Music on deck moves both crew and compass
After navigating Scaramouche in the 1972 Miami/Montego Bay Race, I was on the beach looking for a ride back to the U.S. Scaramouche was staying to go cruising, but I needed to return. I was asked to navigate another racing yacht, Aura, back to St. Petersburg, Fla., leaving the next day. Close enough for me. I got my sextant and sea bag and switched boats.
Aura was a sistership of Scaramouche, an identical 49-foot thoroughbred racing hull with the best of gear, including complete navigation suites. Scaramouche was more comfortable, with better accommodations, but Aura was no dog; spartan, but comfortable and fast. She had beat us in the 811-mile race by just a few seconds.
We left Montego Bay and set a course for Grand Cayman Island, where a few hours of diving and relaxation on the beach were anticipated. The wind was about 18 to 24 knots right over the stern, so we set the cruising chute, a 2.2-ounce spinnaker with wire luffs and double-reinforced head and clews. Seas were six to eight feet from astern, and we made nine to 11 knots steady, averaging just under 10 for hour after hour. After sunset, the watches were changed, and the two guys on the evening watch decided to sail to music. They rigged out our portable speakers near the helm, and put on a Seals and Crofts tape. I'll never forget falling asleep to "Summer Breeze" as we rolled across the Caribbean under a full moon.
The next morning I awoke well after sunrise (as navigator I was not on the watch schedule) and turned on the loran, expecting to get a quick fix before breakfast. I should have shot morning stars, but this was cruising, not racing, so I was somewhat lax. I was not yet familiar with the fact that loran was nearly useless south of Cuba; I couldn't get a fix, only one very doubtful LOP. I got out my sextant and shot a sun line, which gave me a rough check on my DR distance, as the LOP was nearly at a right angle to our course. I planned to get a meridian altitude at LAN to establish our latitude. Another late morning sun sight seemed to put us about 30 miles north of track. Now I was worried. I rechecked my figures for the last sun line, and shot another one for good measure. We really were about 30 miles north of track, after a run of only 215 miles. We were abeam Little Cayman and Cayman Brak, two small islands some 60 miles NE of Grand Cayman; and on the present course, we would have missed it altogether.
I went up on deck, climbed the mast winches, and shinnied up the spare spinnaker halyard about 10 more feet, giving me a height of eye of about 20 feet, and there on the starboard beam was Little Cayman about eight miles away. I got a sight on it with the hand-bearing compass, crossed that with the sun lines, and set a new course for Grand Cayman, around the north end instead of the south. Looking over the helmsman's shoulder as he came to the new course, I instantly realized why we were so far off course: the speakers!
While we were blissfully rolling over the moonlit Caribbean listening to the tape player, the two speakers were sitting on deck about three feet from the compass, one on each side, silently pulling the needle at least 12° E from magnetic north. I told the skipper and watched as he moved the speakers, the compass swung immediately and quite dramatically to the west.
After we were safely anchored in Georgetown, I did some experimenting. It seems so obvious not to put speakers, which are built with powerful permanent magnets, anywhere near the compass. This applies especially to portable ones, since permanent speakers such as tape players, radios, and radiotelephones can be compensated for. But I found after several trials that deviation caused by our speakers was not detectable when they were at least six feet away. Three feet was definitely too close. Nevertheless, after that, they were kept below!
I hate to think what would have happened had we been 12° east of our course when trying to round Cabo San Antonio in Cuba. A sure grounding would have been the result.
Richard K. Hubbard is a former Coast Guard officer who works at the Defense Mapping Agency's Hydrographic/Topographic Center.