The pouring urethane sidewall thread

MontuckyMadman · Post by **MontuckyMadman** » Fri Jun 20, 2014 5:56 am

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.

gav wa · Post by **gav wa** » Fri Jun 20, 2014 6:14 am

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

backyardskier · Post by **backyardskier** » Sat Jun 21, 2014 1:39 pm

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

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?

MontuckyMadman · Post by **MontuckyMadman** » Sun Jun 22, 2014 11:03 am

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

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.

chrismp · Post by **chrismp** » Sun Jun 22, 2014 11:42 am

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

dbabicwa · Post by **dbabicwa** » Sun Jun 22, 2014 9:17 pm

^
Agreed.

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

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:)

dbabicwa · Post by **dbabicwa** » Sun Jun 22, 2014 9:37 pm

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:

Just my 2c....

gav wa · Post by **gav wa** » Sun Jun 22, 2014 11:20 pm

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 · Post by **gozaimaas** » Mon Jun 23, 2014 12:21 am

The more people trying the more products the better IMO.

chrismp · Post by **chrismp** » Mon Jun 23, 2014 1:15 am

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 · Post by **pmg** » Mon Jun 23, 2014 2:51 am

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

dbabicwa · Post by **dbabicwa** » Mon Jun 23, 2014 4:18 am

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

PS
Smooth 310 trail package 1kg I've paid $30.

gozaimaas · Post by **gozaimaas** » Mon Jun 23, 2014 5:27 am

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

dbabicwa · Post by **dbabicwa** » Mon Jun 23, 2014 6:45 am

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.

chrismp · Post by **chrismp** » Mon Jun 23, 2014 6:52 am

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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The pouring urethane sidewall thread