Just guessing but for starters I'd be sure to replace the typewood that brokewith the same type... balsa for balsa, ply for ply, spruce for spruce, etc. In your caselikely ply. Sand the area that broke down to a flat surface. Cut out and shape the replacement piece and test fit it.Use mediumCA to adhere and thenepoxy or wood glue to reinforce. Triangle stock is good for reinforceing jointstoo.

Remember, getting it functional and secure is more important that beauty. Both is desired but you know how it goes....