Flying wing as cheap and simple option for basic fun flying.

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Doran Jaffas

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In that case you might want to take a look at this Australian side-by-side, two-seat plank glider derived from Al Backstrom’s EPB-1. Something similar with a motor and lower AR wing might work well.

OK...new to flying wings..sort of. What would happen to the stability if an engine large enough to self launch is installed?
 

cblink.007

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OK...new to flying wings..sort of. What would happen to the stability if an engine large enough to self launch is installed?
I would assume the prop slipsteam would disrupt flow across the center section if the engine was in a tractor configuration. We use a pusher configuration with ours, with the thrust line as centered as we could get it!
 

Hot Wings

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What would happen to the stability if
Flying wings are bound by the same formulas as a conventional plane. The only practical difference is that the distance form the center of gravity for most of the forces, except those on the lateral axis, are less. In the case of adding power this means that the change in thrust can have a more pronounced effect if it doesn't pass through the CG and/or the center of drag.

If you mean self-launch as in vertical takeoff.... :eek:
 

Doran Jaffas

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I would like to build one with a 2 place side x side. Anything available? Be a nice addition to my Tailwind W8.
 

Doran Jaffas

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Flying wings are bound by the same formulas as a conventional plane. The only practical difference is that the distance form the center of gravity for most of the forces, except those on the lateral axis, are less. In the case of adding power this means that the change in thrust can have a more pronounced effect if it doesn't pass through the CG and/or the center of drag.

If you mean self-launch as in vertical takeoff.... :eek:
Nope..self launch as in runway style.
 

Sockmonkey

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You know, for a LAR plank I'd be tempted to steal an idea from Nestofdragons and stick those multi-winglets on the tips to reduce the drag. Don't know if that would be better than Hoener tips or not.
One other thing that might work or not would be to add the tiniest bit of forward sweep at the tips.
 

Hephaestus

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Kinda extreme opposite end of the spectrum, typical 80s NASA "GA" study looking at .30 mach and up... But I've learned never post here without technical backup ;)

I've been playing with an a380 style blended winglet on the lazybee model - I'd say if you can play with one easily (I'm just FDM 3d printing mine, then testing Wittman style, old left new right) it's worth the bit of math and cad work to have a look.
 

rotax618

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From my experiments with simple foam models, the rectangular planform was the least stable at slow speed. It tended to shed the vortices unevenly depending on the yaw, the most stable planform had a curved or swept LE.
 

erkki67

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35BAE86F-C1BA-4FCC-9CA7-748DF097FC81.jpegE6B58D6E-C0FE-439E-B2E2-536CE9B0B722.jpeg
both are as simple as it gets, the most successful planes where simple in lines, see the Volksplane, MiniMax, to some degree Vans, aircraft, Savannah, Quicksilver, Zenairs and so on.
sockmonkey, I don’t know how you want to call this plane, but it would fill a niche, that has not been taken so far.
all the fancy, twisted, multiple airfoil, and so on where only produced in small numbers, as it’s to time consuming for the average builder, as an extreme, look at the Horten style birds, how many ribs are to be built, 30+ different and with different airfoils and twisted wings. Yours can be built with 1 single type of rib = 1 jig, not 30!
actually I like both designs, highwing or lowwing plank like you came up with.
 

jedi

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You know, for a LAR plank I'd be tempted to steal an idea from Nestofdragons and stick those multi-winglets on the tips to reduce the drag. Don't know if that would be better than Hoener tips or not.
One other thing that might work or not would be to add the tiniest bit of forward sweep at the tips.
In my eyes this layout begs for a good wingtip application. See Does this aircraft have any use?

Does this aircraft have any use?
Or a more likely solution as in
1593691006452.png
The wingtip add on can be a very simple and easy construction.
Note: The Glasair Sportsman drawing is from a report on applications of the Prandel BSLD concepts.
 

Sockmonkey

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From my experiments with simple foam models, the rectangular planform was the least stable at slow speed. It tended to shed the vortices unevenly depending on the yaw, the most stable planform had a curved or swept LE.
What was the aspect ratio on those models?
 

Hephaestus

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What was the aspect ratio on those models?
Not speaking for him but I recall he's posted a few facetmobile like test models where there was a variety of tip treatments.

What I'm coming to realize is it's all about tip vortex control with the LAR designs. That's largely why I'm still playing with the airfoil and wingtip treatment. My project I've removed 20% of the wing area since I started getting closer to "good" vortex control. Waiting on some better data-logging gear to put useable numbers on it and moving up to a 50% scale build soon.
 

Sockmonkey

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Not speaking for him but I recall he's posted a few facetmobile like test models where there was a variety of tip treatments.

What I'm coming to realize is it's all about tip vortex control with the LAR designs. That's largely why I'm still playing with the airfoil and wingtip treatment. My project I've removed 20% of the wing area since I started getting closer to "good" vortex control. Waiting on some better data-logging gear to put useable numbers on it and moving up to a 50% scale build soon.
I see what you and Rotax are saying. Big tips means a lot of spill, so that spill has to be consistent. I've seen some straight wings with permanent leading edge slots at the tips. Might be a solution.
 

Hephaestus

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I see what you and Rotax are saying. Big tips means a lot of spill, so that spill has to be consistent. I've seen some straight wings with permanent leading edge slots at the tips. Might be a solution.
It could be as simple as some wingtip fences like you originally had - that may be one of the simplest.

Depending on your construction method they don't need to be insanely difficult either. Mine is very much 2 small wings with washout and some very crude lofts - in composite - it's fairly easy. In wood - not a lot different really - think 2 RC wings then make them blend together...

At 1/3 scale I'm just 3d printing them. Still planning the same for 1/2 scale possibly with a spar.
 

rotax618

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You have to forget the 2D airfoil model, with AR <2.5 you dont need vortex generators - the wing planform is the vortex generator so its shape is critical in getting the most benefit from a LAR. I have always believed that low aspect ratio would make the cheapest bang for the buck single seat sport plane provided that 1. The wing loading is low - fortunately that is a no brainer because the wing is the airplane, 2. There is a reasonable thrust to weight ratio.
The benefit of LAR is simpler, stronger, low parts count, compact for storage and provided that you adhere to the above, STOL performance - fast acceleration for a very short takeoff and a steep approach with a flare for very short landing - stall and spin resistant.
 

Sockmonkey

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You have to forget the 2D airfoil model, with AR <2.5 you dont need vortex generators - the wing planform is the vortex generator so its shape is critical in getting the most benefit from a LAR. I have always believed that low aspect ratio would make the cheapest bang for the buck single seat sport plane provided that 1. The wing loading is low - fortunately that is a no brainer because the wing is the airplane, 2. There is a reasonable thrust to weight ratio.
The benefit of LAR is simpler, stronger, low parts count, compact for storage and provided that you adhere to the above, STOL performance - fast acceleration for a very short takeoff and a steep approach with a flare for very short landing - stall and spin resistant.
In this instance, we're not talking about vortex generators, but vortex manipulators to prevent that unstable shedding, and reduce drag.
 
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