POLYURETHANE SIDEWALLS! ...?

a.badner · Post by **a.badner** » Wed Apr 13, 2011 1:37 pm

have you tried it like this?

this way seem easier for me, mostly becasue you can profile core first. but i dont know how it works for you.

richie · Post by **richie** » Wed Apr 13, 2011 2:04 pm

Hi Chris, yep I will be hunting a better deal but I have some to get started with, I have not figured out yet the volume of resin required to pour the sidewalls but I can see its not just a wee bit. With accuracy in my routing templates and base cutting I hope to keep the channel as accurately cut and as narrow as possible still leaving enough sidewall above the edge and also enough hanging over so it is tidied up nicely after pressing and while doing the flash removal. I guess it could amount to 50ml per snowboard or 100ml for a set of skis, possibly less I hope but it will add to the $$$ and I gotta keep the cost down. On the other hand this looks like a much simpler process than gluing UHMWPE on, quicker and at least as reliable bonding I suspect way more reliable and at least as durable too. This kind of pu is often used in 4X4 suspension so its touch as buggery I do agree we need to be mindful of the low temps and brittleness I will do some testing.... cheers

chrismp · Post by **chrismp** » Wed Apr 13, 2011 11:53 pm

@adam: that would work too and would spare me the hustle of profiling the PU, plus it would save me some of that PU, but i wouldn't have a seamless sidewall running all around the board. and i'd have to make my hotbox larger so i could put in the cores in an upright position. and doing two 16h cure cycles for each board would kill me

@50ml for a snowboard is a pretty low estimate. with my method i use about 350ml for one board. the channel i router is 8mm deep, 12,7mm wide and about 3500mm long.
you don't want to make them too narrow, because the 16h cure cycle at 70°C can make the wood shrink.

richie · Post by **richie** » Thu Apr 14, 2011 12:37 am

Chris you are right 50ml is not close, that was a bad rough guess eh! I'll go with your recommendation of approx 1/2 inch wide , so I will need to get a much much better price going on eh! thanks for pulling me up on that I need to think before I type eh! cheers

twizzstyle · Post by **twizzstyle** » Thu Apr 14, 2011 8:34 am

a.badner wrote:

have you tried it like this?

this way seem easier for me, mostly becasue you can profile core first. but i dont know how it works for you.

Ugh, I had to do this on my first pair of skis after the core shifted in the press and I lost my sidewalls. It was a mess and turned out like crap (but I used epoxy, not PU). Routing a channel in the core blank before planing sounds like a much cleaner process to me.

WhitePine · Post by **WhitePine** » Thu Apr 14, 2011 11:00 am

Are epoxy or polyurethane sidewalls typically cheaper than UHMWPE/ABS? Looking at the specific gravity of the pu compared to UHMWPE it would be negligably heavier. So I'm sure the weight isn't a factor. Does it come down to more of a price point issue, an ease in assembly issue or because you could make virtually any pigment you could want with epoxy or pu?

I guess I'm just curious because I haven't yet decided what sidewall material I'm going to pursue.

richie · Post by **richie** » Thu Apr 14, 2011 1:28 pm

Hey Whitepine, my decision to use pu is based on simplicity of construct ion which looks to me a lot simpler and less time consuming than UHMWPE, the reliability of bond long term to timber and epoxy, and the strength and durability and flexibility of the product itself. I have no ski or board building experience yet so all my opinions are based on my own research and experience in other areas using composites and plastics. I am going to give the pu a real good crack I do believe in innovating and not just following the established process, I can see all kinds of uses for pu not just sidewalls but also in making components for my split boards like heel risers for example. cheers, rich

nrgboards · Post by **nrgboards** » Sat Apr 07, 2012 9:27 am

Thought Id post this. Here's a board I built for a friend and I decided to try pouring urethane sidewalls. I really like this process as I've had problems with planing and routing the thin sidewall material when core shaping. Here is the urethane I used(thanks chrismp for info posted in another post) its Smooth-on 380 smooth-cast 90a durometer.

Here is the channel I constructed using sintra plastic and double sticy tape to adhere it to the core, and used little yellow pieces as dams on each end.

Here is the channel before pouring urethane.

Here I used smooth-on neon green urethane pigment and me pouring it into the channel.

You can see in the last 2 pics the other sidewall was already poured. Here it is almost finished I have a 7 degree bevel on the sidewalls in these last couple pics.I got a pretty good match to the tip fill material.

chrismp · Post by **chrismp** » Sat Apr 07, 2012 10:44 am

that is awesome! love the green pigment! i guess i have to order some!

i always love to see people trying out my ideas with success

it's a nice feeling being able to add something to this great source of knowledge.

nrgboards · Post by **nrgboards** » Sun Apr 08, 2012 4:15 am

Thanks for posting the info!!! I've been playing around with the smooth-on by back coating paper printed graphics for topsheets so Ill be posting that under the proper posting sometime soon!!

chrismp · Post by **chrismp** » Sun Apr 08, 2012 4:49 am

you're welcome!

just one question. what made you choose this particular resin system? i know it's cheap, but i think there are systems with better properties for our purpose. did you ask them about the properties when exposed to cold temperatures (i've read that some polyurethanes get brittle when in temps below -20°C)?

i just noticed the epson 1400...that's going to get you nice graphics! which resin are you using to coat it and did you add some sort of white pigment to it?

gozaimaas · Post by **gozaimaas** » Mon Apr 09, 2012 1:51 am

I am going to give this stuff a try also. I made 10 cores this weekend and profiled 2 of them so I am keen to see how the polyurethane goes with the profiled cores.

chrismp · Post by **chrismp** » Mon Apr 09, 2012 2:37 am

with profiled cores your only choice is to pour the urethane into a channel like nrgboards did.
with my method of routering a channel all the way around the core you need an unprofiled core.

good luck!

gozaimaas · Post by **gozaimaas** » Mon Apr 09, 2012 2:55 am

Yeah I realise that.
I profiled cores 2 so I can test the trough method, if it works well I will continue to do it that way as I will save quite a bit of urethane.
If not I will try the mote method. I am prepared to scrap them both if it fails.

chrismp · Post by **chrismp** » Mon Apr 09, 2012 3:18 am

i can't see why you should fail given you're using the right kind of urethane

i personally prefer to router the channel into the unprofiled core since it gives me a seamless sidewall/tipspacer around the whole board. i guess the added material needed for a full tipspacer easily equals the amount of PU used for pouring a full sidewall.

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POLYURETHANE SIDEWALLS! ...?

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