vac bag to gluelam morris chair arms?

[CALA Workshop]

Hey all,

A bunch of questions

I'm working on a bow-arm morris chair and I'm debating on how to best bend the arms.

Dimensions are roughly 1-1/8 x 5 x 36" with about 3" of bend on maybe a

60"radius. Quarter sawn wht oak.

I've done some steam bending, but have been unable to locate air dried stock for this project. Previous attempts to steam bend kiln dried stock have been inconsistant at best.

So....

I'm considering glue-lam and vac bagging.

Are the ~$300 1 cfm vac bag systems capable of clamping up 9 layers of

1/8" wht oak for this sort of form?

do I need to spend a bundle for a 3+ cfm system or look into making my own?

Thanks in advance for any advice. I apologize if this has been asked before, I found a few things but nothing specifically about the capability of the ~ 1cfm ~$300 systems.

Good Day

[PCProffitt]

I'm no expert, but I did build a vacuum press from the joewoodworker.com kit. By the way it is a great kit and I like it a lot, but it isn't the only solution. Whether a specific vacuum press will do it isn't related to how much you spend or how many CFM your pump can handle. Depending on your pump they can all put a huge amount of pressure on your laminate if you have it set up correctly.

CFM has only to do with how fast you evacuate the bag. As long as you use a long open time glue you'll be fine. You just need to test your setup ahead of time. Make sure your cauls are ready, stack your laminates (without glue), tape them, put them in the bag and pull it down. Note the time it takes and check that with your glue's open time. Remember you'll be spreading glue on all those laminate surfaces. Try to have a non-stick surface like wax paper or plastic laminate facing each side so you don't stick your work to your cauls.

In my opinion the major concern is making sure you have a stout enough bag. I bought the 30 mil vinyl from joewoodworker.com. In some cases it might be considered to be almost too heavy. You may be able to find

16 mil and 20 mil vinyl at your local fabric store for $3.99 to $5.49 per yard (54" wide). We did here in Atlanta. Many commercial bags are 20 mil. They do sell pre-made bags now on joewoodworker.com.

If you just get a pump, bag, hose and fittings you can make a quick vacuum press system for way cheaper than $300. Inexpensive vacuum pumps are not too hard to find.

Paul Proffitt

CALA Worksh> Hey all,

[Gary A in KC]

IMHO - I'd think trying to vac bag a laminate glue up would be overkill and a real pain. You have to build a form in either case to match the shape you're looking for. Here's how I've done some laminate glue ups for rocking chair parts (backs and rockers).

Build a form that matches your curve out of MDF (several layers of 3/4 together). I then glued laminate along the curve (to prevent glue from sticking to the form later) and screwed flat metal brackets along the edge to provide a side support to keep the laminated pieces from slipping in the form. Cut a large number of holes through your form for clamps. Then using some scrap pieces of wood I did a glue up on the form. This glued up piece (when dry) then serves as my clamping caul to go on top of the good wood that I'm shaping. I found this to be sufficient for the work I was doing and with a good glue, had very little discernible spring back when it was unclamped. It was actually very easy to do with great results.

You might want to check into some of the Woodworks episodes where David Marks does some laminate glue ups. He does much the same thing as this except he creates a top and bottom to his forms that mate together when clamped around the laminates. Either way works pretty well.

My 2 cents

Gary in KC

[Andy Dingley]

You want it green, not even air-dried. So it's really the wrong time of the year anyway. Split is always better than sawn, even if you have to saw it smooth after bending.

I use mainly locally-felled timber, mainly oak. As we're running short of huge forests here in England, the trees I have are often small and somewhat misshapen. I can easily collect "knees", logs that have grown with a curve to them (they needn't even have reaction wood problems). I prefer to make Craftsman seat backs, arms etc. by bandsawing these curved baulks rather than steaming.