I’ve been looking at different flapped stunt planes and I’ve not seen one where the flaps are a continuous part of the airfoil but rather a more or less flat surface attached to the TE. The last 15 years of my RC flying has primarily been 3D profiles with essentially the same wing/flap/aileron arrangement. In the last several years there have been several designs where the ailerons are more a part of the wing like the majority of full scale stuff. In the 3D profiles, this style of aileron has proven to be way more effective than the flat plates we have been using.
I was wondering if there had been much experimentation in this area for CL stunt.

      There was extensive experimentation with it in the mid-late 60's/early 70s, including the 70 NATS winner. Al Rabe did experiments with airfoils attached to the hood of his car where he concluded that the conventional way was better. I did it myself (and even mentioned it *earlier today* in the stabilator thread) on two airplanes where the hinge line was a conventional wedge and it was highly unsatisfactory.

     Just like everything of a similar nature, people have tried it repeatedly, with mixed results and the best-flying current airplanes do not use this type of flap (in fact several use Al's theory with modifications).

    As an aside, it appears that the LE of the wing is much more critical to get right than the aft part of it. That, too, was alluded to in the stabilator thread.

     Brett

As an aside, it appears that the LE of the wing is much more critical to get right than the aft part of it.

The FRONT 1/3 of the Wing produces over 1/2 of the LIFT . So I left of the back of the wing and made the front twice as long , and doubled it .



Flaps are inegral on this , but are ONLY the span of the empenage ( Tail plane ) . More like a sort of trim tab ,
to create a positive force wash , & stability . a catalist even , leaving the outer un ' overstressed ' so inside stall boundary .

Sometimes. a real off engine run , and at the 71 Oz Wt you could get it missbehaving . But generally V good to fly .
Hitting full up , 45 Deg at elevator ( with balance horns ) as often as not , YOUD GET A CLEAN CORNER OUT OF THE WINGOVER .
Thats justslamming on ( and off ) full wrist .
If one actually paid attention , and flew the corner , Itd pretty much always do it clean ( No bobble ) This is at a aft C G .
With the big heavy ST Silent Muffler on , it was a doodle to fly .
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Maybe with these airfoils you get a differant ball park . say 23 % thick of overall chord , will be differant ' presentation ' of L E
to one @ 23% with flaps @ 20 % Chord ( Width ) . ALSO those aerodynamically Ballanced elevators may not take too kindly to
the olde slack in the pushrod trick , though maybe ok ' thick 'n ' thin ' dead zone ' configuration . ( That had a 3/4 thick at root
Tailplane , but NO Dead Zone aerodynamics .

One of the favourites , in the ' razors edge ' precision stuff , if'n'when you were ' with it ' . If you wernt you soon woke up & got
dialed in right smart , as it sure got your attention . And pulled like stink overhead in good wind . One pi9ece you needed the Van Though. 

When this model gets finished and flown, probably 2025  I'll let you know.

The flaps are part of the airfoil and are just about  .875" in thickness.

CB

I put a reminder in my phone for August of 2025 to check back with you on how it flew

Matt

The question is no question: the flap is a PART (moving part) of the airfoil. You change the camber of it, and this way modify the Cy curves.
I build planes since 1987 with "pollywog" airfoils.
The flap is 30% part of the wing at the core and 20% at the tip, and significantly concave. (Just like a rudder of a fullscale sailplane).
BUT!
My flaps never move more than 18-20°, and my wings are narrower related to the conventional.
E.g. 12" chord (including flap) at the core and 8.4" at the tip; wingspan is 57" . This is a good and succesful wing for an .40 or .51 engine.
It looks small for 52 ozs, but perfect, since this airfoil has far better efficiency.
See:
https://lh3.googleusercontent.com/zL5O1nCRGqdSzY-kqQqhrurmDvulKMEnGvRNLjUIdpfOUzuXa0j6ik-vdbfjC5YDt9iXoRIT-_slrw=w293-h220-rw
and:
https://lh3.googleusercontent.com/bquf9vLA_N3DW-MLPh5IQHnjBxaICLYhD8tnxCmUu8QjtxSnn-bJu8R2Cc39PPP3_NMXiXOelUpZQQ=w293-h220-rw
Warning! If you are not certain to be able to make absolutely warp-free flaps, forget it, and remain by planparallel shape.
Regards: Istvan

...and the best-flying current airplanes do not use this type of flap (in fact several use Al's theory with modifications.   

I have buiilt two airplanes using Shark airfoils with integrated flaps and Shark overall dimensions/arms. Both did not fly really well without me knowing why... However, all of the many original Sharks and Gee Bees I' ve seen so far do undoubtedly belong to the very  best.

Would You think a ' sealed hinge ' would work comparably , Kieth . or is it in the ' homogonous ' airfoil surface ??

Found you need to spall   

Adamisin

  CORRECTLY . Or they wont talk to you . 

Well, here is the Gemini mkIII.  I flew this model in 1992 in Chicopee, MA and won Advanced and placed 2nd in Senior.

Would You think a ' sealed hinge ' would work comparably , Kieth . or is it in the ' homogonous ' airfoil surface ??

Even when the hinge line is recessed on my flaps and elevators, I have found that taping the hinge line still helps performance in the turns.  (Yes, taping the hinge line with this arrangement can be done with no drag/resistance in the controls.  There has to be enough space between the wing TE and flap LE for the tape to go into the hinge line from the wing TE and the attach it to the flap LE inside the space between the flap and wing TE.)

When Al was developing his airfoil for his super semi scale stunt ships (S⁵), he prepared several test sections, mounted them on a test fixture on the hood of his car and ran up and down a runway, measuring the lift at different angles of attack and flap settings.  That is where his rounded section came from.  When he tested the section from my Focke Wulf, he intentionally located the hinge line behind the center of the flap LE radius so that when the flap rotated, the rounded flap LE would slightly protrude above the wing TE.  He did this to seal (although only somewhat and only at max deflection) the gap between the flap and wing TE.  Sounds like a good idea.  However,  I am absolutely certain that this protrusion above the wing section at the flap hinge line disturbed the airflow (as in separation?), reducing the lift that the flaps could otherwise help increase.  (I could go through a long explanation on why I am sure this happens, but I have found this to be so.)

Now, in fact, I locate the hinge line slightly forward of the flap LE radius so that when the flap deflects, its surface starts to pull away from the wing TE surface to make sure that there is no flap LE protruding above the wing TE curvature.

I have used this concept on several designs.  One has a flap that is nearly 1" thick at the center section and tapers to about 5/8" at the flap tip.  The tail on this one is 7/8" at the center section where the elevators are slightly less due to the airfoil section used.  (Finished in top 20 at two Nats.)

Keith