Trimming Your Airplane

 

There's a lot more to getting your airplane trimmed, than just sliding the tabs on your transmitter. A correctly trimmed airplane is much more stable and fun to fly! When building a model airplane, it is important that the plane be balanced and wing incidences be set correctly. Take your time with these procedures! If you don't have an incidence meter, borrow or buy one. This is the only correct way to check and set your incidence. Many times with newer "almost ready to fly" (ARFs) the manufacturer has set the wing incidence and little can or should be done to change it.

 

Check the balance on the CG front to rear, and from left to right. One of the easiest ways to do this is by finding the CG on the fuselage, then finding the center, (left to right) of the plane. Screw in a small eye hook, and hang your plane. It should balance front to rear, and side to side.

 

The engine thrust angle and the CG interact with each other. Yaw and lateral balance create similar symptoms. If you are having problems in this area, check to see if the fin is straight.

 

If you follow the trim adjustment in the link below, and still have problems, check for non centering servos, play in control linkages, and aileron and elevator gap. See pull done menu under Technical for teim procedure.

 

Twelve Things I Learned from Building A Large Scale Gas Powered Aircraft

 

1. Mount propeller horizontal when engine is going into compression. If engine fails in flight it will stop with the propeller horizontal and you will be less likely to break propeller with a deadstick landing.

 

2. If engine has thread on throttle arm, use it to fasten the throttle link. If you use a clevis that is often supplied with the airplane, the engine vibration will soon elongate the throttle arm hole and it may fail.

 

3. If you use a Smart Fly ignition cutoff be sure to cut both ends of the supplied fiber optic cable with a sharp hobby knife. The factory does not always make a clean cut and it may cause an engine ignition cutoff when you least want it.

 

4. If you use a high voltage system for operating servos, make sure all servos are rated for it. Sometimes we are slack with the throttle servo thinking it doesn’t require much capacity and can be any spare servo. Using a servo not rated for high voltage will either cause erratic operation or will fail completely.

 

5. If you use a Desert Aircraft engine using a Walbro carburetor follow the instructions for the Walbro carburetor setup provided in the pull down menu under Technical. It works, is simple and your engine will run with minimum four cycling throughout the throttle range.

 

6. Make sure ignition shielded cable is protected from rubbing against cowling. It will wear through the shielding quickly if unprotected.

 

7. There is a resistor in the ignition spark plug cap (Desert Aircraft). Pull ignition cable straight off spark plug or you will damage resistor and require new cap.

 

8. If you use a canister, make sure it is supported in the center where it is a little heavier or it will become dented from engine vibration. Airplane manufacturers don’t always provide support at the right place.

 

9. Make sure to provide lock washers to mount header (don’t depend on Locktite because heat will soften it). Also, use lock washers everywhere and use Locktite freely to fasten parts not subject to heat because engine vibration will cause them to loosen.

 

10. Don’t run up the engine on the airplane stands. The high thrust produced by the engine will cause hangar rash where the carpet touches the leading edge of the wings.

 

11. You need a hole in the cowl to adjust needle valves. Engine will tune differently with and without cowling.

 

12. Make sure you balance the propeller. A Vess balance ring really simplifies the job.