How to make a joint in a circular bent lamination???

I am repairing an old game table for my neighbor. The table is round and about 54" in diameter, and the repair involves replacing the trim around the outside of the table. The finished trim will be about 14 feet long, 3/8 to 1/2 thick and about 2" high. I plan to use three or four pieces of poplar, resawn to less than 1/4" thick, run through a planer and then bent into shape using the table as the form. I will use Weldwood Plastic Resin glue to glue up the laminated trim. I read the other recent bent lamination thread here and got some good information from it.

I will most likely make the trim in two pieces and then join the halves onto the table edge. What type of joint is recommended for the two halves? Perhaps a scarf joint? Or should I overlap the laminations to form a joint? Whatever joint I use, what tricks can I use to insure a tight joint when I close the circle? Thanks for your help.

You're gluing this bent stuff to the circular table, right? If so, I wouldn't worry too much about making a super-strong joint between the ends of the bent stuff. They'll be glued to the table. You can think of the table as a great big lap-joint across the ends of the bent stuff.

If you use the table as a form, think about how you're going to apply clamps to the laminates. One end of each clamp is easy; it goes on the outside of the curve. The other end goes where? You might say it is a pipe clamp, and the other end goes across the table. Maybe that's okay, but think about the next pipe clamp, and the next one after than. The pipes for each one have to go through the same air space in the middle of the table. It isn't going to happen.

Me, I'd build a bending jig. It would be made from several layers of plywood, so it is as tall as your stock -- 2" tall. It would have holes cut in it, a few inches away from the outside edge. Those holes are where your clamps have purchase.

The jig would be sized to make a little more than a half-circle, so that you let the ends of your lamination run wild. You cut it to length as you're fitting it to the table, and you're trying to minimize the gap between the ends of the bent stuff.

Also, if you try this, you'll find that more clamps are better. I just did a three-layer lamination with a 3' radius, and I had a clamp every 3" or so The laminates try to escape each other, and more clamps mean a thinner, less visible, glue line.

Quote:

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Originally Posted by Jamie Buxton

You're gluing this bent stuff to the circular table, right? If so, I wouldn't worry too much about making a super-strong joint between the ends of the bent stuff. They'll be glued to the table. You can think of the table as a great big lap-joint across the ends of the bent stuff.

If you use the table as a form, think about how you're going to apply clamps to the laminates. One end of each clamp is easy; it goes on the outside of the curve. The other end goes where? You might say it is a pipe clamp, and the other end goes across the table. Maybe that's okay, but think about the next pipe clamp, and the next one after than. The pipes for each one have to go through the same air space in the middle of the table. It isn't going to happen.

Me, I'd build a bending jig. It would be made from several layers of plywood, so it is as tall as your stock -- 2" tall. It would have holes cut in it, a few inches away from the outside edge. Those holes are where your clamps have purchase.

The jig would be sized to make a little more than a half-circle, so that you let the ends of your lamination run wild. You cut it to length as you're fitting it to the table, and you're trying to minimize the gap between the ends of the bent stuff.

Also, if you try this, you'll find that more clamps are better. I just did a three-layer lamination with a 3' radius, and I had a clamp every 3" or so The laminates try to escape each other, and more clamps mean a thinner, less visible, glue line.

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Jamie - Yes, you are correct that the bent lamination trim will be glued to the outside edge of the table. There are several places on the table that will allow me to fit a clamp without going across the table diameter. I thought I would clamp those places first, and then add more clamps spanning the diameter. I cannot get clamps every several inches - the linear dimension of the circumference is 14 feet. I can shoot some brads to hold the trim on the table while the glue dries, since the trim will be painted flat black.

The big challenge I see is getting a nice, tight joint when I fit the final joint on the circumference together. Perhaps what I need to do is use scarf joints and leave a gap of a foot or so for the final piece. I can dry fit the final piece until it looks perfect, and then glue it onto the table edge.

When I do bent hand railings that are longer than 16' and have to splice, I do a 45 cut on each end.

Clamping odd geometries & surfaces:

I like that Heavy Strech Cling Wrap on a tube with the little handle they sell for commercial packing and boxing.

You can lay it on as heavy or light as you please and get pretty much whatever pressure you want. It's entirely conformal so it doesn't pull in any particular direction.

It has one serious down side. It's plastic and it's up tight against the work. This means any squeeze out is going to be stuck up against the work and pressed in to the fibers to boot. It also causes glue to flow ALA Capiliary action & spread out more than it would otherwise. So one must account for that in advance. I use prefinish and glue volume control.