3D Aerobatic Setup

Model Airplane News, Sep 2004 by Somenzini, Quique

Now we can start to hook up the servos to the control surfaces and program the radio. First, center all the trims and zero out the subtrims. It's important to keep the subtrim percentages small; every percentage of subtrim that is used will result in less servo travel. To make the setup process easier (especially for the ailerons), I connect the servos to a spare receiver and battery pack. I then turn on the transmitter and check that the servos travel in the correct direction. This is important because if after you've made all of the adjustments the servo travels in the wrong direction, you'll have to start over-particularly if the subtrim was used.

Put a servo arm on the servo. Depending on the servo's position, the arm should be perpendicular or parallel to the servo's main axis (centerline). If the arm is slightly off center, adjust that with subtrim. Connect the pushrod to the servo and the control surface, and then adjust the pushrod's length until the control surface is exactly at neutral. Max out the servo-travel function (ATV) as well as the rate to 100 percent, and then move the stick slowly and make sure that the servo can move freely from extreme to extreme-if it can, that's great! Check how much the control surface deflects and adjust as necessary. Follow this process with each servo and control surface.

If you use more than one servo per control surface, I strongly recommend that you use a JR MatchBox to properly adjust the servos. The MatchBox allows you to individually adjust the servos so that they will have the same travel and neutrals. Adjusting multiple servos on a single control surface can be a real challenge, and the MatchBox greatly simplifies the process.

This is when I mount the wing on the fuselage, put the airplane on its wheels and do a general check. I make sure that the ailerons are moving the same amount (up and down), and I do the same for both elevator halves. When completed, the 3D setup of your airplane is ready for flight-testing, and you'll have reached the goal of optimizing your plane for 3D maneuvers.

About programming the transmitter: if your radio has only dual rates, set the high rate as your 3D mode. If your radio has programmable flight modes, choose one and name it as your 3D mode. See my "Flight Mode" article in the February 2004 issue of Model Airplane News. One last detail: because the 3D throws are very extreme, be sure that you add exponential before you fly your airplane. Good starting values are:

* Aileron 60 percent

* Elevator 70 percent

* Rudder 30 percent

With these starting values, your airplane's expo will be close to what you'll need. After flying the model, adjust the values to obtain the feel that suits you and your flying style. If you use this setup process, when you arrive at your flying field, the job of trimming your airplane should be very simple and will mostly be limited to adjusting the exponential values.

LANDING/EMERGENCY MODE

I like to set up a flight mode as my "landing" or "emergency" mode. This means that by using a single switch, the airplane will have a normal setup for landing. It should be easy for you to access the switch that this mode is set up on, and that setting should cancel all other flight modes. I have found that this avoids confusion when you must deal with an emergency, when every second counts.