I flew a Sonex with that exact trim system in it for about an hour this morning. Very nice flying plane. Flies very much like the KR except the elevator is significantly heavier and the ailerons quite a bit lighter. The only thing about the plane that I didn't like was the trim system. As the aerodynamic loads would go up at speed, the loads would stretch the trim spring, so it just didn't want to trim up. But as soon as you would start slowing down, with a lesser load on the elevator, the spring would contract and the plane wanted to keep pitching up. The more I slowed down, the more it pitched up, which cause it to slow down and pitch up even more. In effect, when you wanted to go fast, it didn't have enough nose up trim, and when you wanted to climb, it didn't have enough nose down trim. The owner says the trim system is one of the few things they plan to change on the plane. I should mention that the trim works much better with a more forward CG. When the owner flies the plane, he's flying with the CG at the forward limit. The trim works much better in that scenario. With me on board, we were flying right in the middle of the CG range. The trim was more of an annoying distraction than it was effective.
This is the fourth plane I have flown with a spring type trim system, all 4 different designs. Probably the most effective one I've flown was in the Piper Tomahawk, the second most effective was the spring trim system on some of the GlasAirs. The one on my KR is the least effective and will be replaced with a trim tab next time I do major surgery on the plane. The one on the Sonex is easily the most annoying. Of the four different spring trim systems I have flown, none are as effective as the simple trim tab you find on most aircraft. Jeff Scott Los Alamos, NM ----- Original Message ----- From: Craig Williams Sent: 12/09/11 10:44 AM To: KRNet Subject: KR> Spring trim system http://www.sonexaircraft.com/orders/trimfaq.html Has anyone used the Sonex trim system in their KR? I have convinced myself that the this is a good system and want to try it. Craig www.kr2seafury.com
