The pouring urethane sidewall thread

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MontuckyMadman
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Post by MontuckyMadman »

Any time i ever messed witha surf board i broke the fins. Damn rocks, that and i cant surf. They must make them different now.
sammer wrote: I'm still a tang on top guy.
gav wa
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Post by gav wa »

MontuckyMadman wrote:Any time i ever messed witha surf board i broke the fins. Damn rocks, that and i cant surf. They must make them different now.
HAHA nah they haven't changed much, a skinny bit of plastic/epoxy with a 90kg human weight on top of it slamming into a rock at 20mph still breaks. But at least it means your going hard 8)
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backyardskier
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Post by backyardskier »

chrismp wrote:If you have any means to degas the resins before pouring, do it. First degas part A and B separately and then degas again after mixing (mind your pot life though).
Been thinking about this, not to sure if this would work.

Using PVC
Image

Sealing off the bottom and making a cap with a vacuum connection. I have a 5 cfm vacuum pump will it be to much for a pipe like that?
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MontuckyMadman
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Post by MontuckyMadman »

backyardskier wrote:
chrismp wrote:If you have any means to degas the resins before pouring, do it. First degas part A and B separately and then degas again after mixing (mind your pot life though).
Been thinking about this, not to sure if this would work.

Using PVC
Image

Sealing off the bottom and making a cap with a vacuum connection. I have a 5 cfm vacuum pump will it be to much for a pipe like that?
Pretty sure thats a bad idea.
You can use a polycarbonate lid but it has to be like 1/2 inch thick.
pvc or abs is not very strong, hit it with a hammer.
sammer wrote: I'm still a tang on top guy.
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chrismp
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Post by chrismp »

Get a big sturdy old cooking pot (I use an old pressure cooker with a 20mm thick polycarbonate lid). Cheap and easy to get.
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dbabicwa
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Post by dbabicwa »

^
Agreed.

Full vac below, small hole on top, bathroom plug glued with a car tires valve:

Image

Cost $2. Old car tires valve $0, bathroom plug stolen from a wife:)

Using 450ml PE cups for mixing, they are wide enough to go into this pot.

Wear safety goggles tho:)
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dbabicwa
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Post by dbabicwa »

As I see it, and everyone is different, the PU for me works well when is pre casted, and cured off mold.

Than I just use it for my boards as you would use UHMWPE.

And this is not possible with epoxy coz it's too rigid, it breaks, can't be bent, can't be formed after, etc etc. And, epoxy is more expensive.

And colors are nice:



Image

Just my 2c....
gav wa
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Post by gav wa »

I have some epoxy that is 65 shore, not brittle at all and costs only $160 for 6 kilo. The cheapest smooth on price I have found is more than double that. This epoxy has been used for filling voids in timber because it flexes with the wood as it ages, it also excepts colours well and can be used to do effects like marble look and swirls like a bowling ball.

Im not trying to convert anybody, I haven't even gotten to test it yet. But if I like the results I will definitely be posting them on here for others to try if they like.
gozaimaas
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Post by gozaimaas »

The more people trying the more products the better IMO.
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chrismp
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Post by chrismp »

gav wa wrote:I have some epoxy that is 65 shore, not brittle at all and costs only $160 for 6 kilo.
Sounds interesting. What shore scale is that hardness on (A or D)?
pmg
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Post by pmg »

Its 65A (see page before).

I ordered some additive for making epoxy flexible, so will do quite similar tests.
My plan is to pour the epoxy sidewalls in its end shape already (after the core has been profiled), and also pour the 0.8mm rabbet for the edge as well. So no machining after the pouring will be needed, just some sanding for better bonding.

Cheers
Philipp
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dbabicwa
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Post by dbabicwa »

gav wa wrote:I have some epoxy that is 65 shore, not brittle at all and costs only $160 for 6 kilo. The cheapest smooth on price I have found is more than double that. This epoxy has been used for filling voids in timber because it flexes with the wood as it ages, it also excepts colours well and can be used to do effects like marble look and swirls like a bowling ball.

Im not trying to convert anybody, I haven't even gotten to test it yet. But if I like the results I will definitely be posting them on here for others to try if they like.
The problem with epoxy for a sidewall for me is it looses color quite fast. It also yellows.
I am hoping PU will keep the color for much longer.

Shore 90A (PU rubber) I can imprint with a finger nail. Shore 75D (PU plastic), I can't.

Epoxy, I guess, is a way more brittle on low temperatures than PU rubber of the same shore. If anything PU rubber has still 550% elongation break and of epoxy is like 3-6%.

But, really, I think the PU is a go in industrial runs. We talking 30second pot life :oops:

PS
Smooth 310 trail package 1kg I've paid $30.
gozaimaas
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Post by gozaimaas »

Smooth-on 305 works out to be around $40/kg including freight for me. I would love to get it for $30 ;-)
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dbabicwa
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Post by dbabicwa »

Well,

today I've paid 1/2L thinner $18.95 in Whitworths.

Two years ago it was $16.95. It's just a thinner. International #1.

With a PU shipping it's a dangerous goods they are charging for...Crazy.
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chrismp
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Post by chrismp »

PU yellows as well (probably not as fast as epoxy). Smooth-On makes an additive called Sun Devil which is supposed to make the PU more UV stable and keep it from yellowing.
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