Technotalk

Boat/US Magazine, Jan, 2003 by Chuck Husick

This month's column may surprise those readers who believe that we are interested only in things powered by electricity. Surprise! The subject of this column works without batteries. It is a compass, specifically a hand-bearing compass. Every boater should have one and know how to use it.

While most mariners agree that every boat that sails beyond view of a shoreline should have a properly compensated magnetic steering compass, the steering compass can't provide the navigation facilities available from a modest investment in a hand-bearing compass.

Assume you are proceeding on a constant heading when you notice a distant vessel on your starboard bow. Being a prudent mariner you want to keep an eye on the other boat. You note the other vessel's position in relation to a flyspot on your windscreen, knowing that you can then check for a change in relative bearing to determine if you will pass clear, have a close encounter or a collision. Unfortunately the flyspot was, in fact, a fly and it has moved on, depriving you of your calibrated reference point. You need a new visual sight reference. Lacking a grease pencil with which to mark the windscreen, you look for some other reference point, a scratch in the glass or some point on the windscreen frame.

If you were carrying a hand-bearing compass you could have made a note of the other vessel's magnetic relative bearing and checked it again every few minutes. Whatever pucker factor might have been present disappears with the knowledge that you are properly tracking the movement of the other vessel. As you take the relative bearing on the first boat you note that the waters have become crowded, including commercial traffic, some of which consists of tugs with barges in tow. You know the danger involved in misjudging an encounter in this type of traffic and begin to take bearings, noting the identity of the target, the time and the relative bearing of each. In a few minutes and using a pencil and a piece of paper, you will have created a reasonably comprehensive picture of the nautical world around you, all thanks to a compass that works without batteries.

Having survived the voyage through the weekend traffic you reach your destination, a quiet anchorage. You select the ideal place to carefully lower the anchor (having learned long ago that dropping the anchor results in an anchor uselessly buried under a pile of chain), It is quiet, the breeze has dropped to a mere zephyr. You are set for the night, unless the wind picks up and/or the tidal current causes your anchor to drag. You have set the anchor watch function on your GPS or Loran to alert you if something goes awry during the night. But you know that Loran signals may drift a bit at dusk and dawn when a weather front approaches.

There are additional uses for the hand-bearing compass beyond those mentioned. It's an obvious back-up for the main steering compass. It can be used to determine if DC current is flowing in a circuit by moving it up against one of the two wires in a circuit and watching for a movement of the compass card. (This works best when the current is at least few amperes). With prices starting at $25, the value is indisputable.

GPS can be equally squirrelly under some circumstances, including the recently discussed problems created by the interaction of strong TV signals with some types of marine TV antennas. In pursuit of self-reliance, you take out the hand-bearing compass and take a round of sights on distinctive objects on the shore. You try to choose objects that will still be visible when the sun sets, knowing that if something does occur to interrupt a quiet night, it will be when it is black as proverbial pitch. Now you can relax.

Chuck Husick is an engineer, pilot, sailor and the former president of Chris-Craft Boats.