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 Post subject: BoardBuild materials nedeed
PostPosted: Mon Mar 22, 2004 10:16 pm 
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Do i really need a vaccum process in order to build a polyurethane board?

wath is the best way to give the rocker shape on polyurethane?

I might start for a plywood to practise some shapes :))

Cyaz!And...ride da wiiind!


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 Post subject:
PostPosted: Tue Mar 23, 2004 3:30 pm 
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Location: rhode island
urethane ?

do you want to use that as a core material ?

what kind/
what density?

as long as it has sufficient compressive and shear strength it should work ok.

vacuum bagging the skin laminates adds some improvement in strength but is used mostly to get the weight down.
so if final weight is not a priority, it's not really a big deal.
-bill


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 Post subject:
PostPosted: Tue Mar 23, 2004 8:49 pm 
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Urethane...i think so!(almost sure) because is the only material i can easyli get here in portugal and it's cheap! Don't know the kind nor the density...it was the only kind of foam there was!
There are several measures, from 20mm to 60mm...the material it self wasn't very strong, but isn't the stuff you cover it with that makes the strenght on the board?
On that same store there was also kevlar and carbon fibre and special UV gelcoat!!

I'll try some shapes on plywood, what should i use to give strenght to it?!?
TKX
and...ride da wiiiind!


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 Post subject:
PostPosted: Tue Mar 23, 2004 11:39 pm 
Kevlar and carbon, but no decent foam to find? :D

No, polyurethane is good to start with as it is the only foam polyester works with.
Polyester is cheap and therefore better to start building your first board.
(it bites holes in other foams, so only use polyester with polyurethane)
Unfortunately polyurethane is not as strong as other foams with same density...

Strenght is for the biggest part a result of the layers you put on your foam.
Much glassfibers + polyester = strong, but heavy
1 layer of carbon +epoxy = very strong, less weight, 3 or 4 times more expensive(?)

Makes no sense to combine Carbon and polyester if you want to reduce weight.

Try it cheap first. Weight will be a bit more, strength a bit less, but you'll be able to build a quite decent testboard for half the price of an epoxy-carbon board.

If you build it with plywood, strengt will not be a huge problem if you make multiple layers...
And if you want, you can always reinforce with a layer of fiberglass and polyester.
-----------------------
hollow --------
-------------------------

Hope this helps.


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 Post subject:
PostPosted: Tue Mar 23, 2004 11:41 pm 
ooops, something happened with my drawing. :-?

Anyway, you get the picture, right?

Just make some kind of box.


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 Post subject:
PostPosted: Tue Mar 23, 2004 11:43 pm 
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Location: rhode island
I'm sure there is some flavor of urethane foam that would work.
but i cant name any.

most folks use PVC foam like divinycell or Airex.

the foam density is around 80 kg/m^3 (6#/ft^3)

and the compressive and shear strength are around 1.2 MPa each.
(175 psi)

if you found something with the above properties, that would be a good starting point.

if you want to go with wood.
cedar is pretty light and strong.
no glass required.
but some 4 oz glass will help seal it and give it some surface toughness.

1/2 inch plywood will work fine. it's just a little heavy.
-bill


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 Post subject:
PostPosted: Thu Mar 25, 2004 12:54 am 
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Thats true! Kevlar and carbon...but no decent foam :/
They can even order a kind of bee nest kind of foam...
Tkx for all the tips!!!
I'll start with a plywood that is most comum here, maybe with only 2 layers and a reinforced bottom...
What's the best way to"glue" the layers on each other?
How about a clear strong bottom?
tkx again ;)


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 Post subject: ITCHY-SCRATCHY SHOW
PostPosted: Tue Nov 23, 2004 8:53 pm 
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Fiber-glassupply.com


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 Post subject:
PostPosted: Wed Nov 24, 2004 2:46 am 
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Some of the first foam/glass boards I built used Last-A-Foam brand polyurethane foam in 6lb density.

3/4" thick (18mm), not too much tapering at the tips, at the very least 18 ounces/square yard (total) fiberglass on each side with epoxy. I think that is equal to about 600 grams/ square meter on esch side, but I am not sure

They held up pretty well, the weight was a little heavy because I glued three thin layers of foam together with thickened epoxy to make the core - too much weight from the resin. Much better to get the foam in the thickness you want.

The polyurethane foam was super easy to shape, almost too easy. It is pretty fragile stuff compared to pvc foam or corecell. You also have to be very careful to vacuum the dust off before laminating or the epoxy won't bond to it very well.

Cheap (or more accurately, cheaply made) production kite and wake boards are still made with polyurethane foam. I'm pretty sure Naish is still using it in some of their boards. I know for a fact that Liquid Force used to use it in all their boards and I think they still do in the less expensive ones. Others probably use it too, no doubt.

Trent


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 Post subject:
PostPosted: Sun Nov 28, 2004 11:21 pm 
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Location: Oeiras
Corvito,

in portugal you can found easily Divinicel or airex.
Even the vacuum pump you can buid one. Its not so dificult.

So why build a wood board???

Im made my first one withou any experience and it woks very well. The main concern its the rocker tabel, if you build a good one you can make a lot of different boards.

Any help please mail me. :thumb:


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