sheathing C&N

[cpthook]

I have 30ft C&N cutter in Dubrovnik. She was hauled and stripped
last Autumn. The topsides and her beams were in good shape but
rot was found where the keel joins the stern. This explains the
alarming amount of water she was taking on under sail.

Apparently fixing it would have involved considerable expense and
so I decided to have her GRP sheathed instead.

My questions are: is it possible to effectively GRP sheathe over
expoxied Iroko? How can I check they have done a good job and
the GRP is properly "taken"? ie not delaminated and is of adequate
thickness/strength? Can I take the sheathing off at some future time
and do a proper wood repair? What happens if the wood underneath
continues to rot?

I am slightly worried that the sheathing is being carried out outside
and I am being told they have to wait for the right weather. Is this
something to be concerned about?

Thanks in advance.

 

[Mirelle]

The history of glass sheathing is frankly not good. What is the hull construction? I would not do this with a conventional carvel hull.

The underlying problem is not being dealt with - the boat's centreline structure remains weak. The stresses from the ballast keel act through this point in the boat.

 

[cpthook]

hi,

The hull is believed to be a hardwood like iroko. It is carvel and expoxied
throughout. The shroud supports are rotten and around the hull along the
joint between the port and starboard bow from deck to waterline. And of
course the keel/stern join. So she'll still be dangerous after epoxying?
We sailed her down from Split to Dubrovnik last September in relatively
bad weather, oblivious of the damage. Presumably the keel could have
simply dropped off?

 

[Peterduck]

It sounds to me as though you were lucky to get as far as you did. Sheathing is like putting cosmetics on an ugly face to make it beautiful; it's still ugly underneath! I do believe that you have to bite the bullet and address the weakness around the stem and deadwood [keel - sternpost joint]. These are highly stressed areas, and repairs are not being done to make the boat look good, they are being doen to make it stay together, so that it doesn't sink under you. Fibreglass won't look like a good investment when you're swimming!
Peter.

 

[burgundyben]

I think the other are right, you must repair the structure of the boat, absolutley essential, however, in addition I think sheathing with grp is ok, I know of a power boat built 1936 that was sheathed some 30 odd years ago and is fine.

"Who was he?"

 

[fedor]

repairing deadwood?

Folks, completely irrelevant question: how would you go on repairing a rot in deadwood?
As far as I understand it (very roughly) consists of several planks laid on top of each other, tightened by vertical bolts (in some cases the same bolts which support your ballast keel)

I am scratching my head and cannot find any solution.. to completely replace some planks in deadwood you will have to lift the boat by the keel somehow, remove the ballast casting,replace the plank and put it all back together.
I can imagine how ballast can be removed - jack the boat up under the keel, dig big hole, undo keelbolts, casting drops down, boat sits on the supports under the deadwood, forward part of the keel/stem, side legs. But how would you remove planks from deadwood???

There must be some catch..please, enlighten my ignorance!

PS Or, may be you just could chisel out the rotten part, epoxy in some new wood , fair, prime,paint and launch?


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[fedor]

According to what I know, rotten wood under GRP continues to rot even more efficiently than before ( the same concerns new polyuretan varnishes ). The reason for that is that GRP effectively preserves moist already in the timber and microbes thrive in such environment.
Is the rotten area big? Can you just chisel it out and glue in the wooden spline?

(Also, I doubt that your deadwood is made of iroko...can it be fir or oak?)

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[Guest]

Re: repairing deadwood?

Sheathing is a waste of time unless the moisture content of the wood is brought below a certain percentage (I think around 15% without looking it up). And that means hardly ever doing it outdoors in northern Europe, there are just too many stories of it delaminating afterwards to make it viable. Sheathing just below the waterline is only a temporary measure and it will increase the chances of rot developing in the planks, especially if the deck isn't 100 per cent rainproof. The worst scenario is to have it delaminate at sea, pulling the caulking out with it. Others are right; you have to deal with the rot which ideally means re-fastening at the hood ends forward, and that possibly means a new stem (not iroko this time, go for some oak that has been lying around for ten years) and stern post. All that work can be done outdoors, or under a tent.
It will pay to get her to a sympathetic wooden boat builder (or hire one in). You will probably find that some work can be done this year, some the next and so on. Keep us posted on how you get on.

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