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[gp]

Hi all,

I am starting out on my vac bag path. I have had a good look around the forums and think I am (slowly) getting the idea. I am new to all this vac bag stuff, so apologies if this is amazingly simple stuff or has already been posted.

The vac pump is working and am now in the process of getting the other parts together. The main thing I am a bit nervous about is what pressures people are using, and what determines the pressure to use?

Any help much appreciated.

Am going to practice on a couples of wooden fins first, so I don't ruin some expensive foam.

[Moonfish]

hey gp,

this is kinda where trial and error comes in but having said that, for 16kg m/3 eps and below dont go above 8-10hg, for 28kg m/3 and above you, if you are able can pull 28hg. polyurethane is fine to pull as much vac as poss due to it being at least 2 pound.

it does all depend on what your materials are and also what type of bagging your up to, skinning, outer lam, repairs etc. with low density eps your just worried bout crushing the work piece on long pulls of vac.

good luck

[dougirwin13]

I agree Moonfish.

You can ramp the pressure right up with some materials. When I preformed a skin I was up to 25+"Hg and it came out great!

You can also go up fairly high if all the outer skins are are on... Tho probably not 25"! LOL!

As a good rule of thumb, if there's any EPS exposed you won't need to go over 10" to do a good job, in most cases.

Anyone else care to share their experiences?

[tomway]

Anyone else care to share their experiences?

I'm new to this too. It's fun!

I went too low on my foam density and ending up bagging at about 6" to stop deformation. What I did notice is that my foam rocker tables were bending before the blanks started to crush (presumably because they're longer and because I wasn't baggin them to anything stiff) Now I reinforce the sides of the rocker tables and have fewer probs. Something to think about if you're using low density insulation eps for your tables as well as blanks.

[mark venn]

bagging, wood onto eps foam, you don't need to exceed 12-14"hg, do so at your peril
you will probably have to rig up a bleed valve and should have a vac gauge on the bag.
Good luck
Mark

[woody_waverider]

Just picked up an old surgical aspiration pump but the dias were in bar and mm Hg, not "hg but found this handy link for conversions, lookls like its gott'em all, so thought I'd put it up

http://www.brandtech.com/vac_unit.asp

Turns out my pump can pull over 30 "Hg 

[lemat]

For me it's -0,5 to -o,7 bars . I bag wood skin on 1,9# EPS. Never had any problems.

Sorry for my frenglish.