Ski Builders Forum

Hey guys, sorry for posting two questions one after the other but these are pretty much the only questions I have.

UHMW vs HDPE..

I know UHMW has a much higher impact strenght than HDPE. But I was wondering wich one was more flexible.

Im asking because other companies make their plastic snowskates out of HDPE, and I was planning on using UHMW because it would result in a longer lasting snowskate. Thing is, I don't want the board feel (flexibility) to change. What do you think?

Thanks

I need some help... anyone?

Hey Alex,

I have 2mm thick sheets of both UHMW and HDPE in the shop. The UHMW is definitely more flexible, and at the same time, less 'springy'. The HDPE is more stiff and has more spring to it. Both are very abrasion resistant, but the UHMW is certainly the tougher of the two. Both resist bonding with any adhesive. UHMW is 2 to 3 times the cost. HDPE becomes more rigid than UHMW in the cold.

G-man

Thanks alot G-Man! Everything I needed to know.

I was wondering.

If I get some UHMW/HDPE sheets, can I simply sand one side and use epoxy to bond?

Here's the general approach... solvent clean (acetone), abrade, solvent clean again, flame treat, then bond. I'd recommend doing some test pieces prior to the real thing, just to get an idea how your particular method of flame treating is working for you.

G-man

I couldn't believe how much work it took to shape and abraid the UHMW sidewalls on my first board. It was definitaly worth it though. It's heavy stuff, so use sparingly for impact, compression, or dampening locations. You have to flame treat this stuff just right to make it adhere. Most people reccomend by cm/s with a particular flame so much distance from the UHMW after its been abraided. I just go by sight and feel after having practiced on a couple of scrap pieces. You can see the stuff that peels off from sanding/filing start to carbonize and then evaporate if you watch it closely while torching it. Then you back off enough to get a consistent carbonization based on your speed, flame distance, and angle(you may have to shield around corners of already treated surfaces to avoid ruining them). You should be able to rub your finger across the surface. It will have carbon residue on it, but much carbonized (many very small burnt looking peels as opposed to any shine) surface area will remain on the UHMW. Your good to go if the surface absorbs a drop of water as opposed to beading it. Like G-man above said. Clean with acetone. I did this after flame treating and then washing with dish soap and water first though. Carbon skins, pine w/oak core, UHMW sidewalls, and not a bit of separation after 9 days on them. the UHMW is tough stuff that doesn't change alot with temp, but it is tricky to prep and will dull your tools. Do it.

Thanks alot guys! Now just wondering, is it important to bond the HDPE/UHMW like 30mins after the flame treat or can it be done weeks later?

-Alex

It should be layed up within an hour. I used UHMW sidewalls made out of material i buoght form mcmaster on my first few boards. I just sanded them, solvent clenaed them, and then abraded witha propane torch at like 2 inches per second and did a couple passes. The water trick works really well. If you run an untreated piece of plastic under water it beads. If it is properly treated it shoudl sheet and you can def see the difference. I had no problem bonding them and they held up all season through like 15 days of riding harsh new england ice.

I also tried using HDPE as a top sheet, using the same abrade/clean/flame and it didnt work very well, the sheet peeled off pretty easy but it was way harder to get a even flame treat on thin gage plastic cause it would warp easily, i was using .016" plastic, too thin.

What are you abrading the UHMW with? If sandpaper, what grit? Good idea using water to test.

geez I dont even remember, 50 grit maybe I'll look tonight, its been a few months since ive made a board cause im workin on the press.

Hey guys,

If I use 1/8'' thick HDPE for bases, do you think it will be to ''springy'' and that it will delaminate when I take it out the of the mould?

(Consider a snowskate being more drasticly shaped than skis or snowboards)