Message-ID: <000501beefc4$2fe64080$ec818ed1@pavilion>
From: "J. N. Cameron" <CIC@centuryinter.net>
To: "Lancair List" <lancair.list@olsusa.com>
Subject: Tank Sealer; Closing ES Wings; Radio noise update
Date: Thu, 26 Aug 1999 08:08:30 -0500
Mime-Version: 1.0

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    On the subject of the Jeffco tank sealer, try this:  Get two or three of
the small cold packs, the plastic bagged things you put in the freezer and
use to keep your brew cold.  Get several throwaway aluminum pie pans at your
local grocery store.  When you mix up the tank sealer, put two or three cold
packs in one pie pan, then set another on top of it, and mix your sealer in
the upper one.  This helps two ways -- the cold packs prolong the pot life,
and the shallow depth also helps prevent exotherm.  The downside is that the
low temperature does make the stuff a little tarry to apply, but after a few
seconds on the glass surface, it warms right up and can be brushed out.  By
doing this, I found I could mix up a fair quantity and still get it on
before it started to smoke.

    Regarding closing the ES wings, I think I used between 2 and 3 quarts of
Hysol for each wing.  The spreading tool described in the manual was not
very useful, as it tended to drag the Hysol along and not give the proper
buildup.  I just shaped the Hysol on top of the spar and spar caps with
tongue depressors.  How much you will need will depend on how close a fit
you've gotten with the flox buildup on top of the spar, but I tapered the
Hysol/flox final mix so that there was maybe 3/32" at the spar edges, and
probably 1/4" at the center.  After doing the flox releases (took me 2 or 3
to fill the space), you can check the gap with modelling clay, as per Marv's
suggestion, but clean well afterward -- I found that the clay left greasy
marks everywhere I put it.
    You want enough to get really good squeeze-out everywhere.  Better to
have globs of excess Hysol droobling around inside than to have voids.
After all, what can you add, maybe a pound or two to the total weight?
Incidentally, cover everything like aileron bellcranks with masking tape or
plastic bags because the Hysol will definitely ooze into some places you'd
rather not have it.
    Weighting the wing skin during close-out is also pretty critical, and do
put some long boards over the spars before stacking on weight.  If you
don't, the wing skin will come out wavy as the dickens.  You'll probably
have something like 400 pounds of weight on the wing to properly apply
pressure.  Over that large an area, it takes a lot of weight to get all that
Hysol (plus a bit of flox) squeezed out properly.
    Finally, it would be fun to hear from anyone who has actually managed to
close out a wing with epoxy/flox rather than Hysol.    I cranked the A/C
down in my shop to a rather uncomfortable level, worked as fast as I could
and had help mixing, and still barely managed to finish within the pot life
of the Hysol.  With epoxy/flox it would have to look like one of those old
speeded-up movies (Keystone cops with rubber gloves)!  The Lancair folks
should probably just delete that stuff from the manual, if they haven't
already.

    Good luck!  With two coats of the Jeffco sealer and plenty of Hysol
during wing closure, I haven't had any fuel tank leaks.

Radio noise update:  Following some of the many excellent suggestions by LML
subscribers, I have done two things, one of which apparenty cured the
horrendous noise I was getting through my headset during COM transmit.  Step
one was to remove the audio alarm input coming from the Jim Frantz
annunciator panel.

    Step two has to do with the way I wired my passenger seat headset jacks.
When I built the panel, I brought a lot of things to plugs at the two lower
corners, so that I could drop the panel in and later connect up with mating
plugs coming from wherever.  For the rear seat headset jacks, I used audio
connectors that I thought were shielded.  When I went back and a had a look,
however, I realized that one half of the plug was not shielded, and the
shield therefore was not continuous through the plug.  The audio leads from
the plug to the rear seat jacks were probably acting like an antenna,
feeding stray RF directly into the audio panel.

    To definitively say which of these two steps did the most good, I need
to plug the passenger wiring back in and fly again.  Whichever it was, the
noise has been dropped by maybe 90%, and is now at an acceptable level.

Temperfoam seats:  I promised a report after flying from Texas to Wisconsin
with my new Temperfoam (=Conforfoam) seats, but instead of doing that, we
spent most of the weekend evacuating ahead of hurricane Brett, then getting
everything put back together again.  Fortunately, at the very last moment
Brett veered west and went in through the King Ranch, an area in which
almost no one lives.  N82500 went to Alice to a very stout steel hangar,
then back here again on Tuesday.  The seats are very comfortable -- you're
just not aware of them at all.  Nice.

Jim Cameron,   LNCE  N82500

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