fourrings wrote:
Don't forget that holes in the rib will compromise strength. A
"doubler" rib forming another box behind the controls will help.

There will be five 1/4" holes (and 1" apart) in a horizontal
arrangement. You think that will be a problem?

Probably not. Round holes help the stress travel right by. I was
thinking of a square box placed into the rib. In a load carrying part,
round holes are better than square holes with round corners, which are
better than square holes.


I just came back from HD. Found three possibilities for 3/4"
plywood: Sandeply, Oak, and Birch. Sandeply is $32 per sheet and
others are $40. Which would be ideal for the ribs and cross-sections?

The choice with the highest number of plies and fewest voids. Ideally,
you'd get cabinet grade Baltic or Finnish birch plywood. There are
versions of this with "paint grade" face veneers that aren't that
expensive, but you may need to order it at the Pro Desk.

More plies equals a stiffer rib and more edge wood for the skin to glue
up with.