Christchurch and District Model Flying Club
Sloping Off - our newsletter

TRIMMING AN AEROBATIC MODEL, BY SIMON COLE

I was asked by a few people if I would make the trimming chart I was working from at the talk on Wednesday available, attached is a pdf of the chart from the GBRCAA together with some intro blurb below.

"The attached trimming chart I used as the basis of my talk on Wednesday is aimed primarily at aerobatic power models with a symmetrical wing section and neutral flying characteristics, however, a lot of it carries over into sport and fun/3D type models. Much of it is trial and error but you will learn a lot about how your model flies by interacting with its trim characteristics.  Change only one thing at a time in small increments and re-evaluate ideally in low wind and calm conditions. Everyone will opt for a different "feel" when trimming but taking off with a new design putting in 5 clicks of up trim, a few clicks of right aileron and a bit of right rudder trim to keep it straight and leaving it at that may not be the best solution. I have often built two identical models for F3A competition flying, identical equipment, servo and radio set-up but they will both fly slightly differently, even the top end custom built Oxai models costing over £4000.00 !!

Remember always set your CG first and then stick with it, using the same weight lipos if electric powered. If you change your CG it will change all the other trimming parameters, even those you have not set or checked. As just one example, changing your CG can affect pitching in knife edge. Even if you don't fly a lot of knife edge your 1/4 roll headings during a normal slow roll can all potentially wander, it may also have affected your model's sensitivity to aileron differential causing yaw changes and heading loss against a previous axial set up.

Try to approach trimming as a whole new enjoyable sphere to your flying and modelling rather than a laborious chore getting in the way of having fun on the sticks, if you are not in the mood, forget it and just fly. However, the better, more precise and predictable you make your model, the less your brain has to do, the more enjoyable, satisfying and fun it will be to fly"

Good Luck

Simong

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