Need Sleep

Treasure Cay
No LL

After two nights sitting up on anchor watch, I was ready for a good night's sleep last night. We went to bed about 10 and I was out like a light. Around 1 AM the anchor dragging alarm on the GPS woke me out of deep REM sleep. Sometimes the alarms are spurious because the GPS iteration didn't converge. Spurious positions usually get replace by correct ones within a few seconds. Nevertheless, I had to get up and watch the GPS to see if the alarm was real or not. It was!

Darn, I was too tired to go running around re-anchoring in the middle of the night. Besides, the wind wasn't strong, just 15 knots or so. I resolved to wait it out to see if the anchor continued to skip across the bottom or not. After 10 minutes, it became clear that we were holding position. I went back to bed for a half sleep. Every 15 minutes or so, I would wake, stare at the GPS screen, decide we're OK and then back to sleep.

This morning I took this picture of our historical track on the GPS screen. As you see, it is crystal clear how our trajectory draws an arc as we swing at anchor. It is also crystal clear what woke me at 1AM. Abruptly the trajectory jumped from one arc to a distinctly different one. Also clear is a spike pointing lower right which marks one of those spurious positions calculations when the iteration failed.

Sometimes the anchor chain snags on the bottom. As the snag breaks free that causes the swinging arc to increase in diameter and to shift center point. If that happens we are not really dragging.

Last night's dragging was real. How do I know? We had 70 feet of chain out, and the GPS sensor is 20 feet from the bow. That means our circle of swinging is 2*(70+20)=180 feet in diameter. If I accurately set the anchor alarm reference in the center of the circle, then we should be within 90 feet, if I set it on the circumference we could be 180 feet away. The new arc was 180 to 220 feet from the alarm reference. We must have dragged some. Most likely 50 feet or more.

Today we came back through The Whale again. Good. I was beginning to fear that we would not be able to pass The Whale in time to meet Nancy's plane next Tuesday. Yesterday I heard some gossip that said that The Rage was predicted for today because of a storm 500 miles NE of here. That would have make The Whale impassible for several days. Now we don't have to worry about that any more.