West Epoxy on top of timber clincker launch

[EdgarCove]

Hi all....Following my previous post.... the epoxy applied to the hull of my launch...was painted...which I have now sanded (the paint) off....my question is....can new epoxy be applied on top of the previous epoxy?

Steve

 

[oldbloke]

Short answer.... Yes
Long answer, when epoxying it is best to apply before the previous coat is fully cured so you get a chemical bond, obviously it's much too late for that. You will get a perfectly good physical bond as long as the surface is properly prepared. Epoxy is very good at sticking given half a chance

 

[EdgarCove]

Thank you Oldbloke...when you say "surface properly prepared"...is that with a primer of some sort....or just a sanded surface well cleaned ?

 

[debenriver]

No primers required. The existing epoxy has to be sanded to a matt (but not polished) finish before applying new and as much as possible of any traces of conventional coatings, paint etc. got rid of.

Best to read the WEST boat construction book – it's available as a free download – and covers every aspect of working with their epoxies, fillers etc. New construction, repairs, renovation etc. It really is the marine epoxy "bible".

Having said all that, epoxy coatings are really not that great for traditional clinker construction. I would instead concentrate on sanding as near down to bare wood as you can and then using conventional coatings.

You may find that the fastenings (assuming she is copper nails clenched over copper roves) need hardening up.

Cheers -- George

Download it here Gougeon Brothers On Boat Construction Book | WEST SYSTEM Epoxy

 

[Hacker]

Also wipe over with acetone after sanding (and wear decent gloves, acetone is nasty and will melt cheap latex gloves).

 

[oldbloke]

Lots of fairly slight variations of advice. I don't think that there is much point is lessening the amount of epoxy you have on the hull as your not going to get rid of what's lurking between the planks. That which is on the outside will be doing a good job of protecting the wood. I'm not sure I would be putting more epoxy on, although it won't fo any harm, having got a good surface I would just go onto a good yacht enamel or varnish

 

[debenriver]

The OP doesn't say whether it's just epoxied on the outside or both inside and out. It does make a considerable difference.

If it's just on the outside, then moisture will ingress into the timber from the inside, but will also be able to evaporate again. So it probably isn't doing a lot of harm, even if not much good. Unless it's actually bonding the planks one to another – i.e. proper bonding in the plank laps – then it's not adding any rigidity to the structure and won't stop it leaking when first put in the water – in fact it will impede the hull swelling and taking up because only one side of the timber can absorb moisture to any great degree.

If it's inside and out, then it's basically trying to encapsulate the hull. The big problem with trying to epoxy encapsulate a traditional clinker hull is that there are so many points of failure. Every copper nail head and peened over rove is potentially a failure point; every wedge-shaped gap between the planking and the underside of the timbers is again a potemtial failure point. And unless the plank lands have been well prepared and possibly filleted, they are a likely failure area too.

It's not just water as a liquid, it's water vapour as a gas, that is equally important. As humidity rises and falls the moisture content of timber rises and falls causing swelling and shrinking. Epoxy encapsulation, unlike conventional coatings is vapour proof, as well as waterproof – which is why it works.

But a failed epoxy coating is dangerous because moisture gets in at the failure points and then can't evaporate fast enough – so you will see the timber going black and then rotting under the epoxy.

That's why I'd probably try to get rid of it – and I design wood/epoxy sailboats and have been responsible for building some 40 or 50 of them, including the first wood/epoxy boats built professionally in the UK.

Cheers -- George

EDIT:

Looking back at the other thread, I see that it's only epoxied on the outside – so forget what I sad about encapsulation! So all it's doing on the outside is impeding the hull taking up really. Pretty certainly not adding any structural significance. So yes, just sand and varnish with conventional coatings. Try to use a varnish with good UV resistance, like Epifanes, else the epoxy will simply degrade and go milky and be even more difficult to deal with.

If the hull doesn't take up after about a week or so, then you may need to harden up the planking fastenings.

 

[RunAgroundHard]

This is a gooid manual for epoxy type work Adobe Acrobat

The advice is good for non West brand epoxies. See Page 10 and 11 for preparation of epoxy surfaces to be subsequently epoxy recoated. It recommends 80 grit sand paper and removing dust and cleaning with solvent before applying more epoxy. The final finish will, like varnish, require further sanding with different grades and more epoxy.

Good luck with your project.

 

[EdgarCove]

Many thanks to all for your replies...I guess that whilst sanding the paint off...may as well carry on a little longer and remove the epoxy too.

Steve

 

[Keith 66]

If you have epoxied a trad clinker boat you are wasting your time trying to harden up fastenings, All you will do is crack the epoxy layer allowing water in. There is no point epoxying just one side all you are doing is applying the kiss of death. I have seen so many good wooden boats ruined by epoxy. Its a bodge.

 

[EdgarCove]

Hello and many thanks all for advice given ...and being a 'newbie' in the boating world is why I have posted the question.

Keith 66....Having 'restored' many classic cars i have had to.. on more than one occasion overcome a 'bodge' carried out by previous owners.... the extent of work and expense being relative to the final value...that is why I think it is helpful to ask advice.
Steve

 

[DownWest]

Hello and many thanks all for advice given ...and being a 'newbie' in the boating world is why I have posted the question.

Keith 66....Having 'restored' many classic cars i have had to.. on more than one occasion overcome a 'bodge' carried out by previous owners.... the extent of work and expense being relative to the final value...that is why I think it is helpful to as advice.
Steve

EC, boats are 'slightly different' to classic cars. Keith66 is a solid source on boats..
I recently rebuilt a space frame for friend's classic car. It had been in a bad accident way back and was quite twisted. So not just replacing corroded tubing in the space frame, but getting it all straight.
It is now a remarkable example of the breed. He did comment that if his garage burned down tomorrow, but if he still had the chassis plate and could do it again, he would still be ahead.
Old clinker boats need special care. You are the tempory guardian..

 

[Keith 66]

Thanks! Epoxy is often seen as the cure for everything & a technological short cut, in practice it can be excellent or it can be a disaster.
My old boat Billows is a case in point a fine 21ft sailing tripper boat built in Rye in 1938 she was planked in fine grained white pine or spruce, her owner for many years liberaly applied linseed oil & cuprinol to her lands & when we bought her in the mid 80's she had been abandoned for many years & was badly dried out. Many would have said she was a perfect case for epoxy coating. I knew that this was never going to be an option due to the oil & tar soaked into her hull. She was stripped right back & we soused her inside with gallons of boat soup, Boiled linseed, turpentine, clear cuprinol & stockholm tar.
Her refit took 18 months & upon launching she leaked badly for a few days but took up rapidly. Her sawn oak floors had quarter inch gaps under them & took many weeks to swell back to their original size.
Now suppose i had epoxied her? or even refastened those floors? what would have happened?
The answer is the swelling timber would have pulled the rivet heads halfway through the planks at best.
Epoxy would have killed that boats hull.
Her deck was covered in glass cloth & epoxy, the best place for it!
After a few months she sailed again & was tight & dry. Not bad for an 80 year old boat that had never been refastened.
Another boat that i have epoxied is a vintage motor launch built by saunders in 1905, her sewn plywood hull being made from thin 1/8" veneers was an ideal candidate to be done in epoxy as most of it was seriously damaged & had to be removed. Effectively she has had a new cold moulded hull laminated onto the original inside layer of the old one.
Its about picking the right method for the application.

 

[Keith 66]

Other thing to consider if using epoxy. If the hull or timber is contaminated with oil or antifreeze you will have hells own job getting epoxy to stick It simply isnt practical to degrease old sump oil from planks when its soaked right through.

 

[Poignard]

A clinker-built hull is an assembly of moving parts.

They might not move much but enough to crack epoxy. And then the water gets in and starts rot.