Sail and power: status, wind and applicable rules

A photograph of a mast does not determine whether a vessel is legally sailing. Rule 3(c) requires being under sail without using propelling machinery.

A sailboat using mechanical propulsion is power-driven in that state. The distinction affects encounters and signals, not merely its commercial model category.

The first panel separates states of the same fictional hull; the second explains the wind relationship used by Rule 12 without depicting a manoeuvre. A boat’s design does not fix the legal state in which it operates at every moment.

Rule 12 lies in Section II, applicable to vessels in sight. Paragraph (a) concerns two sailing vessels approaching with collision risk.

Section I remains relevant, and Rule 13 overtaking may be decisive. “Both have sails” therefore does not finish the assessment.

Retain actual classification, visual condition, risk and overtaking relationship. Additional Rules 9 and 10 obligations in channels and traffic schemes also remain.

A diagram that omits those conditions can help explain wind geometry but cannot independently determine all responsibilities in a real encounter.

With wind on different sides, Rule 12(a)(i) assigns the duty to keep out of the way to the vessel with wind on her port side. With wind on the same side, paragraph (a)(ii) requires the windward vessel to keep out of the way of the leeward vessel.

These relationships do not depend on which boat is faster, more expensive or larger. Windward relates to where wind comes from and leeward to the other direction.

They are wind references between vessels rather than fixed north and south positions on a map.

For Rule 12, paragraph (b) defines windward as the side opposite that carrying the mainsail; for a square-rigged vessel it uses the largest fore-and-aft sail. This legal definition should not be replaced by looking only at a flag or the bow direction.

Mainsail position is particularly important in an aft-wind depiction. Our drawing identifies the main and wind origin so that the relationship is visible rather than depending on decorative colour.

It is a geometric teaching comparison and supplies no sail-handling or course-change instructions.

Rule 12(a)(iii) addresses uncertainty: a vessel with wind on the port side seeing a vessel to windward, whose wind side cannot be determined with certainty, must keep out of the way. It does not say that any uncertainty about any vessel always creates that role.

The subject and other vessel’s location are express conditions. It accompanies the general requirement to treat doubtful collision risk as existing, without being synonymous with it.

The questions concern risk and responsibility respectively, and should remain separate in an explanation.

Rule 25(e) requires a forward cone, apex downwards, for a vessel proceeding under sail while also mechanically propelled. Its daytime display relates to Part C.

At night classification affects applicable lights rather than authorising random mixtures of arrangements. Merely having an engine fitted, or an electrical operation without propulsion, should not automatically be equated with using propelling machinery.

The encounter condition must correspond to actual operation and the exact provision, rather than the name “sailboat”. Signals communicate that state but do not remove the other duties.