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I did return to the manuals to find out why I was using #80 sand paper for
surface prep instead of #40.  The 320/360 manual in the first chapter
covering the various building techniques says to use #80 in the section
describing how to prepare the surface for the structural adhesive, the next
section where it describes prep for glass bonding it omits the reference to
a grit number.  There are various places in the manual where it instructs to
sand the surface and then clean with MC.  I believe that this is a
mistake.......a communication error, and the author intended to say bond
according to the steps in Chapter 1.  Whatever the manual says, my informal,
unscientific experiments indicate that cleaning after sanding is not a
proper preperation.  I did get the bond to fail a couple times when cleaning
last.  But the bond has never failed when sanding last.

Curtis Krouse N753K

-----Original Message-----
From: Fredmoreno@aol.com <Fredmoreno@aol.com>

>
>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.)


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