As far as getting bushings stuck, I modifiedour accelerated
tailplane kit which had the inner bushings debonding pretty much right
after we received them in 2003.
Mutilated the stabs from bottom and
installed a very very minor tapered CF tube. It was from a rowing skull
(garbage picked) and I selected the section that was just about the proper
size for outboard bushing, but lead in on the inner bushing was slight
over. This way you get the support needed with essential no more
friction.
When laying up, always first ply of BID is with
Redux/peelply. Redux sticks much more better to Stainless or any sort of
metal as a matter of fact, so I always use Redux for first ply over metal,
peelply then complete layup with Aeropoxy laminating resin.
Inner and
outer bushings were scored and scuffed very well, they ain't goin anywhere
with the glass layup on them and CF tube.
Using shoulder screws to
hold in place instead of pip pins. They have seals so no need to have
drain. Also a detent.
I still elongated the torque tube (also a
spar!) in event any slop ever developed no rotational force would be
applied to outer bushings.
This was long before mod 73:
http://www.europaowners.org/modules.php?set_albumName=album220&op=modload&name=gallery&file=index&include=view_album.php
Since I was at it fit of our pins was very poor. Factory tried sending
oversized pins, then 10MM reamer and pins with still a poor fit.
Ireamed holes, then sized them by sending through progressive larger
pins (.0001 increments), then custom machined and hand lapped dogbone
shaped pins (dogbone so when sending interferance fit pins through
theydon't oversize first hole, dogbone isonly a few thousands
undersized) and used corrosion proofing paint as a lubricant on cold pins
when installing. Also used green loctite but fit was very good on pins:
http://www.europaowners.org/modules.php?set_albumName=album224&op=modload&name=gallery&file=index&include=view_album.php
And since I was working on aft section of aeroplane and thinking,
removed about 15% stress on drive pins. Added mass balance weights to lead
edge of stabilators whioch allowed removal ofmass balance weights
off mass balance arm. IfI am going to need aft weight anyway with
914 and airmaster XS, might as well make weight do a worthwhile
task.
Another note:
On the new style mass balance arm, there is
a thin locknut on the beefier lower fitting. When you tighten this locknut
it is essentially taking all the load! I didn't like that very much,
althoughI have never heard of any problems, I found an AN castelated
nut that had 3 times or more as many threads as the thin one
supplied,and fitted it instead while assembling with Locktite. Think
about it, for most part weight is putting a compression load on the
threads of thelower fitting (positive Gs anyway) and the threads are
under compression. Now you tighten this thin stop nut and you are now
pulling on threads that are now under tension. Guess what the only thing
keeping threads under tension is? The few threads of the thin nut. These
few threads are taking all the load.I have three times as many
threads with castelated nu compared to supplied thin nutt.
Ron
Parigoris
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