5.Let's-build/Rotor-Blade.md

@@ -20,6 +20,7 @@ Following variables are used:
 | minimum wood thickness H | 25   |
 | chord C                  | 80   |
 | M                        | 200  |
+| N                        | 140  |
 | B                        | 67   |
 | A                        | 33   |
 | D                        | 10   |