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 Post subject: Advice on glassing
PostPosted: Thu Feb 24, 2011 6:42 am 
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I have read a lot of great threads on this forum but have not found anything that addresses my question on how much glass to use. I have a 140 x 46 cm light wind board just about ready for glass. See the photos below. The core is two ¼” 5 ply birch plywood sheets. In order to lighten it up I took out some material and replaced it with foam. Even with all the missing wood the board is still very strong. It has too much flex but I suspect glassing will correct that. I was thinking double 6oz top and bottom. I don’t know if that will be enough. Any suggestions for strength vs. lightness.


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 Post subject: Re: Advice on glassing
PostPosted: Thu Feb 24, 2011 7:09 am 
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Location: Guadalajara, Mexico
I would go whit
unidirectional 10oz + and 6oz of your cloth for deck and the same for the bottom,,,, the unidirectional fiberglass is great for stiffener without to much weight


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 Post subject: Re: Advice on glassing
PostPosted: Thu Feb 24, 2011 4:13 pm 
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What kind of foam?
That matters, but anyway,
6oz x 3 layers top and bottom would be good and strong,
the 10 uni + 6 might be strong enough,
and it wouldn't hurt to run an extra layer of 6oz deck patch on top between the footstraps.
Also how much does it weigh?
If it it is heavy ( > 2.7kg?) already, carve out more wood and go with the 18oz total glass.
However you go, with that much foam you probably want a deck patch to resist buckling....
Looks like a sweet outline though
Good luck, post results.
It's all an experiment, have fun.


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 Post subject: Re: Advice on glassing
PostPosted: Thu Feb 24, 2011 6:42 pm 
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Location: Ottawa, Canada
The typical layup for a board might be 3 layers of 6 oz on each side if you had a 1/2" corecell core and thinned it to the tips and rails (unless ridden really hard). And the foam before glassing is pretty flexible. Surely that unglassed thing must be a good bit stiffer than just foam on its own. I would not go more than 2 layers of 6oz each side if I was doing it. Maybe an extra patch or 2 under heels where they sit on foam, but that's about it. (depends if your deck pads have plates, and on what that foam is)

If you are really heavy and ride it hard you might need more. If you are a lightweight looking for lightwind cruising, I bet you could get away with 9 or 10 oz on each side instead of 12.

Nice idea, I wonder if this is a good way to get some lightweight benefits of foam, and some wood-like pop in the board.

Peter


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 Post subject: Re: Advice on glassing
PostPosted: Thu Feb 24, 2011 9:14 pm 
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Quote:
wood-like pop
=dimensional lumber, not so much with plywood :-?


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 Post subject: Re: Advice on glassing
PostPosted: Fri Feb 25, 2011 1:17 am 
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Yeah, that's probably true. I also have no idea if birch is the right wood for that feel either. Maybe if you mix foam and wood you get better elastic properties from the wood if it is more in the skin, as opposed to through the board like stringers.

I expect guys have played with mixing foam and wood, but I have not seen much or anything written about it.

Peter


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 Post subject: Re: Advice on glassing
PostPosted: Fri Feb 25, 2011 6:26 am 
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Thank you all for the input. I think the wood frame has a lot of strength but I will beef up the deck to compensate for the vulnerability of the foam sections. I’m planning on using Peters shop vac bagging technique. I’m not ready to shell out for a vacuum pump just yet. Here are some answers to a few of the questions I saw in the thread. The foam is 4 lb density Last a Foam. Right now the board is pretty springy so I think it may have some pop although I have not advanced to popping just yet. I chose Baltic Birch because it was the best quality I could get my hands on. This is my first and most likely last plywood board. Plywood is tough as nails and really hard to shape. I have ordered some Paulownia and I also want to try a Divinycell core as well. I’ll post up after the board is done and I have had it on the water a couple times. Thanks!


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 Post subject: Re: Advice on glassing
PostPosted: Fri Feb 25, 2011 5:33 pm 
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What are the rails made of?


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 Post subject: Re: Advice on glassing
PostPosted: Sun Feb 27, 2011 6:54 am 
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Rails are epoxy and micro balloons. I was considering urethane but defaulted to what was comfortable.


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