Trimming a Kolb & Changing Elevator Incidence

We had a problem with the FSII wanting to act tail heavy, even though it wasn't. W & B were right where they were supposed to be.

We initially trimmed out the tail heaviness by drooping the ailerons. Drooping or reflexing the ailerons (or flaps, or both) is basic SOP to trim a Kolb.

If a Kolb feels nose heavy, even when it isn't, adjust the pushrods to raise the trailing edges of the ailerons or flaps until it feels normal. Reflexing the ailerons (or flaps) up moves the wing center of lift forward, & makes it feel less nose heavy.

If it feels tail heavy even when it isn't, lower the trailing edges of the ailerons or flaps. This moves the wing center of lift aft, the tail comes up, the nose goes down. Now it feels less tail heavy.

However, in order to get this particular airplane trimmed correctly, it required so much aileron droop that the ailerons felt heavy, which made sense, because now they were always hanging down into the airflow, and under load. So we decided to try raising the front of the stabilizer a little.

Nothing fancy, got a length of .080 x 3/4" steel strap from Tractor Supply, cut out four brackets, and drilled three 3/16" holes in each bracket.

The middle hole in the new brackets is used to bolt the new brackets to the original equipment welded bracket through the original hole in the original bracket, the one used for the stabilizer bolt. Fill the inside space tightly with washers or a spacer bushing so that you can tighten it properly without deforming the original bracket. Then you drill holes through the original bracket and put another AN3 bolt through the bottom to keep the new brackets from twisting or moving.

The final AN3 bolt goes through the top hole which is above the original hole. You have now raised the front of the elevator a bit and you ought to be good to go. Note that it would be easy to put extra upper holes in the new brackets so that you could test fly & adjust to find the optimum location. We went about 7/8 of an inch up and got lucky. Your results may vary...

Heavy Ailerons

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