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vaccuum veneers

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pennswood
Posted: Tue Jun 03, 2008 10:17 am Reply with quote
Joined: 14 Sep 2003 Posts: 213
you can use vacuum bagging to make decks.
the real problem is that is it a slow process.

you cant really go for all 7 layers at the same time.
not enough pressure to get it all forced into deeper concave areas.

you need to limit your "pressing" to 3 layers at a time.

i suggest 2 layers first "press for at least an hour,
then go in and add 3 layers the center plys, anotherhour,
then finish off with 2 layers.

so you see it takes up to 3 hours,
then you let it all out of the bag and they will relax,
meaning it will lose concave and nose tail kick.

it will make a board,
bu it is not as strong, or efficient as hydraulic hard molds.
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frokster
Posted: Tue Jun 03, 2008 10:22 am Reply with quote
Joined: 29 May 2008 Posts: 22 Location: Wevelgem, Belgium
mosu101 wrote:
24ng is that 24 Hg as in 24 inchs of mercury???

just a guess (hugh pressure if it is 24 inchs of mercury)


If it is 24 inchs of mercury, then thats 0.82bar = 0.82 kg/cm� = 11.8 pounds/inch� (psi)
Way less then what wood-glues require.

Deck are pressed with a 10 times higher pressure.


AM I WRONG ?

ps there is something about vacuum pressing on page 4 or 5 of this manufactureres forum. A lot of questions, almost no answers... and it ends with Ted Hunter of Roarsomething selling his product. Skinny is earrushin' quiet about the whole thing... Is this the holly Grail ?
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skinny
Posted: Tue Jun 03, 2008 11:04 am Reply with quote
Joined: 12 Sep 2004 Posts: 2706
Heres the deal......
You can press 7 plys at once. It can be done in about 6 hours. It will build enough pressure to bond the veneers. It is not the holy grail. It is a viable method worth learning about. I should add that a six hour layup time is not quick by any definition.
I use a modified Joe woodworker version of a large vaccuum container pump, with a tank resivour and a controller switch. The pump itself is unremarkable. I am at a higher elevation than most. The thing is that pressing force is reduced by every foot you are above sea level.
If I always took no for an answer I would be learning nothing.

Its seems like you can grasp the idea, now start working on it if thats what you want. This area if info is completely studied and the info is out there. Look into marine applications as they are always at the forefront of this kind of lamination. Ted Hunter is selling a product, however he shares some important technicall info.

I do belive that if you want to make more than one deck at a time, you need a compression press. The pressing force used in multideck presses is always more than what is needed per individual deck, the reason for this is that the force generated is reduced by each veneer added, most presses are designed with greater pressing force than they reqire at a minimum.
Oh yeah one more thing, get ready to lose some materials, you will have a learning curve for sometime before the decks are of quality.
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skinny
Posted: Tue Jun 03, 2008 11:24 am Reply with quote
Joined: 12 Sep 2004 Posts: 2706
"ng" is a measurement of atmospheric force, or -1 atmosphere. This is never the same for all locations, as stated before your elevation determines your base "gravity" or atomspheric pressure at normal atmospheric pressure. So at sea level 1 "gravity" is the highest naturally occuring in an oxgen atmoshpere......Underwater the pressure is increased, thats why people can get "the bends" while diving. After pressure is increased by diving deep underwater the person is pressurized, when they surface the pressure is lowered and tiny bubbles in their blood expand and cause sickness.

As you rise up the Sierra Nevada mountains and up to the elevation of my dusty garage, you lose some atmospheric force for each foot elevated. So my baseline atmosphere is less than the people on the coast. NG is relative to where you are in elevation.

What my pump does is it multiplies this force by about 24 times the baseline.
Do you know about the thermal expansion of glue,water,wood under pressure?
It happens under heavy gravitaional fields and under large forces of external pressure.
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skinny
Posted: Tue Jun 03, 2008 12:14 pm Reply with quote
Joined: 12 Sep 2004 Posts: 2706
One last thing.....
If you begin to understand the force that is bonding the veneers, comes from the earth. You will understand the correct preparation of materials, and you will be able to determine your limits of bonding force. Remember there is no extrenal pressure bonding the materials. Things like extreme radius curves, and sharp corners, and voids of contact......all detract from bonding force.
For example, if I were bonding a mast, out of fiberglass or carbon, my preparation of materials becomes ultra important. Smoothe surface contact of the membrane "bag", even airflow "breathers, like felt or mesh", surface area "how many points does the vaccuum line connect over the top of the object"....details to determine correct use of bonding force.
This is not pushing or pulling force, is like a crushing force. It has a limit and if used correctly, you can make almost anything with it.


Last edited by skinny on Tue Jun 03, 2008 12:28 pm; edited 1 time in total
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vaskateboards
Posted: Tue Jun 03, 2008 12:25 pm Reply with quote
ORDER OF THE SKULL ORDER OF THE SKULL
Joined: 23 Aug 2004 Posts: 8333 Location: DC
you are on craig

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frokster
Posted: Tue Jun 03, 2008 12:36 pm Reply with quote
Joined: 29 May 2008 Posts: 22 Location: Wevelgem, Belgium
Some of the things said above, i already knew... some of it is new, and makes me believe that it IS something to dig into...

I must confess that i already build myself a vacuumpress. 2 actually. one with a 2nd hand "pro"vacuumpump which does -0.75bar (meaning 11 psi = 0.76kg/cm�) and one with an old frige-compressor which does -0.8bar.

It seems indeed a wonderfull way of making one-of-a-kind decks.

But then i started thinking about the glue and "why are decks made at much higher pressures ?"
I started to have doubt about the whole thing... so the vacuumpresses ended up in the corner of my garage, collecting dust (bad for vacuumpump !).

Maybe it's time to give it a go anyway...
Maybe it's a "fast" way to build a prototype deck for testing... before making a concrete mold...

Let's find out... i might come back to share my experience...

muchos thanks for the info and the stoked "ambiance" (?) !


Last edited by frokster on Tue Jun 03, 2008 11:29 pm; edited 2 times in total
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frokster
Posted: Tue Jun 03, 2008 2:30 pm Reply with quote
Joined: 29 May 2008 Posts: 22 Location: Wevelgem, Belgium
vaskateboards wrote:
you are on craig





whatever he's on, i want some !

still a bit lost on the ""ng" is a measurement of atmospheric force ..."-thing though...
but hey, wisdome comes not all at once...
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frokster
Posted: Tue Jun 17, 2008 9:03 am Reply with quote
Joined: 29 May 2008 Posts: 22 Location: Wevelgem, Belgium
i've did some tests with vacuum, and: YES, it seems te work in a very beautifull way.
BUT i stay with my point on the glue: Woodglue needs more pressure then what vacuum can provide.
In theorie: with vacuum-bagging you can only press as much as the atmosphere: +/- 1bar or 15psi.
While the glue needs about 5 times more.

SO: pump up the pressure of your atmosphere. The atmosphere around your vacuum-bag.
Put the vacuum-bag into a pressure-chamber and pump it up to 4 bar (60psi).

you wouldn't be able to use a foam-mold 'cause of the force, but you'll keep on needing only 1 part of a mold, the pressing air is your "negative" mold.

On the other hand: what happens with the whole thing when you get it out of the "machine" into the normal atmosphere ?


Any thoughts on that ?
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frokster
Posted: Tue Jun 17, 2008 9:12 am Reply with quote
Joined: 29 May 2008 Posts: 22 Location: Wevelgem, Belgium
does anybody has any experience with different types of vacuum-foil ? Nylon or PVA ? PVA-foil streches up to 500%, so they say, but doesn't it gets between the plies of veneer ?

I would need to buy a lot of foil in once, for a fairly big amount of money. So before doing that, it would be good to know if is works OK.
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