Reply-To: <DAP@DParsons.com>
Reply-To: lancair.list@olsusa.com
From: "Don Parsons" <DAP@DParsons.com>
To: <glcasey@gte.net>, <lancair.list@olsusa.com>
Subject: RE: Tank sealant
Date: Fri, 4 Jan 2002 17:22:27 -0600
Message-ID: <NFBBJEBNCMJEBKBPBJPCGECLCGAA.DAP@DParsons.com>
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Disposition-Notification-To: "Don Parsons" <DAP@DParsons.com>

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>> ... the skin ... moved slightly and now the "squeeze bead" is not right
at the edge of the rib cap, leaving a strip of thin Hysol exposed ... I
could "see" through the wing along the edge of the ribs.  I assume this thin
layer of Hysol is an adequate fuel seal, correct?

Gary,

I decided to refer to the manual (for me the ES, Ch 10, Pg 3) to see what it
had to say, and found that it actually gives us 3 options: 1) a thick coat
of epoxy resin, 2) an extra layer of fiberglass wetted out thoroughly
(better), or 3) use a fuel sealer compound designed for this purpose (best,
in this case Jeffco 9700). As a result of some of these questions, I have
been trying to find a definitive written source that explicitly states that
Jeffco 1307LV and Hysol 9339 are both fuel safe once they have cured, but I
have not found anything yet. The first 2 options listed above imply that
Jeffco 1307LV is, and the procedure for closing the wing using Hysol 9339
imply that it is too.

Exposing a thin strip of cured Hysol 9339 to fuel along the bond joints
should not be a problem. If it was, then we all would have a problem because
this happens in all ES tanks as a by-product of the process described in the
manual. I believe this is also the case for IV and LNC2 tanks as well.

As a side point, I noticed that the manual calls for a 1/16" to 1/8"
overlap, not the 1/4" that I mentioned earlier this week just going by
memory.

When you say "I could 'see' through the wing along the edge of the ribs", I
hope you are not describing a "void" when you say "see through". If that is
the case, structural strength issues will be a much bigger problem. From the
wording in the rest of your question, I suspect this is not the case.

If you are worried because you do not have the overlap at all between the
Hysol 9339 Adhesive and the Jeffco 9700 Sealer... given the first option the
manual offers for sealing the tanks, it might be OK (assuming that there are
no pin-holes or other small leaks in any of the exposed surfaces). The point
of going through the sealing process is to insure that there are no leaks at
all no matter how small. If the exposed surfaces are along the cap strips, I
would suspect they are fine. If the exposed surfaces are on the inside wing
skin prepreg surfaces, and there are any pin-holes, you may have a small
amount of fuel leaking into the Nomex core. That would not be a good thing.

I hope this helps...

------
Don Parsons
Houston, TX
DAP@Lancair-ES.com
http://www.Lancair-ES.com/
ES-166-FB / N198TD (Reserved)

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