[artdutra04]

1. Draw center lines for the center of all of your ribs, and tweak the geometry as needed to make sure all of the ribs look good.
2. Convert all center lines to construction sketches.
3. Select all of these construction lines and use the offset line tool to offset them.
4. Use the power trim tool to remove all unnecessary line segments.
5. Extrude cut the holes.
6. Use feature fillets to add fillets to all of the corners. I almost never use sketch fillets, as they can be difficult to remove / edit later on.