How to make urethane sidewalls

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prospectsnow
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How to make urethane sidewalls

Post by prospectsnow »

I built a trough to make profiled urethane sidewalls. I'm getting some pretty good results.

The trough is just some angle iron with abs plastic as the bed. Supports to give the profile are a few scrap peices of base material and paint stir sticks.

I have the profile pretty close to my core although it needs some small adjustments. The goal here is to make it 5mm in the middle and 1mm on the ends. I found it tough to go that thin on the ends so It really ends up more like 8mm in the middle extended out to 3mm on the ends.

in the pic I have some shrink wrap to create a leak proof basin. You can see there are some wrinkles that transfer into the end product. I've got a couple ideas on what I can do to flatten it out. I'll post later...

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The next step is to pour the mix in the trough and let it hang out for a while...

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To get the bubbles out takes some work. Careful mixing helps. Warm temps help. After pouring, the flame torch is gold. Do some flame passes over the material to pull the bubbles to the surface.

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I then cut out the slabs into strips with at utility knife narrowly avoiding stitches, but plenty of blood. A good sanding and flame treatment make the sidewalls bond well to the core.

At this point I'm sanding down the high spots, which sucks. Once I dial in the depth and get the wrinkles out it should minimize the work.

Some downsides, it isn't really all that cheap. After time and labor, it gets pricey. upside is that this material is seriously durable and bash resistant.

I'll plan to have these available for everyone here. Hit me with a PM at the moment. I'll put them up on the website soon as well...
http://prospectsnowboards.com/the-shop/ ... materials/
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jvangelder
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Post by jvangelder »

The one thing im curious about, how does it bond?

prospectsnow
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Post by prospectsnow »

Testing is promising.
The material tears before the bond tears.
Expect to sand and flame it.
I actually tore out some sidewalls on a few older boards and poured. Got tested out at hood by some guys and they said it survived a good beat down.
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bobbyrobie
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Post by bobbyrobie »

Looks pretty good, what type of urethane are you using?

What i was thinking of doing was milling out some sort of thick sheet of mdf etc then pouring in some urethane into the mold. Most of the urethane manufactures i contacted though said their products would be to brittle for that type of application. another option would be to just mill individual pieces so you wouldn't need to rip a large piece down into smaller pieces.

prospectsnow
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Post by prospectsnow »

What are they saying is brittle? The cold or the mold process?
I'm using smooth on because it is really easy. Other guys are using other stuff that has better mechanical properties, but requires some setup.

An MDF mold would work as long as you have a proper nonstick layer. One hurdle is making thickness to spec because the liquid is and cures quickly. I go a little thicker and sand it down to the core profile.

In the pics I was using shrink wrap which caused some funk in the surface. I switched to Mylar and get a better result for my nonstick surface.
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Followalong
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Post by Followalong »

Where did you get the urethane mix?

prospectsnow
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Post by prospectsnow »

Smooth-on.com is the place to go.
This stuff is pretty awesome. easy to color, I even ripped out some old sidewalls on boards and poured in urethane to repair.

Talked to tech support, they said it holds its properties at 0F.
I'm a proponent.
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jvangelder
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Location: Southern NH

Post by jvangelder »

Are you using urathane rubber from smooth-on? if so which one? I just browsed all of them and never read anything about bound-ability

-Jacob

gozaimaas
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Location: Nagano Japan

Post by gozaimaas »

I just poured one of my cores with smooth on 305, one of the most basic urethane plastics they offer. I will report my findings.

gozaimaas
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Post by gozaimaas »

40 mins after pouring the urethane is set hard, bond is excellent and it flexes beautifully. Looks like a winner so far.

skidesmond
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Post by skidesmond »

Nice. Been following this thread. Another guy in SB was pouring urethane sidewalls directly into a channel in the wood wore. Any problems with air bubbles or does it look solid throughout?

gozaimaas
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Post by gozaimaas »

Looks solid, some foaming and expansion occurred on the surface in areas but most of it is very dense and extremely flexible.
Please excuse the mess, this was a late night spur of the moment operation :-)

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Last edited by gozaimaas on Tue Sep 18, 2012 4:35 am, edited 2 times in total.

gozaimaas
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Post by gozaimaas »

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chrismp
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Post by chrismp »

that other guy was me! i think i was the first one on this forum to try this method and i still think it's the best way to make sidewalls especially if you have access to a cnc to make the channel.

pouring the sidewalls takes less time than having to profile sidewall slabs, attach them to the core and make tipspacers.
adhesion to any of the materials used in a ski is better than with uhmw even without sanding and flaming. the slightly rough surface i get from profiling the cores is enough to achieve a good bond.

the only downside of polyurethane are the air bubbles and that it's hard to machine. i cut the flashing on a bandsaw with a fine metal-cutting blade and do a rough finish of the sidewalls with a stone grinder like this one:

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then i finish the sidewalls with a router.

gozaimaas
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Joined: Fri Feb 10, 2012 4:17 am
Location: Nagano Japan

Post by gozaimaas »

I just rout my channel from a template.

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