Monday, February 4, 2008

Glue lam, forms, biscuits and top cap

Here's one set of forms used to make the "glue lam" panel top caps. A stack of thin strips is glued into a sandwich and clamped between these forms so they'll dry in the desired shape. In the upper left of the pic you can see the resulting glue-lam top cap laying on top of the panel.
These same forms have already been used to pattern-route the curved rails, and they'll be used again as a caul to attach the top caps to the panel frames. There's a separate set for the headboard because the radius of it's curvature is different than that of the footboard.

I just bought a biscuit jointer. Biscuits don't add strength to a long-grain glue-up like this, but it keeps things aligned while gluing and clamping. The only effort here is to get the slots centered in each of the pieces, since they're different widths.
The trial fit.

The glue-up. The biscuits automatically align the top cap, which makes the glue-up as stress-free as a glue-up can be. The form is used as a caul to distribute the clamping pressure evenly across the curved surface. Of little note: since the curves are true arcs (instead of parabolic arcs formed by bending something and tracing it), the position of the caul left-to-right doesn't matter much. There's a bit more hanging off the right side than the left, but I didn't even notice until uploading this pic. If this were a parabolic arc, that would mean that parts of the caul would be exerting no pressure.

The top cap for the headboard isn't a very good glue-up, but I'm going to try to salvage it with epoxy or cyanoacrylate. I don't know if I have enough stock left to make another, and it's not a fun process.

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