The more equipment that is installed on the plane, the more load the wing will need to take. To prevent the wings from flexing too much, the plastic spar can be replaced with a carbon one.
2. Masking tape
3. Carbon rod (5/16" OD or 8 mm)
4. Original spar
1. Line up the two spars to get an idea of where you will have to cut the carbon spar.
2. Wrap the the location that you are going to cut the carbon spar with masking tape (only a few times around is necessary). The tape will prevent the carbon from fraying when it is cut.
3. Mark the carbon spar where it will be cut, using the plastic spar as a length reference.
4. With the hacksaw, cut the carbon spar.