Stuka Question: Talchik method for wingtip washout.

[Jay B. Scott]

Can the moderator or someone verify something for me? I read an unheard of (by me) technique for wingtip washout in a 1/8th scale Stuka from a 1981 AMA article by R. J. Talchik. He said that he coupled the inner and outer control surfaces to act as a strip aileron. He said that he drove the outer control surface less than the inner one, and this simulated wingtip washout. Although he did not go into how he drove one less than the other, I assume that if one were to use one servo per wing, it could be done by using a larger bellcrank for the outer one than for the inner, just for example.

What I haven't comprehended is exactly how his method of driving the outer control surface less than the inner creates wingtip washout. Is it because no matter how one maxes out the coupled-strip ailerons, the outer portion is never going to go down far enough to cause the wingtip to stall? And he also didn't mention how much less to drive the outer one compared to the inner one. Does 1/2 as much seem reasonable? And how does this set-up apply to take-offs and landings? I guess I'm just having a hard time thinking in terms of any other concept besides having the wingtips bent up in the back for wingtip washout.

I am limited to 5 channels on my radio, and so I thought it might be a cool idea to use the 5th for a bomb drop rather than for flaps on my Marutaka Stuka kit. Talchik's method would not only give me a good excuse to do this, it also sounds like it would take care of the sluggish roll characteristics of this bird as well--just as long as I can get away with not using flaps!

[Paul Wilson]

I can see how it could be done. You would have to have diferential throw in the outer surfaces so that they would go down less than the inner in the down position and more than the inner in the up position. If you just had it moving less than the inner surface it would be below the inner in the up position creating wash in. I do not know how effective this would be but it could be done quite easily mechanicaly with one channel. To set it up just find out how to set up diferential throw on the aileron surface.
Good Luck
Paul

[Paul Wilson]

Just to add an opinion, I would much prefer to use my fifth channel to add flaps, especially for scale effect instead of the bomb drop and work out a mechanical release for the bomb activated by one of the control surfaces ( probably a slight flap up movement ). Then you get the best of both worlds.
Good Luck
Paul

[Jay B. Scott]

Thanks for the suggestions, Paul. You know, speaking of differential throw, I never did figure out how that was done. The first time I ran into that concept was when I was building a Four Star 40. The designer had the aileron torque bar posts bent forward slightly, and this was supposed to have the ailerons deflect less down and more up. That didn't make any sense to me, since the servo still travels as far in one direction as in the other.
But you're right about using the flaps for that cool scale look, not to mention that they're functionally a good idea for slow, stable landings. And the mechanical release for the bomb is brilliant! My fifth channel is a toggle switch, so I could just set it up to toggle quickly on and off the first time to release the bomb without the flaps doing any more than just moving down and back up a ****hair!