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Re: Epoxy over polyester?

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  • etap28
    I have complicated feelings about polyester. It wasn t that long ago that all glass boats were built out of polyester. It s perfectly OK stuff, as long as you
    Message 1 of 32 , Sep 2, 2011
      I have complicated feelings about polyester. It wasn't that long ago that all glass boats were built out of polyester. It's perfectly OK stuff, as long as you understand what it can and can't do. It'd dirt cheap compared to epoxy, you can do two or three times as many layups in the same amount of time, it sands like nobody's business (save massively in sandpaper), and as somebody already pointed out, it doesn't sensitize the skin. Also you can build damn strong hulls out of the cheapest stuff, roving and matt. Yeah--it really stinks. That's what respirators are for! I fixed a 14' hole in a j30 deck/hull with Cflex and polyester--the boat was originally polyester anyway. Vacuum bagged balsa core. These are not considered shabby boats, or weak, and people sail the living c--p of them, though most boatbuilders today turn their noses up at balsa and/or polyester--the upward escalation of materials snobbery. The next project was a C&C Landfall that had giant hurricane holes in the sides--I used vinylester in that one because that's what it was made of originally. That's a step up in quality (stronger, less porous), but much harder to sand (kind of gummy). The next project was a new keel on a 48 footer, and that was WEST all the way. Polyester vs epoxy is to some extent an apples and oranges thing--the stuff I did on that 48 footer would have been impossible with polyester since it would have kicked violently in the middle of the long, involved layups, but structurally it would have been fine. (The end result was an encapsulated keel that will outlast the rest of that crappy hull by ten to one.) I guess I'm just saying--polyester is very versatile, very cheap, very quick to work with, completely indifferent to mixing ratios, is not fussy at all about temperature (throw in a little more catalyst if it's cold out), has built a ton of really long-lived, strong boats, and when laminated on ply will last for longer than most people want to keep an insta-boat anyway. . .
      All that said, I wouldn't put the stuff on high grade plywood, but let's say a Gypsy made out of A/C, or a Windsprint, or something of that ilk--heck yeah. Good for 10 or 15 years. I think a lot of the prejudice is the success of the epoxy industry at demonizing polyester--and also the newer boats are all SCRIMP because it saves money and makes faster hulls when you've got a high glass-resin ratio; and SCRIMP (vacuum infusion) wouldn't work with polyester (sets too fast)
    • Stefan Topolski
      In his book he did restore sailing yachts with it - his stories include one being indestructable until it got cut in half by a steamer off shore. All the Best,
      Message 32 of 32 , Oct 4, 2011
        In his book he did restore sailing yachts with it - his stories include one being indestructable until it got cut in half by a steamer off shore.

        All the Best,

        "One gathers peace as a feather in the palm of one's hand."    -anonymous

        Stefan Topolski  MD
        Assist. Professor, U. of Massachusetts Medical School
        Clinical Instructor, U. of New England
        Founder and Director of
        Caring in Community, Inc.  501(c)3
        1105 Mohawk Trail
        Shelburne Falls, Ma.

        El sep 17, 2011, a las 5:06 pm, John Kohnen escribió:

        Vaitses's method was intended to get some more years of working out of  
        fishing boats and other workboats. I don't think I ever read of him  
        touting it for yachts.

        A fellow I knew got ahold of a nice-looking British built double-ended  
        sailboat that had been cold-molded over. The work had been done in Port  
        Townsend, wooden boat capital of the west. That doesn't mean that  
        _everyone_ in Port Townsend knows what they're doing. <g> One day he cut  
        or drilled into the hull to mount something, and after he got through the  
        cold-molded outer shell he ran into -- compost! :o( From the outside the  
        boat looked great, from the inside it looked OK, in between was a layer of  
        very rotten wood, sandwiched between the cold-molded shell and a thin  
        layer of good wood on the inside of the planks. <sigh> He ground off the  
        cold-molded shell and discovered that just about every plank needed to be  
        replaced. He never got very far into the project before he lost heart, and  
        the boat was eventually broken up by the boatyard. If he'd never cut  
        through the outer shell maybe he'd have gone voyaging, and maybe the boat  
        would have brought him back. <shrug> After he knew that there wasn't much  
        of anything holding that outer shell to the rest of the boat he didn't  
        dare take her to sea.

        The example many people give of a boat that was cold-molded over  
        successfully is a British cutter that spends most of its time around South  
        Georgia -- where it's _cold_ and the rot spores are probably in  
        hibernation. <g> I'd be very suspicious of any traditionally built wooden  
        boat that had been covered with glass, using polyester or epoxy, or had  
        been shelled with cold-molding.

        On Thu, 15 Sep 2011 09:27:44 -0700, dave wrote:

        The vaitses method always makes me cringe when I hear about it. I guess  
        in the case of a boat with a really terminal hull, great interior and  
        great rig.... it might,just might, pay to do that, but if you're going  
        to build a new hull over the old one, why not cold mold? The part  
        nobody's talking about is fairing the new polyester hull. That's a huge  
        labor investment, unless you just don't care and decide to paint the raw  
        polyester, in which case you've built yourself a totally unsaleable  
        hulk. Either way, you've built yourself a totally unsaleable boat, so  
        you better love it for the 15 or so years it'll last before that  
        well-sheathed rot finishes its business; but if you fair it, at least  
        it'll look like a boat.

        John (jkohnen@...)
        A fool and his money are soon elected. (Will Rogers)


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