Updating Electric Devices on the Mast

Mar/Apr 2003

After we dropped our mast for renovating the rig, we also took the opportunity to update electrical items. The internal mast wires run in 1 1/2-inch foam-pipe insulation. The wires in and out of the insulation looked and tested okay, so we didn�t run any new wires inside the mast. The masthead running lights and masthead VHF antenna have hull-level duplicates, since a running-light failure at the masthead at night in a seaway can be dangerous and difficult to repair.

In an emergency, most sailors can live without other masthead electrics, such as wind-speed indicator, apparent-wind indicator (AWI) and the masthead strobe. The masthead strobe is illegal offshore in any event. If the spreader lights fail, a flashlight can be used to light up the foredeck. Since the VHF antenna raises the mast height beyond the 55-foot waterway bridge clearance, we moved it to the radar post aft. A masthead VHF antenna has a greater range than a VHF antenna mounted on the stern radar post; however, signal attenuation using a long inside-the-mast co-ax cable can result in VHF range not much different than a lower antenna height, with shorter co-ax, at the radar post. Eliminating the VHF cable inside the mast is one less wire to fail. The fewer electrical circuits at the masthead the better.

Part of the reason for unstepping the mast was that some mast electrics had failed; the AWI indicator and strobe didn�t work, and the spreader lights were out. Knowing that most electrical problems on boats are connector problems, the connectors to the wind-speed and API instruments were untaped and inspected. As expected, the plugs and jack were corroded. The connections were cleaned with fine sandpaper, and we stripped the wires back as necessary to get clean connections. A final test was to use an ohmmeter at the mast-heel connector. In our case, approximately 5,000 ohms should be read between API terminals.

The Aqua Signal Tri-Color/Anchor/Strobe unit was removed and tested using 12 volts. New bulbs were installed as a precaution. The strobe bulb was not replaced since we�ve had poor luck with strobe bulb life in the past. The large separate strobe, attached to the life sling, could be run up the mast in an emergency. One less thing to go wrong at the masthead. We cleaned the Aqua Signal contacts, reinstalled the unit and taped the base with self-vulcanizing tape. We checked the connections to the Aqua Signal circuits at the mast-heel connector with a 12-volt battery. The range light tested okay.

Both spreader lights had failed. One bulb had burned out, and the wires were frayed inside the spreader on the other. New marine-grade wire was fed through the spreaders. The spreader power-feed wires inside the mast tested okay and were led outside through an existing hole in the mast at the spreaders. The spreader power wires were butt-connected and taped to the new light wires. New spreader bulbs are designed to be grounded through the stainless-steel socket attached to the spreader. The spreader light bulb was isolated from the socket using a rim of tape, since dedicated ground wires are provided for each mast circuit. As some protection from lighting damage and poor grounds, we do not use the mast as an electric ground. Only the standing rigging is grounded to the mast. The spreader lights can be tested with an ohmmeter or a 12-volt battery at the mast-heel connector. A resistance of 1 to 2 ohms is normal. The spreaders were reattached to the mast.

The two mast-heel electrical connectors are aluminum, screw-together, 30-year-old, military specification surplus connectors with gold-plated contacts — used with army tanks and such. One connector is used for masthead instruments, the second serves lights. These military spec mast-heel connectors have never given us any trouble. The outside of the connectors are coated with lanolin to prevent corrosion.  

By Ocean Navigator