Sculling in light air
The situation
Becalmed near the leeward mark, an Opti sailor waggles the tiller back and forth to wiggle the boat forward toward the mark.
The question
Is wagging the tiller (sculling) to move the boat allowed?
The ruling
No. Sculling — repeated forceful movements of the helm to propel the boat — is prohibited by rule 42.2(d). In light air this is heavily watched. There's a limited allowance to scull to turn the boat (for example, when starting to tack or gybe, or to turn for a tactical reason), but you may not scull to drive the boat forward through the water. Repeatedly waggling the tiller toward the mark breaks rule 42 and can be penalised on the water.
Wagging the tiller to move forward is sculling — illegal under rule 42. You can steer, not scull.
Opens the situation on the boat-length grid — scrub it and see exactly how the boats meet. Free, no account needed.
Rules cited
See the underlying rule: Rule 42 — Ooching.