Vacuum Press vs Pneumatic

[dimension4]

I don't have any experience building skis just yet, but I want to get started.

I am particularly interested in making the skis as light as possible, so using material like carbon would be ideal.

Could someone explain the advantages and disadvantages to both the pneumatic and vacuum setups with carbon core skis?

I understand that with a traditional wood core the pneumatic system is probably the way to go.

TY

[doughboyshredder]

SEARCH. READ. LEARN.

Then ask questions.

[dimension4]

Awesome reply [/quote]

[jvangelder]

SEARCH. READ. LEARN.

Then ask questions.

did you actually read his post? or just post based on the thread title?



I have no actual experienced in vacuum molding whats so ever, how ever my father work place does a lot of compressive molding of carbon fiber for the aerospace industry. they do compressive over vacuum for a reason.

-Jacob

[dimension4]

I'm thinking the pressure of a pneumatic press may break the carbon core.

[doughboyshredder]

This has been discussed ad infitum.

with a vacuum press you can get at most 13 psi.

With a pneumatic press you can get anywhere from 5 to 100 psi.

What type of core has nothing to do with what type of press.

I remember when I first came here. I read for weeks. Every thread. Too many people come here and don't bother to read anything and then they post very basic questions.

For any core, whether it be honeycomb, balsa, foam, etc. you have to determine the pressure that the core can withstand and then adjust your press accordingly.

What does carbon core mean anyway? Do you mean a carbon honeycomb? Or, are you confusing carbon fibers with core materials.

Like I said. SEARCH. READ. LEARN.
Then ask questions.

[twizzstyle]

Doughboy's got good advice.

I'll second the question about your core... How are you planning on making it? You said you have no experience making skis, what experience do you have with composites? If none, you need to start with a wood core to get the basics down first. There is a lot to learn building skis or snowboards before you get too advanced!

I always vote for pneumatic presses. Only pros to vacuum is that is much cheaper and much safer. Lots of guys get amazing results with vacuum (look at OAC's work... It's outstanding and he uses vacuum), but you just don't get the same pressing force (i.e. squeeze out, i.e. weight savings) that you do with a firehose.

[dimension4]

Like goode

[skidesmond]

Like goode

Do a search on Goode in the forum. Awhile back somebody posted a pic of a broken Goode ski. I believe it also had foam in the core too. Are you using foam too or all carbon? I don't know much about Goode skis other than what I've seen here and on the Goode website. They're a very light ski. Building a rather expensive first ski. I'd use a light weight wood such as poplar for a first ski. Save the expensive stuff after you get some experience.

[doughboyshredder]

goode skis are foam core with vertically oriented carbon fiber sandwiched in the core.

Therefore, the actual question is what kind of a press should I use for a foam cored ski. And, the answer is...............................................

[twizzstyle]

Therefore, the actual question is what kind of a press should I use for a foam cored ski. And, the answer is...............................................

Water press, duh :p

[powderho]

[/quote]

they do compressive over vacuum for a reason.

-Jacob[/quote]

And that reason probably is because they can't afford an autoclave. We make over 400 different aerospace parts and 98% of them are vacuum molded and then cured in an autoclave. The others are RTM'd.

[twizzstyle]

Yeah if you bring autoclaves into it, that changes things completely. The main limitation with vacuum bagging is you're limited to ambient pressure, and without an autoclave as doughboy said its about 14psi depending on your elevation, and the weather. If you have an autoclave you can go as high as the chamber will take. Not really feasible for the home-ski-builder

[dimension4]

Water press, duh :p

you using a water press with any success? i read a discussion once on that topic, using municipal water supply for a press. wouldn't want to have a swimming pool where one wasn't intended...

[twizzstyle]

you using a water press with any success? i read a discussion once on that topic, using municipal water supply for a press. wouldn't want to have a swimming pool where one wasn't intended...

No, I was joking with my response. I am 100% against water presses. They offer no real benefit over air, and just set you up for leaks and badness. Like someone else once said, a minor air leak you can live with. But a minor water leak and you've got ruined skis, and ruined molds, and a wet shop floor.