If you have ever made a paper aeroplane you will know they rarely fly first time. You often have to tweak the wing surfaces and after some trial and error you eventually get it to glide. This is trimming. It is a technique to adjust the flight surfaces of the plane so that it flies in straight and level in a stable way. The same principle applies to model planes and you may be surprised to learn that even large planes and airliners need to be trimmed during flight. The pilot (or computer) sets the trim control inside the cockpit when the plane is airborne and cruising.
To trim a model plane we need to adjust the tail surfaces. i.e. the elevator flap on the tail-wing and the rudder flap on the tail-fin. See photo below.
Initially you will not know if your plane needs trimming until you have test flown it. Before you do this check that you have fitted the wings correctly (i.e. not upside down or back to front). Also ensure you have placed the battery inside the body so that the plane is properly balanced ( Do this even if you are testing the plane in power free glide). Choose a calm day to do the trimming. Most of these models are very light and very susceptible to gusty conditions. Whether you choose to trim your model with power 'on' or power 'off' is up to you. If you have bought a stubby model such as the 'Transcend' or the 'Mini-Flyer' then use power 'on'. If you have bought an efficient slender model such as the 'Oriole' or the 'Falcon' then you trim these with no power. If you choose to trim the model with power 'on' then the only pre-condition is that you do not vary the power setting during the flight and do not use the steering controls or you will get misleading observations. Observing the plane is key to making the correct trim adjustments.
Hand launch model by throwing horizontally (parallel to the ground). Observe the direction it flies or glides.
- If the plane veers too much to left adjust rudder slightly to the right (about 1 mm each time).
- If it veers too much to the right adjust the rudder slightly to the left (about 1 mm each time).
- If it nose dives too steeply you should raise the elevator flap on the tail only slightly (about 1 mm each time)
- If it pitches up too much and drops it's nose, you can reduce elevator deflection slightly.
The real art is to find a balanced setting so that the plane will climb gently or glide gently to the ground in a reasonably straight path.
Note. 3 and 4 channel planes can often be trimmed during the flight (via the trim controls on the handset). Only if the travel of the control surface reaches a limit, is it necessary to re-adjust rod and flap position settings on the ground.
FIRST POWERED FLIGHT
When you feel the model is more or less ready, you should apply maximum throttle and hand launch directly into wind. Keep watching the flight behavior of the model as it flies. If the model turns when it should be flying straight, adjust the rudder slightly to counter this as described above. If the model flies too fast and fails to climb, the elevator flaps may need slight adjustment upwards.
When the flight is steady, keep applying maximum throttle and let the plane climb. Relax the throttle when you have reasonable height. You can now practice your turns.
- Fly on calm days to reduce risk of crashing or losing the airplane.
- Try to avoid flying too high. Signal will be lost and plane could glide far away. This is especially true on breezy days.
- Take a small roll of sticky tape or duct tape to the field to be ready for any quick fixes.
- Finally keep fingers away from spinning propellers. Ouch!
For lasting repairs (as opposed to temporary fixes) Copydex is an excellent all purpose adhesive and works well on expanded plastics. This is available in most DIY stores and comes in a plastic bottle.