Putting a new gel coat on old GRP!

[Zagato]

I am pretty sure you can put a new gel coat over old GRP on caravans. I wondered if anyone has done it, or heard of it in the boat world. It's probably prohibitively expensive to justify doing it but I think I read about one boat that had been done unless it was just cut back and polished!

If it can be done it might be worth doing if you intend to keep a boat for a long time!

EDIT this would be for the cabin, decks etc

 

[bikedaft]

would be good to be rid of painting the hull...

phoned a commercial grp repair firm - they reckoned to do it properly a mould would be best... (moulds for our boat probably disappeared about 20 years ago)

so not got very far on that one

 

[All_at_Sea]

Gel coat paint

I disagree it can be done and l know people that have done it. It goes on like paint and is then being cut back. All you are doing is adding a thin layer to the hull, the cutting back process gives you a good finish. It is a bit expensive but tougher than paint usually.

 

[bikedaft]

would love to hear more...

does it have the same expected lifespan as the original grp? delamination? etc

presumably if you get all the paint off and prep the surface with enough care these will not be issues? etc

(hate painting, would rather go sailing!)

 

[Zagato]

Hadn't thought about the hull, as you say you can cut the hull GRP back and re-do it. Many places will do this for you and have info.

I was meaning the decks, cabin etc which I didn't make clear!

 

[vyv_cox]

I have seen it done, on a 38 ft yacht in Greece. A DIY job done by a couple. They ground off the old gelcoat, faired as well as possible using sanders, then rolled new gelcoat on. Finally flatted with wet and dry and polished. Looked superb when finished but was a long job. They painted decks and cockpit with two pack paint and reckoned it was far easier to work with the gelcoat than the paint.

 

[john_morris_uk]

We had our topsides ground off and re-gelcoated a few years ago. The end result was very very good and has been much admired. It cost a bit but it was worth it.

 

[Coaster]

We had our topsides ground off and re-gelcoated a few years ago. The end result was very very good and has been much admired. It cost a bit but it was worth it.

Can you please tell us the name and contact details of the contractor?

 

[SAMYL]

Is that not what they do when treating osmosis? Peeling the gel coat off and replacing with a new coat of tissue and resin or whatever?

I would like to get it done on an old fibregalss bodied car.

 

[johnphilip]

What benefit with gel coat?

I gather the OP was considering the inside of the boat but our experience with topsides seems relevant.
In 1987 ther was a BIG wind and our Hunter Delta was dragged along the river bed on her side, leaving the topside as though it had been very coarsly sanded. Solution, professionally applied two part Blakes(now Hempel) The result was a really tough finish which has stood the test of time. I believe it is tougher than Gel coat. We no longer own the boat but still see her occasionally on the Orwell and the blue hull still looks good, not faded as happened with all the original Hunter gel coats. That's a long time for one application of paint.

 

[nimbusgb]

It's a labour intensive job but perfectly feasible.

On a 12 metre boat you have about 25 square metres of topsides gelcoat to sand back, coat and then cut back and polish. Work on a starting price of around £200 / sq metre.

 

[Avocet]

Is that not what they do when treating osmosis? Peeling the gel coat off and replacing with a new coat of tissue and resin or whatever?

I would like to get it done on an old fibregalss bodied car.

A car would be a nightmare. It's a hard enough job on a boat, but because boats are relatively simple shapes, it's just about do-able. a car, with all it's complex shapes and shutlines would be an absolute nightmare. Also, you can get away with the sort of finish on a boat that would be totally unacceptable for a car.

 

[Reverend Ludd]

What about using a coating of Vinyl ?

Saw an article in one of the mags and it looked pretty good.

 

[alahol2]

I'm a bit confused (not unusual). How does gelcoating differ from flow coating, which is often mentioned in other threads?

 

[bignick]

Flowcoat is just gelcoat with wax added, which rises to the surface when curing. As a result you can't overcoat it as nothing is supposed to stick to it. You therefore need to build up the gelcoat to fill any imperfections, cut back flat and then add a final layer of flowcoat. The wax layer helps protect the gelcoat which is left. Or you can just use gelcoat then give a really good polish. Or coat with one of the acrylic sealers.... etc etc. You can get the wax additive and add it to the gelcoat yourself if you like to make your own.

 

[alahol2]

Ah, so only one coat of flowcoat possible, makes sense. Thanks.

 

[William_H]

Gel coat

Agree with Johnphillip. A 2 pack polyurethane paint both sticks better and is tougher than original gelcoat.
Gelcoat of course sticks well when the boat is built because it is chemically bonded to the hull. But polyester resin (gel coat) does not stick so well to cured polyester resin. Both epoxy and polyurethane stick better than polyester but of course epoxy is not good in sunlight.
I would recommend a 2 pack paint over the original gel coat. I brushed polyurethane on my hull. It is no where near as good as spraying for gloss etc. but polyurethane is very poisonous as a vapour. I find that the hull and deck get marked so each winter I can easily touch up the paint so while it never looks brilliant it never looks really tatty.
One problem is that paint will smooth out your non skid on deck. You can use non skid paint or Intergrip particles in the paint but never quite as good as original. good luck olewill

 

[nimbusgb]

2 pack paint will never stick as well to the original as gelcoat will.

Having refinished 2 aircraft in gelcoat and owned one with a 2 pack refinish I am talking from experience.

8 years on the first regelled aircraft was as good as the day I rolled it out of the workshop. 2 years after repainting the other was showing signs of paint delamination.

 

[bikedaft]

2 pack paint will never stick as well to the original as gelcoat will.

Having refinished 2 aircraft in gelcoat and owned one with a 2 pack refinish I am talking from experience.

8 years on the first regelled aircraft was as good as the day I rolled it out of the workshop. 2 years after repainting the other was showing signs of paint delamination.

yip

got a 39 year old boat with original gelcoat, comes up well with oxalic acid

got another boat that was painted (well) 3 years ago in 2 pack paint. will need repainted in 2-4 years :-(

 

[nimbusgb]

Let me just say that car paints are incredible. They shrug off abuse. My 11 year old white Ford Galaxy never went under cover and spent 2 years in a Greek boatyard, unloved and in the salt and heat. A quick wash and the basic paint was back to as good as new.

It just doesn't stick to glassfibre as well as it could and I suspect that the lack of a clear coat might have a lot to do with the apparent lack of longevity on boats ( and aircraft ).