Ailerons on slow-flying models?

[astroboy]

I'll soon be starting a project that will have a rather low wing loading--6.5-7 oz./sq. ft. From what I've read(and experienced), ailerons don't work very well at low speeds; one post I found in a search on the subject said something to the effect that models of Piper J-3s have little or no aileron response on final approach. I'm wondering if that effect is based more on absolute airspeed, or if configuration, stall speed, etc, of the model contribute significantly as well. If the latter is true, the model will have a flat-bottomed, 51" wing, 7.4" constant chord. It's a high-wing monoplane(Stinson Voyager), and I believe the dihedral is 3.5 degrees on each wing.

I'd like to add the ailerons--the plan is R/E/T--but if they won't do much good, I can save the better part of an ounce by leaving them off.

Thanks,
Jeff

[DeaninMilwaukee]

I've never heard any relationship between wingloading and aileron effectivness, and I have two planes below 5 oz sq/ft that fly great with ailerons.

The most relevant one is this:


gws pico F converted to full house. 320 in'sq, 10 oz.

All I really did was tape a carbon spar under the LE,
( NO dihedral!), and added pretty decent sized ailerons in foam. Aileron response is excellent and powerful. A very agile plane.

Go ahead and add the ailerons. Adds fun to the plane. Just make sure size and throws are healthy.


Dean in Milwaukee

[Ollie]

All control surface effectiveness decreases as the inverse square of the air speed. If you halve the airspeed the control surface is only 1/4 as effective.
Also, adverse yaw increases as the square of the coefficient of lift. Slow speeds mean strong adverse yaw.

That is no excuse for leaving out ailerons. There are several things you can do:

1. Fly with a generous stall margin even in the landing approach.
2. Use lots of differential aileron throw. Two or three times as much up aileron as down aileron will combat adverse yaw to a significant extent.
3. Use lots of aileron throw.
4. Use lots of rudder throw (at least 45 degrees each way).
5. Increase the dihedral a degree or two in order to increase yaw to roll coupling which will make the rudder more effective a slow speeds.
6. If you have a computer radio, switch in aileron to rudder coupling for slow speed flight.
7. If the controls are too sensitive at high speeds, use low rates or exponential to desensitize them. Don't forget to switch back to high rates for slow speed flight.
8. Keep the wing loading as light as possible and use an airfoil with low mean camber.
9. Keep the wing tips as light as possible so the ailerons don't have so much inertia to overcome.
10. Seal the aileron hinge line.

[Sparky Paul]

I've tried ailerons on gas-bag 2Ms... and removed them. The rudder worked just as well.
My park flying Tiger Moths use rudder, no ailerons, and are quite manuverable.

[Sparky Paul]

I've tried ailerons on gas-bag 2Ms... and removed them. The rudder worked just as well.
My park flying Tiger Moths use rudder, no ailerons, and are quite manuverable.

[BMatthews]

Go with the ailerons but also mechanically couple in the rudder to work with the ailerons. This will not only counter any adverse yaw effect but sharpen up the response.

In the past I've helped train newcomvers. When they suggest that they want something aerobatic I give them a show using their own "gentle" trainer. The secret to the fast rolls and snaps is using the rudder in harmony with the ailerons. I suspect this would work equally as well on parkflyers.

Look at the Tiny with it's coupled ailerons and rudder. And that's a sharp maneuvering model design.

[Normg002]

I would recomend a rudder , they work just as well

[BIGSAPPY]

Ollie
I agree 100% with ollie, follow his sugestions and I believe you will be happy with the result.
Jerry

[vintage1]

I'd go along with Ollie too, in my limited experience.

You need a lot of area and deflection to get authority at low speeds, but if you don't want loads of odd looking dihedral. you will need the ailerons. I haven't had too much problems with adverse yaw top be honest. But mechanical or computerside differential will take care of it, and rates and expo will calm the plane down at higher speeds.

[astroboy]

Thanks for all the suggestions; the one I'm not sure I agree with is the aileron-to-rudder coupling. I would rather add rudder manually, unless there's a compelling reason to do otherwise.

Jeff

[Terry S]

It all depends on what this plane is for. If its not aerobatic then you dont NEED ailerons.If you do use them and couple them to the rudder it makes turns beter/easyer. If you go for rudder only then it is still possable to fly too slow for it to work if the dihedral is too low. The choice is yours !

Terry

[Flight Engineer]

Go with ailerons. You don't need a rudder.
Remember that if you use rudder to turn an aircraft you are relying on the secondary effect of the control surface. A rudder should be used to counter the effect of the prop stream on the fin and to counter slip or skid in a turn. On multi engine aircraft it is used to compensated of engine out asymmetric flight.

[Terry S]

F.E. you seem very fixed in your views !
>Go with ailerons. You don't need a rudder.
How can you say that ? Some aircraft will not turn on ailerons alone, they will just bank !
>Remember that if you use rudder to turn an aircraft you are relying on the secondary effect of the control surface.
Yes you are correct in what you say but there is nothing wrong with relying on the secondary effect, many airplanes fly very well this way, some even full size (not many).
With the CORRECT amount of dihedral the turns are close to perfect and beter than some people can manage with ailerons and rudder.
>A rudder should be used to counter the effect of the prop stream on the fin and to counter slip or skid in a turn. On multi engine aircraft it is used to compensated of engine out asymmetric flight.
True but not realy relevant in this case, we are talking about a VERY light model not a full size aircraft.........

[PDK]

Hi Jeff,
The choice comes down to your own preferences and flying style. Personally I would go for ailerons every time. The plane you are building (have built?) is scale (and the original had ailerons!) of a reasonable size and would benifit asthetically. I feel the controls with ailerons are more responsive and the plane goes where I want it to go (just my views:D). The planes I fly I will only use the rudder for aerobatics (something you may or may not do), scale flights to balance the turns (coupled rudder/aileron just makes this easier no "compelling" reason) and for landing, especially with a cross wind (it looks great to land wings level, yawing to one side and flying straight down the strip!). Also the rudder will give you more control if the aileron alone becomes less effective.
Getting back to your original Q. Ailerons are definatly less efective at lower speeds (pylon recers have extremly small surfaces and throws) I would follow Ollies sugestions and you can't go wrong.

If you fit ailerons and rudder you can use both.
Regards
Phil