apply edges to ski, base last why not?

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justplanesteve
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Joined: Mon Sep 12, 2022 8:24 pm

apply edges to ski, base last why not?

Post by justplanesteve »

I want to build a full torsion box.
Rational being "not much" but also "why not" since we all decide to build for personal exploration reasons.

That off my chest, until modern times my familiarity was with old-school straight skis. The (cracked) edges were screwed on, and then the bases applied over the screws and flange, between the thin raised edges. During the 60's & 70's it was even possible in some cases to send your skis back to the factory and get new bases, or even bases and edges applied. IOW, the ski was built first, then the bottoms applied. EG, my ancient VR17's

It seems that modern user-built and small lot custom builds are all started by cutting our the ski shape in the (non dimensionally stable) plastic base, and then bending & gluing the edge to it, and building the ski on top. The edge becomes the control for the rest of the machining, including the sidecut.

Do large scale production builders use this same process?
Are the structural shapes of a production ski really defined by the base and edges, or vice versa?
If so, what does the "mould" look like?
I would like to build the shaped, pre-bent core with parallel carbon faces as one pressing. Then add on a fiberglass tube, topsheet and the base and edges as a separate pressing. What techniques were used for alignment in the past?

Thanks!
smt
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chrismp
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Location: Vienna, Austria

Re: apply edges to ski, base last why not?

Post by chrismp »

Yes, base and edges are what define the shape of the ski. Check out this video from Stöckli skis to see what the molds and technique look like:

Most hobby builders use flat molds instead to be able to press multiple shapes in one mold. For this the edges are attached to the base with superglue before pressing.
justplanesteve
Posts: 7
Joined: Mon Sep 12, 2022 8:24 pm

Re: apply edges to ski, base last why not?

Post by justplanesteve »

Apologies for belated notice: mountain opened, i got busy & forgot to check back. :)

Thank you for the Stockli video.
I sort of assumed from looking at actual Stockli skis that they probably build them like most (all?) smaller niche builders, as layers on top of/starting with the bases with edges glued on. I am familiar with that construction from personal tours, and from online videos.

I don't think that is true for skis like my Atomic (non-titanal) Vantage 83's. Nor some others, with rounded top edges that flow over and down to the edge platform. I want the sidewalls to be defined in the mould, and not cut them back as a trimming op after laminating (to preserve the torsion box).

OK, lets consider history "backwards" - how were skis like original VR17 built?

Thank you!
smt
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chrismp
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Re: apply edges to ski, base last why not?

Post by chrismp »

SMost probably the same construction method on those Atomics that you're referring to. The pulled down topsheet is a construction method called "cap" and has been mostly used on older skis and modern cheaper models.

The only difference in the construction is that the cores and sidewalls are already in their final shape and the top mould is designed to wrap the topsheet down over the core. Still, the base and edges are processed the same as in that video I posted.

Many home builders with vacuum setups use the cap construction too, as you can get away with a ski that doesn't have a plastic sidewall and the vacuum membrane makes it easy to wrap the topsheet and upper fibers around the walls of the core.
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