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Old 01-28-2014, 07:46 PM   #21
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I like epoxy and Cabosil, but micro balloons sand much easier. Epoxy and milled fiber is stronger than either. All that being said, I generally use sawdust, or if I need a really smooth surface I use sander dust. On occasion I have used plain white flour, non rising of course . I NEVER and will NEVER use polyester for any boat repair. Anything encased in epoxy will not absorb water.
Really should read up why poly or vinylester is the better repair material for some repairs and yes, Epoxy does absorb water...some way more than others and some little, but still absorbs (read West System tests...and that's just one of many that confirm it).
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Old 01-29-2014, 08:44 AM   #22
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O lot of folks use poly and vinylesters, I don't. Epoxy is more expensive but is far superior to either of these in every way. it's a little more difficult to mix and takes a little practice to use correctly. there are a lot of different types of epoxy designed for different applications. A flood coat epoxy would not be good for laminating. A thin laminating epoxy will work as a filler when thickened with additives, but a thick epoxy will be stronger and require less filler. Polyester resin over plywood is a good example of why I dont use it. The layup has to be so heavy to keep from delaminating that you can actually use thinner ply. At minimum you need to use a 24 ounce fabmat layer, then a fill coat followed by a scrim cloth to make it smooth enough so you dont have to fair as much. Its a pretty heavy layup but it works. Its also heavy. Epoxy on the other hand over ply (3/4, say for a deck) would require 2 layers of 10 ounce cloth, thats it, with little fairing if you do a decent job. Much lighter, just as strong, no delamination. I buy Epoxy from U S Composites. Its much cheaper than any others and they have an excellent selection. Anything from a 1 to 1 general use epoxy to a 5 to1 super strong epoxy. I use a lot of the 635 thin in 3 to 1 for laminating and 1 to 1 thick for filling and gluing. They also sell "boatyard poly" and I sometimes use it for building fg items. And I have read everything I can get, and researched, epoxy/poly. Back in the day poly was what we got, all we had. I used a lot of it. Experience has shown me that epoxy is better.
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Old 01-29-2014, 09:20 AM   #23
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It's not better for large flat section repair because it has different properties and can create flex spots that will fail the surrounding polyester...been know to happen quite a bit.

EVERY major yard /glassman I know uses poly or vinylester repairs for large sections but will use epoxy for bonding, filling smaller to mid sized holes (thruhull size) or high structural repairs.

While epoxy is better "glue" it's not the best product for every job.

I too buy from US Compsites as I completely stripped my hull bottom and laminated a 6oz cloth/epoxy barrier under Interprotect 2000 last eyar. I also glassed all my decks after teak removal which if I wasn't buying bulk epoxy and were really just a top coat, I would have used vinylester.
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Old 01-29-2014, 06:46 PM   #24
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Agreed, sometimes we need to "build" a section then put it into the structure. We build it with polyester then tab it in with epoxy. Poly and vinyl are great for building boats, just not for repairing. I see you did not use vinylester to laminate your barrier layer. Why is that ?
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Old 01-29-2014, 07:39 PM   #25
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Could have but didn't...50/50 shot and after talking with Interlux they convinced me to go all epoxy for a real thick barrier coating...either system I'm sure works fine.

Poly and Vinyl are used by some big yards I have heard from and the guys I work with for hull buildups after large sections have been removed for damage etc...and they are just faired in, not tabbed with epoxy.
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Old 01-29-2014, 07:59 PM   #26
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Epoxy on the other hand over ply (3/4, say for a deck) would require 2 layers of 10 ounce cloth, thats it, with little fairing if you do a decent job.
Multhullers would generally use 3/8th ply and a single layer of 8oz.
I have even been on 30 ft cruiser/racers that have only used 1/4 ply on decks and hulls, but I felt the need to walk dainty on these ones.

You can build amazingly light and stiff structures if you get your framing right
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Old 01-29-2014, 09:09 PM   #27
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I made a repair to the bottom of my lobsterboat almost 3 decades ago using 3 gallons of polyester resin & a sack of glass microballons. It involved an area near the stern 4' X 5' and 2" deep at its center (a defect in the initial molding of the hull). I remember screeding it off like concrete while upside down in the snow. Epoxy was completely unknown to me.
That repair is still there and has never chipped or loosened in all that time and quite a pounding over the years.
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Old 01-30-2014, 07:58 PM   #28
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Epoxy would not have been the thing to use "in the snow". That is one reason most folks like polyester resin, it will go off and set up, and its easy to use. that and CSM makes polyresin a no brainer.
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