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 Post subject: Epoxy removal from clinker hull
PostPosted: Sat Mar 05, 2011 9:38 pm 
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Hi, I am very tempted by a restoration project of a Yachting world dayboat of traditional clinker construction. However the hull has been coated with epoxy both inside and out, and then painted over. I am not sure if the epoxy needs removing or not, and if it does what the best method is?

I have heard that a heat gun and scraper works, but is slow. Is it possible to have the hull sand blasted, but with something softer like walnut shells, to remove the epoxy without damaging the wood?

Overall the hull appears to be sound but a few of the ribs in the bottom of the hull have cracked and a couple of pieces have broken off (up to about two planks from the centerboard case). To repair the rib is it possible to splice a new piece of wood onto the existing rib, or should the whole rib be replaced? If this worked I guess I may not need to completely strip the hull.

Thanks in advance for your advice,
Tom


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 Post subject: Re: Epoxy removal from clinker hull
PostPosted: Sat Mar 05, 2011 10:26 pm 
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Location: Oxford (Work) Coteswold Water Park (Sailing)
The significant problem with epoxy coated hulls is that water gets trapped inside and the epoxy stops the wood from breathing. This causes rot - often invisibly, inside the wood.

So its certainly worth checking carefully that this has not happened before you begin - it may sadly not be worth the effort if there is a lot of soft wood under that hard epoxy. Often old wood boats get 'epoxied' to get another few years of life out of a boat that is failing instead of repairing properly and ensuring a long life. A new wood boat, epoxied from scratch so to speak, seems to last much longer than an old one 'preserved' in this way....

I hope you find that it is worth it though - and if so there is lots of info about how to remove epoxy in the forum - as many different ways as there are boats that have had epoxy removed!

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 Post subject: Re: Epoxy removal from clinker hull
PostPosted: Wed Mar 09, 2011 10:02 am 
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It may depend a bit how thoroughly the hull was stripped before the epoxy was put on. I know its not quite the same but I had one boat that had been coated in resin and glass but the original varnish had not been totally removed so the sheathing just pulled away in large patches. Polyester resin isn't a glue like epoxy but keep your fingers crossed that there is some old varnish left to seal the timber and try a heat gun. Walnut shells might work, maybe some one has used them on epoxy and can advise.

Epoxy responds to abrasives quite well. If you try a sander I would suggest using a spong drum sander in a drill as they don't clog up and cut with the grain; find one here http://www.axminster.co.uk/black-and-de ... rod481332/
They take a bit of getting used to. keep it moving smoothly along the planks, keeping it always level on the wood. etc. otherwise it will eat the wood. With care they will get in quite close to the corners and scrapers should do the rest. Not a very quick solution but I think quicker than a belt or orbital sander. It will throw the dust every where however.

Just as a matter of interest is the inside epoxied as well? if not everything John said will certainly be true.


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 Post subject: Re: Epoxy removal from clinker hull
PostPosted: Wed Mar 09, 2011 5:26 pm 
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Location: Sitting on the bank of the Tamar
Oh we love this kind of question....

First thought is that it depends on the epoxy.

some comes off very easily with a bit of heat. had it stick to the insides of a cover on a hot-day and go so soft you could push a nail into it,

But other makes don't tend to get budged much and abrading seems like the best way.

Sometimes, just using a good cabinet scraper is as good as any way.

you just have to try all sorts of ways,

But would put heat at the top of the list.

eib

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 Post subject: Re: Epoxy removal from clinker hull
PostPosted: Thu Mar 10, 2011 3:32 pm 
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Thanks for your responses. I have since spoken with an experienced craftsman who was involved with the restoration of the boat a couple of years ago when the epoxy was applied. His view was that the underlying wood was still solid and dry, and there was no need to remove the epoxy. He thought that new pieces of wood could be spliced in where the ribs had broken, requiring only epoxy to be removed around the rib area. I think this sounds like a good approach and I will still need to steam bend some new rib sections, which will be a good skill to learn. I will check the planks over to make sure they are all sound, if not I guess I will have to get busy with the hot air gun, scraper and sandpaper!

thanks,
Tom


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 Post subject: Re: Epoxy removal from clinker hull
PostPosted: Thu Mar 10, 2011 4:07 pm 
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Sounds to me like a good plan.

my only slight worry....of little consideration I guess....is that Epoxy is or can be much harder to patch into than varnish.

This is for me one of the other worries about, or problems with coating in epoxy.

Applying epoxy seems to often change the colour of the wood, or maybe the way light effects the wood underneath. It can look great, but if you get any damage and have to strip some off for repairs etc. it can be very hard to try and patch in and get the wood to look the same colour after you have repaired the patch.

Of course, it helps if you know the brand of epoxy used originally and also what varnish was used. And of course doing this can be hard with varnish too....but still, for me I have found that patching in varnish is easy enough, but patching in epoxy can be damned hard.

But given the choice, I would do exactly what you suggest. So good luck

cheers
eib

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Firefly F2942
IC GBR242
MR 638 - (for sale)
Phelps Scull
Bathurst Whiff - in the workshop
Tideway on the bank & 15ft Looe Launch (on back-boiler)


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