I am in the process of constructing an antique reproduction Victorian bed. The footboard is 4/4 solid walnut running horizontally.
It must be secured to a 5 inch square vertical post. The original antique had the footboard connected via a mortise and tenon joint that was approximately 30 inches long. I’m concerned that it I try to connect the pieces in the same manner, the expansion of the horizontal footboard will be restricted by a glued joint of that length and the footboard will crack.
Should I break the tenon into 6 inch segments and leave 6 inch voids in between to let the expansion happen or would someone have a suggestion that might be more mechanically sound?
Any help would be appreciated.
Replies
If you do as you suggest, you'll still have the post side of the joint being 30", no matter what the humidity, while the 30" tall headboard will be trying to be anything from 29 1/4" to 30 1/4". The headboard is likely to split. Instead, I'd firmly glue only 6-10" of the headboard to the post, and let the rest of the headboard be a sliding joint so that the headboard can grow and shrink. One way to do this is to cut a 30" mortise in the post, but apply glue to only the top 6-10" of the headboard tenon as it goes into the mortise. The bottom of the headboard can slide up and down in the mortise without being obvious.
There are several options:
1. Just glue the top portion of the tenon, like Jamie suggests. You could also add a second cross-piece at the bottom, behind the footboard where it won't be seen, to eliminate the leverage on the top of the joint. If you don't add the second cross-piece, I would glue the wide panel in the middle instead of the end.
2. Jeffrey Green suggests in his book American Furniture of the 17th Century pre-compressing such panels by clamping them tightly across the grain while they are being glued up. The idea is that putting the joint in compression will allow for some future expansion without splitting. I haven't tried it, but it sounds logical.
3. Build your bed in the dead of winter when the indoor humidity is as low as it can get, or find some other way of drying it more. The panel will never shrink any more from changes in moisture content. You then have to worry about future expansion breaking the joint. Using a glue that allows creep would mitigate that a little.
4. Divide the footboard, not just the tenon, into narrower pieces, if the design allows it. You could add a decorative groove or molding at the joints.
5. Use plywood.
6. Don't worry about it. This isn't mechanically sound, but you might be surprised and never have it crack. Also, a lot of wide panels, especially on older furniture, are cracked, and some people prefer a reproduction that is built like the original, design flaws and all.
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