Question 1

When preparing a "pilotage plan" for entering an unfamiliar harbour or anchorage (i.e. a written/sketched plan used instead of relying on the chart alone while manoeuvring), what should the plan typically include?

Accepted Answer

A sketch or notes identifying key transits and leading lines, clearing bearings, the sequence of buoys/marks to be seen and their expected appearance, depths and hazards along the route, and contingency actions (e.g. what to do if an expected mark is not sighted) — prepared in advance so the skipper is not trying to read a full chart while also conning the vessel in confined waters A pilotage plan distils the chart into the specific, sequential information needed during the entry itself (transits, bearings, marks, hazards, contingencies) — reducing the workload of cross-referencing a full chart while also handling the vessel in close quarters.

Question 2

When taking a visual position fix using two compass bearings of charted objects, why is a third bearing often taken if a suitable object is available?

Accepted Answer

Two bearings give a position at their intersection, but a third bearing forms a small triangle ("cocked hat") where the three position lines meet — the size of this triangle gives a visual indication of the likely accuracy of the fix and any compass error, helping the navigator judge how much to trust the result A two-bearing fix gives a single intersection point with no indication of error; a third bearing reveals a "cocked hat" whose size is a practical, visual guide to the fix's reliability.

Question 3

Using the "rule of twelfths" to estimate the height of tide between low water and high water, what fraction of the total tidal range is gained during the first hour after low water?

Accepted Answer

1/12 of the range The rule of twelfths approximates the rise/fall over each hour of a (roughly) 6-hour tide as 1, 2, 3, 3, 2, 1 twelfths — so the first hour accounts for 1/12 of the total range, the slowest rate of change near the turn of the tide.