Lew Hodgett wrote:

RG asks:



I need to add 3 coats of cloth to re-enforce the hull of my boat. I seem


to


remember that one should NOT wait 24 hours between each application, or


one


would have to sand/grind the surface to wax??? Is that correct, and what


is


the best time to lay the second and third coats?

The area is about 4 x 4 inside of the hull, so I can pretty well time the
applications as I please. All help appreciated. Thanks RichG



"Brian Nystrom" writes:



You have options.

1) You can lay all thee at once, if you feel comfortable doing so. One
shot, all done. You may be less likely to end up with excess resin in
the laminate this way.

2) You can allow the epoxy to reach a "green" cure between layers. This
makes subsequent layers easier to position.

3) You can allow 24 hours and still be able to lay consecutive layers
without sanding (assuming that you use a non-blushing epoxy), as the
epoxy will take longer than that for a full cure and will still
chemically bond between layers. While it varies from one product to
another and with the temperature during curing, some will still
chemically bond within 72 hours.

4) You can wait for a full cure, then sand between coats. This produces
a mechanical bond only. 1, 2 or 3 three if preferable.



All of the above get the job done.

Personally, I purposefully wait at least 48 hours between layers for the
following reasons:

1) Can feather the edges of the glass to have a smooth transition between
layers.

2) Level out any uneven surfaces and any resin blobs that maybe you missed
during lamination.


You can do both of these things with a scraper when the epoxy is still
too soft to sand. It's less work and it doesn't create dust.

--
Regards

Brian