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 Post subject: ? on building xps foam board
PostPosted: Mon Jul 26, 2010 10:06 pm 
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'im a beginner and want to build a board i have some xps foam lying around and want to build it out of that. would this work?


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 Post subject: Re: ? on building xps foam board
PostPosted: Mon Jul 26, 2010 10:31 pm 
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Joined: Mon Jul 26, 2004 6:50 pm
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Location: Wolfe Island Canada
At first glance you think it will work. But after you ride it for a while it will delam. Strangly expanded polystyrene foam works and MANY surfboard builders use that now. You can get 1.5lb eps at home depot really cheap. You must use epoxy and NOT polyester resin.

Stan


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 Post subject: Re: ? on building xps foam board
PostPosted: Mon Jul 26, 2010 11:15 pm 
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What kind of board?


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 Post subject: Re: ? on building xps foam board
PostPosted: Mon Jul 26, 2010 11:22 pm 
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i heard if you puncture it with small wholes it wont delam

it's going to be a twintip board


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 Post subject: Re: ? on building xps foam board
PostPosted: Tue Jul 27, 2010 1:22 am 
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The holes might actually work. But I suggest if you go to the trouble of making a board get some good foam like corecell.


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 Post subject: Re: ? on building xps foam board
PostPosted: Tue Jul 27, 2010 4:39 am 
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i'll probably try a corecell board later this season


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 Post subject: Re: ? on building xps foam board
PostPosted: Tue Jul 27, 2010 8:37 am 
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Joined: Tue Feb 24, 2009 1:43 pm
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Location: Iv.G.-Slovenia
Hi

I strongly recomend not to use EPS. I've been using it on a couple of my boards and they didn't last 10 sessions.
1. I used it on top of 5 mm plyboard. While the board was bending the EPS on top of the board was compressing so much, that the material didn't take it anymore (got tired) and the top glass-epoxy laminate cracked.
2. I replaced this EPS layer with poplar plyboard, but I used EPS on the edge of this layer 10X15mm, and on the edge of the 2. bottom plyboard layer, so I could easily sand the edge as seen on the pic. And guess what! The board delaminated in the middle, where there was less material to bond to, under 2 sessions, because EPS doesn't hold ass said before.
Image

Making holes won't generaly improve the deal. Maybe it will hold 10 sessions, maybe not.
And making only pinholes won't help, because the epoxy won't even force the air out of the hole and you should laminate both sides at once. If not, the second one would have a bad bond, because, the epoxy holds bad to cured epoxy.
Don't get me wrong. EPS bond's OK in the area which is raw, if you sand it. But that's about 0,5 mm deep. The other part of the plate is torn away easily.
EPS is for house insulation and that's the way it should be.


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 Post subject: Re: ? on building xps foam board
PostPosted: Wed Jul 28, 2010 1:56 am 
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Cores have the function of keeping top and bottom laminates apart. When flexed, one laminate is in tension, the other one in compression, and the laminates get displaced and the core is subjetc to shear. The laminate in compression tends to buckle and either crash into the core or it will try to delaminate. So a core needs to have enough compressive strength to withstand the riders weight and the compressed laminate to crash into the structure of the core, enouth shear strength in order to soutvive top and bottom laminate displacement and enouth peel strength in order to avoid complessed laminate to depart form the cores surface.

PVC foam = good compressive strength, good shear strength, poor peel strength
PU foam = fair compressive strength, fair shear strength, poor peel stremgth
EPS foam = poor compressive strength, poor shear strength, fair peel strength
Wood = good compresive strength, good shear strength, goog peel strength

Of course, foam density and wood quality play an important role as well. Common EPS foam used for insulation and/or building supply has not enough density to be suitable for board production, compressive strength is very poor.


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 Post subject: Re: ? on building xps foam board
PostPosted: Wed Jul 28, 2010 8:04 am 
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This is how my first construction looked like. Like Aeberl said EPS has poor compressive strenght. I had that in mind, so i reinforced it with carbon piece under the pad in heel area, but I ignored the fact, there will also be a lot of compression on the upper side of material, when the board is bending. Maybe some wooden stripes would help, but it would change the caracteristics of the board seriously.

Image


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 Post subject: Re: ? on building xps foam board
PostPosted: Wed Jul 28, 2010 2:50 pm 
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I have started a board using extruded polystyrene (I think). This is pink closed cell foam. It is pretty dense and free to me. Does anyone have experience using this? I was planning on using epoxy resin with a process similar to the video on another post. I made a board out of plywood last year with the same shape and was happy with the way it rode but it was way to heavy.


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