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unstable horizontal stabalizer

cgoldy

cgoldy

Registered User
Moogerah Queensland Australia
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My horizontal stabilizer on my Back Country kit has allot of slop. The tube on the horizontal stabilizer is the same diameter as the bronze bushing in the jack screw tube and has forced it into the tube. How can I fix the bronze bush so as it stays flush with the end of the Jack screw tube? Cut off self tapping screws? Centre punch the outside tube to hold the bronze tube in place?. Epoxy?

Please help
 

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Colin,
The bronze bushings on mine are the same as shown in your second picture. Flush with the end of the jack screw tube. There should be no gap between the stabilizer and the trim tube. You could do one of two things.
1. Make a spacer washer to go between the end of the stabilizer and the trim tube.
or
2. Rotate the tube in the stabilizer 90 degrees or replace the tube. Push the leading edge of the stabilizers against the jack screw tube and re drill the tube. There should not be any slop between the stabilizer and the trim tube.

There is so much shaking in the tail, particularly at take off power, that you want a minimum of slop.
 
Common problem. The stabilizers were not pulled up good when the holes were drilled to hold the stabilizer to the liner tube. Though people have turned the tube 90 degrees in the past and re-drilled I would not recommend that after talking to Charlie Center of Crosswinds STOL. His dad had a liner tube break and they attributed it to someone drilling another set of holes in the tube. I have taken a piece of safety wire and wrapped around the gap and taken the slop out and I have replaced the liner tube and re-drilled. I think part of the problem is that fabric gets in between the stabilizer and the jack screw carry-thru and over time the fabric wears through and you get the slop. Had this happen on my Dad's airplane a while after we rebuilt it.
 
Colin,
I screwed up when I initially fit everything and drilled. I was not happy with the end play in the stabs. I went ahead and ordered both new front and rear tubes from Jay DeRosier. I felt I would rather have new than spaced or multi drilled. Now they are tight and solid.

Jay
 
Steve Pierce said:
Common problem. The stabilizers were not pulled up good when the holes were drilled to hold the stabilizer to the liner tube. Though people have turned the tube 90 degrees in the past and re-drilled I would not recommend that after talking to Charlie Center of Crosswinds STOL. His dad had a liner tube break and they attributed it to someone drilling another set of holes in the tube. I have taken a piece of safety wire and wrapped around the gap and taken the slop out and I have replaced the liner tube and re-drilled. I think part of the problem is that fabric gets in between the stabilizer and the jack screw carry-thru and over time the fabric wears through and you get the slop. Had this happen on my Dad's airplane a while after we rebuilt it.
Click to expand...

I have the same issue on my Smith Cub...instead of safety wire I used 25# test mono filament fishing line. Has worked for 1400hrs on a long (84") prop O360.

Lou
 
I did the safety wire trick on mine. I think it was as Steve said, the fabric wears away and you get some slop. Put the safety wire (or monofiliment) on and go fly.
 
yes, the safety wire trick works great with a real -18, because the bushing has a flange, so it can NOT slide inside tube like yours did.... the safety wire probably will not work for you for long, it will just eventually push bushing in farther, I would think.. but have not seen it..

you can have someone with a metal lathe make a washer in a few minutes to fit... that would be best.. that spans from tight on inner tube to slightly larger than outer tube,

heck there's a product for some one to offer, some shim washer kits... would be worth $20 to you for a small kit....

do NOT drill extra holes, as stated... very unsafe...
 
mike mcs repair said:
yes, the safety wire trick works great with a real -18, because the bushing has a flange, so it can NOT slide inside tube like yours did.... the safety wire probably will not work for you for long, it will just eventually push bushing in farther, I would think.. but have not seen it..

you can have someone with a metal lathe make a washer in a few minutes to fit... that would be best.. that spans from tight on inner tube to slightly larger than outer tube,

heck there's a product for some one to offer, some shim washer kits... would be worth $20 to you for a small kit....

do NOT drill extra holes, as stated... very unsafe...
Click to expand...


I'm kind of alarmed you guys would put safety wire around the liner tube to take up some slop that does not matter.

Combine Stainless (hard) safety wire around a steel (soft) tube with vibration and dust....

What do you get????
 
It has been fine for me. Interesting thought though. I will cut mine off and inspect. Basically it is just like a washer and is free spinning.
 
Tim, The liner tube is chrome plated 4130 condition N. .032" play at the inboard of the stabilizer allows some knocking to go one at the stabilizer tips. I try to eliminate any play in the tail because I believe it helps wear the elevator and rudder bushings along with the jackscrew. Safety wire is pretty soft.
 
Slop would be about an 1/8th but this translates to alot of movement. I have new inner tubes ready to install but if I move the stabs inboard anymore the stabs will pinch the fuselage when trimmed full nose up. The turned up spacer would be the go. Pity that is beyond my ability!

Colin
 
The space between the stabilizers should not change as you trim. If you put a spacer in there you have to take the stabilizers off anyway so why not just replace the liner tube?
 
What I was saying is that I just can't replace the tubes without some sort of spacer because the stabs already touch the fuse when trimmed nose up. They will jam if they are moved inboard anymore
 
behindpropellers said:
I'm kind of alarmed you guys would put safety wire around the liner tube to take up some slop that does not matter.

Combine Stainless (hard) safety wire around a steel (soft) tube with vibration and dust....

What do you get????
Click to expand...

My pa11 had some slop when I got it and one of the old Cub guru's had me wind in some fine copper wire, I had to add some more about 50 hrs later but it was good for another 500 hrs after that.

Glenn
 
When assembling the tail section on kit airplanes the relaxed position may not be ideal when it come to the clearance issue. It's a balanced fit as well as an encouraged fit. I had two bushings machined to take up the 1/8th inch on each side. I did this to preserve the squarness of the installation with no preload. I think I remember removing material at the rear stab tube ass. to allow the front to come in but still bushed it for a perfect fit.
 
I find it surprising you have to go through all this rig-a-maroe on an experimental. Do they have the longerons to far apart? Never had a problem on a certified Super Cub.

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Yes, mine has a flange on the bushing. And still nice and tight. Thats what i like about this website. its something i always took for granted on preflights and never did. Now i think i will start grabbing the front of the stabs and see if they wiggle or not just for a piece of mind.
 
Mike, I reckon you have worked it out. Where would I get the flanged type of bushings and do you think they will fit into my tubes????

Your a genius
 
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