I'm in the market for a new GPS and I know many have an anchor alarm feature. For those unfamiliar with that feature, you set it after you're anchored and should your anchor drag while you're sleeping it sounds an alarm so you can get up and take care of the problem once it drags past the amount of feet you set it for. That's pretty straight forward. But I got to thinking, how many feet do you set it for? Obviously it depends on the amount of scope you have out but boats normally swing in the wind so if there are 100 ft from your anchor to the boat on the water surface (obviously more than 100 feet of scope out) you could swing 200' from one side to the other if the wind shifts. But if your anchor drags your could drag more than 200 ft in the "wrong direction". So, when anchored, what numbers do you like to put into an anchor alarm? More important, do you think anchor alarms are trustworthy or do they give you a false sense of security.
These are the things that drive me crazy when Sine Qua Non is up on the hard. Thanks in advance
Setsail728@aol.com
GPS Anchor Alarms
Moderator: Jim Walsh
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Bill Goldsmith
Re: GPS Anchor Alarms
Warren:
I think the right radius setting for the anchor drag alarm is a function of the conditions at the chosen anchorage in light of your real-world experiences anchoring your boat. Where I do most of my anchoring (Lower Hudson River) the bottom is mud and my Bruce holds first time, every time, even when swinging around. I don't even bother using the alarm there.
However, when chartering in the BVI I was on an unfamiliar boat in relatively unfamiliar territory. When anchoring in Marina Cay, there is a tight anchorage on a lee shore. Last year I set the alarm for 100 feet despite having 150 feet of scope out. At 3AM the alarm woke me up and I found that we had merely swung around with a wind/current shift but still holding. It was comforting to know that the alarm worked and also comforting that we were not dragging!! And that anecdote was prior to the elimination of SA! The point is that if the anchorage were not near a lee shore I would have considered setting the alarm at 200 or 250 feet. I don't mind being alerted to a major wind/current shift, but again it depends on the anchorage. In a secluded anchorage, let's say, half a mile from any dangers, and you want a good night's sleep, the you could set it for 300 feet or more on a 150 foot scope.
Great topic!!
Bill
goldy@bestweb.net
I think the right radius setting for the anchor drag alarm is a function of the conditions at the chosen anchorage in light of your real-world experiences anchoring your boat. Where I do most of my anchoring (Lower Hudson River) the bottom is mud and my Bruce holds first time, every time, even when swinging around. I don't even bother using the alarm there.
However, when chartering in the BVI I was on an unfamiliar boat in relatively unfamiliar territory. When anchoring in Marina Cay, there is a tight anchorage on a lee shore. Last year I set the alarm for 100 feet despite having 150 feet of scope out. At 3AM the alarm woke me up and I found that we had merely swung around with a wind/current shift but still holding. It was comforting to know that the alarm worked and also comforting that we were not dragging!! And that anecdote was prior to the elimination of SA! The point is that if the anchorage were not near a lee shore I would have considered setting the alarm at 200 or 250 feet. I don't mind being alerted to a major wind/current shift, but again it depends on the anchorage. In a secluded anchorage, let's say, half a mile from any dangers, and you want a good night's sleep, the you could set it for 300 feet or more on a 150 foot scope.
Great topic!!
Bill
Warren Kaplan wrote: I'm in the market for a new GPS and I know many have an anchor alarm feature. For those unfamiliar with that feature, you set it after you're anchored and should your anchor drag while you're sleeping it sounds an alarm so you can get up and take care of the problem once it drags past the amount of feet you set it for. That's pretty straight forward. But I got to thinking, how many feet do you set it for? Obviously it depends on the amount of scope you have out but boats normally swing in the wind so if there are 100 ft from your anchor to the boat on the water surface (obviously more than 100 feet of scope out) you could swing 200' from one side to the other if the wind shifts. But if your anchor drags your could drag more than 200 ft in the "wrong direction". So, when anchored, what numbers do you like to put into an anchor alarm? More important, do you think anchor alarms are trustworthy or do they give you a false sense of security.
These are the things that drive me crazy when Sine Qua Non is up on the hard. Thanks in advance
goldy@bestweb.net
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D. Stump, Hanalei
Re: Half the distance to nearest immovable object......
Warren,
Seriously though, if you set it to alarm after a 100' drag, the area covered is 200' across. Anywhere on the circumferance of the circle, you have only dragged 100'. If the GPS isn't ship powered, I would think you would run the hand held batteries down.
Second question, No, I don't rely on anchor alarms. If it's a boisterous night (weather, not crew!) I sleep very lightly and rouste out often to check things on deck. (Don't anchor near Hanalei on a rough night, you may see an underware or less(heaven forbid!)clad individual pacing the deck looking for problems.
It's fun, isn't it ????
Dave Stump
Captain Commanding
s/v Hanalei
Seriously though, if you set it to alarm after a 100' drag, the area covered is 200' across. Anywhere on the circumferance of the circle, you have only dragged 100'. If the GPS isn't ship powered, I would think you would run the hand held batteries down.
Second question, No, I don't rely on anchor alarms. If it's a boisterous night (weather, not crew!) I sleep very lightly and rouste out often to check things on deck. (Don't anchor near Hanalei on a rough night, you may see an underware or less(heaven forbid!)clad individual pacing the deck looking for problems.
It's fun, isn't it ????
Dave Stump
Captain Commanding
s/v Hanalei
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matt cawthorne
Re: GPS Anchor Alarms
Warren,
I have a loran with anchor watch and used to use it all the time. On previous boats I had anchors drag and for a long time would not sleep while I was in command of the boat. That made boating less enjoyable than it could be. I used the anchor alarm for a couple of years. The decision on how large a circle to set was based on how close other things were, how the wind was blowing and how much sleep that I wanted. Since the US Navy could focus the Greenbury point communications array in our direction a wakeup was guaranteed at least once every month or two. If you plan to set 100 feet of line out then set the watch point when you drop the anchor. That way you can set the alarm for 100 feet plus the error of the unit. If you set the unit when you have the anchor set you can set it to an even lower number if you feel confident that the wind direction would stay constant over the night. Beware. You do not wake up relaxed when an alarm is going off. I changed my approach. If there is any chance of the anchor dragging I just set a second anchor. That way I sleep well. Having lots of chain and properly sized anchors helps one sleep well. We have been in conditions where 40% of the other boats in the anchorage have dragged in a storm, the dinghy was twirling like a pinwheel on the end of the painter and did not drag. As the years pass and I gain experience sleep is the norm rather than the exception. Mostly I feel that it is because of being conservative with the anchor and rode.
Matt
mcawthor@bellatlantic.net
I have a loran with anchor watch and used to use it all the time. On previous boats I had anchors drag and for a long time would not sleep while I was in command of the boat. That made boating less enjoyable than it could be. I used the anchor alarm for a couple of years. The decision on how large a circle to set was based on how close other things were, how the wind was blowing and how much sleep that I wanted. Since the US Navy could focus the Greenbury point communications array in our direction a wakeup was guaranteed at least once every month or two. If you plan to set 100 feet of line out then set the watch point when you drop the anchor. That way you can set the alarm for 100 feet plus the error of the unit. If you set the unit when you have the anchor set you can set it to an even lower number if you feel confident that the wind direction would stay constant over the night. Beware. You do not wake up relaxed when an alarm is going off. I changed my approach. If there is any chance of the anchor dragging I just set a second anchor. That way I sleep well. Having lots of chain and properly sized anchors helps one sleep well. We have been in conditions where 40% of the other boats in the anchorage have dragged in a storm, the dinghy was twirling like a pinwheel on the end of the painter and did not drag. As the years pass and I gain experience sleep is the norm rather than the exception. Mostly I feel that it is because of being conservative with the anchor and rode.
Matt
mcawthor@bellatlantic.net
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Warren Kaplan
Re: GPS Anchor Alarms
Thanks Matt and everyone else for your input. I haven't done alot of anchoring lately but I hope that will change this year. All your advise is welcomed.
Warren
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Warren
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