Advice on Setting Anchor Drag Alarm

[contrail]

Originally Posted by akprb

That is one of the problems with Raytheon plotters, the alarm is not the loudest.

I contacted Raytheon regarding this and if they had an external speaker. The answer was no.

Anyone else bump into this?

Thanks!

Years ago, I had an Apelco (Raymarine) radar with the same problem. I opened it up and wired in a connector which then went to a very loud pizzo buzzer. Would have woken the dead in hurricane force wind and worked very well. I am sure it voided the warranty, but I was more concerned about having a loud alarm. I can remember, but I think my interior wire ended on an already installed connector in the case, to which I connected the cord to the buzzer. No point in an alarm that cannot be heard in ALL conditions.

[contrail]

I guess I do it a bit differently. First of all, I set the anchor, which, in my case, involves gradually increasing the throttle over a period of several minutes. My final throttle setting, depending upon the boat and its engines, will be somewhere between two thirds and full throttle, in other words, I set the anchor hard. On my cat, that means with both engines. I hold this power setting for a good minute. During that period, the catenary of the chain is close to as straight as it will get. Using the ship's compass, I see what bearing the chain goes (usually a bit to port, due to prop walk). I add thirty feet, the distance from the bow to the GPS antenna, subtract a bit for the catenary and anchor chain angle, and then use this distance and the bearing to place the chartplotter cursor where the anchor IS, rather than on an assumed position based upon where I dropped it. Every anchor, at some point, will move some distance to get itself set, some a lot more than others. My procedure eliminates the guesswork involved.


I note the distance to the anchor, and as long as I stay within that distance, I have not dragged, although I may move around quite a bit. I look at the screen, from time to time, to see where I am relative to the anchor, but as long as I am less than the distance to the anchor, we are OK.


I set the alarm relative to the boat's position, NOT the anchor's. If I am in a tight anchorage, that distance might be as little as 40 feet. In other anchorages, it may be hundreds of feet. When I set it close, or when it is less than the distance I will move with a reversal in current, I fully expect to get awoken at some point, which is useful if only to check things out. If the distance is larger, I don't expect for the alarm to go off.


If the alarm goes off, the first thing I check is where I am relative to the distance to the anchor on the chartplotter. If I am within that, by definition, I may have moved, but I haven't dragged. Sometimes I am anchored for hours, sometimes for days or weeks. But I run the alarm and the chartplotter throughout. However, depending upon circumstances, I might change the alarm position and distance margin, several times. That can change. The anchor position must not.



In 1991, when I got my first GPS, I marveled at how much easier it was to set an anchor alarm than to take bearings on things that might be hard to see in the dark, and monitor for drag, that way. I agree that it is still as important a feature as any other, as regards the GPS system, but the many keep strokes it takes me to set it leads me to believe that it is a less used feature than it should be.

[belizesailor]

Originally Posted by akprb

I do not like the apps but prefer the alarm on the ships GPS or Chartplotter.

This is an INVALUABLE TOOL.

I’ll set a fairly small radius to start then over the first hour our so move it out if it goes off.

If you desire a truly good nights sleep at anchor this is one other function to become intimate with ;-)

Trouble is you need to be pretty "intimate" (close) with most to hear them.

Im "intimate" w my app also...I take it to bed with me. [emoji16]

[Mike Banks]

You could also try the "Yew Beaut!" alarm which has never been known to fail and can be set for as little distance as a metre or three.

You will need a small anchor, a length of string-trimmer nylon cord, set to whatever distance is the depth of water plus tidal difference plus ten metres or so as a minimum. This is wound on to a reel made by gluing two spools together, so that one of them takes the string trimmer cord.

When you lower your anchor, you also throw the small anchor overboard with it, making sure the small anchor beds itself just ahead or alongside the main anchor. Set your main anchor, and your baby anchor, them wind in the spool until there is a bit of slack in it. Pay out as much slack as you think is suitable for tidal rise and wind drift, and set the brake on the spool. More on the brake later.

From here you can use a mechanical alarm such as pieces of springy hacksaw blade with a small nut and bolt to act as a striker in the end with a hole in it--and a loud bell from an old telephone or fire alarm. If the anchor drags, the small anchor will hold enough to ping the bell and let you know the boat has moved. Alternatively, I make switches out of a plastic clothes peg, which has copper contacts fitted to the ends with hot melt glue. The wires to these contacts complete a circuit from a battery to a loud-as-hell alarm adapted from a smoke alarm. A plastic label is placed between the contacts and the label connects to the string trimmer cord--hence to the small anchor.

If your boat drifts more than the amount to which you have set the reel, the reel turns, pulling the string which puls out the plastic label and sets off the alarm. Cost about five bucks for the glue, screws and plywood and brackets on which the thing is mounted--the reels you can buy or make up. My prototype used old fishing line reels.

The second reel is a friction brake, used to set the distance once the small anchor is set. A length of chord and a weight with two turns on the reel is fine--the use of a rubber band is easier--but there is a remote risk of it snapping in the night.

Lotsa luck. Allow enough slack for the vessel to turn with the tide--just in case your anchors do not land roughly in the same place. I throw the small anchor beyond the main anchor--one does not want the main anchor to foul it.

If you expect the tide to turn, set your alarm clock to that time, so you can adjust the system if necessary. This idea is not new--it was used on sailing ships. They used a bell and strikers set in a wheel. When the ship drifted, the striker wheel turned, and the striker spring was pulled back against a stop peg. When it came free as the wheel turned further, it sprang forwards with some force and struck the bell. The man on anchor watch could hardly fail to hear it.

[ozsailer]

[QUOTE=noelex 77;2680839]This means your anchor can drag about 35m before the alarm goes off ![/QUOTE

In regard to setting of anchor alarm. The Anchor is the centre of your swing radius. If you have 25 metres or rode down you have a total 50 metre arc to swing without setting off your alarm. You cannot set it any other way unless you put a fore and aft anchor down. I consider 35 metres a small distance in which to realistically react.
Another comment indicated about having an anchor watch at all times. Once again realistically when cruising this is just not practical in most circumstances unless you have a large crew.
An anchor alarm is not fail safe and should be treated as such dependant on area where anchoring, weather conditions etc.


Greg H

[contrail]

Originally Posted by Mike Banks

You could also try the "Yew Beaut!" alarm which has never been known to fail and can be set for as little distance as a metre or three.

You will need a small anchor, a length of string-trimmer nylon cord, set to whatever distance is the depth of water plus tidal difference plus ten metres or so as a minimum. This is wound on to a reel made by gluing two spools together, so that one of them takes the string trimmer cord.

When you lower your anchor, you also throw the small anchor overboard with it, making sure the small anchor beds itself just ahead or alongside the main anchor. Set your main anchor, and your baby anchor, them wind in the spool until there is a bit of slack in it. Pay out as much slack as you think is suitable for tidal rise and wind drift, and set the brake on the spool. More on the brake later.

From here you can use a mechanical alarm such as pieces of springy hacksaw blade with a small nut and bolt to act as a striker in the end with a hole in it--and a loud bell from an old telephone or fire alarm. If the anchor drags, the small anchor will hold enough to ping the bell and let you know the boat has moved. Alternatively, I make switches out of a plastic clothes peg, which has copper contacts fitted to the ends with hot melt glue. The wires to these contacts complete a circuit from a battery to a loud-as-hell alarm adapted from a smoke alarm. A plastic label is placed between the contacts and the label connects to the string trimmer cord--hence to the small anchor.

If your boat drifts more than the amount to which you have set the reel, the reel turns, pulling the string which puls out the plastic label and sets off the alarm. Cost about five bucks for the glue, screws and plywood and brackets on which the thing is mounted--the reels you can buy or make up. My prototype used old fishing line reels.

The second reel is a friction brake, used to set the distance once the small anchor is set. A length of chord and a weight with two turns on the reel is fine--the use of a rubber band is easier--but there is a remote risk of it snapping in the night.

Lotsa luck. Allow enough slack for the vessel to turn with the tide--just in case your anchors do not land roughly in the same place. I throw the small anchor beyond the main anchor--one does not want the main anchor to foul it.

If you expect the tide to turn, set your alarm clock to that time, so you can adjust the system if necessary. This idea is not new--it was used on sailing ships. They used a bell and strikers set in a wheel. When the ship drifted, the striker wheel turned, and the striker spring was pulled back against a stop peg. When it came free as the wheel turned further, it sprang forwards with some force and struck the bell. The man on anchor watch could hardly fail to hear it.

I once knew a fellow who used a similar system, attached to his big toe! Never failed to wake him up

[UFO]

Thanks for all the replies

[noelex 77]

Originally Posted by ozsailer

In regard to setting of anchor alarm. The Anchor is the centre of your swing radius. If you have 25 metres or rode down you have a total 50 metre arc to swing without setting off your alarm. You cannot set it any other way unless you put a fore and aft anchor down.

Greg, I think you are getting the radius and diameter confused, or perhaps you are centring the alarm on one point in the swing circle rather than over the anchor. If you have 25m of rode out you do not have a swing radius of 50m (as you indicated in post #6), but a swing diameter of 50m. Try drawing a diagram and I think it will be clear.

If you have 25m of rode out your bow will indeed potentially move 50m away, but the bow will never be more than 25m away from the anchor.

So with 25m of rode out and the anchor alarm centered over the anchor. The alarm distance needs to be 25m (not 50m) + the distance from the bow to the GPS aerial + a reserve for GPS errors.

This above formula does not take into account the water depth which will reduce the swing radius and the stretch in the snubber which will increase the swing radius. These effects are slight, tend to almost cancel each other out and so are usually ignored.

Rather than using a formula often it is easier to use the chartplotter trace, but the formula is a help to understand what you are trying to achieve.

The idea is to normally set an alarm that will not go off if the boat moves around swing circle but will alert you as soon as possible if the anchor moves. As others have pointed out occasionally it is helpful to set the alarm differently so that it will also sound an alert if there is a significant windshift. This requires different settings, but is easy to do with the better alarms.

[savagebee]

I am very happy with the app that I use on my GPS enabled iPhone. It's called "Anchor Alarm - Anchor Watch" and it enables you to freehand draw a safe area around the boat on a scaled satellite image. It shows a graphic of the boat to scale according to the boat dimensions you have set up. You also set the location of the GPS device inside the boat.
If there is a strong wind blowing and forecast for the night I will set the area to be very close at the limit of rode in that direction and wider on the other side. Very useful to set limits for example if you are getting too close to a reef area. You can also decide to set an area that will cause the alarm if the wind or current changes direction.
One other great feature is the ability to send an email or phone a number (Apple does not allow this unfortunately) to alert you when off the boat.

[sy_gilana]

I dont trust any electronics if the anchorage is iffy. I prefer not to anchor there, but if I feel I MUST have an anchor alarm....


I have a length of cord tied to a lead dive weight, throw it overboard from my cabin hatch, and leave the wooden plank with the rest of the line on the sole, (or tie it around your privates if your a heavy sleeper). Boat moves...clunk-clunk-clunk.

Look Ma, no batteries.

[boom23]

Just FYI, most Vesper AIS products have anchor alarm built-in. This way, you can leave only the AIS on, instead of all the electronics. I have installed the Watchmate XB-8000 on two boats and I really like it.

https://www2.vespermarine.com/?gclid...8aAjFvEALw_wcB

[Cadence]

Originally Posted by sy_gilana

I dont trust any electronics if the anchorage is iffy. I prefer not to anchor there, but if I feel I MUST have an anchor alarm....


I have a length of cord tied to a lead dive weight, throw it overboard from my cabin hatch, and leave the wooden plank with the rest of the line on the sole, (or tie it around your privates if your a heavy sleeper). Boat moves...clunk-clunk-clunk.

Look Ma, no batteries.

I'd opt for a toe.

[alphabravo2]

Can someone tell me what happened to the Drag Queen App?? I am looking for it to install on my new phone and cannot find it?? Did GARMIN screwed up again??

[jtsailjt]

I've tried a couple of these apps on my iPhone and unless I increase the swinging parameters to something way beyond what would be useful, I get false alarms at some point during the night. I assume this is probably mostly due to imperfect GPS signal reception inside my fiberglass sailboat. But I have a friend with the latest and greatest Raytheon chartplotter with an external antenna and he was complaining of the same false alarm issue. Not sure what parameters he had set though so too small a swinging circle inputted may have contributed to this.

I understand that if you really are dragging, in most cases you want to be notified of it just as soon as your device figures out that you've moved, but since GPS positions do seem to wander around a bit for various reasons, it would be a good thing for these alarms to have a dampener, or a variable delay programmed in so if you knew your GPS reception wasn't great and you are in a location where you can afford to not be notified immediately, you could tell it to now awaken you unless your position remained outside the designated radius for a longer time period that you could choose in order to avoid false alarms. Do any of the existing alarms have this feature?

[Training Wheels]

Originally Posted by alphabravo2

Can someone tell me what happened to the Drag Queen App?? I am looking for it to install on my new phone and cannot find it?? Did GARMIN screwed up again??

I just got an iPhone 8+, and Drag Queen won’t work on it. The message I get is that they need to update the app for it to work on the newer phones.