Flaps or flaperons

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WonderousMountain

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Hi Mac,

I'd go with flaperons, although I agree with much intelligent discussion on the matter, reality is you'll get good performance out of them & top speed flight is not going to be a critical parameter for your use. However, you will want to get good geometry out of it. A lot of planes are just good enough.

Sincerely,
CK LuPii
 

Victor Bravo

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Why not just invent smart flaps that using sensors and a control box can augment each phase of flight either automatically, or upon pilot command.
Paolo Iscold has done just that:

 

Bigshu

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Flaperons are a big step down compared to separate flaps and ailerons. This is especially true if you are building a constant-chord wing with no twist. When flaps are deployed, this creates an aerodynamic twist in the wing which greatly improves the handling and safety of the wing at low speeds. Flaperons trade all that in for a bunch of adverse yaw and a wing that is more likely to send you into a spin. It is a double lose design compromise that, in my opinion, is generally not worth the small parts count reduction that comes with flaperons.
Which, of course, is why Van's uses them on the RV-12, both the kits and the S-LSA. A sure double lose!
 

REVAN

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Dear Revan,
From the opposite perspective, ailerons that droop with flaps provide a shallower angle of attack for the outer wing panels. Most of those STOL planes don't droop ailerons as deep as flaps. For example, flaps might droop 40 degrees while ailerons only droop 30 degrees. This means that outer wing panels stall later/steeper angle of attack and you maintain aileron control part way into the stall.
I don't quite see the "opposite perspective" here. I think you are agreeing with me, as your example promotes that added mechanical complexity is warranted to preserve maintaining an adequate level of aerodynamic wing twist to improve low speed handling performance and spin resistance. With separate flaps and ailerons, you have the option to include the mechanics to droop them, but you can't do that if the wing is built with flaperons. With the mechanics to droop the ailerons, one could also include the ability to reflex them which would be beneficial in cruise and at high speeds. Whether the added complexity to include these features is worth it depends on a lot of factors that likely go beyond the scope of this thread. Suffice it to say that most planes don't incorporate these complexities, so we can assume that for many people the performance gains are not worth the costs.

Which, of course, is why Van's uses [flaperons] on the RV-12, both the kits and the S-LSA. A sure double lose!
Lots of planes use flaperons. It's a design choice. Just because a statistically significant minority of aircraft use a particular design feature, doesn't mean that it is a good choice for everyone. In fact, it suggests that is probably a poor choice for most people or it wouldn't be in the minority.

I'm an aero engineer with many years of experience working in control systems. To me, handling qualities are a high priority. Flaperons are not an attractive design choice to me. I tend to pay a lot of attention to wing design, the wing's lift and drag distributions and how that feeds back into aircraft handling qualities. Many (if not most) EAB designers are more interested in making something simple that can fly. Details of a wing's lift and drag distribution and how that feeds back into aircraft control, adverse yaw and spin tendencies are often relegated to rule-of-thumb status or TLAR engineering.

If we use the market as a guide, separate flaps and ailerons are generally worth the cost. If I use my engineering background as a guide, I think separate flaps and ailerons are generally worth the cost. Your mileage may vary.
 

Victor Bravo

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IMHO, both sides are right.

There are a lot of times where simple and reduced parts count are the goal. Avid Flyer et ses derives, Zenith 700 series, etc. Those are all very successful airplanes, and the simplicity has paid off despite the loss in max. control authority, performance, low-speed handling, etc. etc.

There are also many many other airplanes that separate the flaps and ailerons and achieve those handling improvements, at the cost of a little extra fabrication... and that works perfectly well for what those airplanes were built for (Cessna, Piper, etc. etc.).

I personally believe that if I were building my own design, a little extra time and fabrication would be worth it to get some improvement in safety or max performance. But if I were trying to manufacture that same airplane, or convince people to buy a kit, then it might be worthwhile to be able to advertise fewer build hours, lower parts count, lower kit cost, etc.

There's also a weight difference, one-piece flaperons can be lighter than two separate control systems. I believe I read a story about Van designing the RV-12 and just about pulling his hair out trying to save weight without weakening the primary structure. Saving 3 or 4 pounds of control runs and pushrods might have allowed him to use a .020" thicker spar cap, or the next size up in D-tube leading edge skin or something?
 

Pilot-34

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You live where the experts are. What are they saying? I have a friend with a fancy Cub that can fly some weigh, but it is not LSA by a long stretch
Aeronca Sedans seem to be popular to haul moose........what’s that tell us ?
 

Aesquire

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There's also a weight difference,...
There are different weight issues in different "classes" of aircraft.

Regulation weight issues are arbitrary Requirements, so if you need to stay under an arbitrary "empty weight" like U.S. Pt103, it makes zero difference if you want a 400 hp. V8 for a power plant, you cannot fit the category with an engine heavier than regulatory empty weight.

Regulatory weight limits usually are to have cheaper insurance or cheaper training/licencing or to fly at all when other "classes" are denied you for whatever reason.

Other than rule based weight issues are just part of aviation from the Montgolfier Brothers to Boeing hypersonic airliners. There's a cascade, or avalanche effect as a heavier item requires a heavier structure, requiring a bigger wing, which all is heavier, so you need a bigger, heavier engine, requiring heavier landing gear........ In a death spiral. It's a brutal truth in rocketry, or VTOL flight.

and now I really want to fly an AS-W20!

My advice to the OP is count your grams, and follow the reality of the math. He's got a regulatory limit, that's really going to make the 2 desires hard. Those are hard core Bush STOL, & cargo capacity.

I suspect that fabric covering and carefully choosing featherweight instruments are good ideas. My usual, oft repeated advice to not skimp on wing area, or tail size, to gain a little more speed may apply too.
 

Pilot-34

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No but in a discussion about simplicity and flaps and hauling moose meat they do seem a Pertinent example.
 

TFF

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My point is a field dressed moose is 500-800 lbs. LSA has 1320 to work with total. If I had a 500 lb moose meat, me at 240, 10 gal of fuel 60 lb, and another 30 lb of stuff. That’s 830 lb of stuff. That leaves a 490 lb plane for LSA unless you want to leave some of that moose for the bears. Who cares about flaps at that point. Even if you don’t care and fly over gross, you are struggling until you can take off at 2000lb. My little one seat biplane weighs in that 490 range without the engine. If we can take off more than LSA, moose is possible. LSA is fine for certain things in Alaska, but not a heavy hauler.
 

Bigshu

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Many (if not most) EAB designers are more interested in making something simple that can fly. Details of a wing's lift and drag distribution and how that feeds back into aircraft control, adverse yaw and spin tendencies are often relegated to rule-of-thumb status or TLAR engineering.
I'd like to see some proof on this claim. Chris Heintz did most of the Zenith designing, Pazmany has at least a couple of successful EAB designs, Schlitter with Rans seems to be a thoughtful and successful designer. Monnett has had several successful designs, Obviously Van Grundsven puts a lot of time and money into design, the guys that started Cirrus, the list is longer than this, but you get the point that all these guys, with all these designs, were probably concerned with more than just "making something simple that can fly". I'm glad that you have a lot of knowledge and skill in aeronautical engineering, but until you have a design that's outselling the certified guys combined, like Vans does, maybe you can concede that the successful EAB companies are on to something. Last time I checked, we're all posting to "homebuiltairplanes.com". We can navel gaze about the theoretical optimum in all phases of design, or we can build to the best of our knowledge and capabilities, and make compromises that are a lot more involved than "making something simple that can fly".
 

Pilot-34

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My point is a field dressed moose is 500-800 lbs. LSA has 1320 to work with total. If I had a 500 lb moose meat, me at 240, 10 gal of fuel 60 lb, and another 30 lb of stuff. That’s 830 lb of stuff. That leaves a 490 lb plane for LSA unless you want to leave some of that moose for the bears. Who cares about flaps at that point. Even if you don’t care and fly over gross, you are struggling until you can take off at 2000lb. My little one seat biplane weighs in that 490 range without the engine. If we can take off more than LSA, moose is possible. LSA is fine for certain things in Alaska, but not a heavy hauler.
Lol when I was in high school I made a bit of spending money carrying moose out of the woods for those who hunted all day and were suddenly faced with the prospect of a 40 mile trip with 800 pounds (surely a world record) of moose to get out of the woods.
I suspect the OP is thinking multiple trips in a plane ✈(Any plane) looks like far more fun than those same trips on foot with a hundred pound pack on your back.
 

WWhunter

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I'm no aeronautical engineer, but my son is an aerospace engineer...or as he says, yes I am a Rocket scientist. LOL
Anyway, from a personal and flyer aspect, I always refer to my experience in a Kitfox and Murphy Rebel, of which I own and fly. The Murphy Rebel is designed to be built either way, ie. with normal/typical flaps and ailerons, or built with the flapperons. The vast majority of Rebel owners will tell you that this plane performs better with the flapperons than it does with the split flaps/ailerons. Granted a great many of these planes are on floats if that makes a difference. Also, the Rebel can be built as an LSA or with a higher gross EAB.
 

REVAN

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Many (if not most) EAB designers are more interested in making something simple that can fly. Details of a wing's lift and drag distribution and how that feeds back into aircraft control, adverse yaw and spin tendencies are often relegated to rule-of-thumb status or TLAR engineering.
I'd like to see some proof on this claim. Chris Heintz did most of the Zenith designing, Pazmany has at least a couple of successful EAB designs, Schlitter with Rans seems to be a thoughtful and successful designer. Monnett has had several successful designs, Obviously Van Grundsven puts a lot of time and money into design, the guys that started Cirrus, the list is longer than this, but you get the point that all these guys, with all these designs, were probably concerned with more than just "making something simple that can fly". I'm glad that you have a lot of knowledge and skill in aeronautical engineering, but until you have a design that's outselling the certified guys combined, like Vans does, maybe you can concede that the successful EAB companies are on to something. Last time I checked, we're all posting to "homebuiltairplanes.com". We can navel gaze about the theoretical optimum in all phases of design, or we can build to the best of our knowledge and capabilities, and make compromises that are a lot more involved than "making something simple that can fly".
Observe all the EAB aircraft with Hershey-bar wings and rudders. To me, this is evidence enough for my claim. Why do this if not because it is simple and it flies?

How many EAB designers actually look at induced differential wing drag as a function of aileron deflection? I haven't done a survey to get a real answer to this question. However, my bet would be on the answer being pretty close to the number of EAB designers that are designing flying wings. A tailless aircraft has to have a yaw stable wing, so differential induced drag becomes a critical part of the design process. However, this is a difficult analysis to conduct, and that is probably why few people tackle flying wing projects.

The evidence of EAB aircraft in existence suggests (to me, anyway) that most EAB designers start with choosing a 2-D airfoil section and then use that to design a rectangular wing that is big enough, strong enough and light enough to meet their speed and load requirements. They ponder the questions regarding the differences between flaperons vs. ailerons and flaps, and make a decision that seems about right for their application and priorities. Then to make sure that this wing, which has received little to no attention regarding its differential span-wise drag distribution, will be controllable, make sure you have enough tail volume via rule-of-thumb guidelines. A more advanced design might include frise-ailerons to counteract the yaw instability inherent to the wing's general planform, but that is usually the extent of attention paid to this aspect of wing design in many EAB aircraft.

Please note, I'm not condoning anyone for doing this. There are only so many hours in a day, and this process has produced many successful aircraft. It is simple and it works (most of the time).
 

Aesquire

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Observe all the EAB aircraft with Hershey-bar wings and rudders.
The Market likes Hershey-bar wings.

You're right that it's seldom an optimized lift distribution priority.

Builders like near identical ribs and nice single curvature surfaces. Hershey-bar wings also have nice predictable stall characteristics.

I don't think it has anything to do with the designer being lazy or ignorant, It's just market demand.

It's a pity Dean Wilson's Explorer Ellipse didn't sell well, lovely wing.

If you follow some threads here, you'll see some proposed designs that focus on simplicity of building, ability to cram into a container of predetermined dimensions, and aerodynamic efficiency, etc. You chose your priorities and roll from there, & never can have the perfect solution.

With molded composites you can have lovely compound curves and even easier building, but at a price. Or you can have labor intensive building for cheaper. You choose. It's the old joke, about private detectives, you can have it cheap, fast, and quiet. Pick two.

And lots of guys don't like or have allergy issues with composites. In Metal, wood, or fabric pretty curves have their price there, too. Compromises.
 

youngwerth

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I fly a Pipistrel Virus SW (flaperons) and a Lancair ES-P (flaps). Although they are both great airplanes to fly, the Virus is really unique, especially in calm air. Aileron control is amazing, like it's on rails in the sky. I've always assumed it is due to the length of the control surface.
 

Riggerrob

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"
... It's a pity Dean Wilson's Explorer Ellipse didn't sell well, lovely wing. ...
"

Yes, Ellipse has a beautiful wing, almost elliptical. To be precise, Ellipse wing is almost the same planform as the Schumann wing favoured by modern sailplane and Formula One racers. All the taper is in the gracefully curved leading edge and the trailing edge is almost straight. Dean Wilson knew that the curved wooden leading edge was beyond the skills of the average amateur, so he offered a kit with pre-built wings.
 

Bill-Higdon

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How about the system used on the Northrop P-61, N-23, & C-125? Small ailerons on the outboard portion of the wing and differential spoilers for roll control & the rest of the trailing edge used as flaps
 

BJC

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Lets say you were going to build a light sport aircraft and i mean light . And your purpose was strictly back country bush flying . Hunting , hauling moose meat . Real STOL FLYING . Ive lived in ALASKA all my life and hunted in some real remote places . . My question is reguardingwing structure ailerons , and flaps or flatirons? oh and i forgot to mention first time builder so simplicity goes a long way .wich would suit my purpose better
Are you asking for input on a unique design that you are contemplating?

What is your definition of “real STOL FLYING”?

What is your maximum takeoff and climb to XX altitude distance?

What is your useful load requirement?

Your range requirement?

An option not mentioned, but could meet many of your wants, is to build a wing with traditional ailerons, but without flaps.


BJC
 

Arkan

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I have been reading through the comments here, and there does not seem to be a real answer beyond personal choice. As a first time designer, I am planning a Hersey bar wing, with Flaperons and deployable leading edge slat, that can be stowed to rest flush on the wing when not needed. I am still working on that design in my head, but i think it will work.
 
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