International 14, epoxy or not?

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International 14, epoxy or not?

Post by Fantasia »

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I am restoring my vintage International 14ft racing dinghy No. 521 Tiptoes (1948), built by Uffa Fox Ltd. The carvel hull is ribbed and the "planks" are nailed. The outer planks (veneers) are 3mm thick and laid along the line of the hull, the inner planks are 2mm and are laid diagonally. In between the two skins is a textile membrane that I am told might have been oiled silk, but looks more like cotton sailcloth. This was supposed to be a waterproof membrane. There was no adhesive used in the construction of the hull.

The problem that I have is that the hull is far from waterproof and I would like to sail it. She has not been sailed for over thirty years and has been stored in the dry and the planks have shrunk. The boat would be varnished inside and out and I have removed the varnish from the outside so far.

The boat is almost entirely original, including cotton sails and wooden spars (already restored).

The dilemna that I have is whether to introduce epoxy resin into the construction of the the hull in the form of a coating, and adhesive and possibly even cover the hull with an epoxy/glass fibre scrim to ensure that it does not leak and to give more structural integrity? I can see the attraction of using epoxy, which I have used many times in the past; but its use on such a historic hull concerns me. What other treatment might I use?
Possibly just loads of good old fashioned sticky varnish?

Any ideas or do I just accept that her sailing days are over?

Thanks, John Hartley
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Re: International 14, epoxy or not?

Post by Ed »

I don't think her sailing days need to be over....

but you might have to answer a bundle of other questions:

How wet do you mind being when sailing?

How hard do you want to sail her? (Does sailing equal racing?)

How important is 'originality' to you?

How long do you want this boat to last? 5 years? 20 years? Another 60?

I know many people will have firm opinions about what you should do, but I think any method you use will have compromises to be made.

Personally, I would advise you talk to those who have traveled this road already. Obviously Jamie Campbell and Andrew Thornhill. I am sure you already have their contact details, but if not, you have friends who will happily supply them. You could also ask some of the vintage 14 owners at UTSC or Laurie Smart, who has re-built or worked on many of these boats.

If I was so blessed as to be working on tiptoes, I would certainly ask these guys before making my mind up....

If I couldn't ask them and was forced for an opinion......I would most probably go down the route of using a thin non-setting wood-oil (deksolyer or maybe linseed oil/turpentine) first as a 'supple sealer' and then lots of varnish on top.

or.....

If pushed, I would also consider using a very thin 'wood-seal' or 'wood-hardener' first that would really sink deep in. (examples would be UCP (RIP), Blakes Woodseal (RIP), Eposeal, well thinned epoxy or well thinned G4), then put lots of good supple varnish on top.

The first will be less watertight, but will not damage the boat in any way and allow her to continue for many many years of gentle sailing. The second would/should work nicely to make shell watertight, but will certainly make subsequent repairs harder, but stays away from making a new 'plastic' boat on a wooden shell.

I would avoid using any scrim or cloth with epoxy, this just doesn't look right and in my opinion will in the end 'limit' the life of the craft, by swapping a few years of 'hard-use' for many many possible years of gentle use and care.

But this is just me and there will be many others who will be more 'pro' and more 'anti' than me :-)

Anyway, I would ask Andrew, Jamie & Laurie first.

cheers

eib
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Re: International 14, epoxy or not?

Post by Rupert »

Possibly worth speaking to Colin Henwood of Henwood and Dean, in Henley, too. He did an amazing job on a pre war 14 for Andrew Thornhill many years ago, and he normally restores Thames Slipper Launches.

There are many ways to skin a cat (apparantly!) and as many ways to get boats back on the water. Epoxy would be a short term solution to getting the boat useable for the next 10 years, I'd say, but she would never be the same boat again.
Pretty sure Uffa never meant his boats to be around this far down the line anyway - they were designed to win races for a few seasons, so keeping them as they were built would be an exercise of long term love...
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Re: International 14, epoxy or not?

Post by Nessa »

gthe epoxy on Agammenon is so horrid I am paying someone to get it off for me. then it will be replaced by a two pack varnish and more varnish on top of that.

I think. :roll:
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Re: International 14, epoxy or not?

Post by Ed »

Well.....the epoxy fans will be along in due course :-)

Personally I think it is important to clarify how the epoxy is used.

John is right when he differentiates between:
introduce epoxy resin into the construction of the the hull in the form of a coating, and adhesive and possibly even cover the hull with an epoxy/glass fibre scrim
using epoxy as 'glue', 'coating', 'laminating system' or 'primer-stabiliser' are all very different uses.

Personally, I am happy to use epoxy as a glue or as a deep primer/stabliser, but don't like seeing it used as a coating or to sheath wooden hulls.

But, this does depend on the hull construction. Coating or sheathing a clinker hull is a complete no-no in my book.....but 'some' moulded hulls such as Fairey hulls, 'can' 'possibly' 'in some cases' be coated or sheathed.

But the problem to my mind with this boat is that this kind of construction - the two-layer carvel with silk barrier film lies somewhere between the two and I am not sure what I would recommend - hence wanting to do a fair amount of research first. I think it largely comes down to how stable can the hull be or do you want it to be. If you presume that there will be or that you want there to be some 'movement' then I think you would want to stay away from using a hard primer such as epoxy/blakes/UCP/G4, but if you reckon it can and you want it to be 'rigid' then a hard primer will certainly help.

But as we have said.....the 'how long and how hard do you want to sail' question also comes into play. If you want the boat to last long enough that you think you might wish to replace some wood in the hull, then the job will certainly be a little harder if a hard primer, especially epoxy has been used. On the other hand a hard primer will keep water out of the wood more effectively, which could 'arguably' lead to a longer life.

decisions....decisions....

eib

ps I am sure someone will say sooner or later......"Well Uffa would of used Epoxy if he could...." and I am sure that is right. But if he had had epoxy, he most probably wouldn't of been building in the way he did anyway.
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Re: International 14, epoxy or not?

Post by Fantasia »

Thank you very much for your replies, I know that the ultimate decision lies with myself; but I was just trying to sound out to find if there are other choices.

By sailing I really mean racing and if racing I do not want to be going around the course bailing continually (she only has one smallish telecopic tube bailer). I know that her fragility will restrict the conditions in which I could sail, but it would be nice to take part in some events with some confidence of her not falling apart.

I have already talked to some of the names already mentioned and will talk to others. In the meantime I shall carry on scraping the varnish from the inside, which will keep me quiet for a while, however decision time is getting closer and closer.

Thanks, John
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Re: International 14, epoxy or not?

Post by JimC »

I don't really see epoxy coating working well with that style of construction...
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Re: International 14, epoxy or not?

Post by Ed »

Please do tell us what you decide and if appropriate, tell us what advice you have had so far. I am sure we could only all learn from it.

Best wishes

eib
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Re: International 14, epoxy or not?

Post by rme_01 »

I suspect an epoxy coating (let alone a scrim) would be a big mistake for this form of construction. No doubt it would seal and stiffen things up a bit in the short term but because of the inherent movement would probably result in cracking in the future with the attendant problems. I have a 37 Uffa 14 of the same construction and wild horses wouldn't induce me to go down that route albeit perhaps I am more motivated by pride of ownership than winning races. She is an old lady and I accept that limitation. By contrast I have used a West saturation coat on the bottom of my 57 Fairey which is destined to be sailed regularly. In that case it was felt that the hot molded construction was sufficiently bullet proof that movement would not be an issue.....I hope that proves right!

I would be interested to hear how you get on.
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Re: International 14, epoxy or not?

Post by Ed »

Totally agree on both accounts!

no to any 'coating' of epoxy on this construction - especially not with any 'scrim' or 'cloth'

and yes to the careful use of epoxy as a saturation-primer on a Fairey boat.

But we are not really arguing on this - no-one has suggested a heavy 'coating' was a good idea..... yet :-)

the more interesting question is: Could one use epoxy as a 'saturation-primer' on this construction????

As I said.....I would certainly consider it.....but would need to really think about it and might well come down with using a 'safer' option, but I think it would most probably really would help to make the boat more water-tight and I think it wouldn't have most of the 'dangers' associated with an epoxy coating/sheathing. It could be a viable compromise?? As I said at beginning, whatever you do is likely to be a compromise at some level.

But I am by no means sure on what is best here and really look forward to hearing what is proposed in this case after full research of current 'best practice'.

eib
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Re: International 14, epoxy or not?

Post by Rupert »

The wood in the old 14's would expand and contract as it got wet and dried, in the same way that traditional boats do, hence the oiled silk or calico (?) between the layers. Epoxy between the planks would crack after a while, I'd have thought, even as a primer, and the epoxy which runs down betwen the planks would stop the wood expanding and cause it to bow, maybe. What happens when it sticks the wood to the silk?

By now the oil will be gone, so the boat will be far leakier than when new. Would soaking the boat in linseed oil help to replenish the oil in the silk? I guess someone must have tried it?

Is there a vintage 14's website?
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Re: International 14, epoxy or not?

Post by Fantasia »

My heart and conscience say no to epoxy, apart from the repair of a few broken elements.

I appears that the joints were simply caulked with white lead originally, prior to varnishing. I would not think of using that evil material, but perhaps some other form of soft filler might help.

It would be disappointing to invest a huge amount of work to find that she was little more than a collander; but then there is no guarantee that she would sail well by modern standards anyway. These might be the risks that I have to take.

I have tried to increase the moisture content of the timber by draping her in damp hessian and leaving her outside in the rain for a couple of weeks last autumn; but although she did take-up a bit the gaps were still concerning. My theory is that she would have been very damp at some time in her life and everything would have expanded to its max and strained the fastenings apart. Therefore the expansion and contraction now does not reach the limits require to create a seal. Also the cell structure of timber does change if it is dried beyond a certain point. However I am still tempted to go and put her in the lagoon behind the sailing club at HISC and leave her for a while to see if she will plim-up.
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Re: International 14, epoxy or not?

Post by Michael Brigg »

It is my own feeling that boats like these which are not held togetrher with glue need a permeable finish because of this construction. Epoxy will seal the sructure and prevent the differential expansion of the various materials as moisture is taken up.

As the different components expand, they knit together until they get to a sort of setting point, a bit like making jam, when quite sudenly the whole structure will aquire stiffness. Until that point it all looks terribly fragile.

I haven't tested the theory yet, but I know my Clinker 14 was alot stiffer than it is now and the only difference is that it is currently very dry.

If you are going to soak her I have been consistently advised it must be sea water.
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Re: International 14, epoxy or not?

Post by rme_01 »

I would be very careful about your idea of leaving her in a lagoon to “take up”. This might be beneficial on a carvel hull but would I suspect simply make matters worse in this case. My reasoning is to do with the anisotropic behaviour of wood e.g its tendency on changes of moisture content to swell/shrink by significantly different values according to the direction of the grain typically 40 times greater across the grain than longitudinally (all to do with the hygroscopic nature of the hemicellulose and the angle of the microfibrils in the S2 layer - sorry about that but we foresters love our subject!). In a carvel boat that is fine as the planks when wet simply push harder against each other with immaterial longitudinal distortion. On a cross laminated structure however these forces would be working in different directions putting considerable strain on the bonding. In a glued laminate these strains are well spread albeit in extreme cases failure will occur (soaked plywood for example) however where the laminates are joined together by rivets as in this case then I suspect movement around the fastenings takes place leading to loss of stiffness with the attendant leakage. The more extreme the moisture content change the more extreme the problem; if the boat was built in an unheated shed in Cowes ferry with a MC of say 20 and subsequently stored in a heated garage with a MC of 10 or less then shrinkage would have occurred. This would have been reversed when the boat was stored outside again but by then the damage around the fastenings would have been done. I don’t incidentally accept the idea of permanent cell shrinkage. Cell wall collapse can occur in the growing tree in severe drought conditions but not be in seasoned wood.

I appreciate that doesn’t help much in solving your problem. I am not familiar with the idea of soaking in linseed oil and would be interested to know more. Certainly it would restore the lustre and subtleness of the wood and might gum up some of the openings but I am not convinced it would affect the physical properties beyond that. Refastening and replacing the membrane is I imagine out of the question so that leaves epoxy saturation (incidentally Ed that is what I meant when I said coating). I am not keen on that albeit perhaps more for sentimental rather than practical reasons!

As an aside a recent technique for reducing timber movement in window frames etc. is to heat-treat the wood. The theory is that this involves the degradation of the hemicellulose resulting in a significant reduction in movement albeit with a loss of some strength. I often wonder whether the longevity of the Fairey hulls has something to do with this.
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Re: International 14, epoxy or not?

Post by Fantasia »

rme_01 wrote:I would be very careful about your idea of leaving her in a lagoon to “take up”. This might be beneficial on a carvel hull but would I suspect simply make matters worse in this case. My reasoning is to do with the anisotropic behaviour of wood e.g its tendency on changes of moisture content to swell/shrink by significantly different values according to the direction of the grain typically 40 times greater across the grain than longitudinally (all to do with the hygroscopic nature of the hemicellulose and the angle of the microfibrils in the S2 layer - sorry about that but we foresters love our subject!). In a carvel boat that is fine as the planks when wet simply push harder against each other with immaterial longitudinal distortion. On a cross laminated structure however these forces would be working in different directions putting considerable strain on the bonding. In a glued laminate these strains are well spread albeit in extreme cases failure will occur (soaked plywood for example) however where the laminates are joined together by rivets as in this case then I suspect movement around the fastenings takes place leading to loss of stiffness with the attendant leakage. The more extreme the moisture content change the more extreme the problem; if the boat was built in an unheated shed in Cowes ferry with a MC of say 20 and subsequently stored in a heated garage with a MC of 10 or less then shrinkage would have occurred. This would have been reversed when the boat was stored outside again but by then the damage around the fastenings would have been done. I don’t incidentally accept the idea of permanent cell shrinkage. Cell wall collapse can occur in the growing tree in severe drought conditions but not be in seasoned wood.

I appreciate that doesn’t help much in solving your problem. I am not familiar with the idea of soaking in linseed oil and would be interested to know more. Certainly it would restore the lustre and subtleness of the wood and might gum up some of the openings but I am not convinced it would affect the physical properties beyond that. Refastening and replacing the membrane is I imagine out of the question so that leaves epoxy saturation (incidentally Ed that is what I meant when I said coating). I am not keen on that albeit perhaps more for sentimental rather than practical reasons!

As an aside a recent technique for reducing timber movement in window frames etc. is to heat-treat the wood. The theory is that this involves the degradation of the hemicellulose resulting in a significant reduction in movement albeit with a loss of some strength. I often wonder whether the longevity of the Fairey hulls has something to do with this.
Thank you for your very interesting reply, the timber science is particularly interesting. I must say that I agree and have little hope of the hull returning to its original form. The MC is currently below 10% and I think that the damage to the fastenings has already occurred.

My ever changing mind is now settling towards simply revarnishing with some staightforward varnish and plenty of it. Then rig her and sail her to see what happens. If she sinks I may loose heart, but she would still look very pretty and I would have done her no harm.

I do have another problem in that the garboards are split along the line of the hog. I'll take some images to illustrate this. They may need some localised repair.

Funnily enough I also had a suggestion from elsewhere to remove the outer skin (having supported the hull shape with frames/moulds), repacing the membrane and re-fastening the outer boards in their original positions with some additions to make up the shrinkage. Nice idea, but I am sorry that the boat is not worth that much effort in my eyes and the treatment is rather too interventive
Last edited by Fantasia on Thu May 19, 2011 12:00 pm, edited 1 time in total.
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