Coastal Skipper and Yachtmaster Quiz · Chartwork and passage planning
This course to steer covers a two-hour passage, with both hours of tide laid off from the start. How long is the line marked with a question mark, struck from the end of the tide to the ground track?
A chart plot. A ground track with two arrowheads runs from the start to the right towards the destination. From the start two tide lines with three arrowheads are laid end to end at right angles to the track, labelled 1st hour 2.0 M and 2nd hour 1.0 M. From the far end of the tide a line with one arrowhead runs to the ground track, meeting it at a short dashed arc before the destination. The length of that line is marked with a question mark. Caption: boat speed 5 knots, passage time about 2 hours.
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10 miles. The triangle must use the same length of time on every side. Two hours of tide have been laid off, so the closing line is two hours of boat speed through the water: 2 times 5 knots is 10 miles. Its direction is the one course to steer for the whole passage.
