cockpit_clara
new user
Reged: 21/05/2008
Posts: 3
Loc: at sea
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please excuse what may be obvious to you experienced folks, i am a newbie.
What does it mean, marine ply epoxy sheathed what would i look for in so far as faults, problems? etc
many thanks
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Tranona
regular
Reged: 10/11/2007
Posts: 1466
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Could be a can of worms - but could be great. The key things to look for are
Delamination of sheathing (which should be glass cloth) from the ply
Water ingress at edge of ply if not completely sealed
Overlaps at chines or around transom and stem
Anywhere holes have been drilled for fittings
If done properly this is a very good method of construction, but expensive and difficult to do properly, particularly on an existing boat.
You can get good technical information from Wessex Resins who distribute West epoxy.
Hope this helps
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boatbuilder
regular
Reged: 05/04/2005
Posts: 1692
Loc: Millbrook, Cornwall
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Go to library and get" Gugeon bros on boat construction" it will tell you just about all there is to know on the subject. 
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meldrum
regular
Reged: 01/05/2008
Posts: 81
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I would definitely go for sheathing on a ply boat, providing it is done correctly. My yacht a 44 year old water witch was sheathed when built and the hull and ply is still in good condition.
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oldharry
regular
Reged: 30/05/2001
Posts: 3906
Loc: North from the Nab about 10 mi...
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I agree with Meldrum: a plywood boat has an average life expectancy of around 25years. Sheathed, and properly maintained, that can be more than doubled. Properly epoxy sheathed from new is best of all as you get all the benfits of a timber hull, with the durability of epoxy. But - and its a key factor - it MUST be done from new before the boat ever sees the water. All modern glues need the wood to have less than 15% moisture content - preferably half that to adhere properly.
A polyester GRP sheathed hull on the other hand will last about 3 years.... !
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If you cant fix it, get a bigger hammer...
Edited by oldharry (23/05/2008 22:50)
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Tranona
regular
Reged: 10/11/2007
Posts: 1466
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Older sheathing used a process called Cascover which is cloth set in cascamite glue and which was even more tricky to get right than epoxy. But if it is right it is IMHO unbeatable. Mine was done in 1963 by the firm that was the forerunner of Wesex Resins and the hull ply is like new. Where I have repaired it in places like the stem where you can get damage, I have used West and glass cloth.
Unfortunately they only did up to the gunwhales so there has been rot on deck and coachroof and I have always used epoxy, reinforced with glass cloth if necessary for repairs.
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Englander
regular
Reged: 07/09/2001
Posts: 15310
Loc: Barcelona/Bollyolics
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My boat was cascover sheathed from new, in 1965, to 6" above the waterline, there is no rot in the hull atall and never has been. So it does last if done well. There is some damage to the keel edges, due to crushing of the keel, when put on blocks, when slipped, but I repaired this area, with just thickened epoxy, this has lasted 10 years so far, and I have just checked it.
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