POLYURETHANE SIDEWALLS! ...?

a.badner · Post by **a.badner** » Mon Apr 11, 2011 2:49 pm

THere probably is a thread for this already, but the search function suck and the google doesnt bring anything up;

Has anyone used PolyUrethane sidewalls yet? If so, how did bonding, and procedure go? and suppliers?

chrismp · Post by **chrismp** » Mon Apr 11, 2011 2:55 pm

yes, works fine. i pour them with PUR-resin into a channel i route out on the core blanks.
prior to that i used stripes of PUR-board that i glued to the core using polyurethane glue.

they're incredibly tough and bond very well with epoxy, but they're a pita when it comes to machining them.

chrismp · Post by **chrismp** » Tue Apr 12, 2011 2:58 am

a.badner wrote:THere probably is a thread for this already, but the search function suck and the google doesnt bring anything up;

http://lmgtfy.com/?q=polyurethane+sidew ... m%2Fphpbb2

a.badner · Post by **a.badner** » Tue Apr 12, 2011 5:01 pm

its so sinister :'(

a.badner · Post by **a.badner** » Tue Apr 12, 2011 5:10 pm

no thread for this... :(

can elaborate a little bit more on the process to create the urethane sidewall?

do you just pour urethane resin onto the side of the core like this : http://www.skibuilders.com/howto/skicon/sidewalls.shtml ... ? does it stick?

MontuckyMadman · Post by **MontuckyMadman** » Tue Apr 12, 2011 6:00 pm

Stop sucking please

richie · Post by **richie** » Tue Apr 12, 2011 6:29 pm

Hi, my reaconing is polyurethane sidewalls are the way to go, that said I have not made a single ski or board yet so this is just my opinion based on other eexperience and research.

Polyurethane sticks like shit to a blanket (timber and epoxy), its easily poured into a channel. The key is to chose the correct material as there are so many grades of polyurethane for so many purposes. Try a waterclear version, its tough as - used for car and 4x4 suspension bushes. This can be tinted and comes in many hardnesses so a little trial and error might be needed there.

Cheers

falls · Post by **falls** » Tue Apr 12, 2011 8:43 pm

hey chris
do you route the channel in the side of your cores after profiling or before?
Something like a router bit for making the groove of a tongue and groove joint, or a slot cutter? then make a dam on the upper and lower side the whole length of the core and pour it in?

richie · Post by **richie** » Tue Apr 12, 2011 9:33 pm

my plan is to pour the sidewall before profiling, I'm using a 3hp router with 40mm 2 flute cutter same as Mike Magruder uses, so I hope it cuts the polyurethane ok it should. My polyurethane is 90A hardness water clear , so hopefully although its pretty firm it should cut well. This to me seems far far easier than using UHMWPE with no real disadvantages, time and results will tell eh? I'm finally pretty close to my first build, my profiles are being cncd right now and materials all coming, my profiling table is 1/2 built and is hopefully going to leap forward in the next 3 weeks.......yeah right! cheers

oh yeah I mean to say Tim, I am not pouring it into a slot in the side of the core but into a full depth channel in the top face following the sidewall end to end curvature approx -5mm inward and +2 outward, roughly....... cheers, Rich

looking back in the forum it looks like this is the trough method, but using polyurethane instead of epoxy means a durable well stuck sidewall with less hassle.......

G-man · Post by **G-man** » Tue Apr 12, 2011 9:56 pm

Most polyurethanes become brittle at colder temps and shatter easily when flexed. It's a good idea to freezer test samples before putting a lot of time and money into something that will fail when it gets cold. Water clear PU is especially brittle when cold.

G-man

richie · Post by **richie** » Tue Apr 12, 2011 10:04 pm

sure will be watching for that, although the specs looked pretty good when I checked it out a while back, will let you know

cheers

chrismp · Post by **chrismp** » Tue Apr 12, 2011 11:41 pm

the stuff we use is called Adiprene LF950A with the E300 hardener. it has outstanding properties even at really low temperatures. only downer is that it's a brownish color and pigments don't look as good as with a clear system.

what resin did you get, richie?

we router a board-shaped groove into our core blanks with a 1/2" straight two flute router bit. the PU-resin is then poured into the groove. the resin we use needs to cure for 16h at 100°C, that's what the hotbox i posted in another thread is for.
the cores are then planed on the underside until the sidewalls start to show. after that we cut the core profile into the upper side of the core.
that way you get a core with a seamless sidewall/tipspacer that sticks to the core really well.
i just wish the polyurethane wasn't that hard to machine...

falls · Post by **falls** » Wed Apr 13, 2011 12:00 am

I see what you guys mean! What I was thinking in hindsight seems a pretty stupid way to do it!

Plunge router and top bearing copy bit for the groove?

richie · Post by **richie** » Wed Apr 13, 2011 12:08 am

http://www.barnes.com.au/catalog/barnes ... 0WC595.pdf

this is the brew I am using

cheers
Rich

chrismp · Post by **chrismp** » Wed Apr 13, 2011 1:06 pm

@falls: way too sophisticated

i just draw the outline of the board on the core and follow it with the router.

@richie: that stuff is really expensive! i pay about 15,- EUR for each kilogram.

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POLYURETHANE SIDEWALLS! ...?

POLYURETHANE SIDEWALLS! ...?

Re: POLYURETHANE SIDEWALLS! ...?

Polyurethane sidewalls

sidewalls

cold and brittle

the stuff I'm using.....