Re: Just Curious and Just For Fun
well in 1996 (before interwebs) I put a transom in a 1974 performer using 7oz cloth and boat yard resin (poly) and marine plywood it lasted until 2011 when I went and drilled holes for some trim tabs and water poured out. the wood had turned to mush. So currently I am redoing the entire boat in marine plywood and epoxy using tip's from here but mainly following this rebuild as a guide.
Bateau2 - Builder Forums • View topic - Seacraft 23 - shine
I am planing this boat to last the remainder of my life in serviceable condition.
This is a typical result when the wrong products are used in the wrong way.
Cloth and polyetser don't go together, instant failure point. Water pouring out of the transom and the wood being mulch has nothing to do with the resin (sort of), it has to do with the combination of products and the methods used.
Please don't take offense to this, as none is inteded.
Here is a copy and past from something I wrote a couple years ago.
I deal with many different markets in the composites industry, not just the marine end of it and for the most part I agree with XstreamVking.
Since I don't see bond failure as an issue in anything I've built or repaired with polyester or VE over the last 40+ years and it isn't really an issue for the my customers, which have built many thousands of boats themselves, it seems the bond issue is more a case of poor workmanship or bad design. The prep needed for either type of resin is the same, epoxy may let you do a poor job with a little better chance of success though.
When I see bond failures it’s typically when a rookie decides to do a F/G repair on his boat (insert any item in place of a boat) and heads down the hardware store. They buy whatever resin it is that has been sitting on the shelf for a couple of years and some cloth (no mat), no sand paper, acetone, or any other needed items. They pull the boat out from under a tree in the side yard, use a damp cloth to move some of the leaves away and make a feeble attempt to wipe off the green and brown gunk that has accumulated on the surface for the last 10 years. At this point they remember they should sand the surface, so they go back in the garage and find an old piece of fairly fine grit sand paper that has been used many times on other projects. Now they make a couple of half hearted passes over the surface with the sand paper, which instantly clogs up with the damp green gunk still on the surface. It gets one more wipe with an old rag that was last used to check the oil on his truck and he now feels he’s ready to catalyze some resin.
Now, how much catalyst to add…..was that 2%, 20%, 50%...and how do you know what 2% is…or did they say 2 drops per quart…oh well, it’s not that important, I’ll just poor a little in…oops…too much (I think). Now where is that old paint brush I used to do the trim on the windows a couple of years ago…..there it is…wow, maybe I should have cleaned it better…sort of stiff. OK now I just pour some resin on the surface and lay this 1’x1’ piece of cloth on it, I only “prepped” a 6”x6” square, but it should be fine…maybe even stronger. Let’s see, what do I do with all this extra resin…it sure took a lot less to wet out that piece of cloth than I thought. I think I’ll just pour the rest of it around on some of the other cracks to strengthen other areas too…don’t want to waste it. Looks like rain…good thing I’m done…now I’ll go in and have a beer.
A week later he heads to the lake puts the boat in the water and it doesn’t leak, it was a successful repair. Two weeks later he runs over a big wake while pulling a tuber and the repair starts to leak, he reaches down and grabs a corner of the cloth that is sticking up, the part he couldn’t get to lay down, must have been because it was folded over. He pulls and the cloth comes right off with little effort. That night he goes on line and asks on a boat forum why it failed, he tells them he did everything according the directions but it still failed. He is told that polyester resin is very weak, won’t stick to anything and that he needs to use epoxy, so he orders some online the next day. While waiting for the epoxy to arrive he starts to clean off the “failed” polyester resin and finds it is sticking in some areas and won’t chip off. This time the neighbor sees what he is doing and offers him the use of a small grinder, this speeds things up dramatically and removes all of the old resin and green gunk that was still on the surface. The epoxy is delivered and so is some biax, he also ordered the roller and squeegee the guys on line said he would need, plus he picked up some new brushes.
This time he remembers its a 1 to 1 mix (and with a little work he can figure how much of each that is), stirs it well and from his experience before, plus the advice from the forum he uses the correct amount of resin to wet out the several layers of glass to build the surface back up and works all the bubbles out.
This time the repair holds up, now he goes back online to the forum, he’s one of the experts on the forum now because he’s done a repair before, and tells everyone how bad polyester is and that they should never use it and epoxy is the only thing that works. Sound familiar.
Back to the other stuff.
If properly designed an epoxy hull will be no stronger than a polyester or VE hull designed for the same use, only lighter, this is where the DIYer comes up short. They tend to use about the same laminate schedule as they would with polyester or VE, so they have the same weight with a much higher cost and an over built part, or repair, this results in no advantage or benefits from using epoxy. I hear people frequently say that you will save weight by doing an epoxy repair, well it would need to be a very large repair to make a meaningful difference in the weight savings. You may save the weight of a six pack on a large repair...and well….that may be very important to some people…more beer.
As for strength, most epoxies list their physical properties after being post cured, if you don't post cure it don't expect to get close to them. Also any medium to slow cure epoxy really needs to be post cured, they fall well short of the listed properties without this step.
The other issue with strength is when using low viscosity epoxy infusion resins is they tend to be much weaker than higher viscosity resins. This has to do with how they reduce the viscosity. What can happen is the physical properties can drop to a level equal to, or below those of a VE resin.
Even the many thousands of low quality ski boats built to very a low price point with the cheapest polyester resin available rarely have an actual resin/glass failure, the wood rots and they tend to hold up OK until the wood it nothing more than pulp. And even then the owner has no clue there is an issue until his foot falls through the deck.
As for high end custom or semi custom boats, why not use epoxy, it’s a great product and will allow you to build a much lighter craft. These tend to be purchased in relatively small numbers by people that can afford this type of toy, not the everyday guy.
As for the type of boats repaired or modified on this site, epoxy may be a good choice for them, that is if your plan is to put the largest outboard on it you can and then push it to the limit. Although a VE is easily up to the job. For the many more that just want their ski or fishing boat back on the water, I can’t see a good reason for using epoxy.
