Stop That Flickin!
How to trim a F3F Model.
The first step for me is to build/assemble the model correct the first time. Solid linkages and a serviceable installation. No double centering and no slop. On tails I will test the pushrod linkage by pushing down on the control surface with enough pressure to move the servo (power off) and see if there is any excess pushrod flex. If so reinforce the pushrod to the fuse. Keep all pushrods as straight as possible. This means no bends, no kinks, no arcs. Its better to use as much servo travel to move a surface as possible. Using the inner hole on the servo arm and 100% EPA is MUCH better than using the outer hole on a long arm and dual rates! Why? When the servo moves 90 deg through its travel you get better resolution and torque with a small arm over a longer arm and 10 deg travel to get the same control movement. You lose torque, control and feel.
Stage 1 set up: First flight.
Stage 2 set up: Tweaking.
Stage 3: Turning. Elevator set up.
If the model feels soft around neutral then a little reverse elevator exponential is needed. (I only needed this on one model in my life so don't get carried away) Don't increase the total throw to get that "feel" in neutral. Increasing the total throw will get you stuffed into the hill. Remember we just fixed that. Or. Learn to fly with the new feel. Your probably reading this because you want to move higher up in the comps and are having problems and your "Personal Feel" is not working for you. Try it this way and see if you get faster times.
Stage 4: Trailing edge.
What does "snap flap" do? It adds camber with up elevator. Why? Most of our sailplane airfoils are more efficent in a turn with a little camber. The camber reduces the drag on the wing in a high alpha condition like a pylon turn. This extra camber is not needed in a straight line only where we ask the wing to carry more load. SOme
It looks like a lot of work but you can get real close on a good afternoon. Don't make 100 changes at a time or you won't know what worked and what did not. When you think you have it perfect do some tweaking on the CG and see if more performance is hiding in the model.
A lot of problems can be dialed out or dialed in with the computer radio. Be careful. I like to adjust while flying but this might cause more trouble if your TX is too complicated.
Race day. · KISS = Keep It Simple Stupid. Don't set up your radio so you need to flip 16 switches on and off to get through a flight. Don't make it so hard on yourself. Do a pre flight before you enter the ready box and be ready to launch with your helper by your side when the pilot on the course is at lap 5. Keep the contest moving. I love it when I hear the 'Experts" telling guys that 5 cell packs and long servo arms are needed for lightning quick response to get you out of trouble. If you do it right you don't need lightning quick response and the slop and double centering problems that come with it. Lightning quick response is what go you INTO trouble! Be Smoooooooooth.