Glassing over ply decks etc.

[whitewings]

I have a similar question to "GRP people in Hamble" - Eric_Cartman.

I own a T24, GRP hull, ply decks, cockpit and cabin coachroof etc. Great under sail, but some of the ply is begining to look a bit sad. I read a recent article in PBO where someone glassed over ply decking and it was mentioned there was going to be a subsequent feature on this. Its the usual story, I don't have much money but lack the skills or environment to to the job myself. Can anyone recommend a company (s.coast/soton) who would make a good job of this at a reasonable price. What kind of bill would I be looking at?

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[Prospero]

At the SIBS last year I picked up a leaflet from Wessex Resins (West System) offering two courses on using epoxy, one for beginners, an introduction, and the other on the repair of GRP boats. The courses are held on a Saturday and cost £105 each including lunch. I did the introductory course in February and intend to do the more advanced one in the future. The course gave the opportunity to play with epoxy, assemble a toolbox and one left with a collection of materials, altogether a day very well spent. Among the techniques demonstrated was glassing over wood. The cheapest way by far, IMHO, would be to do the course, I think they run them in the Autumn and Spring, and then do the job yourself. You leave the course full of confidence in your abilities with the material and certainly to date it has not let me down. Wessex Resins are at Cupernham House, Cupernham Lane, Romsey, Hants. SO51 7LF, Tel. 01794 521111. If you're going to SIBS you should be able to talk to them there.

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[LittleShip]

GRP is probably not the best covering for ply, as it sticks too, rather than bonds too!! You should use epoxy for this job. Have a look at this site and give Rob Hewitt a ring if you need advice. I have no connection other than a satisfied customer
<A target="_blank" HREF=http://www.epoxy-resins.co.uk/>http://www.epoxy-resins.co.uk/</A>

All the best


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I wish I'd been born rich instead of good looking ?

 

[pampas]

Didnt know a thing about glassing over wood, but have been assured by our local supplier that Polyester Resin does not bond to wood very well and will eventually part company. Use Epoxy and light woven roven, the task seems daunting, but is quite easy if one can get under cover(Sheet), low humidity and not to cold, preparation will pay off in the long run, Good luck its not so hard as you think and a lot cheaper to do yourself. If you are going to have a go buy a container of PARR (LOctite resin remover) for your self its great for cleaning hands.

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[Joe_Cole]

John,

If you are based in Gloucester then give Matrix Mouldings, in Bristol, a call. If you speak to the boss then he'll be more than helpful, he knows about boats and is a mine of information. Better still go and see them. Really helpful people, after 10 minutes talking to them you'll be wanting to do the job yourself! The number I have is 0800 0744788, but it may be out of date. I think that they have a web site.

Joe

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[oldharry]

GRP as such on old ply is a recipe for disaster! Polyester resin does not stay stuck to wood for long, and water is drawn in as the bond fails, and stays there. Water + wood = ROT! Its the fastest way to wreck a plywood boat.

Epoxy is a distinct possibility, BUT and its a big BUT: the ply must have a low moisture content - around 15% - which is not always acheived even with new ply if it has not been properly stored. Any higher and the epoxy simply cannot bond.

Snag 2 is that epoxy is not cheap! And if you can not do it yourself, then it will be a great deal more expensive. First of all ALL the paint has to be removed - absolutely all of it, exposing the bare timber. This is even more difficult than it sounds with old wood where the paints may have penetrated the grain.

Snag 3 the underlying ply must be sound. The expensive epoxy coat will just come straight off again if rot has already got hold.

Far cheaper, better for the boat, and for your pocket have the old ply off and replace it. If there is rot, this will not be difficult, and you will also be able to check it has not got in to the frames and gunwaling a distinct possibility where there has been water ingress.

Once your nice new play is in place it is well worth coating or sheathing it with one or another of the available epoxy sheathing systems, which will then outlast the hull.

And that raises the next point.... if the decks are that bad, what state is the hull in? Before you start throwing quite a lot of money and effort in, is the hull sound enough to be worth it?

The beauty of plywood boats is that they are infintely and easily repairable. The problem is that once they reach a certain age (around 25 years as a rule for an unsheathed hull) they start needing an infinite amount of repair....

I have a 23 year old plywood Eventide which was Cascovered from new, and it is in excellent condition - except where water has penetrated past 'add ons' that were not properly bedded and sealed down, and a point where a 'repair' was done and resheathed with Polyester resin a few years ago (looks like impact damage). The whole lot and quite a bit round it has to be replaced this winter.

A couple of years ago A guy in our yard bought a plywood Seamew that had been GRP sheathed. It leaked a bit so he invetigated - the entire sheathing 'came away in his hand' - literally! Sadly the ply beneath was beyond redemption. But as someone said in the bar that night - at least he had a mould to lay up a new GRP hull for himself!

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[William_H]

I agree with oldharry. Polyester on wood is hopeless. Epoxy is better but expensive. Any plastic work needs warm conditions so you may run out of time if you intend to do the job outdoors. if the wood is bad I suggest replace the ply. If not replace it then clean it up. I think if it was me I wood then give the wood lots of proper wood paint, primer undercoat etc or alternatively clean off all the paint and give it lots of Polyurethane 2 pack paint which should penetrate the grain and strenthen the wood. You can't use polyurethane over oil paints as it disolves the old paint. I am not sure my advice is good but this way would keep the boat original and be easier to do and to continue to do.
The problem with polyester resin is it really only sticks to itself and it shrinks in the hardening process. To successfully sheath a deck you would need to put so much glass and resin on that the wood becomes redundant because if the sheath is not thick enough it starts to flex and separate from the wood. Then you can end up with it too heavy. If you do go fibreglass definitely do it yourself. You can practice on old wood first and it really is fun. But then I am one who would rather do it myself badly than pay someone else to do it well. DIY compulsion. regards will

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[oldsaltoz]

Please note:

Epoxy resin is not that expensive when you consider the following.

Standard wax or poly resins require a ratio of 3 parts mixed resin to one part cloth (or chopped strand).

Epoxy resin requires a ratio of only one part mixed resin to one part cloth.
provides a secondary bond and is stronger but less flexible but a lot lighter.

NEVER used chopped strand with epoxy resins, you will end up with too much resin [expensive]
and a weaker structure.

epoxy resin cloth is designed to be rolled out to the max, leaving a lot less resin and weight than a wax based system
Because you end up using less resin and less cloth to get the same strength, epoxy is not that expensive.

Avagoodweekend.............



<hr width=100% size=1> Old Salt Oz /forums/images/icons/cool.gif Growing old is unavoidable. However, growing up is still optional.

 

[whitewings]

Thanks to everyone for all the advice. I think I need to learn more about the materials and different processes/applications on a short course.



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