PU sidewall mold?

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dbabicwa
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PU sidewall mold?

Post by dbabicwa »

Hey guys,

hope you have awesome winter time! Or summer seabreeze as we do.

Ok, so I've started making a PU pre made rails (sidewall) for my kiteboards.

Using a pressure chamber for post curing on 60psi, absolute great stuff at first. Using aluminium "U" profile 10x10mm (outer dimension) which is too big. Need 1/4" inside.

Thinking to make a mold of something so PU does't stick and easy do demold.

Tried to route a channel on perspex but no good. Perspex burning. Tried using a saw as well, too rough results.

Now trying to use a wood, sealed and varnished before pouring PU.

Basically something like this:

Image

Inside must be 1/4". So when I demold and sand the PU, it goes nicely in a 1/4" core channel.

Any ideas how to and what to use?

Thx
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falls
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Post by falls »

a lot of molds are made of silicone which not much sticks to
Don't wait up, I'm off to kill Summer....
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dbabicwa
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Post by dbabicwa »

Cheers Falls,

will consider a silicone. However it is more about how to make a mold?!

Made of what? Wood might be good but with a router I just can get a perfect result. CNC maybe, but costs a lot.

One suggestion is to water cut some 6mm thick perspex strips than glue them together to get a perfect surface for a male mold (which is $$$).

Other suggestion is 6mm melamine strips. Might be cheaper. Duno.

Tomorrow I'll check local plastic CNC guys for some options. Will see..

Thx.
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MontuckyMadman
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Post by MontuckyMadman »

We used to pour rubber in wax troughs for mold making. Tough to explain what we did but we used preextruded sticks of wax and then poured wax over it to make a smooth surface in the troughs. Cheap and easy and you can reuse and releases easy.
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bartinair
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Post by bartinair »

I used plastic cable raceway with great results! even able to raise ends to create thinner sidewalls towards tip/tail.
Used a little wax to provide good release.
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dbabicwa
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Post by dbabicwa »

bartinair wrote:I used plastic cable raceway with great results! even able to raise ends to create thinner sidewalls towards tip/tail.
Used a little wax to provide good release.
Nice. Pls tell us more, is it 1/4 inches?
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dbabicwa
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Post by dbabicwa »

Done.

I've swallowed a price. Got the professionally made HDPE mold. Now we talking.

Now I can make 6 x 10(max) x 1700 mm rails. This means 2 rails per board, different colors per rail.

The HDPE is absolute dream to work with!

This are my first PU pre made rails with fantastic finish on sides and bottom. The top is sanded anyway when placed in a core.

Image

It's a pity I've made an error in measurements and can'Tt put two molds in the pressure chamber at once. Might fix it latter.

Basically the mold goes into the pressure chamber on 50psi for two hrs.

The PU goes off the mold like with no strength at all. Just like peeling off.

There are absolutely no air bubbles in rails. It looks like a factory made piece of plastic.

Cheers!
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dbabicwa
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Post by dbabicwa »

My new batch!

this one is 327, transparent, nice fluorescent colors, can take a night photo
when charged with a light. They look awesome in a dark. Better than expected.

Post cured on 60psi, and heat cured on 55C for 3hrs.

Image

Image

A day photo tomorrow:)
gozaimaas
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Post by gozaimaas »

Cool!
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MontuckyMadman
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Post by MontuckyMadman »

what is 327?
sammer wrote: I'm still a tang on top guy.
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dbabicwa
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Post by dbabicwa »

Thx

SmoothOn 327.

This is the idea:


Would be awesome for you guys:)
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MontuckyMadman
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Post by MontuckyMadman »

ELONGATION AT BREAK IS 10%?
UHMW is 250% doesnt sound like the right stuff.
http://www.smooth-on.com/tb/files/SMOOT ... MBO_TB.pdf
sammer wrote: I'm still a tang on top guy.
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dbabicwa
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Post by dbabicwa »

Hm,

MM, horses for corpses.

In Australia, UHMW costs as gold:(

But I am very interested in the elongation break?! I can't imagine where would that be on the sidewall? Hitting a rock?

Are they any PU's with better elongation break or I shouldn't worry with a kite boards?

Thx
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MontuckyMadman
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Post by MontuckyMadman »

Elogation is relation to the elasticity of the material. Kite boards dont flex like skis and boards. I didnt realize u were makin kite boards. Im lookin for a hard 65ish d material with high elongation. The adiprine is the material it just has a 3 min pot life. Nightmare. Chemtura also has the duracast but it has to be cured at 250f for like 4 hours.
sammer wrote: I'm still a tang on top guy.
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MontuckyMadman
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Post by MontuckyMadman »

Horses for corpses????????
sammer wrote: I'm still a tang on top guy.
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