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olandrea
12-14-2007, 11:37 PM
I found this on the www:

Bear in mind that the epoxy glue does not fail, it is much stronger than the wood. What fails is the wood surface just beyond the minute glueline saturation. One surface generally just tears apart the wood fibers, while the other surface remains well coated with epoxy (and some wood fibers from the weaker surface).
True cold-molded construction employs many, very thin, veneers. It should really be thought of as a fiberglass hull, with wood fibers instead of glass fibers. Imagine what would happen to the fiberglass cloth layers if they were not fully and completely saturated with resin.
The Gougeon Bros. book on cold-molded construction repeatedly mentions 1/8" veneers, at one point stateing 3/16"-maximum.
Even at 1/16" veneer thickness, the glueline saturation is still only 1/100" (at best) on each side of the veneer. There is still dry wood in there, unless of course you scratch the surface on your dock or trailer. Once moisture gets sucked in between waterproof glue layers, it cannot evaporate out, rot ensues.

G. Schollmeier
12-15-2007, 12:51 AM
Isn’t air along with water required for rot?

Jay Greer
12-15-2007, 01:43 AM
The same is the reason for the failure of plywood; the supposed bonding of two materials of a different modulus of elasticity. Over time the wood tears away from the glue line leaving a fine layer of delaminated wood.
Jay

Todd Bradshaw
12-15-2007, 03:55 AM
Yes, rot requires air. You can certainly damage a cold molded boat, but the resin coating on the surface will take a pretty good knock as it's harder than you might think it is. Once you actually get some experience with epoxy, you'll have a better understanding of it's hardness. I've run over rocks by accident with fully-loaded wood/fiberglass/epoxy canoes and literally watched a hump move along the floor as we passed over the rock. It makes a horrible sound and leaves a scratch in the outer filler coats of resin, but most of the time it doesn't go deep enough to mar the fiberglass layers themselves. Wood/epoxy cold-molded and strip constructions have a successful track record that goes back for decades, but I don't believe anyone has ever claimed that you can't damage it by running into something or that if you do damage it, it won't need some repair work.

If you can follow directions (which is very important because a hell of a lot of beginners either can't or unwisely choose not to) then you can build a beautiful and quite usable boat that will last many years with reasonable care. As far as the quote you posted - if you're actually building a boat, you have far more important things to worry about than theoretical scenarios like the one posted above. If you nail the dock and scratch all the way down to bare wood, stick a piece of duct tape over it and fix it when you get home. Problem solved - or at least it will be after you learn not to run into the dock.

ishmael
12-15-2007, 06:47 AM
If you get a ding that breaks the epoxy, don't re-seal it in a timely fashion, and the boat is out in the weather with rain getting into the ding, it is a recipe for rot pockets. Some of it depends on what the substrate wood is. Woods that are inherently resistant like cedar will, obviously, rot less quickly.

Epoxy has opened up building to amateurs who previously probably wouldn't have built a boat. Think of all the stripper canoes and glued-lap skiffs out there. But it's not a panacea. My preference, if I were to build a little lapstrake skiff today, would be to take the extra time and find some good cedar and some good white oak. Epoxy can be a miserable mess to work with. It must be pretty pricey these days, too.

Two cents.

olandrea
12-15-2007, 08:28 AM
Very interesting! Would it be helpful to prevent rod (not to prevent that water comes trough a scratch) if the veneer would be treaded with CPES be for lamination. The CPES should be go trough a 1/8" veneer.
"If you can follow directions " where do I gat directions? From the book The New Cold-Molded Boatbuilding?
Thanks Olaf

billy c
12-15-2007, 08:45 AM
in the cold mold process you are using roughly 3" wide eighth inch thick strips of wood or marine plywood laid at 45 degree angles. if you were to get an intrusion of water, the epoxy coating between layers and strips of ply would stop the advance and saturation of water to that small area. repair on that area would be relatively easy to attend to . obviously visual checks and maintance of the hull on a regular basis for any cold mold hull is the key to longevity.
-Billy

Gary E
12-15-2007, 09:23 AM
in the cold mold process you are using roughly 3" wide eighth inch thick strips of wood or marine plywood laid at 45 degree angles. -Billy

Doesnt that depend on how big the boat is??

How about a 50 ft sportfish with twin 1500 hp diesels??
you going to build that with skimpy 1/8 in ???

Raka025
12-15-2007, 10:39 AM
Sure, why not? It's the numbers of layers that count. Though using thicker plywood would be more economical from a cost of build standpoint.

billy c
12-15-2007, 10:46 AM
the cold mold is in the areas that have compound curves, not able to be formed with plywood. that would most likely mean that not all areas of the construction would require the cold mold process. the parts of the build that need cold mold would have to be eighth inch or less to be compliant with the process

LeeG
12-15-2007, 12:06 PM
Very interesting! Would it be helpful to prevent rod (not to prevent that water comes trough a scratch) if the veneer would be treaded with CPES be for lamination. The CPES should be go trough a 1/8" veneer.
"If you can follow directions " where do I gat directions? From the book The New Cold-Molded Boatbuilding?
Thanks Olaf


Seems to me you're finding ways to use epoxy more than solving a problem if the exterior fabric/coating is appropriate to the size of hull.

I'll defer to folks who've built big boats using epoxy, I haven't, but it seems that that much CPES aerosols would be a construction/health issue.

Todd Bradshaw
12-15-2007, 12:17 PM
The only epoxy products which will come close to stopping moisture penetration are those which are 100% solids (resin). CPES is about 70% solvents. When the solvent evaporates out it leaves holes in the coverage - which would be 0% solids in those areas, so you do the math. It may be a great tie-coat for paint or varnish, but CPES adds nothing to an epoixy surface and unless you're absolutely sure that all the solvent has floated away, it may actually reduce the ability of the resin to do it's job properly.

Books: Go buy a copy of "The Gougeon Brothers on Boat Construction" and read it cover to cover. Just about everything you need to know about getting started working with epoxy and about several different methods of cold-molding a boat is right in there, step-by-step (including large cold-molded jobs using a mixture of plywood layers and veneer layers on compound curves).

olandrea
12-15-2007, 10:03 PM
I know CPES will not stop moister penetration there for it is not made but Smith claims that it can stop or prevent rod because wood impregnated with CPES changes the natural wood cellulose (which fungi and bacteria find tasty and easily digestible) into epoxy-impregnated cellulose, which resists attack by fungi and bacteria.
Olaf

paladin
12-15-2007, 11:48 PM
If you are intent in building a boat, and wish to cold mould it, and also have it reject marine critters from using it at a burial banquet, there are other ways to do it.....dissolve as much copper naphthanate in alcohol as you can....cut your wood to size, brush on/slop on the copper solution, let it dry. if you have time, do it a second and third time.....but the final wait is at least 24 hours after the final coating, then use cpes and then full strength epoxy for binding the layers.......every cut surface of the wood will be coated with epoxy in the end, and a deadly poison will be on the wood and in the wood, just waiting for a hungry critter of any kind

olandrea
12-16-2007, 08:43 PM
That's a pretty strong cocktail!