aeronautical Airplane Flap Design

[afterburn 549]

For the Airo Engineers out here....
Hinge points on Flaps Or better -
When deployed and in use , Whats better, ??
To have the leading edge of Flap slightly above top of wing contour?
(so to run some top air over ?)
Or as in most applications they hinge on center and it stays that way through the travel.
I notice on jets there is allowances for air to be passed both directions.
You cant make a mistake here with your answers...LOL
This is for a couple RC airplanes we making .No one is going to be sued LOL
Some of the Old HIGH performance Fighters even had flaps under the wing so no top Boundary air was there at all !
So....after much thinking..........i am thinking I do not know much at all

[oldE]

Sounds like fun!

I'm NOT an aero engineer and I can't remember the last time I stayed at a Holiday Inn, but looking at your application, it is in reality a low-speed situation.

The forces exerted on a surface don't always "scale well" when making models.
I'm guessing you need air movement over both surfaces of your flap to gain the full effect.

That opinion was worth exactly what you paid for it!

Best
Les

[abisel]

Well, whatever you choose will depend on complexity to build on an RC.
Commercial airliners use a combo of Fowler and Slotted, which is why you see those huge hinge farings under the wings.

[afterburn 549]

I guess slotted is sort of what i was describing.
Only with the leading edge of flap just a little proud of the top of the wing.........Like everything there is a dozen ways to accomplish task at hand.............. Hoping some one will break dwn pros and cons.

[romad]

For an RC airplane I would not over think it. I believe what you are trying to describe is a Fowler flap, a fowler flap is doing two things, its changing camber and increasing area. a simple flap would be more than functional for RC planes.

Newton's third law is the real explanation. Bernoulli's principle is the mechanism of how a wing makes lift. What a wing is doing is creating a down ward flow of air, in simple terms a push of air in the opposite direction of the lift. Thats were the term "with enough power you can make a barn door fly; or how airplanes fly upside down, and the reason the split flap works on fighter aircraft. Boundary layer and complex air flow are all considerations in making lift, but if just flying RC aircraft is your interest the more complex anaylsis falls under just good to known. Now if you are more interested a wind tunnel might be in your future.

[afterburn 549]

I dont want to reinvent the wheel..........I am sure there is a simple answer.
I realize jets use them at % rates and even act as air brakes LOL
Yea enough Power and Snoopys Dog House will fly. Thats not he question
Too me it looks like I am getting no where fast here.....

[romad]

As said, in an RC application you will not know the difference. The slotted set- up will just be a little harder to build. Oh and it might look better.

[afterburn 549]

well its going to have a 12 foot wing span..........so dont presume too much

[romad]

Oh a 12 foot wing that makes all the difference.......the least you will need is a multi element fowler with laminar flow control and winglets, you might have to consider leading edge slats, but generally that's only required with wing spans over 12 foot.

[onewhippedpuppy]

My aero classes were a long time ago, but I believe the primary purpose of the slotted flap is to promote airflow over both the top and bottom surfaces of the flap. The slotted or fowler flaps would be difficult on an R/C, you'll need some sort of flap track and jackscrew type arrangement as the flaps deflect both downwards and move backwards. Pretty complex. I would go with some sort of plain flap for ease of construction, and just focus on getting the area right. If you just want to go low and slow with short takeoff/landing distances, you could also consider adding leading edge slats.

[tevake]

An other thought is that the wings will be dismounted , so the linkage will have to be simple to disconnect.
Looking out the window on big commercial jets, I see the type called Fowler in the earlier post. Never had heard that name for it.

Cheers Richard

[afterburn 549]

I am still wondering through time and space. Reynolds ventries Bernoulli's, boundry Etc ...so i am perplexed........some flaps want to stand the nose on end...others just give a nice soothing Float affect.
Now.to hinge the flaps so their leading edge goes slightly above the main wing trail edge seems ( when deployed ) like there might be a advantage..
Doing two things at once?

[Joeaksa]

Would agree with Matt above but also the jackscrew stuff would weigh more than you would want on an RC airplane. Runway length is usually not an issue so just go with something simple and cheap.

[afterburn 549]

Its all simple........just a matter of direction........I HATE going in REVERSE.......a jack screw on small scale would be pretty ez..........and with todays servos...it could just push the flap out

[Tim Hancock]

RC airplanes typically do not fly like their full scale big brothers. Reynolds numbers and all that... On top of that, your 12' wingspan model if 1/4 scale dimensionally, will not be 1/4 of the weight. The RC will be much lighter I am sure. Example: a 1/4 scale aerobatic RC might weigh 30-40 pounds while it's full scale big brother weighs 1200 pounds. Messing with airfoils is a waste of time typically when it comes to RC. A flat squared off chunk of foam will typically fly about the same as an airfoil shaped piece of foam in the lighter/slower realm of RC aircraft.

As far as flaps go, too much flap (area/deflection or both) and you get a nose down pitching moment. With an RC model, one can simply program in some nose down elevator mix to compensate. That said, the simplest way to add flaps on an RC model is to simply turn the ailerons into flaperons... In other words program the ailerons to droop when throttle is chopped and mix in a touch of nose down elevator as needed.

[afterburn 549]

Thanx........and so far i know this and "scale effect" wnig load and all............
BUT
Has anyone tried what i am asking ? or does anyone know the result(s) LOL
B4 I head off to crazyville

[crustychief]

Originally Posted by afterburn 549

For the Airo Engineers out here....
Hinge points on Flaps Or better -
When deployed and in use , Whats better, ??
To have the leading edge of Flap slightly above top of wing contour?
(so to run some top air over ?)
Or as in most applications they hinge on center and it stays that way through the travel.
I notice on jets there is allowances for air to be passed both directions.
You cant make a mistake here with your answers...LOL
This is for a couple RC airplanes we making .No one is going to be sued LOL
Some of the Old HIGH performance Fighters even had flaps under the wing so no top Boundary air was there at all !
So....after much thinking..........i am thinking I do not know much at all

The best flaps I have built for R/C use robart hinge points from under the flap in about a 45 degree angle. It has the effect of a slotted / fowler hybrid of sorts.
Control Surfaces | 2BFly

[crustychief]

My t-34, Skylane and Super Cub use these. I have a giant telemaster that I added split flaps on, they also work great. I do not think you want the leading edge of the flap to go above the wing.

[afterburn 549]

In My LIL Brain if the leading edge stood proud when deployed..........
Effect - will either act as a speed brake
Or or as super flap...the boundary layer is at its limits SO this idea must be wrong OR - will, / would have been applied and in service somewhere in real life...............

[beepbeep]

What is the motive power? Jet, electric or pistons?

If jet, You could (arguably) try to go for blown flaps?