non pneumatic press

[gnarshred]

So i don't really have the resources to pull of a pneumatic or vacuum press, but I know that there is a way to get good even pressure from a clamp press or otherwise. My problem is the top mold. Since there wouldn't be a bladder to fill the space, i would either need to make sure that the top mold is the exact profile of ski or find some material that would fill the space between the top mold and the bottom to make sure that there aren't any places not getting any pressure. If i don't make the top mold the specific profile of the finished ski then there would be places not getting pressure etc. etc. bad things ensue. But i cannot think of any materials that i could use to provide a buffer between the top and bottom mold while still transferring all of the pressure to the ski. Are there any solutions to this problem?

[Ottolegbone]

I have been following this forum for some time and I have been wondering how to set up a decent clamp press for a while.

I was considering trying to set up a vacuum press with an added clamp system to help squish things together better and help bonding.

I was thinking that there might be some benefit to using a closed cell foam on the top mold to even out clamping pressure.

As a source of durable closed cell foam I was looking at the foam used for camping sleeping pads (blue and yellow pads). This thought crossed my mind while browsing the Mountain Equipment Co-Op website.

I'm not sure how well this will do with distributing even clamping pressure on the tips and tails.

If you Google the Exotic Skis website and browse a bit you will find a ski called "The Claw" that is manufactured in the US north east (Vermont I think). There's a mpeg movie on "The Claw" website showing a press that looks like it uses hydraulic automotive type jacks.

Just my thoughts. Kids, dogs, mortgage, looking for a new house will keep me from building anything for some time yet.

[Idris]

A vaccum press need not cost more than $10. An old refregerator pump, some plastic sheating and sticky tape is most of what you need.

[gnarshred]

even if it's cheap i don't feel confident in my abilities to make a pump that will generate enough pressure. I feel that I can get more pressure using mechanical means rather than air. But, I just can't figure out how to get a good clean seal between the top and bottom molds.

[bigKam]

i remember seeing a video on the Claw Skis website that shows the use of a clamp-style press -- using car jacks, i think. maybe it will give some ideas...

http://www.clawskis.com/

[RoboGeek]

well.. some of my previous experience might work good here..

If you can either make an exact mold of your ski shape out of anything you have - clay, scrap wood, whatever, then make a shallow mold form out of wood. Fill it with plaster of paris and invert your ski design into it.
When it hardens, spray it with mold release and apply a thin layer of fiberglass over it.
When thats hard, remove it and reinforce the backside with more glass, wood, metal, etc

That will give you an exact fit to the top of your ski. You'll just have to figure out how to get it strong enough for the pressure you want

[gnarshred]

i think i may try finding some foam or better yet, i have a friend who's dad is the head prof of engineering at dartmouth and they have a five axis cad machine that can mill anything i want out of any material. i'll look into if that is a possibility. We made some bike stems a while back out of billet aluminum that turned out real nice.

[big_game]

What I don't understand is the cat track in pneumatic presses---
shouldn't the cat track prevent you from getting equal pressure in the lateral direction? (Assuming you aren't uniform in the lateral direction-- like raised torsion forks or whatever)

Also, in the "ask an expert" interview, the guy keeps referring to "sandbag presses". I did some research and can't come up with much... but can sand bags be used as a substrate between the top mold and the ski? My guess is they would break or settle funny and produce a very very bad ski.

[RoboGeek]

sandbag press is basically just laying sandbags on top of your mold. The sand conforms to the shape, and the weight presses the same way anything else does.
There are problems getting even weight distribution unless you lay them just right - and the core tries to shift for the same reason.

I think its the cheapest form of press though