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Old 23-12-2009, 14:05   #31
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this is really a simple project.. If the thickness of the foam was indicated, I missed it but the thicker, the stronger and the laminate can vary with that thickness. I'll assume about 1/2 inch? maybe more? I would use 600 or 800 DB gram clothe to make sure, or whatever is available cheap (know someone finishing up a big project with excess?) and any resin that is cheap, poly is fine! And it isn't toxic like epoxy, not that this small project will be a big risk but if you do use it keep the stuff off your skin and avoid fumes.

Wet the foam, lay on the clothe, consolidate well, work all the air out and trim excess on the edges with stanley knife when green. "Q" cells for filler on a finish coat, sand to taste and coat. I would just use epoxy primer and polyurethane top coat but there are other options of course. Whatever matches the adjoining surfaces best/easiest/cheapest.

For a nicer finish on the layup, I like to use peel ply. More even surface and already keyed in for subsequent work.

I know some brilliant boats of foam and poly, most ply boats I know use vinylester but epoxy is my choice for underwater. It is less permeable than any other so osmosis is avoided. But I hate epoxy's toxicity.

Polyester works fast so you must also... epoxy sets slower so you must wait...

except for special purpose variants, poly and vinyl shouldn't be expected to stick to epoxy but epoxy will stick to them.

Do in the shade, moderate temp and low humidity.

fun little project... but I call it a turtle top.

Cheers

Peter
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Old 23-12-2009, 14:17   #32
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Hi. how are you attaching the hood to the cabin roof? Are you building it as a completely separate item and then attaching it or getting the underside to a finished surface and then bonding/glassing over top to secure/waterproof and fair it to the cabin roof?

The reason I ask is that if you want to use glass and resin to attach the hood, and possibly fair it in so it looks as if it always was, you'll have to use epoxy. Polyester is just not a good enough bonding agent for an application of that sort.
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Old 23-12-2009, 22:05   #33
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Rum! Yum!
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Old 24-12-2009, 11:37   #34
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thanks for all the great info.

To answered a few questions:

The divinycell is 1/2"

I will attach the hood by expoxying in a few small bolts that will then go through some existing holes in the cabin top.

So I have decided to go with epoxy. Anyone care to suggest a lay-up schedule? They guy at TAP plastics told me I needed 4 to 6 layers of glass on each side. That seems excessive to me? Any thoughts.

Thanks.
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Old 24-12-2009, 12:32   #35
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all depends upon the weight of cloth in ounces
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Old 24-12-2009, 12:40   #36
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i was going to use a combination of 8.6oz and 5.6oz e-glass.
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Old 24-12-2009, 19:41   #37
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I'd use one layer of lighter cloth, each side, with one or two layers of tape on the external radius. If you're going to walk on it, put two layers outside. Sand fair, then a finish coat. If, when you are finished, you aren't satisfied that it's stiff enough, you can easily add more, but I think you'll be pleasantly surprised. I love epoxy.
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Old 06-01-2010, 20:41   #38
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Why hasn't anyone mentioned Vinylester resin? Seems like the perfect compromise between epoxy vs. poly.

BTW you don't need to use epoxy for what your doing. If it was a composite raceboat than different story.
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Old 06-01-2010, 22:21   #39
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Hi unfurled

I did briefly.. " I know some brilliant boats of foam and poly, most ply boats I know use vinylester but epoxy is my choice for underwater."

I think vinyl is nearer epoxy for strength but the project under discussion is really low stress. I like to keep costs down where ever I can so look for what works for the $$.. But every skipper gets to make their own call.

I got a kick out of.. "They guy at TAP plastics told me I needed 4 to 6 layers of glass on each side." Now there's someone who will make salesman of the month.

Cheers
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