Flying wing for high efficiency

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John Newton

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I agree, on fllying wing models I have built with sweptback wings a large amount of elevon defelction is needed to roll the model due to the effective dihedral opposing the roll.
 

karoliina.t.salminen

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I see this thread is active again and Aircar was speculating practicality sometime last year. Actually for this consideration that is not so relevant even though he has been quite much on topic unlike some others. I can refresh the idea of the thread in simplified manner:
- I was about comparing a tailess design for a such case which needs to both satisfy requirement of low fuel consumption, long endurance and long range but also has to meet certification level criteria on low speed handling, including reasonable rotation speed and landing speed. Lets forget all practicality because to objectively consider this kind of concept we can forget that what it carries and if there are even pilots on board. So why is not relevant, but what and how are.
- we already know that a tailed design can go with much smaller wing area but the interesting thing about a pure wing is that is it really that much worse when compared against tailed designs as none of the tailed GA designs on market actually can claim to be extremely optimized as far they could be optimized, e.g. typical Clmax for a tailed GA plane seems to be in region 1.9 instead of something nearer to 3 which could be possible in a optimized design and the gap between the flapless wing and the tailed plane to me at least, looks narrower.

Pure wings are simple, clean and uncluttered looking designs that just tend to please my eye, a bit similarly than e.g. a product from Apple that is clean and stylish and simple in a bit similar manner but on another industry obviously. And the shape could lead to simplified mechanics and low part count. I opened this thread due to my interest in flying wings and flying wing design, so feel free to continue adding comments which are aligned with the topic.

Please all keep on topic and don't degrade the thread with off-topic. Flying wings are interesting to me and I believe to many others as well, and to have this thread to be useful, should only discuss about them. There are several pages of crap in this thread that could be cleaned up to benefit the actual topic, e.g. all references to any pedalling and similar BS.

I have a flying wing already and it flies by itself (and is extremely well flying except on stall sometimes it may come down in a tail spin kind of condition) and I like it although it is boring because it was designed and made in China. Thinking of designing and building my own wing next, on that scale (ie. very low Reynolds number).
 

John Newton

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Joined
Dec 5, 2012
Messages
430
Location
Derbyshire, England
I see this thread is active again and Aircar was speculating practicality sometime last year. Actually for this consideration that is not so relevant even though he has been quite much on topic unlike some others. I can refresh the idea of the thread in simplified manner:
- I was about comparing a tailess design for a such case which needs to both satisfy requirement of low fuel consumption, long endurance and long range but also has to meet certification level criteria on low speed handling, including reasonable rotation speed and landing speed. Lets forget all practicality because to objectively consider this kind of concept we can forget that what it carries and if there are even pilots on board. So why is not relevant, but what and how are.
- we already know that a tailed design can go with much smaller wing area but the interesting thing about a pure wing is that is it really that much worse when compared against tailed designs as none of the tailed GA designs on market actually can claim to be extremely optimized as far they could be optimized, e.g. typical Clmax for a tailed GA plane seems to be in region 1.9 instead of something nearer to 3 which could be possible in a optimized design and the gap between the flapless wing and the tailed plane to me at least, looks narrower.

Pure wings are simple, clean and uncluttered looking designs that just tend to please my eye, a bit similarly than e.g. a product from Apple that is clean and stylish and simple in a bit similar manner but on another industry obviously. And the shape could lead to simplified mechanics and low part count. I opened this thread due to my interest in flying wings and flying wing design, so feel free to continue adding comments which are aligned with the topic.

Please all keep on topic and don't degrade the thread with off-topic. Flying wings are interesting to me and I believe to many others as well, and to have this thread to be useful, should only discuss about them. There are several pages of crap in this thread that could be cleaned up to benefit the actual topic, e.g. all references to any pedalling and similar BS.

I have a flying wing already and it flies by itself (and is extremely well flying except on stall sometimes it may come down in a tail spin kind of condition) and I like it although it is boring because it was designed and made in China. Thinking of designing and building my own wing next, on that scale (ie. very low Reynolds number).
Some good points, any sketches on what your wing is going to look like? I am currently working on a scaled up version of my R/C tailless design (featured in my previous posts on this forum), the idea is to combine good handling, simplicity of construction and good all round performance/effeciancy. I have chosen a sweepback of 20 degrees to give good pitch stability and reduce the twist needed, parallel chord for simplicity of wing construction, partial span drooped leading edge to eliminate tip stall and increase angle of attack range for little drag increase, winglets for increased span efficiency and good directional stability and a pusher prop.
 

karoliina.t.salminen

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I am not that far that I would have anything to show yet, just some random simulations on XFLR5 (basically finding out about low Re airfoils) and nothing concrete on conclusive yet. Basically I am aiming at something that looks a bit like the Skywalker X8, ie. it has a center section that extends forward from the wing for internal storage volume, but one that is made of fiberglass and is a bit bigger than the X8. I would like to fix also the problem of tip stalling at high angle of attack leading to unrecoverable spin. It will have moderate sweep and been also thinking about a bit larger AR than the X8, but not sure how much. I should maybe implement drag rudders because X8 has a rather generous dutch roll tendency, if you aggravate it by rolling rapidly from left to right to right to left to left to right to right to left, it will be quite soon in a stall condition (and may spin to the ground as a result), would like to stabilize the yaw axis as well (my X8 flies now with flight stabilizer - rock solid unless you make it dutch roll violently, going to replace it with Arduino-based stabilization). I need to check your thread then, might get good ideas from your design.
 

John Newton

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As regards dutch roll, a common problem with winglet equipped swept flying wings, this is due to too great a dihedral effect and too small a fin area. My design does not suffer from dutch roll. Interesting you mention the Arduino, can you programme these? I know a Lecturer planning to use these in an R/C application.
 

captgrizz

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Orange, Texas somewhere near there
In what little research I have done on flying wing aircraft. all full sized models I am familiar with were extreamly dangerous to fly in adverse conditions. And if I know anything about flying conditions get adverse regularly no matter how careful one is. The modern flying wing jets have computers to keep pilots from making mistakes and thrust vectoring for added control. During the second world war the Germans had what possibly the most successful flying wing until the 90s. it was a twin engine pusher light cargo plane. 60% of them crashed over a 10 year period. the reason for conventional aircraft design is stability in flight that is why the small wing in the tail is called a stabilizer. John Dyke attacked the efficiency problem when He designed the Dyke Delta and desided that a liftbody with a multi angled wing was the answer in his opinion. His is a very sturdy design and flys fast for its power and payload in a small plane. I prefer flying low wing airplanes but the truth is high wing aircraft with an aerodynamic pod fuselage and aft located stabilizer and ruder are the most stabil and efficient and safe aircraft to date. Whether they be a Piper Cub, a Cessna Skymaster, a Aerocommander 680E an MU-2 all aircraft with many many hours of safe flight in a wide variety of conditions. Flight is a compromise of conditions that balance out. Safe flight is a tighter compromise that give up a little speed and efficiency for a greater likely hood of getting home safe. I have raced everything from aircraft to cars and motorcycles, and though those all gave me a thrill because I could do things with them one couldn't do with normal aircraft and vehicles none of them are what I would chose to haul my loved ones around in. Well I have most likely said too much Good luck with your designing as for sucking off air to maintain laminar flow on a high lift wing the only way I know to do it is with an eduction system set up on the exhaust of a turbine or jet engine. GRIZZ
 
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John Newton

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just aircraft superstol has some really nice simple automatic slots that should cure tip stall. they can be installed on just the outer wing section. Super Stol, Just Aircraft's Super Stol light sport aircraft at E.A.A. Sun-N-Fun 2013 - YouTube
Intriguing, very simple and elegant design, like they way they only deploy when required, best of both worlds, no additional drag at high speed, no tip stall at low speed. Thanks captarmour, I'll have to see if I can get more info on the exact hinge geometry.
 

Norman

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like they way they only deploy when required, best of both worlds, no additional drag at high speed, no tip stall at low speed.
Actually Handley-Page type automatic slats do produce some drag even when they're closed because the panel lines trip the boundary layer farther forward than it would naturally transition on a smooth wing. Not a problem on STOL aircraft because they aren't designed for efficient cruise anyway but low drag airfoils are low drag because they have long laminar runs. Generally speaking if you are using low drag airfoils you need to keep the wing as smooth as possible back to the transition point. Without computer control the main advantage of a flying wing over a conventional layout of the same wetted area is the extent of laminar flow. It's very hard to get any laminar flow on a fuselage so they're usually high drag. For examples of low drag fuselages look at modern sailplanes and the Piaggio Avanti
 

Norman

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In what little research I have done on flying wing aircraft. all full sized models I am familiar with were extreamly dangerous to fly in adverse conditions.
Most flying wings were dangerous because those designs were flawed. In 1939 two Horten H-III s reached 16,000ft in a thunder cloud. Both planes were destroyed by hail but I imagine the express elevator to doom was a rough ride. The first sailplane to cross the Andes was a Horten H-XV. Flying in a wave is smooth but crossing a range is a bit more demanding. In fact, given that it was in the mid '50s, it was probably mostly inter-thermal flying so not an easy trip
 
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John Newton

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Messages
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Actually Handley-Page type automatic slats do produce some drag even when they're closed because the panel lines trip the boundary layer farther forward than it would naturally transition on a smooth wing. Not a problem on STOL aircraft because they aren't designed for efficient cruise anyway but low drag airfoils are low drag because they have long laminar runs. Generally speaking if you are using low drag airfoils you need to keep the wing as smooth as possible back to the transition point. Without computer control the main advantage of a flying wing over a conventional layout of the same wetted area is the extent of laminar flow. It's very hard to get any laminar flow on a fuselage so they're usually high drag. For examples of low drag fuselages look at modern sailplanes and the Piaggio Avanti
So from a cruise drag point of view, which is better, partial span drooped leading edge or automatic slats?
 

Aviator168

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So from a cruise drag point of view, which is better, partial span drooped leading edge or automatic slats?
With automatic slats. You better make sure slats on both wings are synchronized. Slats in a lot of the older planes are spring loaded and they are deployed when air speed is below a certain point.
 
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