Need to make a cheap vacuum bag for 1 off use
#11
I need to make a vacuum bag that will fit a board 8' x 16" wide. It's a 1 off type project so I don't want to spend a whole bunch of money doing it. If I'm able to veneer both sides at once, then I just need to have this last 1 time. I was thinking about using the thickest plastic drop cloth available but don't know how to seal it up so it doesn't leak. Any ideas?
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#12
You can seal vinyl plastic with standard PVC pipe cement. That's how I made my vacuum bag. Tape might work, too, for a one shot deal. If you have a boat "window" fabricating shop nearby they may have some vinyl cut offs for cheap. Otherwise, 6 mil vinyl might last for a couple of glue cycles.

John
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#13
If it were narrower, I'd suggest a roll of foodsaver bag material.

I use aircraft composite rolled nylon bag material for my vacuum bags. You would have to order it though.

I use these guys...

CST sales - vacuum bags

You would also need a way to seal the bag ends (they sell bag clips) and, of course, a vacuum port. I use the aluminum ports used in the composites industry here too.

This system works very well for flat stuff.
Rocket Science is more fun when you actually have rockets. 

"The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government." -- Patrick Henry
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#14
I made a bag out of vinyl material from a fabric store. Might be perfect for what you need.
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#15
Thanks All. I'll check out the fabric store for vinyl. I have the PVC cement.

The prices listed at the site Mike uses were actually really good. I have also been looking for bag clips, too, and they have them. I emailed them for a shipping quote. And I wouldn't have to do any gluing, just clip both ends of the bag.

Mike, the nylon bags your source sells is just 2mil thick. To protect my poly bag (maybe 4mil), I use kitchen towels as my breather fabric which also prevents my boards from digging into the corners. Is that enough to prevent these bags from going holey? At those prices, it wouldn't be a huge loss, but they seem like they're made for multiple uses.

Thanks,
Paul
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#16
Oh yeah, I've seen vinyl at the fabric store, too. Seems like it might have been around 10 mils thick, which would be plenty for an occasional use bag.

John
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#17
That's a great source. Thanks.

John
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#18
Got mine at a local hardware store, bought the heaviest vinyl they had and the bags last surprisingly well. Basically, you only really need to make a tube as either end can be clamped with a V-groove board and a dowel. I use a tire valve to hook up to my vacuum pump. One thing you will need is an onion or potato sack, throw it in on top of the work piece and it will create channels for the air to escape.
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#19
check Walmart . one with a sewing department( not all have them)
they sell 4 different thickness of vinyl, like for slip covers. All I use, very cheep.
Life is what you make of it, change your thinking, change your life!
Don's woodshop
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#20
atgcpaul said:


Thanks All. I'll check out the fabric store for vinyl. I have the PVC cement.

The prices listed at the site Mike uses were actually really good. I have also been looking for bag clips, too, and they have them. I emailed them for a shipping quote. And I wouldn't have to do any gluing, just clip both ends of the bag.

Mike, the nylon bags your source sells is just 2mil thick. To protect my poly bag (maybe 4mil), I use kitchen towels as my breather fabric which also prevents my boards from digging into the corners. Is that enough to prevent these bags from going holey? At those prices, it wouldn't be a huge loss, but they seem like they're made for multiple uses.

Thanks,
Paul




The bags are intended for one-off use. The parts you would typically make would be worth thousands, so the bag cost is immaterial.

However, I generally get several uses out of a bag. One must protect sharp corners and a small square of vinyl, fabric, or such is sufficient if you don't do as below.

I generally use a full-size caul made from two side smooth tempered or untempered 1/4" hardboard cut for about 1/4" overhang. I just use a sanding block to slightly round the corners and no other treatment is necessary. Over that, I place a same-sized piece of plastic window screen. (You get the rolls from your big box home center). The vacuum port goes in the middle of the part and the screen allows vacuum everywhere. Use screen on both cauls. I blue-tape the screen to the caul and blue tape the entire sandwich together. You have screen, caul, veneer, glue, substrate, glue, veneer, caul, screen. Slide the entire thing in the bag.

In a following post, I'll re-post my entire "how I do it" diatribe since posts here only last a year. I've learned to archive things like this just in case.
Rocket Science is more fun when you actually have rockets. 

"The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government." -- Patrick Henry
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