Sgian Dubh
Established Member
Something like as seen below I'd suggest if you want good control and reliable results, although you can get steam bent wood to bend in multiple planes as a free bend, but the end results would vary from piece to piece. I took the photograph below at ercol, and it's also shown in my above post.
You can see there's essentially three U shaped metal channels linked together at the two corners. There's additional flat bar strengthening the horizontal pieces in the photograph which is for the chair back. The two pieces sitting vertically also have a piece of steel bar welded in place to keep the leg parts parallel and the right distance apart. You can also see towards the left top corner a piece of chain that controls the folding of the leg holding part of the former, and on the right in that corner you can see there's a convex block to fold the wood around. The convex block may be wood attached to steel, but I don't remember if that's the case.
Obviously, ercol worked out how to do the job and invested a fair amount of time and money to make lots of these jigs for the specific chair model they sell: I can't remember what model it is, but they must sell enough of them on a regular basis to have made it worthwhile investing so much into reliably making lots of parts the same repeatably.
To make a one-off piece it would probably be necessary to make something similar, but perhaps you could get away with something not so well engineered. In ercol's case their investment in their bending forms or jigs is now probably somewhere in the region of a miniscule fraction of a penny per chair, but for a one-off it could (would?) be a significant expense. Slainte.
