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chrishelen

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On the underside of my hull there are one or two, maybe more little holes in the paintwork revealing the ply,the ply itself seems to be in good nick,my question is what is the best method to fill these in and make it water proof again?
 
Is the ply sheathed, or epoxied? If so epoxy filler once the wood has dried out. If just an ordinary paint coat, sand back making sure the paint is sound and properly adhering to the timber, prime and undercoat in the usual way, then fair up using a filler before applying topcoat or antifoul - or just live with a bit of a dip in the paint coat where you cant see it!
 
Its sheathed in cascover by the looks and on futher investigation it has lifted in some places where the ply is screwed into the beams.
 
Cascover is a good system and extends the life of the hull considerably. Repairs: you need to clean back and cut out the sheath anywhere it is loose, making quite sure you are back to a sound bonding. The ply needs to be thoroughly dried out (use gentle heat) then you can patch the area using a fine woven glass cloth and epoxy. A small area can be done using epoxy filler.

Alternatively, if the wood is very damp, epoxy will not take, so buy some Cascomite resin glue (a white powder which is mixed with water to make the glue), and repair it with that and suitable glass cloth.

Others may know what other glues can be used succefully.
 
Thanks Harry,i was at the boat earlier,the biggest hole in the sheathing when cleaned back to sound is about an inch,do you think epoxy filler would do the job?
 
Yes, but be a bit careful if the wood is wet underneath. Epoxying will bridge the hole, but unless it seals to the timber, could leave a void. If water then gets in the wood will start to rot under the sheathing. Same appllies anywhere the sheath has lifted. Epoxy needs ply with no more than 15% moisture content
to bond 100% - thats around what you would find in new ply from the store, so it does need to be really dry to get a good seal.

If the boat's been out for several months it will probably be OK for an epoxy repair, but if not you would probably do better with Cascamite, which is activated by water anyway, so is more likely to adhere to moist timber better.

Cascamite is a synthetic resin glue based on Urea Formaldehyde, and is also marketed as Resinmite or Extramite. It has a much longer shelf life than Epoxy, is cheaper, and is what was used for the original sheathing anyway!
 
I have a cascovered Eventide (was yours built by Hartwells?) and I have always used epoxy and glass cloth to make repairs of the type you describe. I make sure the ply is dry and score the outer veneer before coating with epoxy thickened with silica. Then laminate the cloth to bring it more or less level with the existing sheathing then fair with epoxy/microballoons. I have repairs more than 20 years old that are still good.
 
Yes, I learned about cascover repairs on an Eventide too (non Hartwells). Epoxy is fine, provided the wood is dry enough, but I have seen it lift off timber that was too wet, and it does seem Chrishelen is concerned his wood is too damp for an epoxy repair at this stage.
 
Thanks Tranona,my eventide was built by Barry Jones at Burnham between 1984-6,she is Marine ply on the hull and cascovered from the gunnels down,she came out of the water at the end of November last year and is going back in in March,Whilst i was crawling about underneath the hull on saterday i was alarmed to see a speck of bare ply through the antifoul,scracthing at it with my finger nail pulled a little bit more off until i got back to sound paint each about an inch in dia,there are 3 or 4 areas like that usualy ontop of screws holding the ply in place,all i want to do is make these watertight,the ply looks dry and sound.
Chris.
 
Chris

I suspect that the heads of the screws were either not filled or filled with something like Brummer stopping before sheathing and adhesion is locally poor. However, I am surprised that the sheathing has failed to the point that the ply is exposed.

I would still go for taking the damage back to sound sheathing and using epoxy. At this time of year you may have to raise the temperature for a cure. The most effective way is to make a tent around the area with polythene and use a fan heater (assuming you have electricity).

Hope this helps
Stewart
 
Thanks Stewart, itd only one or two screws at the moment,i will wait for a bit and decide on the best course of action,Thanks again.Chris.
 
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