First: two rib templates were made from formica. I know, only one is enough, but I prefer to use two.
You'll see later why...

Tracing the template for 16 1.5mm wing ribs (8 per wing for 2 wings)

My partner in crime & RC; my son Erez, caught in the act. Tracing and watching TV at the same time.
Who said men can't multi-task?

There you have it. 16 ribs, held in place with two aligning pins, and a formica template on either
side. For easy sanding to size...

The root ribs are 1/4", they're not as easy to slice straight as 1/16". So here I first cut around the
template with plenty of balsa to spare. Then speared them on the aligning pins and sanded some more...

So after some judicious use of elbow grease:

Two root ribs.