WWA Info Exchange

I needed to put together a larger flat panel vacuum frame for the cabinet doors I'm veneering for the kitchen. I needed something 36" by about 50". Having built a couple smaller ones in the past I was loathe to mill all the strips for the internal support, notch all the joints, blah-blah-blah. I came up with the following.

A piece of 1 1/2" polystyrene rigid insulation (pink foam stuff) with 1/4" plywood or MDF laminated both sides. Ordinary Titebond glue bonds the polystyrene to wood quite well. I glued 1 1/2" solid lumber around the perimeter onto the bottom, cut the foam to fit inside the 'frame' then glued the foam in, gluing the top on at the same time. I used a piece of 3/4" plywood over the top to distribute the weight of some concrete blocks and a couple buckets of sand I had lying about.

Polystyrene has little resistance in shear so I wouldn't put a great deal of faith in my panel in bending mode. But with the vacuum pressure distributed by the 1/4" facing it has plenty of resistance to withstand the compression of the vacuum pump.

A side benefit beyond being a quick way to build a really flat panel is that it's a good bit lighter, size for size, than torsion boxes built the traditional way.

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Nullum Gratuitum Prandium

Cheers - Dennis

NPDH

Bill

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Amateur Bill
O'Fallon, MO
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If a man speaks in the forest, and no woman hears him, is he still wrong?

I'm in shape, round is a shape.

Are you sure that the vacuum wont take all the air out of the foam and cause it to collapse? I don't know. I'm just saying that it could happen but, then again maybe the polystyrene is ridgid enough to hold up and stay flat without air in the cells.
If it does shrink down and let the 1/4" ply move, you have lost the flatness that you need. Maybe the glue will seal the box well enough that it won't be effcted.
Just being devils advcate.

Rog

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Dont badmouth no strangers, they just friends you aint met yet.

An ounce of responsibility is worth a pound of State and Federal laws.

I spent most of my money on woodworking
tools and beer, the rest I just wasted.

I wasn't very clear in my verbal description, Rog. Here's a sketch of the assembly:


See ""

As you can see, the foam sheet is sandwiched between the two sheets of plywood with the hardwood frame around it all. In reality the foam is closed cell so does have a moderate amount of compressive strength.

The best adhesive I found for bonding the vinyl tubing to wood inside the lower groove was Alcoa aluminum gutter seal. I taped the 40mil sheet to the outside of the upper frame with gorilla tape and hinged it at the back.



See ""

The vinyl tubing provides a great seal -



See ""

These are a few of the panels I've gotten done thus far:


See ""

The larger ones are actually pairs of doors I laid up as a single sheet to get a continuous grain match across both doors.

Now the fun begins ....


See ""

_________________
Nullum Gratuitum Prandium

Cheers - Dennis

OOOHHHHH! Oops I thought that you were putting the torsion box WITH the pannels INSIDE a vacuum bag to keep the pannels flat when you pulled the vacuum.
What do I know? I just rembered seeing a lady put a foam pillow in a plastic bag and pulling a vacuum using a floor sweeper then putting the pillow (now collapsed) into a shoe box. (I swear you could put 42 sweaters into a small suitcase using that method.)
I knew the lady was pulling the air out of the cells in the foam and thought maybe the same thing would happen to your rig.
Sorry.

Rog

_________________
Dont badmouth no strangers, they just friends you aint met yet.

An ounce of responsibility is worth a pound of State and Federal laws.

I spent most of my money on woodworking
tools and beer, the rest I just wasted.

Very smooth,
I like that set up.

I thought you'd be using a larger sheet that was trapped by the frame.
Any memory problems in your top sheet? (yes I know a loaded question, but I hope you take it in the spirit it is meant...)

eric

Now THAT is an elegant solution that bears some consideration-- seems like it would be light enough to hang on the wall too....

Thanks for sharing
Lawrence