behind the CG, he could have just cut the tail off!

On his earlier versions they were smaller.

They are at 90 Degrees relative to each other, the same as a V-Tail, approximately twice the angle of a Jodel.
 
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WINGITIS

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Here is a diagram that shows them well behind the CG.

It also lists them as Ailerons, but that does not change the fact they have rudder effects the same as a V-tail.

So going back to my first comment it would have been interesting to know if he had locked the traditional rudder/elevator in place and tried to fly it!?

Because removing the tail would have surely cut the drag by a bunch, he could have then put the ailerons on the top wing, thus retaining traditional controls.
 

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WINGITIS

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If the prop thrust is enough, like the Blackfly, it does increase the air speed over the wing(78 MPH when stationary) and thus the extra lift is generated.

Otherwise the Blackfly would not work.

On the Merlin the thrust may not be enough to make a massive difference, but he claims a largish difference in his video.

Attached are the Blackfly calculations I did back in 2019.

BLACKFLY 1.png
 
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Island_flyer

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They are not ruddervators, just canted ailerons that happen to be attached to the interplane struts. They may look odd but are apparently completely unremarkable in practice.

View attachment 116004
Very interesting concept. A little heavy compared to the Avid Flyer (which came on the market about six years later). I suppose the big advantage of the AS.37 configuration would be a short wing span for easier storage, maybe. The idea of the slipstream blown across the wings sounds good for STOL, but the Avid Flyer was significantly lighter (511 pounds empty vs. around 880 for the AS.37), and had much shorter takeoff and landing numbers. It looks like each design in its original form had 65 hp. I'd love to see a modernized version of the AS.37.
 

cluttonfred

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Sorry, but for a control surface to have a significant impact it must create lift force with a surface area acting through a lever arm of a certain length, hence the comparison of aircraft tails done using tail volume. The AS.37 just does not have enough lever arm to provide significant directional inputs. They are just ailerons as proven on multiple flying aircraft. Here’s another, the Starck AS.27 racer.

C2AA514F-7CA1-421E-A3B3-3585D142CD07.jpeg 55770694-C92D-4721-8AE5-2E7F3760F00C.jpeg 83974C30-8EB9-4DDE-B792-50493E5C3765.gif

They are BIG surfaces for just small YAW adjustments, and are behind the CG, he could have just cut the tail off!

On his earlier versions they were smaller.

They are at 90 Degrees relative to each other, the same as a V-Tail, approximately twice the angle of a Jodel.
 

WINGITIS

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Sorry, but for a control surface to have a significant impact it must create lift force with a surface area acting through a lever arm of a certain length, hence the comparison of aircraft tails done using tail volume. The AS.37 just does not have enough lever arm to provide significant directional inputs. They are just ailerons as proven on multiple flying aircraft. Here’s another, the Starck AS.27 racer.

View attachment 116102 View attachment 116103 View attachment 116101
If they were horizontal I would agree with you but they are at 45 degrees, EXACTLY as a V-tail would have, on the AS37 they are far enough back from the CG to work as rudders if you think of it as a flying wing with no tail, also they have good leverage by being that far out on the rear wing!

We will just have to disagree on it.

Or someone could test it in X-PLANE.
 

cluttonfred

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It’s not the angle that matters, it’s the lever arm. The directional impact due to the rudder input of the canted surfaces is negligible since it has almost no lever arm. The impact of adverse yaw due to drag at the down aileron would be far more pronounced as it has the whole wing half span as a lever arm. With a little differential aileron rigging that would be eliminated and also overpower any directional impact (slight adverse yaw) from the canted surfaces.
 

WINGITIS

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There is plenty of lever arm, in terms of both width and the distance from the CG, the tail only has the distance from the CG!

The length from the CG to each actuator is proportionally similar given there is two, never mind the larger area of the wing mounted ones!

AS37 CG LEVERS.png
 
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