Sunday, August 28, 2005
The echo sounder
The echo sounder provides a readout of the depth of the water adjusted for the draft of the boat; when the depth gauge reads zero we're aground - Ellen tested the zero calibration in Poole harbour!
The echo sounder documentation says its only designed to work accurately to a depth of 180 metres. As we crossed the Bay of Biscay so we sailed beyond the bounds of the continental shelf with charted depths of over 4000 metres. Initially the depth gauge responded with a sensible "Deep" rather than attempting to calculate the depth. However occasionally it would display alarming depths like 1.8metres. Although the inner workings of Kika are day by day becoming more familiar to me - there are still many mysteries lurking behind the panels and mass of wires. On our third day at sea an alarm started sounding. I started a frantic search for the cause of the alarm – engine overheating? - (no we're sailing) Gas alarm, Sea-me detecting another boat? Battery monitor, egg-timer. No, no ,no, no. Finally I traced the sound down to the depth alarm, which triggers an alarm at 0.5metres. For the next day the depth alarm would intermittently start beeping - normally as I was just about to drop off to sleep.