2 servos per aileron needed?

[casketdan]

Just bought a assembled Lanier 87" extra 300 with a dle 55. Set up to run 2 servos per wing. Not going to do any 3d. Do I need 2 per wing? Thanks

[Twowingtj]

casketdan Even though you don't intend to do 3D flying, there are other factors that come into play. Most model aircraft of this and simular design, have very large control surfaces. This plane has full span ailerons in addition to their wide cord or front to back measurement. So even a small deflection requires more force than say a warbird of simular size.

There are a lot of different factors that come into play like aircraft weight, flying speed and more. One tool that I use is a servo torque calculator, linked below. When you use the calculator, treat the result much like you would when choosing an ESC for an electric power system. Give yourself about a 20% overhead on torque needed. That way you have a torque cussion.

One other thing to consider is where the design places the servos. With a plane designed for two servos per aileron, the servos are spaced so that they share the pressure equally across the span of the aileron. If you only use one servo to drive them, it would be a good idea to place the servo more toward the center of the aileron. This would help prevent the aileron from flexing at the "undriven" end.

[casketdan]

Thanks for the detailed and complete response. Will certainly take your advice. A follow up question, though. The manual says 3 aileron y harnesses. One for each wing and the third I suppose to run both wings through one channel on rx. This OK, or do I need a second channel, one for each wing. Would rather keep it simple if possible. Thanks.

[Twowingtj]

The Lanier Extra is a 1/3 scale model. Trying to go too simple could lead to challenges that are hard to overcome as well as "flyability" issues. What transmitter are you using? With that info, we can come up with set-up that best fits with what you have. Thankfully, not having flaps or retracts gives you more channel options.

[casketdan]

Futaba T6K with a Futaba 2006 rx. Will set up with 2 elevator servos and Y harness and pull pull rudder. Would like to use channel 6(flaps) for my kill switch.

[casketdan]

I guess I'm just a little confused by the manual calling for 3 aileron y harnesses, which infers running both wings through one channel.

[Twowingtj]

It does imply using one channel for all four aileron servos. One leg of the first Y going to each wing and a Y to each of the two aileron servos off that. That works fine if all four servos have the arms at exactly 90 degrees when centered. That is rarely the case.

You have adequate channels to put each wing on its own channel. That would be a good choice.

If you are going the two servos per aileron route, you want the pair of servos on each aileron as closely matched as possible for servo arm position at neutral.

If you have a servo tester, set it to zero or neutral. Connect each of the servos to it. Place the servo arms on them that you plan to use.

Pair the servos up, by wing, that are most closely matched. By doing this, you reduce the chance that the two servos, attached to a single control surface, fight each other as they move through the range of travel.

The same idea applies when running your two elevator servos on a Y. Even though they are seperate, if they move at different angles, it could induce a slight roll.