Glued clinker, hot air guns and a little leak

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Michael4
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Glued clinker, hot air guns and a little leak

Post by Michael4 » Fri Nov 28, 2014 5:20 pm

I've not worked on a glued boat before.

I'm pondering stripping and re-varnishing some of the inside of MR950 (Desperation) which is glued.

I remember reading somewhere that someone wrote that they melted the glue out of a boat using a hot air gun. Is this a 'turn of phrase', a horror story or is it something to be wary of?

As the season draws to a close I notice that she is leaking a little. I guess we spent too much time standing in her and heaving on a jammed halyard, might have opened up a seam.

My plan is to run a little fillet of brown Sikaflex along the outside of the seam. It will be almost invisible. Not sure whether to seal first and varnish after or vice versa.

What would you do?
Tideway 206
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Sold the 'Something bigger and plastic', it never got used.

chris
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Re: Glued clinker, hot air guns and a little leak

Post by chris » Sat Nov 29, 2014 11:10 am

I would investigate joints first and reglue where necessary as the first solution. Use an old blunt knife and see where the glue has 'gone' then clean out the old glue perhaps with an old hacksaw blade and use epoxy. Make sure it is all bone dry too.
I don't know that hot air used carefully should do too much damage to the old glue but, unfortunately, 40-50 years will have.
The other thing is to really check the integrity of the ply itself. On my ply-merlin the inner layers are failing in places as it is inferior timber to the outer layers. This could let some water in yet the actual plank to plank joint is sound still.

Ian Malcolm
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Re: Glued clinker, hot air guns and a little leak

Post by Ian Malcolm » Sat Nov 29, 2014 4:25 pm

Common modern glues (e.g. Epoxy or Polyurethane) soften significantly at elevated temperatures and loose much of their strength. West System say "damaging heat" for their epoxy is prolonged exposure to temperatures over 110 deg C, and below that temperature it will regain full strength when it cools. If you try to burn off paint or varnish from thin planking that is solely epoxy fastened its very likely to spring apart if there is any residual stress.

Phenolic and Resourcinol glues are NOT significantly softened by elevated temperatures low enough not to damage the wood, but if the wood is overheated and even trace amounts of moisture are present, steam pressure in any micro cracks or voids in the joint can damage it no matter what glue is used.

Getting back to your leaky boat:
It may be worth carefully masking off inside and out, then setting up to pull a vacuum on one side of the crack so you can suck the glue into the crack from the other side. It is *VERY* difficult to get any glue that is more viscous than thin superglue to penetrate a hairline crack effectively, and no matter what you do to rake out and clean the crack, you will probably be left with hairline cracks at either end (though if you've just raked out the main crack, at least they will be likely to be fresh with clean surfaces). Maintain a small pool of glue over the whole length of the crack. Shut off the vacuum and remove the equipment when the glue comes through the other side the full length of the crack, then scrape off excess glue before it sets and tape over anywhere the glue is likely to run out of before it cures.
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Michael4
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Re: Glued clinker, hot air guns and a little leak

Post by Michael4 » Sun Nov 30, 2014 3:29 pm

Thanks for the suggestions.

Regarding stripping the inside, frankly I'd rather not but when the boat gets wet some of the area around the non slip grit goes 'milky' which implies to me that water is around. I'd happily rub it down but with that non slip sand in it...

Regarding the leak, I'll try and find it first then report back, careful that my rootling doesn't make it worse.

I know there is also a crack in the centre board case where the bolt has been overtightened but Gorilla tape has solved that one. Indeed Gorilla tape has also waterproofed the garboard seams on my Tideway and has stayed in place since March. Only just pulled it off to do the job properly and it was still firmly stuck. Excellent if expensive stuff!

More soon.

Michael
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Stephen Hawkins
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Re: Glued clinker, hot air guns and a little leak

Post by Stephen Hawkins » Mon Dec 01, 2014 10:14 am

Michael,

Sorry to hear about potential leaks on Desperation. I had no indication whatsoever that there were any issues with the glued planks when I was working on her - stripping the outer varnish. I would check the bailers.

I suspect that the nonslip floor has been varnished over on more than over occasion, which would have been difficult to key for the new coat. I suspect that is where the 'milkiness' is coming from. When dry, perhaps you could use a wire hand brush to remove any loose stuff and re-key, just in the floor area. Then recoat with a thinned varnish, rather than a full strip and re-varnish. Might keep you going for a season or two.

:(

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Re: Glued clinker, hot air guns and a little leak

Post by Ed » Mon Dec 01, 2014 1:34 pm

Gosh......this is why I like this forum so much.

Some damned good advice there, with a choice of approaches to fixing. Brilliant.

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Michael4
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Re: Glued clinker, hot air guns and a little leak

Post by Michael4 » Mon Dec 01, 2014 2:24 pm

Steve,

It really isn't that much of a problem and to reassure you I reckon we broke the old bird after all she didn't leak (apart from c'board casing) when we got her.

By way of checking I'd already (Gorilla) taped up the bailers so they are not the guilt party. I'm pretty sure that it happened when I was try to get the main up when the masthead sheave was jamming. We were afloat and I was standing on the floor heaving on the halyard with all my might. Since one heaves 'up' on the halyard this would have significantly increased the pressure downward...one learns...

The wire brush sounds like a good idea. I have learnt my lesson stripping the insides of boats. Not much fun and unless you pull off the deck and do the whole thing it ends up looking patchy.

Oh...and yes, I'd like to preserve that patina!

Michael
Tideway 206
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Sold the 'Something bigger and plastic', it never got used.

Michael4
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Joined: Fri Jan 03, 2014 5:25 pm
Location: West Sussex

Re: Glued clinker, hot air guns and a little leak

Post by Michael4 » Mon Dec 01, 2014 4:59 pm

Just been out in the garage for a little scrape...

A nice sharp tungsten bladed scraper takes the loose surface off the varnish nicely, without heat. Fortunately it looks as if the non-slip grit is in the top surface so this comes off as well leaving much of the 'original varnish' intact.
This should shape up into a reasonable surface to work on and will keep the 'look' of things OK.
Tideway 206
11+
Sold the 'Something bigger and plastic', it never got used.

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