This rib form allows you to bend and shape lute ribs so they can easily be assembled without building a mold. Although this form will naturally produce a "circular" cross-section, with slight modifications you can make a shallower lute back if desired. You can see the form in action here.
These are the first two lute backs assembled with this rib former, without using a mold. The backs are of myrtle wood from the Oregon coast.
To make the form, first glue and screw three layers of relatively clear pine boards together. Draw the lute outline and draw an outer shape about an inch or so larger on each side of the lute outline.
Carefully cut the lute shape first.
Carefully and lightly sand the rib-forming surfaces to remove any large imperfections.
Now cut a piece of poster board the approximate thickness of your lute ribs and secure it between the two form pieces.
Now, screw another support board to hold the two parts together again - this time with the cardboard rib spacer in place. Be careful not to put screws in the way of your band saw path : )
Take the time to setup and check your band saw to the exact angle of your ribs.
Now, slowly and patiently cut your first pass through the form. Look at the end to see the rib profile being cut.
This is the first cut.
Duplicate this process for the other side to get the two pieces shown below.
Use the "scrap" pieces from previous cutting operations to make the final cuts.
You can see the form in action here.