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Apr 08, 2002, 01:23 PM
Registered User

Wing design......aileron question

I've got a 60" wingspan sloper that I want to try to get to roll much faster than it is now. The chord is an average of I think 9" And the ailerons are 1 3/4" tapered to 3/4" from root to tip.

My question. If I were to reverse the taper so the widest part of the aileron were to be at the tip and the smaller part were to be at the root would this increase the roll rate of this wing? I would leave the wing servos where they are, "near the center", and use torque rods that went all the way to the tip's wide part of the aileron to help reduce or eliminate flutter. I'm trying to find ways to increase the roll rate of this large wingspan.

So would this work? Has anyone tried it? I would like to hear of any success and and failure attempts.

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Apr 08, 2002, 02:03 PM
Ascended Master
Sparky Paul's Avatar
Torque rods don't transmit all the servo deflection available to the surface. Aerodynamic loads push the surface back to center the further out from the torque rod end in the surface.
A better solution is use two aileron servos, mounted about 1/3rd of the semi-span out from the center, connected to the surface directly with the usual horn.
(Although that may be the installation you have.)
If the rate of roll is not what you want with it, then the best solution is a different airplane more suited to the task.
Apr 08, 2002, 02:17 PM
Registered User
I do have dual aileron servos but I don't have any servo extensions and they are micro servos so they didn't reach very far into the wing.

But back to the torque rods. Are you saying that torque rods don't give as much throw compared to the regular control horns? So lets say I still have dual aileron servos. But on each I set up a torque rod to get the point of where the rod inserts into the aileron near the tip. Wouldn't this be just like putting a servo out there with a regular control horn? Or am I missing something? So I guess what I'm trying to ask is; say I set up a torque rod and the rod inserted the aileron at lets say 1/3rd the span. Wouldn't this be near the same as just putting a servo at 1/3rd the span and setting up a regular horn?

I sure hope that making sense.?

Apr 08, 2002, 06:05 PM
Ascended Master
Sparky Paul's Avatar
Hold the tip of a torque rod equipped surface, and move the servo. The servo will move, the surface movement will diminish to zero at the tip.
This happens in flight to some extent.
Unless the surface is stiff along the hinge sxis of the torque rod, motion diminishes the further out from where the torque rod ends in the surface.
A direct connection is better.
Micro servos unless they're on steroids won't do much of anything on 30" span ailerons at speed, regardless of the type of connection.
Apr 09, 2002, 08:16 AM
Dave Segal
Have you considered sealing the aileron hinge gap to increase aileron efficiency?

Dave Segal
Apr 09, 2002, 09:32 AM
Registered User
Tis' sealed I do think the dual servo torque rod idea will work though. That with the tapered ailerons which have the widest part of the aileron at the tip.

Apr 09, 2002, 09:55 AM
Lifes 2 short, go sloping
I have a scratch built 72" EPP sloper that has 2" ailerons (no taper) 30" long. I am using 3/16 heavy balsa and covered with ultracote. The servos are mounted 3" off center and I have no problems at all with flex, with the 2" ailerons. the thicker balsa is very stiff and I am using straight 2/56 rods and servo savers. I am also using a 6v battery to increase the speed and torque of the servos, I get a very fast rate and alot of time I forget to turn off my dual rates and it still rolls fast! Don't over think it, just increase your ailerons to 1 3/4" all the way down or use 2" to really spin that wing!!
Apr 09, 2002, 09:25 PM
Registered User
Ok thanks Vinnya42. I'll try what you stated first. Added aileron size as well as stiffness.

I still plan on building your sloper you're talking about. But the day I was gonna buy some foam to practice with I got sidetracked and bought books instead. But what I'm really trying to say is, sounds like a fun plane and I'm still gonna give it a try.

Apr 10, 2002, 08:27 AM
Lifes 2 short, go sloping
Jay, let me know if there are any pointers or ?'s I can help with when you get to that project. Later.
Apr 10, 2002, 07:00 PM
Registered User
Let me see if I understand the problem. JayParke is not getting enough aileron authority. It seems that the part of the aileron near the tip is experiencing more blow-back to center than the part nearest the root.

So would it be advantageous to locate the control horn on the aileron nearer the tip, rather than at the center of the aileron span, so that there is less blow-back near the tip, without overly-compromising blow-back near the root?
Apr 11, 2002, 08:02 AM
Balsa Flies Better!
Umm guys

Reversing the aileron taper the way it was discussed earlier is going to lead to tip stall. If your aileron already moves to a 30 degree deflection or so, more throw isn't going to do much. It's possible that your servo is getting overloaded- but some of these micros have pretty high torque. Just try holding the aileron and applying the servo- see what happens. However, long skinny high aspect ratio wings don't roll fast- nature of the beast.