ORIGINAL: Peter_OZ
you also need to brace on the opposite side right in the middle of pic.
Another weight saving idea would be to dremel out some holes in the ribs if you are able, it is amazing how much you can save by doing this.
Peter... I did both of your suggestions. The triangle stock was easy. Dremelling out the holes took a little longer. Each hole is 1/8" diameter, times 100 holes, plus the four larger holes in the W12's. Assuming an average of 7 lb/cu-ft density of the balsa, I calculate that I cut out 0.034 oz (2.13 g) of weight. Including the 4 servo rails and the 2 FCB's I cut out earlier, I saved 0.193 oz (12.06 g) of weight. It didn't hurt, but was it worth it? I don't know.
I didn't cut out any holes on the ribs holding the servo rails (aft of the spar). I figure I need the strength there to hold the servo rails. Do you see any other areas that I can do more Dremelling?
Josh