Epoxy/Adhesives

There is a suitable "alternative" to epoxy for marine use and that is resorcinol.

Resorcinol is a red resin and pink powder mix, you will see it used in many marine and waterproof plywoods.

Not so common anymore to find, but it is certainly still available. It is waterproof, easy to use, dries well, but has a red stain that needs attention when glueing if you want a clear coat over it.

My choice, stick with a reasonable price epoxy. (and NEVER think you can make epoxy go off quicker bu adding more hardener....yep. it will go off, but it has lost its strength dramatically.

 

In most cases, epoxy curing solutions have to be mixed with resin at their proper 'stoichiometric' ratio. With some curing agents, there may be a wide latitude to this ratio, but the ratio is still the optimum way to combine a given resin and curative.

If you need more or less work time, you must use a different curing agent with either more or less reactivity; changing the mix ratio will not help.


But there exist at least two families of compounds that cure epoxy resin that are classed as catalysts rather than curing agents, similar to the way MEKP is a catalyst for polyester resin. These are the imidazoles and the Lewis acids. These can cure any epoxy resin and do not have a set mixing ratio. Adding more will make the epoxy cure faster, less and it cures slower. Both families exhibit 'latency' meaning that even after mixing, nothing seems to happen, even after several days. These systems need to be kicked off with heat. The Lewis acids are especially latent and have to be kicked with at least 180*F. The imidazoles kick at lower temps, usually around 120*F. Both eventually cure without heat, if you don't mind waiting. The imidazoles cure at room temp. in 5-10 days. The Lewis acids take about six months. This makes them a favorite for room temp pre-preg.

Both families produce good cured state properties; the imidazoles especially produce outstanding properties, especially if you need high-temp service as they will yield a Tg a whopping 50* above the cure temp. and can be post cured at any time. Most amine systems have a 'post cure window', after which post curing does not help much.

Jimbo

 

Jimbo,

Was that from ya head or did you cut and paste.

Good article anyhow mate, and if it came out of ya melon, well all I can say is we are very lucky to have people like you on this forum.

 

you can paint marine ply

 

And loose it after some time.......................
No paint makes it water resistant. Epoxy does.

Lubs, if you look at my gallery you see this:
http://www.boatdesign.net/gallery/showphoto.php/photo/13523/ppuser/11121


why does this picture not come up?
But thats more or less a material for the pro. I do´nt recommend that a amateur builder uses resorcinol.

Regards
Richard

 

I have been researching epoxy now for several days using what everyone is saying to aid my research. I notice that most of you here, at least the senior members, are used to building much larger, fancier, and expensive boats. I also value your opinions due to the knowledge that you possess. But, since I am building such a small fishing 'Jon' boat, I would like to know what you think about the link below. It is a mono-coat clear epoxy that looks like something I would be interested in. It appears that I would only have to buy a gallon of it and apply it, prepping the surface first of course. Please let me know your thoughts.

http://www.supermarinepaint.com/clears-mono-coat-epoxy-2020C.asp

 

J,

The fact that you building a little boat or a big boat doesn't make much difference. The wood will soak up any water it can get its fingers on.

I build small boats (Hybridduckboat.com) and use polyester resin and cloth. While if you believe everything you read on here, my boats should have fallen apart long ago. I fiberglass the inside and outside of the hull and always add a final coat of resin to smooth out the texture of the fabric. I paint the top decks because they typically stay dry. I just made a 10 footer and it cost about $275 and weighs around 80 pounds.

If you can use a gallon of paint, you can use a gallon of epoxy.

Instead of looking at West Systems - check out USComposites.com and see that the costs there aren't as expensive. The guys I know who build the same boats use this epoxy and no-one has complained yet.

Bottom line - if you want it to last more than a year you either have to fiberglass it or epoxy it. If you want it to last long enough to become a problem in a landfill, epoxy seems to be the best way to go.

I still use polyester resin on my boats and like I said, they last long enough to keep me happy - or "nothing has gone wrong yet".