View Full Version : removing grp from wood...

02-11-2010, 08:29 AM
Seen a cheap and rather elegant 25ft wooden launch, looks to me like ex- Thames River Police, 45hp lister diesel...that has been horribly plastered with resin and glass that the owner thinks is a big 'plus'...at least it's watertight...but ooooh so ugly
anybody ever stripped this 'repair' off back to the wood, or should it be smoothed and finished in situ..... ? the outside looks like the inside of a grp hull....

George Ray
02-11-2010, 09:00 AM
I have found that GRP if polyester will peel off after you lift an edge of the laminate. It can be done using chisels, putty knife, flat pry bars ends, blowing compressed air, water under pressure under the sheet edge. Little or no damage to wood in my experience. Scoring the glass to or almost to the wood so the peel can be done in smaller sections is advisable but not alway necessary. Scoring can be a skill saw set to a tiny tiny depth of cut, it can be a side grinding disk used very carefully to sand 'almost' through the glass, it can be a razor knife along a straight edge, it can be a chisel and hammer slowly and carefully making a cut line.

Big wide expanses usually present little problem. Places with cutbacks, curves, molded shapes, etc is where the scoring is really needed.

If it's epoxy resin then it may not peel, don't know.

Ian McColgin
02-11-2010, 10:43 AM
Use a heat gun - be careful! - to soften the bond. That way the lifting George Ray advises will go a bit easier. I go ahead and peal once it's started well into cold areas so long as it's easy and not lifting any wood then shaking the heat gun and pushing the putty knife where it gets a bit stiff.


02-11-2010, 11:18 AM
I soaked a wood hull from the inside that had fiberglass and polyester resin applied to the outside.

I then applied heat from the outside - as that area began to steam, I gently peeled with a putty knife. It seemed to work well - the 'glass came off in strips and didn't bring much wood with it.

There is a definite difference between trying to remove fiberglass that is saturated with epoxy versus fiberglass saturated with polyester resin. The polyester doesn't seem to bond to the wood all that well.

02-11-2010, 11:56 AM
I've used a length of hose fitted onto the spout of one of those old-fashioned metal 5 gallon motor oil cans. With the can half-full of water on top of the stove or on an open fire by the boat (assuming you're working outside) you have a source of wet steam heat. Pry away the FRP sheathing up at the top, and stick the hose down as far as it will go, and let the steam heat do its work. This method is less likely to scorch and burn either the boat or the worker, and I think that the temperature is low enough so that you get fewer fumes from the polyester.
Sometimes the glass cloth or matt will pull off in great sheets, but before going nuts with that make sure that you aren't: a) taking off a lot of wood with the sheathing or b) leaving a lot of polyester stuck to the hull, which will need to be scraped or sanded off. So anything that can relax the grip of the polyester is good.
By the way, the steamer rig described above also works for heating up 5200, which makes it a lot easier to remove, and can be used for steaming wood.
The "deluxe" version of this is a army-surplus "jerry can," which can be laid on its side over a wood fire, or set up on end on one of those portable propane burners that people buy now to deep-fry turkeys out in the backyard.

02-11-2010, 02:13 PM
Having only just got round to the thread on ferro- cement sheathing I see a lot of my thoughts have been addressed, and I am starting to think make good what's there by filling and fairing....after all, aesthetically , unless a wood hull is varnished, the effect will be the same as any well painted hull, and there are advantages of sheathing even if it goes against the purists' grain....

Assuming all's well stucturally, it would certainly be a cheaper way to go with the appeal of the wooden interior being able to have more time spent on it...
as if I need another project right now.....

02-13-2010, 10:21 PM
Grinding down a rough FRP laminate that's been in service is not a good job. First you grind off slime, glurk, paint, then maybe gelcoat, they kicked resin, then you get to the glass.
The problem is that to get a good secondary bond you have to grind down all the resin that's been on the outside, AND remove all grease or oil. With a lumpy hull, that means a lot of grinding of glass to plane off the "humps" of material so that you can grind/degrease the "valleys"
Better than removing the old and starting over? Maybe. That's a big job too.

02-14-2010, 06:54 AM

if the class sheating (epoxy?) is ok, watertight and has a good bound to the wood, I would let it be where it is. Even if it is old, it should protect the hull in a good manner. Remove just the old and loose paint and apply a layer of filler to be sanded by long board and sanding paper.

If the glass sheating is lousy ,loose and not bounded proper to the wood, try a high pressure water cleaner. Sometimes the glass sheating blows off with this alone. If the wood is some kind of hard wood, it normally can stand the pressure of the water cleaner very well. But test it very carefully!!!!!!!

Grrreetings from the North Sea Coast, Michel

02-16-2010, 01:16 PM
Had another good look at the boat earlier, and yes Michel, it seems sound and well adhered so IF I go for it, that's what I'll probably do.... Biggest is problem is aesthetics ... even filled and faired it will I think, look like a toffee apple or something dipped in chocolate....! ....the shape is there but all sort of blurred edges and no hard lines.....The owner is in a mess too, and if it doesn't sell it will get trashed as he can't pay the storage/mooring
Can't bear to see it happen but it might be the outcome if muggins here doesn't step in....