Boat compass

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If you don’t have a compass like this at your helm, it’s time to add one.

I’ve noticed an alarming trend in the recreational boat building industry: Many major boat manufactures are producing boats without a magnetic compass. I have trued discussing this with a few boat dealerships, only to be lectured about what a dinosaur I am. Who needs magnetic compasses when we have GPS chartplotter?

Well, for one, I do. I’d rather skip all of the drama that goes along with the GPS screen going blank, 60 miles offshore, in the dark and of course with a torrential rainstorm, 4-foot seas and a little fog for good measure. At that point, I’m quite happy being the dinosaur with my trustworthy and time-tested companion, the magnetic compass.

The magnetic compass is one of the oldest navigational instruments in the world. Its origin dates back to the Vikings in the 11th century. The first magnetic compass was probably just a simple magnetized needle shoved through a straw, resting in a container of water.

It’s likely it was magnetized using lodestone, which is an iron ore having magnetic qualities. A magnet, as you may know, is simply a piece of metal having the property of attracting other pieces of metal. Most magnets are ferric (iron-based). In its natural state, lodestone — a magnetic oxide of iron — has this property.

So does our planet. As a result of Earth’s core being mostly iron, it has magnetic properties. In fact, it can simply be thought of as a giant magnet, with its poles located at approximately 74°N, 101°W for the north pole and 68°S, 144°E for the south pole.

There are two types of compasses: Magnetic and gyro. We’ll forgo the gyro compass discussion for a future column. A magnetic compass utilizes the earth’s magnetic field to provide a measurement of direction without a power source.

The compass needle points to (or seeks) a location known as magnetic north. For many years, this was in northern Canada, but now it’s moving toward Siberia. For a fascinating explanation of why the magnetic north pole moves, go to https://bit.ly/3k8xW4n. Magnetic north is different from true north, whose reference is the star Polaris, also known as the North Star.

A compass is normally mounted near the helm station of the vessel and is aligned with the centerline axis of the bow and stern. Every compass contains a compass card, which floats in a clear liquid on a tiny bearing so it can spin freely.

The compass card is labeled with cardinal headings, which are the four main points on a compass: North, east, south and west. The card will also have 356 additional one-degree increments, for a total of 360 degrees. Each mark represents a heading your vessel may travel on.

Finally, there’s a lubber’s line, a name which is thought to have originated from the big clumsy fellows or seaman who worked onboard early sailing ships. A lubber’s line is simply a thick line on the compass used to indicate the direction the boat is headed when looking through at the compass card.

If your boat doesn’t already have a magnetic compass, choose one that has a large and easily readable compass card. It will make long periods of steering by compass easier on your eyes.

Now that you understand the basics of the magnetic compass, let’s explore how to use it. The first step is to determine your destination. Next, you will need to calculate a magnetic compass course or heading.

To calculate a magnetic course between two points, you’ll need an updated nautical chart of the area you intend to travel in and a basic understanding of magnetic variation (the mathematical angular difference between magnetic north and true north). You will also need parallel rulers, a pencil and a set of dividers. Once you have calculated your course, you can label it on the chart and use it as a reference to head out on your voyage.

You’re now starting to get brilliant on the basics of how to use a magnetic compass. If you would like more training on this subject (and many others), consider attending one of my Nautical Knowledge 101 boating education classes. During this two-day course, you’ll learn a plethora of topics, including how to calculate a magnetic course on a local Charlotte Harbor chart.

In the event of an emergency, such as a loss of power or a malfunctioning piece of electronics, your magnetic compass may be the only source of information you have onboard to help you safely navigate your vessel back home. Are you sure you want to leave the dock without one aboard?

Capt. Jack R. Sanzalone is a 30-year submarine veteran and licensed USCG Master Captain with 40 years of experience. He is the owner of Boat Tutors and teaches basic and advanced boating education both in the classroom and on the water. Contact Capt. Jack at Jack@BoatTutors.com or by visiting his website, BoatTutors.com.

Capt. Jack R. Sanzalone is a 30-year submarine veteran and licensed USCG Master Captain with 40 years of experience. He is the owner of Boat Tutors and teaches basic and advanced boating education both in the classroom and on the water. Contact Capt. Jack at Jack@BoatTutors.com or by visiting his website, BoatTutors.com.

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