When I converted my plane to a tailwheel, I was still an inexperienced tailwheel pilot but never had any real issue with the tailwheel. But the more I flew, the more I would get the shimmy occurring. I used to think that the real issue was the pilot and not the plane and that certainly has a lot to do with it. But the more I read about the issue in the Glasair Owners Forum, the more I learned about the issues causing that awful feeling on landing
The most important thing to get right is the angle of the tailwheel. I have the Alaskan Bushwheel on my plane and they have a short video that shows the proper set up for the tailwheel. The tailwheel spring tension and angle is critical for getting the best performance out of the tailwheel. Some of the Sportsman/Glastar owners were not happy with the original tailwheel kit from Glasair . The issue was the leaf spring. The feeling was the spring was not set for the proper angle and no matter what they tried, they couldn't get ride of the annoying shimmy.
Glasair looked for a solution and came out with a different leaf spring to try and help minimize the shimmy. The angle is different and it's beefier. I had the original spring so I ordered the new one hoping it would make a difference. Here's my original spring:
Now let me again say there are a lot of things that cause a shimmy. There's the tire pressure, which has to be correct ( I keep mine around 60 psi) and your gross weight. If your tire pressure is low, forget it. And you really have to measure it because just looking at the tire won't do. You especially have to be careful when it's cold outside and the air contracts.
Your gross weight and CG location also will determine if you get a shimmy. A high gross weight and an aft CG will also contribute to a shimmy. Now I don't fly a full gross very often but when I do I try to keep my CG as close to center as I can.
So here's my set up after the new spring.
Not sure if you can tell but the angle is better and the end result is a LOT less shimmy. Now I still get an occasional shimmy with either a crappy landing or some stiff cross winds but in general I'm very happy with the results. Some owners say the angle causes more lateral motion in the spring and I tend to agree but I still think it's a better set up than my original.
I have to say that in a conventional geared aircraft, the tailwheel is really critical. It has to provide all the lateral stability at touchdown and does come under a lot of stress. Now maybe because I land on hard runways all the time or maybe my landings are not always picture perfect but my tailwheel tread wears out quickly. If I get a year out on the tire I'm happy. I never concerned myself with the tire when the training wheel was in the front :)
And one more thing, if you really want to avoid the shimmy, just do a wheely landing and avoid the situation all together.
