I'm in the middle of doing the same repair on my sailboat. I have the
entire interior removed from the boat as I had rotted bulkheads as
well. I used an angle head air die grinder with a rotozip ultra bit in
it. The bit looks like a straight shaft with a very coarse cross hatch
pattern in it. I found nothing that cuts the interior fiberglass
easier or more accurately. After removal of the interior layer of
fiberglass, the rotted and wet balsa was easily removed with a hammer
and chisel. Below the balsa core was the glue that was used to adhere
the balsa to the outer shell. Grind that off. I attempted vacuum
bagging to apply pressure to the new balsa core to the outer shell,
but I could never get it to seal. In the end I found that I could get
good adhesion with epoxy thickened with cabosil. I pressed the balsa
into place and held it either by hand or propped it up until the epoxy
started to kick off. Then came the fiberglass. I used 18-8 stitch mat.
It's heavy and hard to wet out, but one layer appears to be enough. I
used thickened epoxy to keep the overhead peices from sagging.

Before starting this project I read a lot of articles on the internet.
Do a search for "balsa core repair"


Oysters8 wrote in message news.com...
I have several places in the coachroof of my cat that are delaminated.
Two are soft (i.e., wet), one is crunchy (i.e. dry). It's composed of
balsa between layers of fiberglass. I have very little fiberglass
experience, but would still like to repair these myself and was
wondering:

1) where I can get some instruction (lower Chesapeake Bay in Virginia).
2) is it reasonable to ask a fiberglass repair person (I'll pay) to
repair one while I watch to learn. Then I'll do the other repairs. If so,
how do I find this person?
3) can you offer some helpful advice.

Thanks in advance for your replies.

Ed