Industry NB:- We want a better anchor alarm not a better anchor!

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Yes, sometimes I do but it doesn't really help as I tend to have a cup of tea then fall back to check/set it and it might drag for several meters - even 10m in that process....depends on the bottom, speed of boat, etc.
 
I'm pretty well with Talbot on this one, Lemain. An anchor alarm doesn't stop you dragging, the only thing that can do that is proper ground tackle and anchoring technique. I include in technique the ability to select the right system for the available holding ground.
If you are not confident that you are securely anchored you will set an anchor watch, or stay awake. If you are lulled into a feeling of false security by your new high tech anchor alarm the situation might be worse than if you, quite rightly, stayed awake worrying.
On other issues raised: I agree that GPS alarm systems are too sensitive for small crowded anchorages - they beep with every minor movement if set fine enough to avoid collision or dragging ashore; in big anchorages they are great.
I have found that the change in the behaviour of a boat when it starts to drag is enough to wake me and I've heard this from many experienced anchorers.
So, I agree that an anchor alarm that is foolproof would be great but one that only provides false security could be worse than nothing!
 
I have never quite managed to work out the algorithm used in my GARMIN 128 to determine the anchor alarm reference point if you simply leave the GPS switched on in alarm mode the whole time (having cancelled the alarm when you last moved off). It seems as if after a period under-way, once you stop moving for a significant time, it assumes this as the new reference position. Not trusting this though, I either switch the alarm itself off/on or the entire GPS which achieves the same result.

I would much prefer to be able to mark (or enter) a specific position myself as the reference, but this function is only available in 'reverse' as a guard-range.

Vic
 
[ QUOTE ]
I have found that the change in the behaviour of a boat when it starts to drag is enough to wake me and I've heard this from many experienced anchorers.

[/ QUOTE ] I was told that when I was a novice but I have dragged (and seen others drag) when fully awake without noticing anything until they hear someone shouting, or 'crunch'. Take a F5/6 wind and you start to drag, the chain is still taught so the bow is still to the wind and you notice nothing. That's what happened to me and others I know.

Can you tell us what had happened on the occasions that the change in behaviour actually woke you? What were the conditions, bottom, type of anchoring system, and weather? Did you wake up in time? Did you eventually manage to anchor OK in that anchorage or did you go elsewhere, or take a buoy?
 
Having read through the thread...

Firstly, nobody seems to use the anchor watch on the depth sounder, which in some circumstances can be more useful than GPS based, especially in the Med where there is no tide to factor in.

Secondly, and aimed mainly at the poster, if you anchor (and by definition due the the thread - fail) in packed sand full of furrows (typical Med. anchorage), you need a better anchor.

Absolutely nothing wrong with the current crop of main anchor designs. Plenty wrong with what the manufacturers claim, and much wrong with what boat owners judge is an acceptable balance between usability and security. I am constantly amazed at what some boat manufacturers fit as standard, and what some owners treat as acceptable.

All you need to do is ask the innocent question 'what will it take to hold my 5 / 10 / 20 tonne vessel securely'?

I suggest a bigger anchor!
 
There is one potential input to an anchor alarm which never seems to be used; the "heading" of the rode.

In combination with a load cell, it could alarm when the pull reached an angle which is likely to cause the anchor to require resetting.

In combination with a GPS, it could (within a few swings) allow the alarm to establish the actual position of the anchor, and therefore alarm promptly should dragging occur.
 
So if you anchored in, say, a river, with a 2kt stream and no wind, you could gradually drag downstream any number of miles without an alarm? Sounds like a dangerous algorithm. If I had such a device I would like the ability to a) turn it off and b) fully understand what it is doing.
 
I haven't dragged anchor enough times to provide a useful database from which to draw any conclusions. However, as you are probably aware, when a wind-rode boat drags, as opposed to falling back on its rode, the bow falls off faster than the stern and this changes the motion and noise in the rigging to a noticeable degree. This tendency for the bow to fall away is a very reliable indicator that you are dragging and useful when you are going through your anchoring procedure. If you haven't done so try it yourself the next time you anchor. Snub your anchor to a rode that is way too short and then watch what happens. In any reasonable breeze the bow will start to pay off quite quickly.
 
I know that's the marina myth but in practice, in my experience both as a bystander and the vessel in question, the boat fall back with a taught rode. I suppose it's not surprising since the anchor and chain on the bottom still give a fair bit of resistance and sufficient to keep bow to wind.
 
Garmin Alarm.

No, it's not that bad! .... Once the reference point is set it will always alarm when ouside the set range however slowly or fast the boat moves. My problem is understanding how it sets the reference point when you don't do it manually. I have asked the question of Garmin at boat shows but never received a meaningful reply. Maybe it's just an unintended gremlin in the software. /forums/images/graemlins/grin.gif

Vic
 
[ QUOTE ]
Firstly, nobody seems to use the anchor watch on the depth sounder, which in some circumstances can be more useful than GPS based, especially in the Med where there is no tide to factor in.

[/ QUOTE ] I do, when it is appropriate, which it usually isn't. While there is no substantial tide in the Med (though it is up to a metre so cannot be dismissed) the anchorages are pretty flat. Thinking back to our anchoring this year - from April to September from Cabo de Gata to Port Mahon, I cannot think of a single anchorage in which a depth alarm would have been a useful anchor alarm - except to give a warning before beaching - though one has other hazards long before getting to the beach!

In the same cruising period and locations, in reply to this comment:- Secondly, and aimed mainly at the poster, if you anchor (and by definition due the the thread - fail) in packed sand full of furrows (typical Med. anchorage), you need a better anchor. I seldom found an anchorage of packed sand and furrows. There are some, but most of the best anchorages have been taken over by moorings and local boats so you are forced to anchor in undesirable ground such as weed, weed, or more weed. I am told by regulars that the weed problem is getting worse. If it isn't weed, then it's flat rock or very, very hard sand that is almost impenetrable - people sharpen their anchors with an angle grinder.

[ QUOTE ]
All you need to do is ask the innocent question 'what will it take to hold my 5 / 10 / 20 tonne vessel securely'?

I suggest a bigger anchor!

[/ QUOTE ] OK, what do you suggest to hold my 42' 20 tonne gross Nauticat so that we can sleep 'securely'?

Edit:- Set the thread title back
 
As a matter of interest, what size and type of anchor and chain are you using and what scope?

My anchor holds consistently and we sleep soundly at night. On the occasions when the anchorage or weather looks a bit uncertain we keep a proper anchor watch. Sometimes in the med we would ask neighbouring yachts to keep an eye on us and vice versa, and give us a shout if anything changed, to save us all having to stay up all night.

I can't imagine relying on some electronic gadget. I would never get to sleep!
 
Hi, there are other threads going on right now discussing anchors and anchoring techniques and I have discussed in detail what we are using in those threads. The point of this thread is to discuss anchor alarms. If you are not interested in them then fair enough, but I really don't want to encourage digression of this thread into yet another anchor thread; it is supposed to be an anchor alarm thread. /forums/images/graemlins/smile.gif

Please don't be offended /forums/images/graemlins/smile.gif
 
[ QUOTE ]
I don't know what a marina myth is.

[/ QUOTE ]
Old wives' tales
 
Hi there,

No offence taken. I'll have a look for the other thread.

The thrust of my post was really about the soundness of relying on electronic gadgetry rather than good old fashioned seamanship.
 
[ QUOTE ]
Is rode tension "absolutely useless"? You go on to talk about "listening" for sounds of dragging. A load cell in the rode is an excellent "microphone" but, as Brendan says, the problem is how to teach it what to listen for.

[/ QUOTE ]

I think I said that the "AnchorWatch" alarm was useless [as a means of detecting a dragging anchor] - my understanding is that it purely measures rode tension, and sounds an alarm when a pre-set value is exceeded. This seems only to tell you what you already know - that you're relying heavily on your anchor! The web site states [ QUOTE ]
ANCHORWATCH measures and display the load or tension on a yacht's anchor cable.
(...)
ANCHORWATCH warns a skipper when his anchor is likely to drag. It does not wait until the anchor is dragging before sounding an alarm.

By measuring the tension on your anchor cable:

(1) You can test your anchor holding at the time you anchor and make sure it is adequate.

(2) You can determine whether later on, you are stressing your anchor cable to a higher load than the test load.

(3) You can use the theory of anchoring to calculate the amount of anchor cable which you should veer for any wind conditions.

[/ QUOTE ] (Incidentally, the url in the link above has an extra bracket at the end which needs to be deleted).

I agree that a load-cell could give much more information than the magnitude of the tension, and it may be feasible to analyse the "noise" on the rode (detected via load cell or other means) to get some indication that the anchor is dragging. One would have to experiment to determine whether any features could be isolated which were sufficiently characteristic of a dragging situation.

I was originally thinking in terms of analogue circuitry (e.g. isolate the "rumble"), but if you go as far as a load cell and digital circuitry, then there's no limit to the rules you could try. If you've gone this far though, the price will be climbing, and you won't be far off the Marine Direct Anchor Alert system, which (IMHO) is sound in that it measures movement of the anchor itself at the anchor. I've looked at the web-site again, and still think they use accelerometers in the "link" that's attached to the anchor.

[ QUOTE ]
... weed forms a ball around the anchor .... I doubt whether any characteristic sound would be heard in this process.

[/ QUOTE ]

I have to agree! The AnchorAlert may detect this, but I think any system would struggle to detect this, other than a GPS anchor alarm.

I agree the AnchorWatch price is reasonable for a loadcell/readout (£200 ish), but I don't think this gives you an anchor alarm. The Anchor alert works out at a bit over £500 (with the right exchange rate /forums/images/graemlins/blush.gif), which strike me as a bit dear, but YMMV.

No affiliation to either company.

Andy
 
I see. It is strange that sailors such as Larry Pardy and the late Bob Griffith should have noticed, and reported on, this same phenomenon that I have noticed myself. They would be, I'm quite sure, as surprised as I that this is in fact an old wives tale!
I shan't bother your anchor alarm thread further, you clearly have far more experience with dragging your anchor than I have - perhaps the reason for the thread in the first place.
 
[ QUOTE ]
Solution: wait for the new European satellite positioning system to come online, which will be more accurate than the American one... and not reliant on the whim of the US military.

[/ QUOTE ]

As I hear - EU has signed agreement with US to ally Eu system with Us - so that it can be switched off / reduced in accuracy and also I didn't read that it was to be more accurate ? But on that last bit - I don't know ...
 
Well, if you choose to sleep at anchor in the belief that a change in the boat's motion will wake you then I wish you the best of British luck. I can only reiterate that is isn't always like that and you will often find that you only know you are dragging by looking out of the window, hearing someone call, or a crunch. I kid you not. I am perfectly prepared to believe that if anchored in a situation where there is noticeable local sea or swell, your bow might fall away enough, changing the motion, giving you warning, but it is very doubtful, and would be very unreliable.

Pleasant dreams /forums/images/graemlins/smile.gif
 
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