vacuum

For discussions related to ski/snowboard construction/design methods and techniques.

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Freeskier15
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Joined: Sun Nov 20, 2005 3:49 pm

vacuum

Post by Freeskier15 »

hey, I was just wondering how much a difference the lower psi of vacuum press effects the finished ski. Also, if I was to make a heated vacuum press, wouldn't the heat shrink the bag that was put over the press?
thanks for your input, this is a great site!
kelvin
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Post by kelvin »

I've been playing around with a vacuum press, but haven't made a ski from one yet. It seems to me that you could get an equally good ski out of either press. The higher pressure of the pneumatic press could squeeze out more epoxy and therefore make a lighter ski, but I don't think it would make a huge difference. Has anyone tried both and can comment?

As far as temperature goes, most bagging films are rated to 350f or above.

-kelvin
Freeskier15
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Post by Freeskier15 »

it would be easier to make skies with a vacuum press too because you can create a cap with the topsheet and not need to worry about making sidewalls.
bostonski
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Post by bostonski »

Freeskier15 wrote:it would be easier to make skies with a vacuum press too because you can create a cap with the topsheet and not need to worry about making sidewalls.
Is this true?
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endre
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Post by endre »

bostonski wrote:
Freeskier15 wrote:it would be easier to make skies with a vacuum press too because you can create a cap with the topsheet and not need to worry about making sidewalls.
Is this true?
No. for a homebuilder it is not easier to make a cap ski (and why would you want to make a cap ski anyway). To make a good cap ski with vacuume you need to profile the core sidewalls so the plastic sheet will form down smoothly. It is much easier to just let the wooden core go beond the edges and then cut of the extra. a sandwich ski with wooden sidewalls works as good as any ski.

without an autoclave the result with cap skis isn't that good anyway.
ndless fun
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Joined: Tue Jan 01, 2008 7:59 am
Location: Boston

Vacuum Bagging

Post by ndless fun »

Hey everyone...first time posting in this (or any) forum! Much thanks to the creators for putting together such a great knowledge base.

I just finished molding my first pair of skis last month and used a vacuum bag for compaction vs. a press. One thing I would recommend is placing a caul plate on top of your laminate prior to installing the vacuum bag to help even out the vacuum pressure. I used a piece of 1/8" UHMWPE. This helped produce an even thickness ski with a flat top surface. I did not use this technique on the first ski that I molded and the top surface came out somewhat uneven.

Remember to make sure your mold is not porous and has no holes that will allow air to creep in while under vacuum. The closer you can get to full vacuum (~29.9 in Hg) the better as the resultant compaction force will be higher and chance for voids will be lower. In addition, make sure your mold can handle vacuum pressure. For example, if you are using a continious piece of sheet metal for the top surface make sure it is well attached to the rest of your mold otherwise you may end up with a wavy base on your skis.

Hope this helps,

Dave[/img]
Bucky Mullet
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Joined: Mon Oct 09, 2006 5:26 pm

Post by Bucky Mullet »

I've made an epoxy " cap" ski, and although it wasn't easy it wasn't super difficult. I ended up having to press it twice, as the first time the bag didn't wrap around the ski as I would have liked, leaving some rough, uninfiltrated fiberglass sheet. After the second press, I noticed that I still hadn't gotten it right, so I did some patch work a la surfboad epoxy work style. Even though I thought that these skis would snap on their first run down the West Basin (taos NM, welcome snowboarders!!) They have survived ~ 7 days with 2 days being what I could not describe as "babying them". Compare that to a pair of GOODE skis that I received as a "sponsored" package (to compete on 'em in Big mountain comps) that lasted about 3 runs. So, for the "effort" I would give Vac presses an A. Add heat and you'd do even better, but I think that each has it's plusses and the combination of them would be strongest.
That being said, a vacuum setup, with tinkering with the core materials, edge bending / anchoring, addin AVS rubber or metal into the core and adding heat would be a super way to get the knowledge / tools into the shop to be prepared for a kick ass pneumatic press.
Unless you just bought a welder, had a machine shop give you a bunch of steeel and want to just skip to the end :evil:
I hope my shop doesn't blow up.
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