coating a wooden boat with gel coat

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Mollyfish

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Hi everyone
Can anyone please advise me. I've got a rather leaky 30' wooden, carvel-built motor boat. I'd like to coat the whole of the hull - above and below the water-line with gel coat, and also all of the cabin house (everything but the deck). Can anyone tell me how to calculate the amount of gel-coating to buy (ie. how much per m2, so that i can estimate). also, any advice on what exactly to buy would be very much appreciated.

Thankyou
Molly
 
I hope you mean with epoxy resin. Gel coat is merely the decorative,glossy finish (supposedly waterproof) finish for GRP. It's part of the make-up of grp and is in reality, pretty brittle. It won't adhere very well to wood.

Epoxy on the other hand will penetrate the wood (once dried out) and form a tough barrier coat. Even so it doesn't move well with wooden joints. It works well on ply wood boats, quite well on carvel and not at all on clinker.

Have a read of This Article
 
There are all sorts of problems with what I think you have in mind.
The epoxy will soak into the wood nicely if it is done correctly but it will not do much for the joints which tend to move. Further the epoxy will have to be painted because it is susceptible to UV in sunlight.

Many more modern wooden boats are treated with epoxy in a fibreglass substrate. (sometimes known as the WEST system a commercial kit) Fibreglass itself is not the best however because it is stiff and doesn't easily follow tight corners. So you get voids (air pockets) Many years back a product called Dynell was promoted for this purpose. It is a synthetic cloth that is very soft although It think it has some strength and it holds the epoxy in a thicker layer. Done properly on a new round bottomed plywood or veneered boat it can look just like a fibreglass production boat.

My experience on a plywood boat many years back was very disappointing. (true I used polyester resin which is no good) but the fibreglass and resin became tatty and peeled off after only a couple of years.

My suggestion is that you repair the wooden hull leaks in the traditional manner. Sheathing will be just too expensive/ hard work. If you really want a fibreglass boat sell the wooden one and buy a f/g one. olewill
 
A s above fiber/resin sheathing has ruined many a good boat. Don't be put of traditional methods at least for the hull it's usually not that difficult and much cheaper. The notmal problem is that the topping has gone hard and cracked (its a modified version of glaziers putty). You will need somthing to clean out the joints which can be done with an old file or screwdriver but if dooing a 30ft hull would be well worth getting the proper toods frome somewhere like classic marine. At least some of the caulking (cotton string) will come out but get anything loose out and get the plank edges clean. You then drive in new caulking with another special tool (caulking iron) till the seem is firm. When the boat goes back in the planks and caulking swell making the hull watertight. Its finished off with some form of putty which might be putty+red lead or there are lots of different recipies all of which aim to stop the putty hardening to much. Then a coat of paint. Probably no more work than sheathing and should cost less than a gal of rein in materials + tools.

Topsides is more difficult and varies acording to construction. If you have ply cabin tops they can be epoxied. For leaks around the joint between deck and cabin sides I have found stripping off trim, raking out seams and redoing with Sickaflex quite good. Other areas you need to find out whats caused the leak. Give more details and might be able to advise
 
Sheathing an old boat rarely works even with expensive epoxy, otherwise we would all be doing it! As has been pointed out, using polyester resin and glass mat is the quickest way to wreck your boat. The resin does not stick to the timber for long, water gets in and creates ideal conditions for rot - which once started goes very fast as it lifts more and more of the resin off the timber.

Epoxying is also unlikely to work, as the timber has to be dried to around 15% moisture content - the less the better! This of course will have disasterous implications for an elderly wooden carvel hull. In any case getting a decently faired finish over sheathing is well nigh impossible without huge amounts of work.

Next consideration is that carvel hulls are designed to 'work' - that is to allow the component timbers to move slightly against each other. If the whole thing is epoxied, it will stop this happening creating unfair stresses on the old timber when the boat is at sea, or being lifted, which will cause major problems again fairly quickly.

Traditionally built boats require traditional methods of maintenance. As other point out, if you want the benefits of modern boat building materials, get a modern boat! There is no 'short cut' to repairing and maintaining wooden boats.
 
A friend of mine used a non-breathable coating on his carvel hull, the timbers had dried out on the hard and the impervious coating did not allow the timber to take up water and when launched it sank. If you have too then sheath, but don't try just coating wood with a high tech coating
Robin
 
thanks everybody....loads of guud advice! traditional methods seem tricky and risky for a novice - especially under the waterline. I re-did the deck with Sickaflex. It worked in many places, but leaked a fair bit in other! Any other suggestions.....anyting like stretchy rubber paint exist (hopeful i know!).

Thanks everyone.
 
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