One of the newbie things that many RC'ers new to the hobby may get confused about and a critical step in setting up any plane is setting up your throws on your control surfaces. I know when I started out in the RC hobby, I wasn't sure how control surface throws were affected when moving between the holes both on the servo as well as the control horn on the actual control surface. Then there is the other variable of the transmitter. Today's computer based digital transmitters are awesome and can do so many things that the transmitters of old just couldn't do. One of the nice things about the new radios is the ability to adjust your throws right from the radio itself. Both by adjusting the servo travel as well as setting up dual rates and such, you can effectively adjust the throw on the control surface.
One important thing to remember though. It is always the best approach to get the actual physical control throws setup the way you want them before adjusting the throws with the radio. You should view the physical throws as the major tuning of the control surface, and the radio as being the "fine tuning" approach. This way, if you change radios you plane will not be radical all of the sudden with huge throws just because it is being flown with a different transmitter and possibly receiver.
Servo and control horn holes
Many newbies make the mistake and think that the same hole in conjunction with the root of both the servo arm and the control horn do the same thing. This is not correct! They are in fact opposite of each other.
Servo holes
- The hole that is closest to the spindle on the servo itself is the least throw
- The hole that is furthest away from the servo on the arm is the most throw
Control horn holes
With the control horn mounted in your control surface, the below is true:
- The hole furthest away from your control surface has the least throw
- The hole that is closest to your control surface has the most throw
Picture explanation
Pictures are always the best way to explain it. Take a look at the pictures below. The red pen marks denote the most throw and the blue pen marks denote the least throw.
- Control horns
- Servo control arm
Radio
Take a look at our post here to better understand Expo and Dual rates which both help to make you a smoother pilot and have an effect on control surface movement.
Final Thoughts
Setting up control surfaces is a critical step in making sure your RC plane flies properly. It is not an extremely difficult process, however, sometimes even the minor details such as which holes in the control horns and the servo arms increase or decrease throws can be confusing. Hopefully, the above information will help any newbies out there who may be having difficulty understanding how this works or who have had an incorrect understanding of how this works.
