The scarf length bevel is 10 times dimension A (thickness of  the rib cap strip) with the spruce reinforcement block being  16 times dimension A (the scarf length plus extension on  either end of the scarf). The plywood splice plates should  be of the same material and thickness as the original plates  used to fabricate the rib. The spruce block should have a 5:1  bevel on each end.  [Figure 6-15] These specific rib repairs describing the use of one scarf  splice implies that either the entire forward or aft portion of  the cap strip beyond the damage can be replaced to complete  the repair and replace the damaged section. Otherwise,  replacement of the damaged section may require a splice  repair at both ends of the replaced section of the cap strip  using the indicated dimensions for cutting and reinforcing  of each splice. When a cap strip is to be repaired at a point where there is  a joint between it and cross members of the rib, make the  repair by reinforcing the scarf joint with plywood gussets,  as shown in  Figure 6-16 . If a cap strip must be repaired where it crosses a spar,  reinforce the joint with a continuous gusset extending over  the spar, as shown in  Figure 6-17. The scarf joints referred to in the rib repairs are the most  satisfactory method of fabricating an end joint between two  solid wood members. When the scarf splice is used to repair  a solid wood component, the mechanic must be aware of the  direction and slope of the grain. To ensure the full strength  of the joint, the scarf cut is made in the general direction  of the grain on both connecting ends of the wood and then  correctly oriented to each other when glued.  [Figure 6-18] The trailing edge of a rib can be replaced and repaired by  removing the damaged portion of the cap strip and inserting  a softwood block of white pine, spruce, or basswood. The  entire repair is then reinforced with plywood gussets and  nailed and glued, as shown in  Figure 6-19. Figure 6-17.  Cap strip repair at a spar. Figure 6-15.  A rib cap strip repair. A A 3A 10A Face grain of plywood side plates Spruce block Top view Side view 3A 16A Plywood face plates A B E 3A 5A 3A Splice plate D Direction of face grain of plywood C and are  original dimensions. Reinforcement  plates shall be plywood glued and nailed. A B C D E A 10A Face grain  of plywood and are original  dimensions. A B C D E E D C B Figure 6-16. Cap strip repair at cross member. 6-14