Sign in to follow this  
Followers 0

Rudder Bushing Alignment Tolerance - Kitfox III


4 posts in this topic

Posted

I am in the process of changing out my Kitfox Mod III rudder with a Mod IV.

When I fit up the new rudder (still using the original bushings on the vert stab), I find that the lowest of the 4 bushing mounts is 1/4" further forward that the top 3. I.e. you could drop a rod down through the top three bushing guides, but it would then pass behind the bottom guide. Looks like it was built this way from day 1.

Anyone run across this before? What is odd is that the rudder I took off was actually bent to fit (lower part bent forward 1/4"). It did seem to move o.k.

Trying to sort out if this is a big deal or not. I can bend the new rudder to fit, however it will still need to accommodate the non-linear movement (to the tune of 0.15" at full 37 degree deflection - side loading). I assume the tubes will all try to bend to allow motion, but with the fabric on I am concerned about increase loading and fatigue.

One option is to bend the rudder and leave as is (and live with the stresses). The other is to move the lower fuselage bushing out 1/4" and then fill that gap between the rudder leading edge as appropriate.

Anyone run across a similar situation? Are there any tolerances for hinge mounts on tube-n-fabric birds like these?

Share this post


Link to post
Share on other sites

Posted

What you have is the result of hard landings on the tail wheel over time that has caused some bending, stretching or possibly cracking of your lower longerons.  You may want to take the fabric off of the lower section of your fusalage and check it then do some repairs and reinforce it,  In the end, all those rudder pins should line up.

post-75-0-23015100-1418023456.jpg

post-75-0-46588700-1418023466.jpg

Share this post


Link to post
Share on other sites

Posted

Hey Randy, Thank you for the reply and for posting the images.  

 

I should have mentioned it, but in this case the kit is new (has never flown).  Looks to have been possibly a fabrication issue (I have heard from others with the same problem).  Maybe that is one reason for changing over to an adjustable system like on the Model IVs?

Share this post


Link to post
Share on other sites

Posted

The model IV and newer use the moronic rod end bearings in order to facilitate fairings and ribs in the vertical stab and rudder. Supposedly adding speed. IMO they just add complexity.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0