NickNorway
new user
Reged: 11/05/2008
Posts: 3
Loc: Norway
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Hi! I have a 1960 Folkboat that sinks every spring when we launch it. It has so many gaps and dries out every winter. In addition there are 6 ribs that need replacing and some wekness by the mast foot. I was wondering whether sheathing would be an idea? I know that it may be frowned upon, but the alternative is a major re-planking.
If sheathing is viable, then can anyone recommend any books on the subject? I have several questions already such as, Would sheathing sort out the structural problems (e.g. the cracked ribs) or would these need to be fixed anyway?
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oldharry
regular
Reged: 30/05/2001
Posts: 3762
Loc: North from the Nab about 10 mi...
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Sheathing will not remedy broken ribs. You need to put doublers or 'sisters' in alongside them to bring the hull back in to shape, and to restore the strength. The weakness round the mast foot needs seeing to as well, and sheathing is unlikely to make any difference.
IMHO you need to bite the bullet and get the boat repaired properly.
Sheathing? _ what with? If GRP then forget it - it will destroy the boat double quick. Polyester does not stick to wood, allows water ingress which provides ideal rot conditions. Epoxy systems may be possible but will be at least as expensive as doing the job properly, and will require the hull to be dried out to a very low moisture content - around 15% to ensure proper adhesion. That will cause mayhem with your old timber, and once it starts to get moist again it will move further than the epoxy sheath will allow causing all sorts of problems, and quite likely to do more harm than good.
Just a question - have you tried re-caulking the planking? The leaking may be simply the caulking has failed and needs replacing. Assuming she is carvel built that is, and not clinker. A carvel hull will have been built deliberately with gaps between the planks to allow for swelling, and these need to be properly caulked. If she is clinker, then the fastenings are probably loose and she may need re-fastening as you do not caulk clinker.
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If you cant fix it, get a bigger hammer...
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Peterduck
regular
Reged: 10/04/2002
Posts: 994
Loc: Melbourne, Australia
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Sheathing would be the equivalent of a Band-Aid on a broken leg! First you have to fix the ribs, then you have to re-caulk the seams. The 'wetness near the mast-step' needs further investigation. The region of the mast-step is the most highly-stressed in the whole hull, because when sailing the mast is pushing downwards on the keel, and trying to open the garboard seam. If you are not experienced at caulking, get someone who is to show you how, or to do it for you. It is very easy for a newcomer to get it wrong, and damage the plank edges.
Peter.
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Vitalman
regular
Reged: 12/09/2005
Posts: 1202
Loc: Me Cambridgeshire. Boat east c...
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The best way is to remove the deck and all the internal furniture. Turn it upside down and take a mould of the external profile.separate this off and lay to one side.
Make up a mould of the internal profile in the same manner . lay to one side.polish the external profile mould so that it is cosmetically perfect, lay on the gelcoat and then a continuous series of high modulous carbon fibre tows say +5 degrees, -5 degrees, +45 degrees, - 45 degrees, -5 degrees and +5 degrees. Build each rib and stiffener the same with a nomex core, ditto Keel but double up on the skins
Then laser scan the profile of the internal profile and crossload this to a 5 axis milling machine and set it to rout the voids betweeen the fillers so it will exactly match the inside of the internal oulded skin you have made as well.
Replace the keel with depleted uranium so you can lower the c of g
Hopefully all this will enable you to eliminate that evil stuff known as wood.
I could probably do the job for you for a mere £5 million plus tooling and expenses. 
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Live like there'll be no tomorrow
Love like you've never been hurt
Dance like nobody's watching
And keep growing older - not up!
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Big_Southern_Jesse
regular
Reged: 20/10/2005
Posts: 596
Loc: Emsworth, Hampshire
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How long is the boat out of the water each year, and how well sealed is the planking? You've ogt to give the boat a chance to stabilise. if the timber takes up and seals the gaps eventually each year, then the problem is caused by taking the boat out of the water each year. There's no way anyone is persuading me to have our hillyard out of the water for more than two weeks. She's well sealed, but all the loading is different, the hull will start to change shape and the planking will dry out. You can do various things to mitigate all these effects, but it will still happen to some degree. If she's dry and seaworthy by the end of the summer, can you leave her in over the winter?
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Seagreen
regular
Reged: 30/07/2005
Posts: 1216
Loc: ked myself in the locker again...
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Ditto all of this.
Don't sheath. Fix the ribs: this can be done by laminating new ones in place and is not a hard job, tools are nearly all found in everyone's shed. Also, recaulk.
The wetness at the mast step maens that the seams are flexing a bit too much, but remember, all wooden boats are supposed to leak a bit, so think about how much the boat leaks here.
It may be that the broken ribs are near the mast? Fix these and recaulk. You may need to build a slightly bigger "ring" frame (best done in laminate) where you frame right round thee inside of the hull at the mast. This stops the mast and keel moving in relation to each other. A combination of all three and the job's a good'un.
Oh, and once again- don't sheath. Kinder all round if you sell the boat to someone who wants to do the work. Would you sheath a sick horse in epoxy or shoot it?
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"Let Joy be unconfined!"
I'll get her chastity belt keys, then..
http://www.linesquall.co.uk
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Niander
regular
Reged: 25/06/2003
Posts: 405
Loc: Outer hebrides
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[also folkboat]I also need to sister some ribs in the bilge by laminateing after i have laminated i presume i need to put in screws from the outside ?
how far apart would you recomend the screws are spaced?
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Seagreen
regular
Reged: 30/07/2005
Posts: 1216
Loc: ked myself in the locker again...
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Well I'm no expert, but as a rule its two fastenings per plank, certainly for a folkboat where I suppose the planks are 2.5 or 3" at their widest.
I always find making a template from scrap cardboard (keep those flatpack furniture boxes somewhere dry) are excellent for this. cutting blocks to fit the stepping of the inside of the hull before adding the laminate strips is a good idea. And you'll need quite a few G clamps.
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"Let Joy be unconfined!"
I'll get her chastity belt keys, then..
http://www.linesquall.co.uk
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mattyg
new user
Reged: 04/02/2006
Posts: 9
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Just in case you are unconvinced by the arguments here is my experience. I am currently in the process of removing sheathing from my recently acquired 1930's kreuzeryacht. The planks surrounding the chain plates on both sides have been rotting away unseen. From the outside the rot is hidden by the sheathing and from the inside, hidden away by fittings and stripping. The rot certainly escaped the notice of a surveyor. Below the waterline is a similar story. My own inexpert view is that sheathing is a recipe for disater. Your yacht may look fine on the outside whilst inside she is festering away unseen. I certainly wouldn't have wanted to be in a blow with those chain plates holding up my mast. 
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Clifford_Pope
regular
Reged: 28/10/2005
Posts: 715
Loc: Pembrokeshire
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Sheathing a wooden boat is virtually signing it's death warrant. You are saying, I am going to be the last owner of this boat. I want it to look nice for about 5 years, and then I don't care, it can go for scrap or on a bonfire.
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