54 seamanship secrets
HOW TO USE A GPS RECEIVER FOR YOUR SPEED RUN
If you use the GPS speed function, you won’t need fixed landmarks for your
run. Run half-mile legs at each chosen RPM setting; this allows the GPS to
settle down for more accuracy. Record the GPS speed, make a tight turn, and
run a half mile on the reciprocal heading. Add the two speeds, find the average,
and plot it onto your graph. Repeat this method for other RPM settings.
Navigation Solutions in Less than 5 Seconds
Smaller than a sheet of paper and almost as thin, completely waterproof and
easy to use, the nautical slide rule has but one purpose—to solve time, distance,
and speed problems. If you know two of those factors, a nautical slide rule
will solve the third for you.
All slide rules come with a base and two wheels. Use the large wheel to
find the distance traveled. Use the smaller wheel to find your boatspeed or the
time required to travel a given distance. To master the slide rule, remember
these three little-known secrets.
- Know how each scale breaks down
Distance scale (large wheel). Find the printed distance arrow on the base.
Th e distance wheel shows miles on the outside and yards on the inside. For
practical navigation, use only the outside miles scale.
Speed window scale (small wheel). Th e speed window shows whole
knots. Estimate tenths of a knot of speed between the whole mile marks.
Time window scale (small wheel). The time window has three
scales: outside, middle, and inside. The outside shows hours, the middle
shows seconds, and the inside shows minutes. For practical navigation,
use only hours or minutes.
Th is speed/RPM table for the motor vessel Capri Sun is ready to be fi lled out.