The Complete Idiot's Guide to Sailing by Diane Selkirk

Author:Diane Selkirk [Selkirk, Diane]
Language: eng
Format: epub
ISBN: 9781615643257
Publisher: DK Publishing
Published: 2013-03-05T00:00:00+00:00

BETTER BOATING

Take bearings on objects off your bow or stern first. These bearings will change slowest as you move through the water. Take the compass headings of objects off your beam last. Bearings to these objects change fastest.

The nearer the object you are taking a bearing from, the more accurate your bearing will be.

By finding the intersection of three position lines, you can locate a more accurate position of your boat on a chart.

Setting a Course Using Magnetic Bearings Only

Hopefully when you take your bearings and plot your position, you’ll find yourself somewhere along the course line you drew before heading out. There are several reasons to plot a course in advance; the most obvious is you’ll need to know how far you’re going and how long it will take to get there, but you’ll also want to plot a course to ensure you avoid dangers.

Keep in mind this is a simplified method of plotting a course using magnetic bearings only. The problem with this method is it requires a current chart with updated variation and a parallel ruler, and if the compass rose is in an awkward place on the chart it can be tricky. The true to magnetic conversion (outlined next) is the method taught by most sailing schools.

To plot a magnetic course, do the following:

• Scan the chart carefully. Look over your planned route, checking for shipping lanes, reefs, areas of current, and other dangers. Also note landmarks you can use for plotting your position as you travel.

• Draw your course line. Use a parallel ruler to draw a line from your departure point to your destination, or to the first turn in your course.

• Determine the course you need to steer. Place one edge of the parallel rulers along the line and walk it to the center of nearest magnetic compass rose to get your compass course. Write this number above that section of the plotted line in degrees magnetic. For example, 165°M.

• Work out the distance. Determine the distance of the line in nautical miles by measuring it with your dividers and then transferring this to the distance scale on the side of the chart. If the line is longer than your dividers open, measure off a distance from the scale first and then walk the dividers along the course line. Write that number under the course line. For example, 9 miles.

• Repeat the procedure until you have lines drawn all the way to your destination. Add up the distances of each line to calculate the distance of your entire journey. Divide this distance by the speed your boat typically travels to estimate how long it will take to arrive at your destination. For example, if you are traveling for 9 miles and your boat travels at 4.5 knots, it will take roughly 2 hours.

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