MikeWhy wrote:

Is the spreader bar hinged in a bowsaw frame? A rigidly glued tenon
doesn't seem very efficient in tensioning the blade. Does it work well
that way?

The spreader bar is connected to the uprights of the frame with
a "NON-GLUED" mortise and tenon joint. The whole thing is held together
with the tensioning string/rope/wire.

Deb