Help please on Big gaps in Clinker hull.

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Ed
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Post by Ed » Tue May 01, 2007 4:13 pm

OK experts - Any thoughts on this? It is quite a bit outside my area of expertise and would appreciate any input.

I am just re-building an early 50s small open river launch. Built in Looe in late 40s or early 50s' it looks like it may well of been built as a heavy rowing boat and then had a Stuart Turner 2.25 petrol 2-stroke put in 1954ish. On the other hand it may of been originally built with engine. I suspect former as there are rowlock points placed where you could not really use to row as you would be sitting in engine. Can't date boat, but engine from 1954.

She is mahogany on oak, but unfortuneately largely painted except gunwhales and topsides. She is heavy and big and pretty stable.

Anyway, I digress. the boat has been lying in back-yard for 18months to 2 years and dried up a bit (although not much as still outside). I am just in process of stripping, or to be honest peeling off the old paintwork.

My question is:

I have some really very large gaps between the planks. I know that I have been suprised in the past with just how much mahogany will swell....but I don't think I can really just leave it and hope in this case. I also don't want to sink it cos of the Stuart engine.

It is quite apparent that many or most of the joints did have some sealant used before. Some kind of white seam-sealer, which is softish but not bouncy like a silicon sealant. But she didn't leak much - or what came in during high tide, tended to go out again at lowtide.

What do people think is the best approach to rebuild?

It is not a beauty of a boat. It was built pretty agriculturally, think worse than Tideway rather than as good as W&C or Chippendale.

It is pretty much all painted, except topsides. It needs 4 new ribs and although there is not much rot....there might be a few soft areas. It is 15ft long but really big so bit worried about cost of coatings.

Current thinking is to strip back to wood. Cover some areas with wood-hardener and then all with G4. Pack any holes with seam sealant - but which? then paint with G4 paint - maybe Bonda 15-year white or coloured G4 paints.

She will live on the river, lying in mud and baked by sun.

I don't like the idea of Epoxy in this case. Way too much movement in hull and as she lives on the river, water penetration would be inevitable sooner or later into the mahagany and that would spell trouble. I could cover with epoxy and cloth I guess....but I really don't want to go down this route - nor could I afford it.

I could try to stick to traditional methods. But worry that I really will need some pretty good way to make water-tight. Also a bit worried about potential cost. It is going to take tons of coating and G4 is very reasonable in cost.

I do worry a bit about using G4 though....having not used before. My hope is that it will water-proof all the wood, but allow it some level of micro-porosity so the wood can breath a little as we know that mahogany needs in this kind of case. I don't want to get into the situation you have with epoxy, where the coating is 'good' but water is absorbed behind it and then can't get out again because the Epoxy won't let it.

Any thoughts?

cheers

eib
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neil
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Post by neil » Tue May 01, 2007 4:27 pm

The best stuff I can think of is what i used on the Tideway - Jeffery's Seamflex. I don't know if it's still avaialable but I have a load left over after. It weren't cheap but is highly recommneded - came from http://www.tradboats.com/

I only used it on the stem to replace a nasty epoxy bodge, but it looks OK as it's mahogany in colour.
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Post by Garry R » Wed May 02, 2007 10:21 am

Anyone have experience with butyl sealant for lands or garboards which also remains flexible? I have a leak in Gannet somewhere which I would like to fix and suspect the garboard in the mast support area when the jib is tensioned up.

On the Jeffreys seamflex there is a site if you search Google - http://www.covboat.demon.co.uk/covcaulk.htm

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Post by Ed » Wed May 02, 2007 1:37 pm

Jeez.....now totally confused with all those different sealants.

Unless anyone has any other info, I guess I will go with the Jeffery's seamflex.

cheers

eib
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Post by chris » Wed May 02, 2007 1:55 pm

John's Merlin had a few very wide splits. Some had opened to over 6mm wide. I shaped and glued in a sliver of mahogany at least that can expand and srink with the plank.

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Post by Ed » Wed May 02, 2007 2:23 pm

Well agree.....if this was a Merlin....and if it was a small 14ft...and if it was varnished...I would certainly consider this.

But although 15ft, it is an enormous 15ft....not very well made...and all painted. So I just don't think it is worth that amount of effort. But will have a think when it is all cleaned up.

cheers

eib
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Post by Garry R » Wed May 02, 2007 4:16 pm

Never thought that we would see the E word on this site!! Will you be for ever known as Edward the Engine???? Sounds nice though and we should see photos!!

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Post by Rupert » Wed May 02, 2007 5:50 pm

I'd not think G4 would be a good choice for this - it is a little bit too much like UCP, and I'm not sure exactly why, but I'm not sure it would cope with swelling and contracting wood very well. You might be better off with varnol, from Black Dog stores. It is a mix of oil and varnish that you put on while the previous coat is still wet, so you can build up many layers in a day. you can then leave it till it dries, and then put another coat on to bring up a sort of semi gloss. Used it on a clinker tender once, and was very impressed. Besat thing for soaking up is to leave her on a mudbank for a few weeks. The mastic will squeeze out of the joints as the wood expands, and then in theory you will have a beautifully tight boat. I'm not sure that mastic or soaking alone would work, but both together you'll be onto a winner.
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Ed
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Post by Ed » Wed May 02, 2007 9:02 pm

mmmmmmmmmmmmm......know what you mean about the sealing factor of G4, that was really what worried me too. I will look into varnol, but again would prefer to stay away from varnish type coatings as it is all painted anyway.

Have considered just using some good old aluminium pink primer, which I have used on tideway to good effect.

She lives on mud bank anyway, but you would need to be careful about tides as it could be easily enough to sink entirely which would prefer not to do cos of engine.

The 'E' word?

ah yes....a bit daring of me!

But not 'Edward the Engine'- not my name at all!

cheers

Edmund Ironside Bremner
Ed Bremner
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Post by Ed » Wed May 02, 2007 9:14 pm

Varnol looks very interesting....

wish I had known about it before doing the tideway.

Despite others raving about it, I am not sure about Tonkinoil at all, at least not for being on a boat on river in sun for 9 months of year. It seemed to do OK with the sun, but water got under it very quick in the autumn

cheers

ed
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Post by Rupert » Wed May 02, 2007 9:30 pm

I'm sure when I first met you through Andrew T you were calling yourself Ed Ironside - how have you resisted the temptation of a steel boat all this time?
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Post by riverlovejoy » Wed May 02, 2007 10:05 pm

I'll stick my oar in here.

Clinker boats rely on the wood swelling to keep the water out. As they get old grot gets in the seams and as the boat moves the planks move against each other and get worn by the grot and so leak. You can stuff the seams full of sealant it will keep things going for a bit, but basicly the boat's worn out. Working boats often have a short life, the old way was that if your boat was knackered you took the lines and went down to the old bloke by the river and got a new one made.

So do not put any non porous stuff on it. Try getting all the paint off the inside......and then useing several coats of boiled linseed oil and turps put on hot. As to swelling up, one method I read about was to coat the inside with plenty of old sacking and run a hose into it. If you choose a warm few days the planks will swell up hopefully without too much grot between them and you maybe tight for a bit.

If non of the above appeal there is always the old favourite. Ferro-cement sheathing, then it does'nt matter what the wood does.
Riv

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Post by Ed » Wed May 02, 2007 11:57 pm

Well.....I don't disagree with you at all!

And of course with some beautiful old clinker boats like a nicely built Holt Merlin...I would totally be thinking along those lines. As I have said, I have done most of this, including the linseed oil and turps but can't really say that it did that much good at all, although thought it was a fair sucsess at the time(although I admit Chris has done very well with ISKA since she moved homes - mainly by rigorously cleaning between the lands). I also agree with you that many old boats like this are just 'worn out'....but still.... It ain't worth re-building (what would be the point) and I think the turps will stay in the can...I am just thinking of any viable, even if it only lasts for a short period.

she was pretty water-tight when I had her on the water, but this did include a fair amount of filler, much of which looked very much like it had been there for a good many years (maybe not 50 - but could well be 20 - it was well embedded up in there and under quite a few coats of paint and anti-fouling). I know I can fill her with sacks etc etc....but she hasn't been kept inside, in fact she has had water running through her for the winter and I don't think she is that dry at all, so I don't see how I can 'presume' that she will swell back up to close the gaps.

The knux of the problem to my mind is: We know that the mahogany swells when wet....but we also know that over the years the natural oils in the wood are lost and the wood starts to swell a 'larger' amount between 'open' and 'closed'as it is only the water which is entering the wood. It is also more likely to rot (remember I am on a only slightly brackish tidal river)and the large swelling and shrinking stresses the rivets etc - that is where the turps/oil comes in.

This 'can' all be got over by bonding the whole thing together with 'epoxy' as was done to 'Kate' MR2.....but I don't like this approach for many reasons.

But.....is there a middle way.

sealing the wood as much as possible, and then sealing between the lands with soft sealer in case of any swelling.

or.....

do I have to just stick traditional - use aluminium pink primer (remember this boat ain't varnish)and paint - put soft sealer in between the lands if needed and hope for best.

I guess another question for me, is simply how 'non-porous' is G4. Is it like Epoxy which seems to encorage water ingress through any crack,cut, or hole and then refuses to let it out.....or is it like a traditional varnish which seems to allow water in and out at leisure.

I presume it is closer to epoxy....but just wonder if it has same ability to work as a water valve letting water in but not out.

cheers

Ed Ironside

Ah that was another time and place entirely!
Ed Bremner
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Post by jpa_wfsc » Thu May 03, 2007 8:42 am

Dinghy Sailing Magazine addresses this issue this month - page 42. Roger Barnes recommends "Balcotan" ployerethane wood adhesive as it "foams up to fill small gaps". That's on a plywood+glued construction clinker boat.
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Post by Rupert » Thu May 03, 2007 8:58 am

How about a thick coat of tar?
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