I am working on my first kit (Kadet Senior) and putting in barn door Ailerons similar to what is found in their Kadet Senior ARF. From reading the posts here, evidently if one is not careful, the design and/or execution of the aileron linkage can lead to aileron flutter.

What recommendations can you give to someone in the design stage w/r/t the ailerons and linkage to minimize the possiblity of this occurring?

David D. in NC

Use good quality hinges, Get the control surface as close as possible to the wing when glueing. Seal the gap with covering. Use a strong control rod (not soft 2-56 rod that comes with some kits) with horns and clevises that have as little play as possible. Finally use a good quality servo with sufficent torque to be able to handle any load imposed on it. That about all I can think of.

1. keep the gap between the wing and aileron as small as possible. Air getting through the gap increases chance of flutter (and decreases the level of control). I hinge all my ailerons using the covering material (profilm) which means this is zero. Best done as a top hinge for good looking results.

2. use a direct push rod from aileron to servo (and a servo for each aileron)

Having said that, the Kadet Senior should be a nice slow flying trainer type plane. Chance of flutter increases with speed so I would not think that it should be much of an issue here.

Good advice so far, but let me elaborate a bit.

Get them as close as you can, but leave room for the control surface to flex freely. You are better off with a gap (which can be sealed later) than to have a stiff joint which will surely create problems later.

Totally unnecessary with a Kadet. Use the supplied push rods.

Also unnecessary. 1 Standard servo will do just fine (unless of course you're planning on putting a chainsaw engine on it and doing Extreme 3 - D)

Of course, there's nothing wrong with using 2 servos. that would keep your linkage simple. I would not use bell cranks. My preferred method is to run Nyrod through the wing to a single servo in the center.

Thanks for all the great suggestions. Right now I'm leaning towards separate servos in the wing, but not sure whether to put servo INTO wing and make access cover or just put servo at bottom of wing with servo linkage exterior to wing. A couple of fellows in the club I visited have this arrangement and it doesn't seem to affect the flyability. The covered servo is considerably more attractive, but the exposed servo will be easier to maintain.

The engine I will be using is the OS .46FX.

Thanks again!

David D. in NC

David,

If you are going to fly nice and slowly, any aileron hook-up will suffice, including the single servo and dual Golden Rods. if, on the other hand, you are planning to rev up your .46FX and fly full thrlttle, and you are worried about flutter, then you do need to take some precautions.

You have gotten good advice:
1. Keep the gaps small
2. Seal the hinge line. use one servo on each aileron.
3.Try the 2-56 rods, they'll probably be OK unless you are doing steep dives.
4. Try for no, or very little, slop in the control system.

This one will take some constuction changes. Most aileron flutter starts at the tips. If you can move the barn door ailerons in 2 or 3 inches, you will lower the chance of flutter.

The Senior has a good bit of positive incidence due to the flat bottom wing and rounded leading edge. It normally has a climbing tendency with full power. usually 2 (maybe 3) popsicle sticks under the trailing edge, about 3/16 inch, will cure this. Check your elevator trim after you land. If you have down trimmed in, you need to raise the trailing edge a little. If you end up with up trim, you have gone too far.

If you plan on doing acro at high speed, run some weedeater line around the tail tips to strengthen this area. Drill 1/16 holes in the fin and stab tips and the lower fuselage and run the line around and CA in place. Works well and weighs nothing.

When using separate servos for ailerons, I try to recess the servo into the wing as it does look better. The thickness of the wing and the servo have some bearing on this.

Once set up, you should not need access to the servo, just the arm, so dont worry about that. I tend to build a balsa box around the servo so that it can be covered separately from the rest of the wing. Also, if you do need to get to the servo you only need to replace a small bit of covering.