Tailwheel Shimmy and Spring

[jiott]

In the last 50 hours or so (out of a total of 235 hrs) I have begun to develop a tailwheel shimmy problem when landing on paved runways. I had the standard Kitfox 3-leaf steel spring and the optional Alaskan Bushwheel tailwheel. I tightened the tailwheel pivot bolt as much as I dared as was suggested on this forum, and it seemed to help a little but by no means solved the problem. The pivot caster angle seemed very near vertical so it appeared the next thing was to improve this angle by rebending or getting a different tailwheel spring. I bit the bullet and ordered the Grove spring aluminum spring kit from Kitfox. It came with all the brackets and hardware and installation was a snap.

It is a much sturdier spring for backcountry flying, has a better caster angle and is somewhat longer so it raised my tail about 1.75" higher. The results are all good: after 8 landings the shimmy is all gone and it has a more stable feel on rollout. My view over the nose on taxi is improved. Another important improvement I feel is on landing; It is easier to get the tailwheel down a little ahead of the mains (Maule style) so when the mains come down the AOA decreases and sticks you to the runway-kind of like landing a tri-gear. Also if you do a standard 3-point landing the higher tail reduces the AOA so there is less tendency to balloon up in gusty wind conditions. In other words I am pleased with the results.

[rosslr]

Nice report Jim - I looked at them at the factory and was tempted but thought I should use the one I have for now - look forward to seeing it Tuesday.

Cheers

ross

[rv9ralph]

Jim, I read your post several times and my understanding is that you replaced the tail wheel spring with a Grove product you purchased from Kitfox. I checked both product lines and could't find any information.
Could you elaborate on the source and specifications on the aluminum tails spring. I have a Kitfox 3 with a single leaf steel spring.
Ralph

[jrevens]

I would suspect that the solid aluminum spring is stiffer than the steel leaf spring. Is that the case? Some other designs have had experience trying solid aluminum tail springs, with a resultant stiffer ride and more stress to the airframe at the attach points. Just curious.

[Paul Z]

I had my SLSA converted to a tail dragger by the Kitfox Factory. They installed the Aluminum tail spring. I do not find it to be a rough landing or a stiff ride. In fact I find it really nice, especially compared to the Cessna 120 I had. I had a picture of the part number on the Spring I'll have to check my desktop to see if I still have it.

[Dusty]

This looks similar to what I have (mounting is slightly different)
Very good ground handling but very stiff over bumps.
I think the tyre does all the work