From: "Barrett/Burns" <2thman@olympus.net>
To: "Lancair List" <lancair.list@olsusa.com>
Subject: How hard is hard?
Date: Tue, 16 Mar 1999 08:15:49 -0800
Message-ID: <01be6fc8$412f16e0$52ed85c6@2thman>
Mime-Version: 1.0

          <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>>
          <<  Lancair Builders' Mail List  >>
          <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> 
>>
I spent a fair amount of time on the phone with Jefco technical personnel
about a year ago because of a perceived problem with the resin and the
Sticky Stuff dispenser we were using for our composite hinge business at
Barret/Garrett Enterprises.  I was told - and choose to believe - that if
you have less than optimum hardener in the mix, you will have an extended
set time - could be VERRRRRRY long dedpending on how far the ratio is out,
but the final setting strength (read hardness - and other desirable
qualities as well) will be as published.  If you get too much hardener -
even by a small percentage, those qualities will be adversely effected.

I've noticed that when I operate the pump, if I want just a few drops of
mixture, the hardener is slower to dispense than the resin.  Not too
surprising when you think about surface tension - diameter of the metering
tube, etc.  So I think the pump naturally errs (in small amounts) on the
safe  side.

The Jefco rep also told me they've found this product to be extremely stable
over time.  The most likely problem would be evaporation of some of the more
volatile  contents of the hardener if left in an  open container like the
dispenser for long periods of time (like months) at warm temperatures.  If I
recall correctly, he said that product which has been tested after being on
the shelf for as long as two years was shown to function well.

I don't know about you guys, but I've got an awful lot of critical things to
think about and worry over while building this crazy airplane.  I'm not
going to second guess Jefco, Lancair and hundreds of Lancair pilots who have
expressed confidence in the Jefco/Sticky Stuff Dispenser marriage.

John Barrett