epoxy joint

[Gray E Fowler]

Originally this just went to Brian...did not realize that till now....All 
those pump/mix by volume applications are applicable to what I wrote 
below.

Brian

Mixing by weight is always superior. The stuff you are using has a 
hardener in it called polyamide. Polyamide allows for very forgiving mix 
ratio upwards of 20%. Polyamide also imparts excellent adhesive qualities 
to the epoxy. The down side is the high viscosity-not a problem for 
adhesives but is for laminating. Most off the self laminating resin 
formulations contain some amount of polyamide in the hardener to allow for 
mix ratio errors.  Once again the downside is the increase in viscosity, 
which makes the laminating resin more difficult to work with. 
I do not use these type hardeners on Aeroslave planes due to the intricate 
nature of the laminate-core structure and my ability as chemist not to 
make mixing mistakes.  We could never make our planes using an off the 
shelf epoxy such that you have, due to the viscosity problem.



Gray Fowler
Principal Chemical Engineer
Composites Engineering
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