From: Fredmoreno@aol.com
Message-ID: <90a23406.24a324f7@aol.com>
Date: Thu, 24 Jun 1999 02:06:47 EDT
Subject: Preparing for bonding
To: lancair.list@olsusa.com
Mime-Version: 1.0

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I read John Barrett's post on surface preparation for bonding noting his 
observation that for dental cement, a fine abrasive making more surface area 
is now preferred, providing better bonding.  

This supports what I heard at a composite repair course put on by a company 
that repairs composites for airliners.  They also recommend using a fine 
grade sand paper (240 to 320 as I recall) to provide maximum surface area 
with minimum damage to underlying fiber.  They wipe with solvent (twice_ 
prior to sanding and vacuum with a clean brush to remove dust.  Bonding 
within 4 hours of sanding is recommended because the just-sanded surface 
bonds better than one that has been sitting for a while after sanding.  (It 
was described as a "high energy" surface.  I leave explanations to the 
surface scientists.)  

Grinding away with 40 grit seems intuitively superior, but apparently 
science, experience and testing have proven otherwise.

Fred
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