Where/When to set anchor alarm

[LoudMusic]

Originally Posted by aqfishing

It depends on the anchorage. Usually you in a lee shore so the wind is behind i.e, there is room to drag. But should the wind change or a funny blow come through and my stern starts to face the beach, I’d prefer to know sooner.

I would never set my anchor in such a way that I could not comfortable swing 360 degrees.

[JebLostInSpace]

Originally Posted by aqfishing

It depends on the anchorage. Usually you in a lee shore so the wind is behind i.e, there is room to drag. But should the wind change or a funny blow come through and my stern starts to face the beach, I’d prefer to know sooner.

Man we are anchoring in very different situations I think. I've been on the hook something like 300 nights in the past year, and I've never snuggled in so close to the windward shore that I couldn't swing 180 in the event of a wind shift. I've been butt-pucker close to that limit a few times, but never actually hit it.

What I have done is anchor in tidal ranges a whole bunch. I'm typically swinging 180 every 6 hours or so. I don't want the alarm to tell me every time the tide changes. I want the alarm to tell me if the anchor moved. Centering the alarm radius on the anchor achieves that. It also gives me a much earlier alarm than a radius centered on the boat could provide if I start dragging straight back. For me, that is also good news because most anchorages I've seen don't have miles of room behind me. There will be other boats, or moorings, or a shallow hump in the bay, or a reef, or crab/lobster pots... If I put a 100 foot circle around the boat when lying to the anchor, then I can drag back 50 feet before the alarm goes off. Then it's probably 100 feet before I can be on deck with the engine running. That's probably good enough, but not always.

If I was in your situation more often, where a wind or tide shift would put me in a bad spot, even without the anchor dragging, I would sure have a hard time sleeping. But I would get an anchor alarm with the setting to alarm in certain sectors like other commenters mentioned. I wouldn't sacrifice a good early alarm on the anchor dragging.

[Off Trail]

Originally Posted by Barbaria

That is good point, minimizing distance errors will give you better watch performance. We have a center cockpit and the tablet is located more to the center of the boat than usual.

What is your solution adding the missing boatlength?
Is there any anchor apps where you can offset the gps location?

This probably won't help you, but the alarm app for the Vesper AIS system does this. It uses the preprogrammed GPS antenna offset in the AIS, and NMEA data from a heading sensor (if it exists) to track the position of the bow.

In general you need heading data to make this work correctly anyway, as a simple GPS offset can't account for yaw changes, which are common with most boats at anchor.

[garychurch]

Wow...I thought everyone set their anchor alarm on the anchors position. The anchor point is the pivotal point around which the length of the rode will rotate and circumscribe a circle.

If the anchor alarm is properly set you can drift anywhere within the circle without an alarm. Get out of this defined area and the anchor alarm should go off.

Why would you do this any other way?

[s/v Jedi]

Originally Posted by garychurch

Wow...I thought everyone set their anchor alarm on the anchors position. The anchor point is the pivotal point around which the length of the rode will rotate and circumscribe a circle.

If the anchor alarm is properly set you can drift anywhere within the circle without an alarm. Get out of this defined area and the anchor alarm should go off.

Why would you do this any other way?

I conclude it’s just too difficult to comprehend for some because they think the alarm is about where the boat is moving to instead of the anchor dragging. Life’s too short, I just let it go

[Chotu]

As a non-“center of the swing radius” type, I can help you to understand why.

I use an anchor drag alarm if I feel there is some danger of a drag. Such as a named storm, a crazy squall.

Basically, I’m already there when it’s time to think about setting the alarm.

So naturally I’m not taking the dinghy out or trying to motor the boat up to my anchor drop point (assuming I can even guess where that was).

Instead, I just set the alarm for about 2.5 the length of rode I have out.

This protects me from false alarms in the instance of a 180 degree swing and notifies me if there is a major problem. I don’t want to know the anchor worked it’s way 50ft through some mud. I want to know if I’m freely headed toward a lee shore.

So that works. And it’s good enough. Does the job.

Never dragged in my life so I’ve never got to test it out. Usually it just gives me a heart attack when I weigh anchor and am leaving the anchorage after forgetting to turn it off. Ha ha

[LoudMusic]

Originally Posted by Chotu

Usually it just gives me a heart attack when I weigh anchor and am leaving the anchorage after forgetting to turn it off. Ha ha

My wife and I are so proud of ourselves when we remember to disable the alarm BEFORE hauling anchor that we actually celebrate the no-heart-attack moment.

[noelex 77]

Originally Posted by Chotu

I don’t want to know the anchor worked it’s way 50ft through some mud. I want to know if I’m freely headed toward a lee shore.

If your anchor moves it is something that you want to know about. This need not be an anchor alarm, in fact anchor alarms are a less sensitive than other methods, but an anchor alarm is a completely automatic system that keeps permanent watch on your anchor’s position even if you are asleep or otherwise not actually monitoring the situation.

Anchors move slightly backwards as they dig in deeper, but in most substrates with a good anchor this movement is minimal. Slow drags of the anchor are a warning sign that the anchor is reaching its maximum holding capacity. These are often the precursor to the more easily recognised rapid drag.

An anchor movement of 50 feet should be ringing alarm bells.

[Chotu]

Originally Posted by noelex 77

If your anchor moves it is something that you want to know about. This need not be an anchor alarm, in fact anchor alarms are a less sensitive than other methods, but an anchor alarm is a completely automatic system that keeps permanent watch on your anchor’s position even if you are asleep or otherwise not actually monitoring the situation.

Anchors move slightly backwards as they dig in deeper, but in most substrates with a good anchor this movement is minimal. Slow drags of the anchor are a warning sign that the anchor is reaching its maximum holding capacity. These are often the precursor to the more easily recognised rapid drag.

An anchor movement of 50 feet should be ringing alarm bells.

Yeah. I did this really quickly while preparing to do a lamination. So, whatever. 50 feet. 5 feet. Whatever. Typos happen.

Time to do some lamination now. Thanks for catching it

[noelex 77]

Originally Posted by LoudMusic

My wife and I are so proud of ourselves when we remember to disable the alarm BEFORE hauling anchor that we actually celebrate the no-heart-attack moment.

If it goes off when motoring out of the anchorage then you were obviously testing the anchor alarm function was working, which of course is very sensible

[LoudMusic]

Originally Posted by noelex 77

If it goes off when motoring out of the anchorage then you were obviously testing the anchor alarm function was working, which of course is very sensible

Ha ha, fair point! We were doing a sea trial on the anchor alarm

[rwidman]

Ideally, one would set the anchor drag alarm directly over the anchor. This would allow for the radius of the alarm circle to be the same as the length of rode set out.

For many of us, this is impractical. We are busy either handling the ground tackle or running the boat to do this (and of course, we would have to have the GPS antenna over the anchor, not the bow of the boat).

I may anchor at mid afternoon but not set the drag alarm until I'm ready to turn in for the night. So, I have to add the length of the rode to the circle when setting the alarm.

"Why do that?" you might ask. Most of my anchoring (on the US east coast) is in areas with reversing tidal currents. With 100' of rode, the boat can move 200' from one tidal swing to the other.

[Alan Mighty]

Originally Posted by rwidman

Ideally, one would set the anchor drag alarm directly over the anchor. This would allow for the radius of the alarm circle to be the same as the length of rode set out.

For many of us, this is impractical. We are busy either handling the ground tackle or running the boat to do this (and of course, we would have to have the GPS antenna over the anchor, not the bow of the boat).

I may anchor at mid afternoon but not set the drag alarm until I'm ready to turn in for the night. So, I have to add the length of the rode to the circle when setting the alarm.

Understood.

The anchor alarms for which to look are ones such as the Android app 'Anchor Alert' from Slim Jim Software. See: SlimJiM Software

The deal with SJS Anchor Alert is that you stand on the bow after you've got the boat at anchor and squared away, point your smartdevice at your anchor, input the length of rode, and ... you have an anchor alert set, centred on your anchor, and with a radius more or less equal to the length of your rode.

You can then add exclusion areas, to mark any portions of your anchor circle that you don't want to visit. And so on.

[chrisr]

we always aim to set the anchor alarm when dropping the hook, but invariably forget

fortunately once we're brought up, we can then adjust the alarm point to the length / direction of the rode and re-set it.

seems a much more user friendly system than trying to remember another button while anchoring.

cheers,

[HabibiDah]

I always set the anchor point directly over the anchor as that is the center of the swing area. In reality, I anchor, then set my anchor point by choosing to place the anchor point a bearing and distance from the boat since I am usually doing other things while anchoring.

I use the features of the alarm to create an asymmetrical safe area that allows for swing, but alerts me if winds change more than I thought they would so I can reevaluate my clearance and anchor position. My safe area usually looks something like the attached image.

My biggest problem is setting the alarm on my phone while standing at the bow and then walking to the stern of the boat and triggering the alarm. That always gets my attention and reminds me to reset the distance from the stern of the boat to the anchor plus 1 boat length.