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Old 06-04-2016, 10:31   #1
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Epoxie sealed hull construction??

I have a small mono hull that was built by a very respected builder...He used 1/8 mahogany sheeting bonded with epoxy and the outer hull is sealed with epoxy..there is no fiberglass cloth on the outer hull....any opinions on this technique??
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Old 06-04-2016, 10:45   #2
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Re: Epoxie sealed hull construction??

One wonders if the epoxy resin without glass would crack with hull flexing over time...
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Old 06-04-2016, 18:55   #3
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Re: Epoxie sealed hull construction??

Sometimes people put a layer of glass on the outside to provide a touch more abrasion resistance. Multi-ply wooden epoxy construction should flex a lot less than fiberglass of the same thickness. Keep the water out and it should last a long time. Luders 16's were built similarly in the 50's (with Resorcinol glue, hot-cured) and are still sailing today. Essentially you have sheets of marine plywood molded into the shape of the boat, instead of flat sheets. Saves a lot of weight by not needing as much interior structure.
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Old 06-04-2016, 19:18   #4
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Re: Epoxie sealed hull construction??

These hulls are very stiff and hardly flex at all.

The epoxy acts as a waterproofing and as an adhesive to bulkheads in this case.

Glass is completely unnecessary in this type of construction.

The sole purpose of adding a fiberglass outer skin is to give the hull abrasion resistance.
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Old 06-04-2016, 20:13   #5
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Re: Epoxie sealed hull construction??

You are most likely describing cold molding, and probably using the WEST (wood-epoxy saturation technique) or something very similar. The Bible on this is the Gougeon Brothers.

For what it's worth, our boat was built this way 40 years ago, only has glass tape at the corner of the deck/hull join, and has been solid and relatively maintenance free for that time.
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Old 07-04-2016, 08:13   #6
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Re: Epoxie sealed hull construction??

You can always add a layer of glass to areas that experience wear like the keel. One thing to note is that epoxy is not UV resistant so it should be painted if left exposed.
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Old 07-04-2016, 08:23   #7
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Re: Epoxie sealed hull construction??

Quote:
Originally Posted by pwilletts View Post
I have a small mono hull that was built by a very respected builder...He used 1/8 mahogany sheeting bonded with epoxy and the outer hull is sealed with epoxy..there is no fiberglass cloth on the outer hull....any opinions on this technique??
Yes, the epoxy resin acts as a sealant, add the glass cloth and you are adding strength and abrasion resistance.
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Old 07-04-2016, 08:48   #8
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Re: Epoxie sealed hull construction??

You should check what epoxy was used. Hopefully is was West ..., and as others said epoxy alone is not UV resistant
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Old 07-04-2016, 09:10   #9
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Re: Epoxie sealed hull construction??

I own a cold moulded coast 30 built by Tim Tuulos who came to Canada from Finn-land. He covered all his hulls in two layers of 2 ounce cloth from new. While the hull was upside down before the keel was bolted on. I would have thought covering a hull with glass cloth after years of use might be a serious challenge in many respects?
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Old 07-04-2016, 10:08   #10
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Re: Epoxie sealed hull construction??

Quote:
Originally Posted by Dsanduril View Post
You are most likely describing cold molding, and probably using the WEST (wood-epoxy saturation technique) or something very similar. The Bible on this is the Gougeon Brothers.

For what it's worth, our boat was built this way 40 years ago, only has glass tape at the corner of the deck/hull join, and has been solid and relatively maintenance free for that time.
You beat me to the cold molded prospect.
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Old 07-04-2016, 10:35   #11
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Re: Epoxie sealed hull construction??

If you talk cold molded epoxy wood then the technique is as old as the world and well proven. No cracking and no rot if right materials used. Many racers in the 80'ies got built like this. There are also new builds, mostly one offs, now and then.

If you talk plywood/epoxy then it is OK and much depends on plywood quality. RM boats are built like this, I think.

Columbus' boats were wood. He did not even have epoxy back then. I think they used tar. They sailed well and seemed fun to sail too.

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Old 07-04-2016, 10:54   #12
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Thumbs up Re: Epoxie sealed hull construction??

If you have a few minutes you might like to look at this link to find out about just how strong cold moulded plywood construction can be

https://en.m.wikipedia.org/wiki/De_Havilland_Mosquito

No fibreglass anywhere, and I believe epoxy is a much better glue than was available in world war 2.
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Old 07-04-2016, 15:12   #13
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Re: Epoxie sealed hull construction??

I think as a pure glue resorcinol is still the best. It might kill you and it has no gap-filling ability and everything has to be heavily clamped -but it is still a great glue and was available in WW2. It is still the preferred bonding agent for brake shoes and plywoods, and if I was building a mast from timber (why would one these days?) I would certainly prefer it because of its resistance to softening with heat. (Hence its use for brake linings).

Getting back to the question. I always use epoxy glass on the wetted side of any timber for its sealing and anti-checking ability and yes, it does help with abrasion resistance. It also adds quite a bit of strength but that is not the main reason for using it--it just makes a better seal and a better surface. It also adds to the weight, so if you are racing your craft it may be better to use something else, or even nothing at all.

Many years ago we used Dynel--but glass is OK just a bit heavier. Epoxy is wonderful stuff--but although not as toxic as the glue it replaced--it is still dangerous stuff. My $0.02 worth.
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