bent plywood lamination help in Seattle area


Hi,
I am looking for some help and advice on a bent plywood lamination furniture project. I have a design and the means to make a mold, but I do not have a vacuum press. I read on the joewoodworker.com site that in order to have enough clamping power to bend plywood to a mold, I would need approx. 9 CFM worth of a vacuum press.
I am hoping to find someone in the area who owns such a powerful beast and might give some advice on it's use. I could probably find one to rent, but I would prefer to be able to pick the brain of an experienced user. I would be happy to pay or exchange services and I will gladly bring my project to your location. Please email me at nlbauers_at_optomet_dot_com if you can help. Please reply to the newsgroup with words of wisdom concerning this project.
Thanks, Neil
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Neil, I just finished making some bent plywood doors for a cabinet. http://www.teamcasa.org/workshop/currentproject.htm Details and pictures here
I did not use a vacuum press but made a mold (cold press) instead. I used bending plywood and 1/8" walnut veneer, it worked out very nicely. I also used Gorilla (poly) glue, it provided adequate open time to make the wood sandwich.
I have used a vacuum press before and as far as I'm concerend, they both work fine. As for a vacuum pump, I used a Air Conditioning vacuum pump that I purchased used and it worked very nicely. I would never use a venturi type pump as they make too much noise and use far to much power compaired to a vacuum pump.
BTW - many auto repair shops - dealerships have old A/C vacuum pump's on older charging stations that they would be willing to part with. I have two very nice ones, $20 each! (drive by gloat)
Dave
PS you spell your last name wrong :) Should be Bower, like mine!
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Thanks Dave,
Nice pictures Dave. I like the clamps-stretching-to-infinity-on- appealing-curve shot. Very Plamann-esque.<g>
I have been noodling on a cold press too, but the shape of the project is one continuous piece with a loop in the middle and several corners. It would probably have to be a multistage glue/clamp job if it were a cold press. I haven't ruled it out, but it seems a more even pressure could be had from a vacuum press. Cold press is the back up plan at this stage.
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"CFM" is an odd sort of measure for a vacuum pump. If it's a vacuum, they're pretty much running at 0 cfm volume flow by definition. So this cfm rating is only really relevant in the initial pumping down stage.
What are you making here ? A device for clamping, or a device for forming ? Trying to pull it into shape with a vacuum will need a large volume if it's to be efficient, but once you have the workpiece to shape and the bag is down, then the flow rate is minuscule, even for a huge piece. There are people who bag surfboards and model aircraft wings that are enormous, just working with a fridge pump. You're not (I assume) a production shop, so you don't really care about the clamp-closing time, other than to worry about glue working life.
Can you apply simple mechanical clamping to get the piece to shape, then enclose it in a smaller bag ? A smaller bag is a cheaper route to fast clamping than a bigger pump.
If you're vacuuming steam-bent timber (with or without glue) then you'll be pumping water vapour out for hours afterwards as you freeze dry it. This may overwhelm a small pump in the early stages.
One thing to watch out for on "vacuum" pumps is that they're rated for vacuum. Some (fridge compressors) don't like running with zero flow and can overheat. So either make you bag leakproof enough that you can switch the pump off when it's under vacuum, or find a real vacuum pump (probably diaphram or vacuum oil filled). I use an old lab pump (circa $50 on eBay last time I looked) which will run happily all day and has adequate volume to hold (but not form) anything. With the aid of string loops etc. for initial clamping I've never found it inadequate to hold anything I wanted to make.
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"Andy Dingley"

I'm sure the OP was referring to the venturi vacuum pump that is powered by compressed air. http://www.vacupress.com/products.htm#airpower
Dave
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Or, if you're supplying vacuum to a device like a gyro or other air motor. It depends on what he's trying to do.
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Hi Andy and Dave,
I am attempting to make a chair out of a single continuous piece of bent plywood. The first photo at this link gives an idea of what I mean:
http://www.design-technology.org/alvar1.htm
I also thought that CFM was an odd metric to use for this, here is the link to information I found about the required CFM:
http://www.joewoodworker.com/veneering/vacuumpumps.htm
I am trying to find a device for clamping the wood to the form while letting the glue dry. Seems to me that a vacuum press would produce more consistent even pressure all around and give better results.
I believe that I am going to need a press that has some power to pull the wood to the form, since the wood will need to be coerced into this form. Getting all this in a bag and then trying to clamp it with only enough power to hold it in place may be a futile effort. Let me know what you guys think.
Neil
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