Sanding composites

Roger wrote:
On 27 Jan 2005 01:04:49 -0800, wrote:

How do you know when you're beginning to sand into the glass cloth?
Do
you simply sand until you
have a smooth finish, then stop? Ot do you keep going?
thanks,

Are you sanding to get a smooth finish or to prepare for the next
lay-up?

If you are getting ready for the next lay-up you are sanding to
"rough
up" the surface to get a good bond to the next layer, not smooth it.

With Vinyl Ester Resin I use 60 or 80 grit (hard to get a smooth
finish with thatG) and just rough up the area. I then vacuum the
area clean and follow up with an Acetone wash. With the area dry or
just barely tacky I do the next lay-up.


For smoothing, as opposed to scuffing, has anyone tried scraping
instead of sanding? Using a scraper like this:

http://www.leevalley.com/wood/page.a...=1,310&p=32669

one can get a finish on wood roughly equivalient to sanding down
to 320 or 400 grit. Scrapers are especially good for removing
bumps and runs in film finishes like shellac and varnish so
I'd imagine that they'd do a good job on hardened epoxies and
resins too.

The cabinet scraper is not a paint scraper, it is a much more
versatile tool. Proper tuning of the scraper is a bit of an
art form but with an understanding of the process and a little
experience one can remove a large amount of material, or only a
small amount with each pass. It is much cleaner and faster than
sanding because it raises shavings instead of making dust.

--

FF