If it just small cracks then laying down more cloth is probably
overkill. I'm going through the same kind of exersize after
removing my teak decks. If the old surface is gelcoat, then
laying cloth over it is a bad idea. The gelcoat will have to be
removed to get to the existing glass. The secondary bond
characterists of resins over gelcoat is not good. The
solution that I am using is applying 2 coats of epoxy barrier,
then a 2-part polyurethane finish.

Doug
s/v Callista

wrote in message
...
I have a houseboat whose roof has a bunch of thin
spider cracks, as well as some a bit bigger. The
biggest ones aren't wide enough to get any more than
a razor knife blade in, if that. I want to put some more
fiberglass sheet on it, and have never done that before.
Having talked to several people about it, the following
is pretty much the impression I've developed about
doing the job, and I'd appreciate any more suggestions
or advice people are willing to sha

· First, use something like a thin wheel on a grinder and
dig out the larger cracks, then fill them in with rosin to
make them strong...if that's not done before sanding,
the cracks will fill up with dust and never get strength
from rosin entering them.

· Sand the area with medium grit sandpaper.

· Clean area with acetone.

· Cut fiberglass cloth to fit the area, then staple in place.

· Saturate the cloth with rosin using a roller. Best to set
up a cover like a tarp, because in direct sun the rosin
could set up too quick.

· After all that has been done and dries, apply gel coat
...I've heard to apply 1, 2 and 3 coats, so as yet don't
have a good idea of how many to apply.

One of the things I'm still trying to figure out, is how to
deal with the excess rosin which will want to drip down
the side of the boat. Can anyone suggest any good way(s)
of dealing with that issue?

On Fri, 13 Aug 2004 17:25:37 -0400, "Doug Dotson" wrote:

If it just small cracks then laying down more cloth is probably
overkill.

I want to add some strength to it. It still feels strong, and
there aren't any spots I feel a danger of falling through, but
it's 30 years old too. I'm thinking if I add another layer of cloth,
or maybe even 2, it should last another 30 years. I'm 45, and
would like it to outlast me.

I'm going through the same kind of exersize after
removing my teak decks. If the old surface is gelcoat, then
laying cloth over it is a bad idea. The gelcoat will have to be
removed to get to the existing glass. The secondary bond
characterists of resins over gelcoat is not good.

Thanks for that. Other people have said the same thing.
I have two possible approaches in mind in an attempt to
overcome that problem.
1. sand it off, down to the old glass
2. apply a layer of 1/4" plywood

(the following is posted twice in this thread):
I've been told that if I use plywood, unless I use marine grade
it will eventually buckle and swell because only marine grade
is treated in a way which removes all moisture from the wood.
So even if I get a good seal on it, unless I use marine grade
the moister which is contained in the wood will make it swell.
That doesn't really make sense to me since if it's not swolen
when I put it on, I don't see why it would swell later if it doesn't
absorb any more moisture, but two different people have told
me the same thing.

The
solution that I am using is applying 2 coats of epoxy barrier,
then a 2-part polyurethane finish.

Doug
s/v Callista

Thanks again....I'll look into doing that.

wrote in message
...
On Fri, 13 Aug 2004 17:25:37 -0400, "Doug Dotson"
wrote:

If it just small cracks then laying down more cloth is probably
overkill.

I want to add some strength to it. It still feels strong, and
there aren't any spots I feel a danger of falling through, but
it's 30 years old too. I'm thinking if I add another layer of cloth,
or maybe even 2, it should last another 30 years. I'm 45, and
would like it to outlast me.

I'm going through the same kind of exersize after
removing my teak decks. If the old surface is gelcoat, then
laying cloth over it is a bad idea. The gelcoat will have to be
removed to get to the existing glass. The secondary bond
characterists of resins over gelcoat is not good.

Thanks for that. Other people have said the same thing.
I have two possible approaches in mind in an attempt to
overcome that problem.
1. sand it off, down to the old glass

The only way to lay down new glass reliably.

2. apply a layer of 1/4" plywood

So how would you bond the plywood to the gelcoat?

(the following is posted twice in this thread):
I've been told that if I use plywood, unless I use marine grade
it will eventually buckle and swell because only marine grade
is treated in a way which removes all moisture from the wood.

I doubt it. From what I understand, marine ply just has waterproof glue and
fewer voids.

So even if I get a good seal on it, unless I use marine grade
the moister which is contained in the wood will make it swell.

I suppose that it depends upon how the ply was stored prior
to you laying it down.

That doesn't really make sense to me since if it's not swolen
when I put it on, I don't see why it would swell later if it doesn't
absorb any more moisture, but two different people have told
me the same thing.

Swollen indicates sever moisture content. It can look totally fine
but still have high moisture content. Once you seal it in then the
moisture can cause problems. The best solution of you feel that you
need additional strength is to grind off the gelcoat and lay down
glass.

The
solution that I am using is applying 2 coats of epoxy barrier,
then a 2-part polyurethane finish.

Doug
s/v Callista

Thanks again....I'll look into doing that.

If you don;t need additional structural strength, then this seems to be
sufficient.

wrote in message
...
On Fri, 13 Aug 2004 17:25:37 -0400, "Doug Dotson"
wrote:

If it just small cracks then laying down more cloth is probably
overkill.

I want to add some strength to it. It still feels strong, and
there aren't any spots I feel a danger of falling through, but
it's 30 years old too. I'm thinking if I add another layer of cloth,
or maybe even 2, it should last another 30 years. I'm 45, and
would like it to outlast me.

I'm going through the same kind of exersize after
removing my teak decks. If the old surface is gelcoat, then
laying cloth over it is a bad idea. The gelcoat will have to be
removed to get to the existing glass. The secondary bond
characterists of resins over gelcoat is not good.

Thanks for that. Other people have said the same thing.
I have two possible approaches in mind in an attempt to
overcome that problem.
1. sand it off, down to the old glass

The only way to lay down new glass reliably.

2. apply a layer of 1/4" plywood

So how would you bond the plywood to the gelcoat?

(the following is posted twice in this thread):
I've been told that if I use plywood, unless I use marine grade
it will eventually buckle and swell because only marine grade
is treated in a way which removes all moisture from the wood.

I doubt it. From what I understand, marine ply just has waterproof glue and
fewer voids.

So even if I get a good seal on it, unless I use marine grade
the moister which is contained in the wood will make it swell.

I suppose that it depends upon how the ply was stored prior
to you laying it down.

That doesn't really make sense to me since if it's not swolen
when I put it on, I don't see why it would swell later if it doesn't
absorb any more moisture, but two different people have told
me the same thing.

Swollen indicates sever moisture content. It can look totally fine
but still have high moisture content. Once you seal it in then the
moisture can cause problems. The best solution of you feel that you
need additional strength is to grind off the gelcoat and lay down
glass.

The
solution that I am using is applying 2 coats of epoxy barrier,
then a 2-part polyurethane finish.

Doug
s/v Callista

Thanks again....I'll look into doing that.

If you don;t need additional structural strength, then this seems to be
sufficient.