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Low Density Sidewalls

Posted: Thu Jan 21, 2021 5:25 pm
by Thelongride
So it seems full length sidewalls are quite a large portion of lightweight touring skis weight, and if there were a lower density alternative one could save quite a large number of grams per ski. The problem is that impact resistance is so closely related to density

Has anyone somehow done an lower weight poly pour? Or perhaps there's a lower density version of abs/UHMW I'm not aware of?

I suppose cap construction is always an option

Re: Low Density Sidewalls

Posted: Fri Jan 22, 2021 4:05 am
by pmg
Hi, my solution is to only have 2.5-3mm thick sidewalls. This adds little weight but offers nearly all benefits of a sidewall. The only possible issue is that on a hard impact on the edge, there is less sidewall to take that impact. But a hard impact with constant edge deformation always is a bad damage to the ski, no matter if the sidewall is thick or thin...

Re: Low Density Sidewalls

Posted: Fri Jan 22, 2021 10:56 am
by Thelongride
Woah, you must have amazingly precise presses! I suppose I could go this route, but I feel that the risk of profiling through a 2.5mm sidewall into the core would happen on a regular basis for me. I need a bit of a larger margin for error than that ;)

Re: Low Density Sidewalls

Posted: Wed Feb 03, 2021 12:00 am
by pmg
Hi,

check this: I use 3 thumbtacks glued to the base to keep the core in position during layup. the core then can't move more than about 0.2mm without getting resistance from the thumbtacks.

Image

Re: Low Density Sidewalls

Posted: Tue May 04, 2021 7:43 am
by 24Dave
I think about this a fair bit. Cap construction with a thin strip of harder wood on the edge to resist edge compression from impacts is definitely the lighter & functional way to go. However most approaches for small scale building require a lot more work in tooling. Plastic sidewalls really make sense due to the ease that they allow a quick nice and sealed finish to a ski or board.

UHMW might be one of the lighter plastics at .94g/cm3. Other types seem to run around 1-1.3g.cm3. Black locust wood sidewalls are practically waterproof and durable and are listed at .77g/cm3. Maybe it is the lightest material that can take some hits and makes an effective seal. (Ipe wood is .87 and even more stiff and harder to work-but easy to find.) I currently use black locust half of the time and cap construction the other half. You will buy more black locust than you think you need though to deal with imperfections and knots etc. It's kind of a hassle for me lately.

There is more to the weight savings though here. The plastic sidewall materials are pretty limp, with no real stiffness or snap to them. A black locust or hard maple sidewall allows the use of more light wood stringers in the core, or a thinner core, so more weight can be shed in the core. The plastic sidewalls seal and finish well but make no other contribution and they weigh more than some of the most durable woods like maple, ash, black locust that can add good stability, damp feel, and snap to a mostly paulownia core.