Cored Hulls and Decks

[PCP]

Originally Posted by boatpoker

Paulo : I think I would believe studies done by independent labs and Standards Societies rather than sales blurbs from the manufacturers of these products

I confess that I had only an idea that Epoxy was waterproof but after a search on internet I have no doubt that there are Hygroscopic and non-hygroscopic epoxies. The industrial uses of non-hygroscopic Epoxies (besides marine) are incredibly large: From computer chips to electric engines and building materials.

http://www.asi-tech.co.il/_Uploads/d...derfill688.pdf

Ecopoxy Systemsâ„¢

620 Underfill Epoxy

Hatteras NC1000 Drives - Tide Tamer

I guess that the confusion here is between composite materials with epoxy resin (that are hygroscopic to some extent) and epoxy resin, that can be non-hygroscopic. The sealant that is applied in several coats to the hull bottom is an epoxy resin and it is an waterproof one. All manufacturers state that and they would be sued if that was not true.

Regards

Paulo

[souljour2000]

I have been using US Composites thin resin..I wonder if it is fairly non-hygro-scopic or whether it sucks for a water-barrier? It seems to be a good product and they have been around for awhile but if the resins they have prove not good as a water barrier then I will try the stuff PCP is talking about from that stitch n glue supplier because imperviousness to water is one of the main reasons I use epoxy as well as it's excellent adhesion to wood and other materials...

[mitiempo]

I think all epoxy will absorb water but very small amounts over a long period of time.

[tommays]

West epoxy which is about the most well know wants you to mix in there 422 Barrier Coat Additive to get the most effective barrier coat and try and get 20 mills of product on the hull

[noelex77]

Epoxy resins are generally reasonably waterproof. The main problem is when applied over polyester resins is that they trap water in the laminate which wants to enter due to osmotic pressure.
An Epoxy barrier coat seems a sensible option for new hulls, but this treatment has not enough history to project future outcomes.
Epoxy treatment on a polyester resin boat that has already been immersed may do more damage than good by trapping moisture.
Why don’t more builders use epoxy for the lay-up? . The additional cost would be small compared to total for the total cost of the boat. Oyster HR etc lets see at least an epoxy option.

[mitiempo]

A lot of builders use either epoxy or vinylester resins now. But there are thousands of boats built in the 70's and 80's before epoxy was as common and when less polyester issues existed or were commonly known about.

[tommays]

From my reading Vinyl Ester Resin seems to be the middle ground of cost VS performance in boats most people can afford


There are a lot of cost issues with protecting the work force from epoxy Allergic reactions which just about anybody will get without a LOT of caution


Neither of my 1981 J24s #2733 or #2930 ever had barrier coat or blisters BUT there were never in the water year round which seems to cause more issues

My CAl 29 has had one so so barrier coat job and is also fine

[noelex77]

Originally Posted by mitiempo

A lot of builders use either epoxy or vinylester resins now. But there are thousands of boats built in the 70's and 80's before epoxy was as common and when less polyester issues existed or were commonly known about.

A thin barrier coat of epoxy or a few layers of vinylester are common, but very few production boat builders use epoxy as the primary resin in hull and deck construction. (There are some rare exceptions such as Hanse)
Epoxy has superior properties, not only in water absorption, but strength, mico cracking etc.
Why more expensive yachts, such as HR, are not usually constructed out of superior materials is a mystery to me.

[PCP]

Originally Posted by noelex77

...
Why don’t more builders use epoxy for the lay-up? . The additional cost would be small compared to total for the total cost of the boat. Oyster HR etc lets see at least an epoxy option.

Not so small. On the 40ft that have that as an option, it costs about 9 000 €.

There is also another problem, Epoxy resins are sensitive to UV and that means that the gel-coat has to be colored and that costs almost as much. That's about 15 000 € on a 120 000 € boat. That's a lot of money.

All European boat manufacturers propose (as an option that almost everybody takes) a hull with a three coat epoxy barrier, for about 1500/2000 €. Most propose also as standard a vinilester outer layer on the hull composite.

Regards

Paulo