Spar 30T 12T 8T (1" minimum) Rib cap Plywood saddle gusset Minimum thickness = T Nailed and glued in place Patch Plywood skin Rib cap 4T 12T 12T Patch Patch Section A-A Section B-B Section C-C Unsupported lap A C C B B B A A C T T T T T T B A Damage B C A A B Front Spar Rear Spar Ribs Trimmed Opening Minimum Radius 5T Saddle Gusset 3T (¼" Minimum) Figure 6-30.  Surfaces patches. 6-22