GRP removal

[BetsieJane]

I've just finished laying up a grp deck on a motor crusier I'm restoring. Unfortunately, I recieved some duff advice and used polyester instead of epoxy resin and so it's got to come off. What is the best way to do this? It is a flush deck approx 20m sq. Cheers

 

[damo]

What's wrong with polyester resin /forums/images/graemlins/confused.gif

There are millions of polyester grp boats afloat

 

[charles_reed]

I'd leave well alone.

The original advice you got probably wasn't duff, as it was what a professional would certainly have used.

Polyester doesn't stick as well as epoxy, but it's far more uv resistant, easier to work, cures faster, and costs less.

 

[oldsaltoz]

G'day BetsieJane, and welcome aboard the YBW forums.

I assume the poly resin has been applied over ply and the concern is that it will not stick long term, is this correct?

Also the joint between hull and deck has been done with poly and is holding timber to poly GRP hull, is this correct?

Give me more details and I may be able to save you some time and money without compromising your build.

Avagoodweekend......

 

[BetsieJane]

Hi, the hull is wood and the grp laid onto new marine ply. Yes, my main concern is that it will not stick properly. Cheers from sunny Norfolk.

 

[Chrusty1]

Did you apply a couple of coats of thinned resin (acetone) before applying the glass mat to the job?

If you did, I reckon it will be ok, as the mat and resin will effectively be sticking to the resin in and on the plywood.

 

[boatbuilder]

The thinner for polyester is styrene, not acetone as this will just flash off. Plywood should be physically scarred then coated with accelerator on the area to be laminated.

 

[Chrusty1]

That is correct it will flash / evaporate off, but not before the resin has soaked in. It isn't really necessary to scar the wood, as the resin will stick well without doing that. Though I would concede that it can't do any harm to do so.

I have been doing it that way for years, and it works.

 

[oldsaltoz]

Ok we all know that poly resin will not stick to timber in the long term or under load, but you can remove the joit between deck and floor and treat this area only with an epoxy, also note epoxy not only bonds well to timber nut also to old or new poly resin resins.

Don't use CSM (Chopped Strand Mat), use only epoxy cloth, crows foot or bi directional is good in this application.

I would also consider grinding off the areas above the main bearers and laying epoxy on the stripped ply.

To aid penetration you can add 30% by volume to the mixed epoxy resin to thin it so that it will soak further into the exposed timber.

I Hope this helps.

Avagoodweekend......

 

[Chrusty1]

"Ok we all know that poly resin will not stick to timber in the long term or under load,"

That is also correct, but if the ply / timber has been given a couple of liberal coats of well thinned poly resin, that is soaked well in, thinned to about the consistency of thick water, the mat and resin applied over, will in effect be sticking to the previously applied resin, and it does stay there. it wont be as strong under load as you say, but a deck covering is hardly under load is it? /forums/images/graemlins/smile.gif

I have used this method on one of my boats, applied about 8 years ago, and it's still completely sound. agree about the cloth though, best to use woven mat, fairly fine, and if the job is done right it can look just like a canvassed deck.