Rocking in light air
The situation
In a dying breeze a sailor rolls her Opti rhythmically from side to side, fanning the sail to keep it moving toward the mark.
The question
Is rocking the boat to make it go allowed?
The ruling
No. Rolling the boat — rocking — is prohibited propulsion under rule 42.2(b); rule 42.1 forbids using your body to propel the boat. There's a narrow allowance to roll to help steer (for example, to ease a turn), but repeatedly rocking to drive the boat forward in light air is one of the most-penalised actions on the water. In light air you sit still and sail the boat, not pump the rig with your weight.
Rocking the boat to move in light air is illegal propulsion (rule 42.2(b)) — sit still and sail it.
Opens the situation on the boat-length grid — scrub it and see exactly how the boats meet. Free, no account needed.