mast wires 368
The lights, wiring, and other electrical gear mounted on a sailboat’s mast most certainly live a hard life. They’re exposed year-round to wind, salt, rain, and sun, so it’s no wonder that they’re so prone to malfunction. What’s more, reaching them and fixing them is often no easy task. Because most of these masthead devices are also critical to safety and navigation, installing them properly and maintaining them faithfully is a must.
If a masthead tricolor goes dark, a converging vessel may not see you until too late. If a strobe doesn’t work when you need it most-you’re in distress or about to be run down-you may not get the chance to discover why it failed. Likewise, if the masthead-mounted VHF antenna stops sending radio signals because the coaxial cable is saturated with water or the connector wasn’t properly soldered, you may find yourself cut off just when you need reliable communication.
The most common mast-wiring failures involve the use of undersized wiring for navigation lights. The guidelines set forth by the American Boat & Yacht Council call for a maximum voltage drop of 3 percent on such critical electrical components as navigation lights-if the voltage available at the battery is 12.6 volts, that at the bulb should be a minimum of 12.22 volts. On boats with tall rigs, the distance from the electrical panel to the masthead and back-the measurement from which wire-size calculations are determined-is significant. The wires need to be of heavier gauge than in other boat-lighting circuits. Even if you have a relatively new boat, do the math on the wiring leading to the top of your spar. Tables to calculate the required wire size for a given length can be found in Charlie Wing’s Boatowner’s Illustrated Handbook of Wiring and in Nigel Calder’s Boatowner’s Mechanical and Electrical Manual.
Due to their miserly current draw, LED nav lights have helped with this problem: You can replace the fixture rather than the wire. Also, 24-volt electrical systems reduce the cross section of the wire required for all DC-powered equipment to a quarter of that required for 12 volts.
Coaxial cable and its connections are also frequent sources of trouble. Many coaxial-cable terminals are improperly installed and poorly soldered. Initially, they may work, but over time, corrosion sets in or water migrates into the jacket, reducing the strength of the signal reaching the antenna or radio. Disassemble and carefully inspect cable connectors for corrosion and to ensure that they’ve been properly soldered-solder should be smooth and continuous, not a mix of blobs or drops-and make certain that water hasn’t entered the cable jacket. Exposed cable connections should be entirely covered with heat-shrink insulation or wrapped with UV-resistant electrical tape; wrap this tape toward the top of the mast to encourage water runoff by creating the effect of a layer of shingles. When your spar is next unstepped, disconnect the coaxial cable from the antenna. With a multimeter, make certain, first, that no shorts are present; then use it to ensure good continuity over the length of the cable. Mast wiring may be out of sight, but for the sake of safety and reliability, it should never be far from your thoughts.
Steve D’Antonio is a regular Cruising World contributor who offers services for vessel owners, boatbuilders, and others in the marine industry through Steve D’Antonio Marine Consulting (www.steved
marineconsulting.com).
