Laminating a 4′ ring Perfect round closed circle?
brooklynwood
| Posted in General Discussion on
Hi,
I need to make a perfect circle out of Ash, about 4 feet round.
Finished size of stock would be around 2X2″ grain needs to follow curve, thats why it has to be laminated as opposed to
segmented wood cut with a router circle jig.
Anyone done this?
Bending a section of a curve seems easy enough; a perfect closed circle seems a little tricky.
Thanks
Replies
pass the salt
I've not done this, so a good dose of salt may be appropriate here. My thought would be to have a center form that is a full circle, thick enough for your pieces, with clamping holes. Then two outer half circle forms that mate with the center. Again, with clamping surfaces radiating from the center. As you add layers, I'd think alternating the butt-joint locations (like laying bricks) would be a good idea. I'm assuming that you plan to steam the pieces for additional flexibility? That might not be necessary if the pieces are thin enough.
Laminated circle
No - I haven't done this.
Now that that is out of the way, Ralph's suggestions are good. However. I don't believe that steaming is necessary to soften the lams. I have laminated many items and have discovered two rules: First make the lams thin; 1/8", 3/32" can easily be cut on the bandsaw. Second, use multiple lams - 5 or more would be great.
If you glue-up in multiple passes, expect substantial spring-back until you have the total number of layers in place. After that, it will be solid as a rock.Rather than a 'hard' exterior form, I suspect that you can do just as well with a flexible caul (a thicker lam for example) In my experience, ordinary PVA glue is adequate.
You will need a full height, inner pattern - probably a screw-up of 3/4" plywood - it will be heavy. You will also need 1" x 2" 'spokes' screwed to the bottom of the form so you can hammer down the slippery lams that want to go any place but into the height (width) you want. Protect all this from excess glue -Saran wrap works but other ideas are as good.
Now - the butt joints. Dry fit first - of course. But a possible alternative is to plan on - design - two or more contrasting inlays at joint locations on the final lam.
Good luck.
Frosty
brooklyn,
I did something similar for a table apron a while back. My apron was a ring of 3/8" bending plywood laminates topped off with a veneer, for a total of 4 lams. The dry run went ok, but on glue up, at one point I felt like the proverbial monkey making love to (to put it politely) a football.
I butt-jointed the internal lams, and off-set the joints from one another, in one glue-up. I scarf jointed the outer veneer (from its top edge to the bottom, traversing the 2" apron width over about 6" of length) and made it a little over-wide, to allow for a little slip and slide in length and width in a separate operation. (It's pretty hard to get an exact length on something like this) The straight grain of the veneer and a tight joint made it nearly invisible.
I covered the outer veneer with a wax-paper-covered caul of 3/8" bending plywood, and used a strap clamp to apply pressure, over a solid circular core. It worked very well.
If you are using solid-wood lams 1/16-1/8 thick in lieu of the bending plywood, I believe it might be easier to do the job in at least three or maybe four glue-ups, to minimise the wrestling, control the mess and limit the open time of all that glue surface. Another pair (or two) of hands will be a help also, to get the glue on in minimum time, and help with the alignment and clamping of the laminations.
Ray
I would laminate up 2 half sections(actually they should be more than 1/2 sections). make up a saw jig so that one could cut some long as possible scarf joints on the table saw. put the 2 halves together and glue them up
ron
They do it all the time making wagon wheel rims in solid stock. Bass drums are also made in large sizes but those are laminated. In either case, you need the right equipment, materials, set up and experience, the "perfect" part will depend on these.
Worked out pretty well.
Had to glue one 1/8 lam at a time to get nice joints.
Can never have enough clamps for this I could of had more.
I will post a whole process on my blog someday soon.
Laminated circle
Wow! You didn't need to ask for advice. You should be giving lessons.
Frosty
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