Hi,
What you don't want, especially if you have not yet set up the wing lift
pins and sockets already, is to disturb the positioning of the seat
back bush as even a millimeter move up and down has a great effect on
the positioning of the wing dihedral to the fuselage. Drilling out opens
up this possibility so I would first consider cautious heat removal.
The trick is to heat the bush quickly enough so the surropunding epoxy
matrix is not heated up beyond a point where the cured epoxy heat
desintegrates, which goes pretty quickly. Epoxy glass matrix is a faily
good temperature insulator so you can work this to your advantage by
heating up quickly and then remove the bush immediately as the epoxy
softens. You will discover that in any case the epoxy in the seat back
bore will be destroyed for sure. It turns into a brown powder incapable
for any further structural design loads. So, after removal of the bush,
you must carefully remove all remaining epoxy in the seat back hole
without taking material from the seat back, though, and then start with
a fresh batch of epoxy glueing it back. I did use the 1/2 inch bolt to
line it all up making sure there was equal movement (play) both up and
down.
I have done several sets of bush removals incuding the 3/8 to 1/2 inch
concersion (which needs to be drilled) and the most useful tool I
discovered was a tapered reamer slightly larger that the inner bore of
the bush which after softening of the bush I quickly inserted and it
clawed it well and pulled it out easy. NOTE: This tool WILL destroy the
inner smoothness of the bush but in consideration of old burned up epoxy
clinging onto the textured outer bush surface which turns out impossible
to remove anyways I always replaced every bush anyways allowing a much
better adhesion to the new epoxy.
There are surprising high bending loads going into the seat back bushed
once the wings flex under load. This is caused because of the slight
differential of mounting locations between wing pin bushes outboard and
seat back bushes more inside the fuselage, with both wing pins taking
the full load of the entire bending forces of the wings. EUROPA
discovered this rather complex 3-D wing spar twisting tendency problem
about 10 years after delivery of the first kit and we all now need the
spar jackets to be added to our wings... In any case, you want the seat
back bushes refitting to be as best performed as possible.
There are some situations like popping off the metal spar cap inserts
which I had to do twice where heat is also a workable solution as I knew
the underlying glue bed of REDUX was thick enough to not transfer the
heat too quickly to the set back epoxy matrix - but I had to rehearse
the sequence before and time it very carefully to pop the cap off as
soon as possible with a tap of a chisel to prevent the underlying epoxy
matrix heating up beyond temperature limits.
Christoph Both
#223 Wolfville, Nova Scotia Canada
________________________________
From: owner-europa-list-server@matronics.com on behalf of craig bastin
Sent: Sat 8/2/2008 9:45 PM
Subject: RE: Europa-List: Wing incidence
<craigb@onthenet.com.au>
Chris thanks for your input, just out of curiosity (and to make my life
easier)
how did u remove the binding bush on your second set to re-bond it. I
was
considering
a half inch drill or bolt into the seat back then heating it to soften
the
redux, is this
how you removed it. I thought the redux doesnt soften till about 400
degrees, which i have concerns
about damaging the surrounding area with that much heat
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com]On Behalf Of Christoph
Both
Sent: Sunday, 3 August 2008 12:09 AM
Subject: RE: Europa-List: Wing incidence
Hi,
There have been comments regarding binding wing pin bushes:
Much of this is caused by a serious flaw in the Europa Builder's Manual:
when initially setting the wing spars (or XS wings) to the cockpit
module
the manual allows you to let them assume any position they like. In
other
words, the wings might hang around at 5 or more degrees wing incidence.
This
uncontrolled condition causes the wing mounting pin to increasingly
deviate
---From the wing bush bore incidence in the back of the cockpit module. So,
if
you just glue in the seat back bush without taking care of approximating
as
closely as possible the 2.5 degree later wing incidence the following
will
happen for sure:
Upon finally setting the wing incidence the pins will now be a few
degrees
off level with the drilled hole level of the seat back bush, thus
binding
like crazy.
Initially I could not believe how stupid I was using a REAMER to ream
through the two wing mount bushes plus the seat back bush. YEAH, I could
now
easily remove the wing pins but the entire set up was now compromised
beyond
any airworthiness considerations. All this was caused because no hint
was
given to incorporate as closely as possible and already at the early
building stages, the 2.5 degree wing incidence so the seat back bush
would
not bind.
I fully came to terms with this much later while upgrading to 1/2
diameter
bushes. While replacing all bushes in the wings I made sure the seat
back
bush had the right angle. This almost solved the problem. However, I did
have some persistent serious binding on one side. In the end I had to
reposition one of the new wing bushes in situ, that is, floxing it in
while
the wings were mounted. Don't ask me how I managed this with the wing
fillets already on and both wings mounted. I had to create a special
sequence of steps and some innovative tools to get this resolved...
The wings are now fully up to mounting standards and go effortlessly in
and
out of the fuselage with the wing mount pins sliding in and out
smoothly.
What a joy!. Oh, by the way, you need to make a well positioned wing
mounting bracket (see picts) to achieve this as well. I can now mount my
classic wings alone, without extra tools and special assemblies. I used
pieces cut from 1/4 inch UHMW plastic sheet which is incredibly tough
but
somehow flexible and slippery when the wing spars glide on it, without
any
chance of scratching or abrasion. Incredible stuff and much better than
the
phenolic sheets!
I hope EUROPA updates the builder's manual to save us many frustrating
hours. It's a great kit, though, I must say.
Christoph Both
#223
Wolfville, Nova Scotia, Canada
Checked by AVG - http://www.avg.com <http://www.avg.com/>
6:59 PM
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