Question 1

During your oral exam you are asked to explain how you would carry out a passage plan for a coastal route on a yacht under 500GT, including the appraisal stage. What is the primary purpose of the appraisal stage?

Accepted Answer

To gather and assess all relevant information — charts, publications, tidal data, weather forecasts, vessel limitations and crew experience — before any specific route is plotted The appraisal stage, the first of the four stages in passage planning (appraisal, planning, execution, monitoring), is where the navigator gathers all relevant information about the intended voyage before committing to a specific track. Skipping or rushing this stage is a common root cause of groundings, as critical information such as a chart correction, tidal restriction, or crew competency limitation may only surface later when it is too late to adjust safely.

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.