The "F" word

[Johnny C!]

Oh...

Have you been able to find the trim tab?

John

[Gary H]

This is what I did

[KevinC]

John - yes we did find the tab (see pictures).  It fell on the runway.

Today I started doing some disassembly.  I found:

-The bolt that holds the two elevator halves together was quite loose.  It is a nyloc, so I don't know why it would be loose.
-I lined the leading edges of the elevator horns up with the leading edge of the horizontal to check 'twist' on the trailing edge.  I believe there should be 3/4-1 inch difference in the trailing edge - there is less than 1/4 on mine.  I will measure again more accurately tomorrow.

Nice flying day in e-WA today.... dang!

k

[taildrgfun]

Kevin my cable attach points are about 2" apart. Looks to me like too much space like you had would make it very susceptible to do what it did. Sorry it happened but sure glad no one got hurt.

[Johnny C!]

So do you think it was not enough off set
on the trailing edge?

John

[KevinC]

John,

I can't know for sure, but it seems likely that the unsupported cable distance is the likely culprit.  Guess we'll find out, eh?

k

[b1x4nqb]

For my slow brain, could you guys describe which "unsupported cable distance" you are refering to?  I see all cables supported and discussions on both the trim cable to the trim tab as well the flying wires for the tail surfaces.  The picture above looks great and all supported for the trim cable and he even has two support stems coming out the bottom of the horizontal stabilator vs. my one.  Is this what you're refering to?  I'm just a slow one here I guess.

Paul, PA

[KevinC]

Paul,

There are two positions possible on the elevator for the square mounting plate/support for the trim cable - one forward and one aft.  I didn't realize that the forward set of tabs were for mounting an electric trim servo and mounted my support on those tabs.  The result was ~5.25 inches distance from the trim cable support (that clamps the 'sheath') to the trim tab arm.  This distance was supposed to be no more than 3" - and from the posts it appears most are around 2".  The increased distance allows the tab to move a little due to the flex of the cable = bad stuff happening.

k

A picture to illustrate too far and a 'mock up' of a proposed solution:

[DaveU]

Kevin,
I know that the thought of more painting sounds bad now, but it might be the best solution to just open up the bottom of the elevator, put a bracket on the right set of tabs and then a little fabric patch and paint.  I worry that the mock up solution might lead to the oscillation and flutter again.  You probably have to touch up paint the trim tab anyway.  I know from experience that a little fabric patching is not difficult, and a patch on the bottom of the elevator will not be obvious anyway.  You could leave the old bracket and just add another, like the photo posted by Gary.

Just my 2 cents worth.  

Dave

[Johnny C!]

I think I will add the second bracket, as well.

Thanks for sharing this with us, Kevin!

John

[Roger]

My thoughts:
After reading the posts on this subject, I measured my distance and came up with nearly 6" from suport post to the trim tab control arm. I layed under the elevator/horiz. stab and decided I really don't want to do anymore fabric work. Let me see if I can put my thoughts down so everyone can understand my thinking and respond. I believe if a person will do a little welding on the bench, we can come up with a little bracket that will work. I am thinking of some pieces of metal about the same size and thickness of the origional bracket metal, and a short piece of straight flat bar of that dimension, riveted onto the top of the elevator hinge,on the horizontal stab. Then, a flat piece of the same size, welded to that piece, only think of it as being in the upright position, (like looking down at a railroad track) , and that piece bolting to the backside of the already installed cable bracket post. Then at the end of the cable barrel, weld another bracket similar to the already installed other post, and another small piece just like the factory piece to capture the cable barrel. I don't think the additional weight would be that significiant as to affect weight and balance. Probably no more then 6-8 ounces. Remember all of the welding would be on the bench.
I'd like to hear from some of you as to what you think of the idea, and if anyone would want clarification as to my thinking, please get in touch at R-Stout@Hotmail.com.
Roger

[KevinC]

I may still do surgery on the elevator and patch it    but this is another solution I came up with last nite.  Again, this is a mock-up and not the final.

k

[Roger]

Just an addition to my earlier post. I went to Home Depot and bought a 3/4 by 2' steel piano hinge and shortened it to the length I wanted to address the aluminum weekness I preceived on the origonal.

[Dave Krall CFII SEL SES]

I may still do surgery on the elevator and patch it    but this is another solution I came up with last nite.  Again, this is a mock-up and not the final.

k

You could maybe also run another small buttress forward to your original bracket for additional support.

[Dave Krall CFII SEL SES]

Just an addition to my earlier post. I went to Home Depot and bought a 3/4 by 2' steel piano hinge and shortened it to the length I wanted to address the aluminum weekness I preceived on the origonal.

We did similar in a stainless steel hinge from AS.