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<DIV>I keep a stock of 1/8” and 1/4” end grain balsa / Carbon Fiber
laminate on hand for just such repairs. That stuff is light and extremely
strong . . .</DIV>
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<DIV><A title=http://www.acpsales.com/Sandwich-Panels.html
href="http://www.acpsales.com/Sandwich-Panels.html">http://www.acpsales.com/Sandwich-Panels.html</A></DIV>
<DIV>.</DIV>
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<DIV style="font-color: black"><B>From:</B> <A title=vanputter@gmail.com
href="mailto:vanputter@gmail.com">Ronald Van Putte</A> </DIV>
<DIV><B>Sent:</B> Friday, June 14, 2013 11:45 AM</DIV>
<DIV><B>To:</B> <A title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">General pattern discussion</A>
</DIV>
<DIV><B>Subject:</B> Re: [NSRCA-discussion] Repairing Gear Block - Guidance
Needed -Added Weight VS Strength</DIV></DIV></DIV>
<DIV> </DIV></DIV>
<DIV
style="FONT-SIZE: small; FONT-FAMILY: 'Calibri'; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; TEXT-DECORATION: none; DISPLAY: inline">I
think you are right to be concerned. Finishing resin is not intended for
structural use and I don't know whether your repair will hold together. I
also don't know what you used to replace the original gear blocks, but I would
be concerned about the use of lite ply. It is not nearly as strong as
aircraft-grade plywood.
<DIV> </DIV>
<DIV>I have intimate experience with landing gear plate replacement, having just
completed a total replacement of the gear plate in my Vanquish. For some
reason, the manufacturer uses cheap three-ply plywood for the landing gear plate
and a landing in a grass field that had a hole in the turf took out the left
side of the gear plate. The plywood opened up where the gear was bolted to
it. </DIV>
<DIV> </DIV>
<DIV>I won't explain here what I did to replace the gear plate, other than to
say that I removed a section of the bottom of the fuselage to access the area
where the gear is bolted to the gear plate and used some ingenuity to
manufacture a new gear plate and install it, using the existing gear plate tab
holes in the adjacent bulkheads. Contact me if interested in knowing what
I did.</DIV>
<DIV> </DIV>
<DIV>Ron Van Putte</DIV>
<DIV>
<DIV> </DIV>
<DIV>
<DIV>On Jun 14, 2013, at 11:26 AM, Larry Diamond wrote:</DIV><BR
class=Apple-interchange-newline>
<BLOCKQUOTE type="cite">
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<DIV style="RIGHT: auto">A bit of a delimma mostly because I don't know the
Pro's / Con's of strength VS weight with various epoxy mixes.</DIV>
<DIV style="RIGHT: auto"> </DIV>
<DIV style="RIGHT: auto">Issue... I damaged LG gear blocks of a 2M Monolog...
It was my fault and I don't think it had anything to do with the design.
Actually I believe the design saved me from a much more difficult task of
rebuilding part of the fuse. The gear block did it's job mostly because I
didn't do mine and I was stupid. Figured I could set a timer up later after a
contest, flying electrics... Uhhh, not a good idea if you going to throw in
any type of redos in 15 - 20mph winds... Just saying... Deadsticks are no
fun... I was also lucky with the main batteries... Not too hot, didn't puff,
and put 5100 and 5150 back into the two 5000 packs... Lesson learned and a
small price to pay ...</DIV>
<DIV style="RIGHT: auto"> </DIV>
<DIV style="RIGHT: auto">Here is what I'm thinking about trying and what I
have done so far.</DIV>
<DIV style="RIGHT: auto"> </DIV>
<DIV style="RIGHT: auto">I removed all the loose wood in the existing gear
block area and dremeled out the wood that was shreaded due to being sheared.
Everything fit back in place without being removed completely.</DIV>
<DIV style="RIGHT: auto"> </DIV>
<DIV style="RIGHT: auto">If I removed it completely and replaced it, I would
have created some damage to the surrounding area (fuse sides and formers)
trying to cut it out or using a dremel to remove.</DIV>
<DIV style="RIGHT: auto"> </DIV>
<DIV style="RIGHT: auto">I glued the main parts back in place with 30 minute
epoxy and let cure.</DIV>
<DIV style="RIGHT: auto"> </DIV>
<DIV style="RIGHT: auto">I then taped up any holes or gaps from missing wood
to prevent the thin epoxy from flowing through.</DIV>
<DIV style="RIGHT: auto"> </DIV>
<DIV style="RIGHT: auto">I mixed a 50/50 ratio (volume) of 20min Finishing
Epoxy (extremely thin epoxy) and micro ballons. I used this very thin mixture
(similar viscocity to motor oil) to fill voids and areas where the wood was
removed so it would be flush with the existing wood. This provided for a nice
level finish of the existing wood block and an unintetional outcome was a
perfect fillet all the way around the block. I was very surprised with the
outcome, much better than I thought it might turn out. This should also allow
me to easily sand down high spots of the cured epoxy flush to the existing
gear block for laminating light ply to the existing gear block for setting the
t-nuts for the LG.</DIV>
<DIV style="RIGHT: auto"> </DIV>
<DIV style="RIGHT: auto">This only added 3 grams of weight minus the weight of
the wood that was removed. Measured the epoxy before and after use. 9 grams
epoxy, 9 hardner, and 1 gram of microballons. 1 gram of microballons is a lot
more than it sounds... After applying the epoxy, I had 16 grams left.</DIV>
<DIV style="RIGHT: auto"><VAR id=yui-ie-cursor></VAR> </DIV>
<DIV style="RIGHT: auto">My next step is to laminate a 3/16 light ply with 30
min epoxy to the top (inside of fuse) of the gear block spanning about 75% of
the length (across the fuse) and the same width of the existing gear block. My
theory is this should offer strength accross the gear block without
over-reinforcing the gear block area and not add unnecessary weight.</DIV>
<DIV style="RIGHT: auto"> </DIV>
<DIV style="RIGHT: auto">Does this sound sufficient or is the risk too great
that the gear block will be too weak?</DIV>
<DIV style="RIGHT: auto"> </DIV>
<DIV style="RIGHT: auto">My concern is that the Finishing Epoxy and
microballoons will not be strong enough. My thought is...it isn't being used
for strength and only for a filler to bond the existing gear block. It appears
that the dried mixture is as strong as a filler/laminate than the original
ply.</DIV>
<DIV style="RIGHT: auto"> </DIV>
<DIV style="RIGHT: auto">It is not too late to cut it out. There is only
cosmetic damage to the surrounding area. I'm concerned that if I try to cut
out the gear plate, I will do more damage and it will be weaker and heavier in
the end.</DIV>
<DIV style="RIGHT: auto"> </DIV>
<DIV style="RIGHT: auto">Larry Diamond</DIV>
<DIV style="RIGHT: auto"> </DIV>
<DIV style="RIGHT: auto">Yes, I have pondered on this since June 1st...
Started putting it back together last
night.</DIV></DIV></DIV>_______________________________________________<BR>NSRCA-discussion
mailing list<BR><A
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href="http://lists.nsrca.org/mailman/listinfo/nsrca-discussion">http://lists.nsrca.org/mailman/listinfo/nsrca-discussion</A></BLOCKQUOTE></DIV>
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