Vacuum Press vs Pneumatic

dimension4 · Post by **dimension4** » Wed Aug 17, 2011 2:47 pm

yep, in theory it could be great, less equipment to buy and maintain, and hey i pay for my water, why not use it right? but I don't need a new swimming pool right now...

Brazen · Post by **Brazen** » Wed Aug 17, 2011 5:49 pm

Well, there's always the chance to grow tilapia in your basement

maximegb5 · Post by **maximegb5** » Wed Aug 17, 2011 7:52 pm

Do you think you had need a fishing permit to eat them for dinner?

Brazen · Post by **Brazen** » Wed Aug 17, 2011 8:10 pm

I'm quite sure there's a government agency that wants your money. Call and ask them before you eat the fish raised in your failure.

Ahhh yeeeah!

twizzstyle · Post by **twizzstyle** » Thu Aug 18, 2011 6:35 am

Brazen wrote:eat the fish raised in your failure.

HAHAHAHAHAHA

dimension4 · Post by **dimension4** » Mon Aug 22, 2011 10:21 am

wow this really drifted sideways fast.

least yall have a sense of humor

Bloefeld · Post by **Bloefeld** » Sun Jan 15, 2012 6:33 pm

doughboyshredder wrote: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.

One torr is all you need to make skis unless you want to be in full scale production.

The key to making good composites is the ratio between fibre and resin and adhesion.

Vacuum bagging is the easiest and least costly way to go about the process.

Some folks have problems in making the bag free of wrinkles. Doesn't matter, put a caul plate over your layup and it will keep the layup itself smooth.

Go to Airtech Inc. for more information of the supplies you need and how to use them.

They can also show you how to do vacuum resin infusion which is probably the easiest way (once you get the hang of it) to get nearly perfect resin ratios with crazy easy dry lay-up.

On the topic of cores and pressure it is merely a matter of matching the compressive strength of the core to the pressure you desire. Remember this though, most aerospace products are manufactured by vacuum bagging and autoclave.

So claims that you will need more pressure to achieve great composites and to get near perfect resin to fibre ratios are for the most part ridiculous.

I too am new to making my own skis, but I have decades in the composites industry, and unless you wish to make skis in a high-speed fashion going through the effort of making a proper pneumatic or hydraulic press is a waste of time and effort.

Keep asking your questions, most of what you will read here will be wrong. Do go online and look at sources for other types of composites, there is a big world of cool stuff going on that should inform what you do while making your skis or boards.

Cheers,

Bloefeld

gladegp · Post by **gladegp** » Mon Jan 16, 2012 3:22 am

Hi Bloefeld, I'm one of the least experienced guys in here but I build a few skis with a vacuum setup.

Bloefeld wrote:Some folks have problems in making the bag free of wrinkles. Doesn't matter, put a caul plate over your layup and it will keep the layup itself smooth.
Bloefeld

Excuse my ignorance, but what is a caul plate more precisely? I understand it's a plate which goes between the bag and the rest of the stack but does it have to be of a special material or could I use for example a thin metal sheet?

Bloefeld wrote: They can also show you how to do vacuum resin infusion which is probably the easiest way (once you get the hang of it) to get nearly perfect resin ratios with crazy easy dry lay-up.
Bloefeld

Wouldn't there be a problem with resin infusion in that the underside of the base would be totally wetted with epoxy?

Bloefeld wrote: I too am new to making my own skis, but I have decades in the composites industry

Keep asking your questions, most of what you will read here will be wrong. Do go online and look at sources for other types of composites, there is a big world of cool stuff going on that should inform what you do while making your skis or boards.
Cheers,
Bloefeld

It's super nice to get experienced people in here. Would you care to share some of your favorite sources for information?
It would be very useful for some of us if you would post subjects in here explaining some of the techniques used by the industry and how we can improve our techniques.

By the way, check out OACs setup, it's quite nice. I'm meaning to build myself something similar one day.
http://www.skibuilders.com/phpBB2/viewt ... c&start=15

Regards
Gustav

Bloefeld · Post by **Bloefeld** » Mon Jan 16, 2012 9:47 am

Hi,

Let me reply to each of your points individually.

A caul plate can be made of anything that is pretty stiff. I use 1/2 inch UHMW so that I don't have a big mess to clean up on it. But a .075 piece of steel cut to shape will work just as well. Make sure to cover them in mold release or it will just be a metal and glass ski.

There are a zillion different ways to infuse, from the top with vacuum ports on the bottom, from the side or even when sealed off from the bottom. The key in infusing skis is to integrate fiberglass into the sidewall. Much like what Solomon did when they made the old Monococ ski.

I'm thinking of using pre-preg fibre to avoid all of the issues with wet-out and still get perfect resin/fibre ratios.

I will put together a list of sites and post them back here for you to take a look at. There are also some excellent trade journals that have free subscriptions that are good too.

Cheers,

Bloefeld

rsotak · Post by **rsotak** » Fri Jan 20, 2012 7:41 am

So even though the vaccum bag process is sufficient for getting compression on the composites, does it provide enough force to shape the core to the ski mold curvature? It seems like that is where the press function would be more valuable in setting the camber and tip curvature.

Bloefeld · Post by **Bloefeld** » Fri Jan 20, 2012 7:50 am

rsotak wrote:So even though the vaccum bag process is sufficient for getting compression on the composites, does it provide enough force to shape the core to the ski mold curvature? It seems like that is where the press function would be more valuable in setting the camber and tip curvature.

Great question and one I had not taken into consideration. I expect that it would flex the core without issue as 15 psig is a lot of pressure.

But would have to test; which is about all one does in this industry.

Cheers,

Bloefeld

OAC · Post by **OAC** » Fri Jan 20, 2012 9:10 am

It leaves more to wish for. Thats why I'm using plastic tips and tails. I know "sammer" does "full core".

sammer · Post by **sammer** » Fri Jan 20, 2012 9:09 pm

I did a couple of full core skis but had to prebend tips and tails.
Now I'm using plastic tip and tail spacers as they conform to the mold better.
Vacuum will not bend your edges to the shape of your tip/tail either.
Just not enough pressure. you will end up with edges bridging and the rest of you materials conforming.
Not a pretty thing after the grind.
I've had a few bridging issues.
If you don't already know edge material is quite hard to bend!
That's partly why I built the tip bender

http://www.skibuilders.com/phpBB2/viewtopic.php?t=3199

Pics on page 2
Still working btw.

sam

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Vacuum Press vs Pneumatic

So many point wrong where to start

Re: So many point wrong where to start

Gladegp

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