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Old 20-04-2021, 12:09   #1
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Where/When to set anchor alarm

Do you set your anchor alarm at the point where you drop the anchor or do you set it at the point where you would like to be/stay?

I normally set my anchor then drift back to where I would like to be. This is the point of reference I use to set my alarm. As we have a cat that likes to wonder, even with a bridal, I use the mid point of her wondering as my reference for the alarm. I usually place a waypoint where I drop the anchor.

My wife and kids are busy with their skippers tickets and they are being taught to set your anchor alarm at the point you drop your anchor.

I disagree. Am I wrong???

My argument is that I do not drop my anchor where I want to lay. I drop it with the aim of lying where I end up. So I set my alarm to warn me when I move away from where I want to be.
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Old 20-04-2021, 12:18   #2
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Re: Where/When to set anchor alarm

If you set it where you lay back to, the alarm circle will have to be much bigger.


Think about it.
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Old 20-04-2021, 12:25   #3
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Re: Where/When to set anchor alarm

Do you want to be alerted only if you're dragging? Then set to estimated position of the anchor.

Do you want to be alerted if you drag or if you swing away from your initial set position? Then set to the boat position.

Your call though as said, the radius should be set appropriately for each case.

We center the alarm on the anchor position and set the radius a bit more than our scope.

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Old 20-04-2021, 12:30   #4
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Re: Where/When to set anchor alarm

If you set the alarm on top of the anchor, you can give the alarm circle a radius equal to your rode (really, you could do a bit smaller depending on the depth, but in relatively shallow water this is probably close enough). Then, even if the wind shifts 180, you're still inside the circle as long as the anchor doesn't move.

If you set the alarm after lying back on the anchor, you have two choices. 1) You can set a nice small circle that encompasses the area you will wander through in the current conditions. Or 2) you can set a huge circle that will contain the area you'll swing to in a wind shift.

Option 2 clearly sucks. The circle in that case is so big your anchor alarm won't go off until you're already on the rocks. Option 1 sounds like it would be good as long as you're willing to reset the alarm if conditions change. However, the alarm is still not going to go off right away when the anchor drags. Because you want the circle to cover some of the area between the boat and the anchor, and the boat is at the center of the circle, the circle must then also cover area behind the stern of the boat. Your boat will only enter this area if the anchor is dragging, but your alarm won't go off. Better to make the center of the circle on top of the anchor.
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Old 20-04-2021, 13:06   #5
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Re: Where/When to set anchor alarm

I do it just like you. I just set a huge circle where I am after the rode is out. M

Why? Because I’m usually already there once the heavy weather hits.

If I am using an anchor alarm, it’s to detect dragging and I don’t want any false alarms. I’d rather it go off when I’m 200ft away so I know it’s real.

That said, I pretty much only set them in named storms and when I can’t see anything and it’s like 50 knots at night.

Setting at the drop point is, of course, far more precise, but it all depends how you use it. I don’t use it as a precision tool.
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Old 20-04-2021, 13:11   #6
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Re: Where/When to set anchor alarm

Depends on what I am trying to achieve and where the perceived risks are for me. If I am in a deep anchorage and more worried about a dragging, then I set the mark when dropping the anchor and the radius equally to my scope (and a little to allow for tide drop). If I am in an anchorage (usually shallower) where my risks are due to an unexpect change of wind direction effecting my lay and putting me closer to an obstacle (ie shallower water or rocks/reef), then I set it at where I lay after setting the anchor and the radius allowing for small variation from that laying position but well short of the obstacle.
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Old 20-04-2021, 22:21   #7
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Re: Where/When to set anchor alarm

It's great that your wife and kids are getting serious education. Sounds like an opportunity to receive input and possibly even admit that they are right and you are wrong. Sailing with a skipper that can bend and even change is a key to a happy boat. Do you want to be right or happy about an issue like this?
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Old 20-04-2021, 23:45   #8
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Re: Where/When to set anchor alarm

We always set the alarm at the anchor drop point. Since our alarm, like most, is a circle, that is the only way you can detect dragging in all directions.
Setting a huge circle is pretty meaningless. If it works, it is only because the act of dragging is not dangerous where you anchored. Having been in hundreds of anchorarges with surrounding reefs, little room due to bommies, too many other boats and ships, etc I will gladly suffer a few false alarms to get an early warning of any real issue,
Big ground tackle is the first line of defense, but there are a lot of times cruising where you anchor in very suboptimal spots. A good anchor alarm helps with the sleep,
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Old 20-04-2021, 23:47   #9
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Re: Where/When to set anchor alarm

Quote:
Originally Posted by aqfishing View Post
Do you set your anchor alarm at the point where you drop the anchor or do you set it at the point where you would like to be/stay?

I normally set my anchor then drift back to where I would like to be. This is the point of reference I use to set my alarm. As we have a cat that likes to wonder, even with a bridal, I use the mid point of her wondering as my reference for the alarm. I usually place a waypoint where I drop the anchor.

My wife and kids are busy with their skippers tickets and they are being taught to set your anchor alarm at the point you drop your anchor.

I disagree. Am I wrong???

My argument is that I do not drop my anchor where I want to lay. I drop it with the aim of lying where I end up. So I set my alarm to warn me when I move away from where I want to be.

Yep, you're wrong.
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Old 21-04-2021, 01:18   #10
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Re: Where/When to set anchor alarm

Always set where we end up hanging, not a huge radius, normally 20 or 30 metres. If the boat changes because of changed wind or current, I want to know this as soon as it happens. Worked perfectly. Yes, sometimes it went off because we just changed the way we were hanging, but overall more likely to know that we might drag when wind/current changes.
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Old 21-04-2021, 03:46   #11
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Re: Where/When to set anchor alarm

This is what the Anchor Watch app we use says.

Add the scope length and the distance that it took the anchor to set and you will have the correct way to set up the anchor watch.
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Old 21-04-2021, 04:22   #12
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Re: Where/When to set anchor alarm

Normally it is best to set the centre of alarm circle directly over the anchor location. In this way if the boat swings to changing wind/current conditions then there will be no false alarm, but if the anchor moves even a short distance (if you set a tight alarm radius) the alarm will alert you.

Occasionally it is helpful to set an alarm that will alert you not only if the anchor moves, but also if the boat swings around to a particular part of the swing circle. Some of the apps include a sector alarm, but this can also be achieved by deliberately selecting a point away the true anchor location . In this way you can create an alarm circle that will produce the desired effect.
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Old 21-04-2021, 04:22   #13
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Re: Where/When to set anchor alarm

Quote:
Originally Posted by Barbaria View Post
This is what the Anchor Watch app we use says.

Add the scope length and the distance that it took the anchor to set and you will have the correct way to set up the anchor watch.
This not quite right, at least not unless you are standing at the bow with the smart phone/tablet.

Using the method suggested, the recorded position will be the position of the smart phone/tablets GPS antenna. If you are in the cockpit this may be 10m or more from the true anchor position. If you swing to the other side of the anchor circle this error is doubled so it can become quite significant. This mistake is a common cause of false alarms.
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Old 21-04-2021, 04:33   #14
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Re: Where/When to set anchor alarm

We have cruised for a lot of years and have always set our anchor alarm to where we drop the anchor and set a radius of swing. On the east coast of Oz we can have strong tide changes that will swing your boat 180 degrees. We set the alarm to go off when we go outside the radius appropriately. Has always worked well for us.



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Old 21-04-2021, 04:47   #15
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Re: Where/When to set anchor alarm

Vesper allows you to move anchor position so you can match your circle to be concentric with the alarm radius.

The iOS app I use allows a late set where you enter distance and point the phone in the direction of the anchor. Picture shows use re-anchoring to straighten out the chain.
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