I'm having trouble with the hookup of my ailerons on my 4*40. When I go to full deflection the clevis on the servo bends such that it pops out of locked. They are the plastic clevis. Is it better to go with a metal one that I can lock into place better or is a ball link a better way to go?

Steve,

It sounds as though something is binding. Is this a 4* with a single servo in the middle of the wing or 2 servos, one for each aileron?

Also, you want to make sure you use a very small peice of fuel tubing over the clevis to help keep it locked.

Ball links are the way to go but plastic clevises should work well on that plane

If you imagine the ailerons centered, and the control horns sticking straight up, you would have the rods going straight from the servo to the horns, if I'm picturing your setup as described. On my 4*, I put an S-bend in my horns so they went from the servo back to the horns at about half their height, then another bend to angle up a bit back at the control horns.

Edit - (I tried to make an ASCII drawing of what I'm describing here, but the board clears extra spaces, so it looked lousy)

At least for me, it seems to let the arm flex a bit, that takes the stress off the servo end of the control arm... If I remember, I'll take a pic when I get home tonight....

Single servo in the middle. What happens is the aileron rod horn gets low compared to the servo arm and the bending is taken out by the clevis at the servo arm and it pops undone when at full deflection. I don't want to count of the fuel tubing to keep clevis closed, it should just be a backup. I want the clevis to stay together on its own.

It sounds as though you may have the control horn on the aileron rod (torque rod) turned down to low. If that is the case then turn it back up near the top of the threaded portion of the rod and use a longer servo arm ( 1 inch each side of the screw hole ).

The other thing you can do is reverse the rod connection at the servo arm. I did Z-bends and came in under the arm instead of on top. With the longer arm, z-bend underneath the arm and the control horns about 1/2 inch down on the torque rods. I was able to get all the throw the ailerons would give me.

Another thought just came to mind. Is it possible you have the control rod turned into the clevis to far that the rod hits the control horn when you get to a certain deflection?

Was wondering how much your "full deflection" is? If its more than 1/2" in either direction then you have way too much and that will be your problem!!!

If I remember right plans call for 5/8"up and 1/2" down

From the manual off of towers web site

Control Throws-
Elevator: Up & Down 1/2" (13mm)
Rudder: Right to Left 1" (25mm)
Ailerons: Up & Down 5/8" (11mm)

Ca you describe how you have the servo arm and control horns setup. Pics would be better if possible

I guess what I should have said is if the delfection is more than 1" in either direction then that "could" be the problem!

No biggie I have a little over 1 inch on mine and had to do what I mentioned in my earlier post to get that kind of throw. (longer arm, control horns near the top, etc...) and that is all she will get. I had moved the horns down to the middle of the rods and had the same problem with the clevises popping loose even with the fuel tubing as backup. If I try to get more the lack of beveling on the wing TE or aileron LE will not allow it and they start to bind.

I believe that may be the problem here but we need pics or a more detailed description

sometimes I rebend those S rods ( the parts that gose into the airlerons).
before gluing the ailerons.
I have the threaded part pionted at a 90 deg. or straight up
might have to knotch the fuselage former a little to prevent binding.
this way full throw is can be maximize.
I also trim of the length of the threaded part.

it also helps me to when setting up the servo control horn.
90 deg/90deg.
I can dial in or adjust with the sub trim on a computer radio.
but it's best to have everything at center as much as possiable manually.

it depends on the angle of how you drilled those holes on the ailerons.
where the S rod goes into.

you might also notice the same problem on the elevators.
they might not be level.

so you must rebend or adjust accrodingly

The ailerons are not binding. I like bubbas Idea with the z-bend under the servo arm. I might also try to readjust the angle that the clevis enters the arm. I already put the control horn about 3/8" from the top. Thanks for all the input

Hi!
Here are some pictures of a servo/aileron set-up in one of my airplanes.
You should always strive for to have as long control arms as possible and as short servo arm as possible, thats the rule.
Regards!
Jan K
Sweden