From: "Barrett/Burns" <2thman@olympus.net>
To: <lancair.list@olsusa.com>
Subject: Hysol again
Date: Sun, 31 Jan 1999 23:51:38 -0800
Message-ID: <01be4db7$b382cbc0$LocalHost@2thman>
Mime-Version: 1.0

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I know I should just shut up, but can't resist making another stab at what
seems logical to me about this issue.

First to answer the e-mail from Ed Sikora, the Hysol that Lancair sells is
Hysol 9339.  I don't know about the 9430 formula.  You might want to find
out what its properties are in relationship to the 9339 before using it for
structural bonds.

In defense of my less stringent measuring method using a small gram scale I
offer the following.  For the most accurate results, one should use an
electronic scale set to zero with a container on it.  Measure out the base
desired and use the ratio to compute the amount of hardener required.  Use
another container to measure the proper amount of hardener, zeroing the
scale with the container first.  Then try to mix the two together presumably
transferring the hardener in to the other conatiner, but make sure you leave
no molecules in the hardener container, or your ratio will be off.

Another choice is to do step one above, then add the appropriate amount of
hardener to the base, but what if you add just one gram too much - or even
one tenth of a gram.  Doesn't that throw off your ratio as well?

When using syringes, it seems impossible to me to get ratios as accurate as
called for.  I use syringes all the time in my dental profession, and there
is no way on earth that we could control dispensed quantities that closely.

To set the record straight, I do make the calculations for structural
batches of Hysol, but then when I measure quantities, I acknowledge the
reality of the practical impediments to accuracy.  It seems that this is an
example of "measuring with a micrometer - then cutting with a chain saw"
that we get caught up with sometimes in the homebuilt business.

By all means, every builder should do every step as accurately as possible
and use his best judgment to ensure that his aircraft will perform to his
(or her) expectations.

I have performed shear tests on junctions between aluminum hinge material
and carbon fiber layups where the surface of the joint was approx. 1" X
1.5".  Some test pieces were joined with Hysol and some with epoxy/flox.
The Hysol was mixed with ratios that were only guessed at - not even
measured.  The epoxy/flox joints broke at about 100 to 200 pounds while the
Hysol joints held to 700 pounds.  The purpose of the tests was to measure
the strength of our graphite hinges, but the results were enlightening
concerning the Hysol.

John Barrett