Anchoring

[NormanS]

I grew up with a wooden boat with a Stuart Turner and my father’s much loved and carefully resuscitated Armstrong Siddeley Sapphire. I tend to pussyfoot around everything, making sure that the revs have dropped right back when going from ahead to astern through neutral, creeping up to buoys and berths, and so on!

My merchant seaman son is far more brutal with the boat’s equipment, presumably on the basis that what’s good for 45,000 tons will be good for twenty tons…

My Stuart Turner had been, in a previous existence, used by the military, to drive a fuel Bowser. (I think).
The main thing I remember about it was that it flatly refused to start if it was hot. Two stroke, with a centrifugal clutch.

 

[wonkywinch]

Raymarine (Lighthouse) have an impressive "anchoring" function in their chart plotters if you like techie stuff. Only problem is I tend not to leave the nav gear switched on all night and so only good for a lunch stop when the eyeball works just as well.

 

[Minerva]

[...]

That makes perfect sense but how do you do it if you are single-handed?

By the time I have got back to the GPS, which is down below over the chart table, the bow is no longer over the anchor.

If you enter anchorage upwind, stop, drop hook and drift back your 'snail trail' on the plotter will have a definite ^ shape. Drop the waypoint for the anchor alarm on the apex of the ^ and bobs yer uncle

 

[Supertramp]

My AIS (Vesper with a display) has an anchor setting and you can edit radius and anchor position. It tracks the boat's movement and alarms if the radius is exceeded. It stands alone, uses tiny current and is on whenever i am aboard. It proved very useful when my anchor dragged at 2.00am without warning on mud with eelgrass.

I appreciate anchoring technique matters but I am amazed when people say they never drag - far better to have some warning than expect it never to happen.

 

[RupertW]

If you enter anchorage upwind, stop, drop hook and drift back your 'snail trail' on the plotter will have a definite ^ shape. Drop the waypoint for the anchor alarm on the apex of the ^ and bobs yer uncle

Great for a lunchtime stop but the only thing you can be sure of is that you will hold in wind and tide conditions no stronger than right now. An anchor hooked under a small loose rock or a weed root will hold perfectly until suddenly it doesn’t.

 

[Minerva]

Great for a lunchtime stop but the only thing you can be sure of is that you will hold in wind and tide conditions no stronger than right now. An anchor hooked under a small loose rock or a weed root will hold perfectly until suddenly it doesn’t.

What's that got to do with setting an anchor alarm, with the waypoint on the anchor, singlehanded?

 

[GHA]

[...]

That makes perfect sense but how do you do it if you are single-handed?

By the time I have got back to the GPS, which is down below over the chart table, the bow is no longer over the anchor.

Even anchoring constantly I still never manage to get a fix where the anchor is, usually forget to take the phone to the bow but even then it's a bit of a fiddle to get the waypoint pressed & solo you're usually a bit involved. What works fairly well is have tracking turned on then usually pretty easy to see where the boat was when the hook dropped, then put in a waypoint 8m further forward or whatever the distance is between the gps antenna & the bow.
Though invariably that's still a bit out, I'll tweak the waypoint position later to line up the waypoint range ring to line up with the boat. you can set the boat icon to actual boat size in opencpn and set where the gps antenna is. Really useful & reassuring in a big windshift, that oversized Spade I have is just great, prob has happened but even anchoring always can't remember the hook ever moving enough to be visible once dug in even in tidal. Also useful to spot if the chain is round a rock or something. Or just hasn't stretched out yet in a wind shift, sometimes if it doesn't look right I'll fire up the engine & give it a blast in reverse to get the boat back on the range ring & check it isn't caught round a rock, better to know early

 

[GHA]

If you enter anchorage upwind, stop, drop hook and drift back your 'snail trail' on the plotter will have a definite ^ shape. Drop the waypoint for the anchor alarm on the apex of the ^ and bobs yer uncle

Bearing in mind your plotter position most likely is the gps antenna, not likely to be at the bow.

 

[noelex]

That makes perfect sense but how do you do it if you are single-handed?

By the time I have got back to the GPS, which is down below over the chart table, the bow is no longer over the anchor.

Even with multiple crew it is not easy to centre the anchor alarm when you are dropping the anchor. The GPS aerial (which is the location used) is not generally anywhere near the bow. An error of, for example, 10m does not sound like much, but if the boat swings to the other side of the swing circle the error is doubled so the alarm will now be set incorrectly by 20m. This is why so many people report false alarms or have to set such a wide margin for error that the alarm is near useless.

The best way is to find the anchor drop position is to look at the track in. Usually the anchor is dropped just as the boat stops and starts to reverse. The track in will record the position of the GPS aerial when the anchor was dropped. However, this position needs to be displaced by the distance between the bow and the GPS aerial. Hopefully this diagram helps.



As an alternative, the anchor position can be given as a bearing and distance from the final finishing point. The bearing is into wind (or current). The distance is the length of anchor chain deployed plus the distance between the bow and the GPS aerial.

These techniques can be used to centre the anchor alarm well after the anchor was dropped, so there is no rush.

If centred correctly, the arc of swing should be around the centre of the alarm radius. Even without a wind shift as the boat yaws you can at least see if it is reasonably correct. The photo below shows a typical trace with the arc of the swing reasonably matching the alarm radius. With a large windshift it is far more obvious if the alarm is centred correctly.



Unfortunately, many chart plotters do not allow adjustment of the anchor alarm position to a remote location, but chart plotters are a generally a poor choice for an anchor alarm device, as their power consumption is high. You can use one of the many apps on your phone or tablet (preferably with an external GPS aerial), or open CPN has a reasonable anchor alarm feature.

 

[Poignard]

Bearing in mind your plotter position most likely is the gps antenna, not likely to be at the bow.

Good point! Mine is on the pushpin.

 

[14K478]

My Stuart Turner had been, in a previous existence, used by the military, to drive a fuel Bowser. (I think).
The main thing I remember about it was that it flatly refused to start if it was hot. Two stroke, with a centrifugal clutch.

The maker’s handbook advises “try a new, cold, plug”. Used to have two and the spanner fitted for instant use just inside the engine box!

 

[RupertW]

What's that got to do with setting an anchor alarm, with the waypoint on the anchor, singlehanded?

Well you are suggesting a way of anchoring that many people would avoid doing so the shape will be a bit different.

 

[Stemar]

Something I just saw playing with my anchor alarm is that Android has a feature that turns off the the gps when the phone sleeps. There are ways round it, the simplest being to prevent sleep when using the alarm, but it's worth being aware of.

 

[Minerva]

Well you are suggesting a way of anchoring that many people would avoid doing so the shape will be a bit different.

I don't understand, why would many people avoid approaching the anching spot by going upwind?

 

[magicol]

Thank you everyone for your really helpful replies and much useful advice. I had attempted to avoid the trap of starting another contentious anchor debate but I guess the strong opinions about this aspect of sailing reflect the potential problems and dangers it presents. It feels no matter how experienced the yachtsman, no one is ever fully in control of all the variables so we are always searching for the best components of this complex exercise. I guess I’m learning that best practice and the most appropriate equipment will differ depending on circumstances hence the often heated debate and the polarising views.
Anyway, what I take from this helpful, informative and strangely reassuring thread is that except for a few very confident contributors few of us are completely at ease when at anchor and probably rightly so.
I will try to be more adventurous in our anchoring next year but I’ll also try to avoid complacency, heed the safety advice offered throughout this thread and aim to enjoy the undoubted benefits and freedoms anchoring offers us yachtsmen.
I’m just not yet convinced I’ll get any more sleep.

 

[srm]

I’m just not yet convinced I’ll get any more sleep.

Having sailed singlehanded including the length of Britain a few times I found the answer for me is to relax and rest frequently. The secret is not to get too tired and really not to become exhausted. That way if unexpectedly woken at night (or during the day) one has a reasonable chance of making sensible decisions.
Having said that being woken or kept awake by adverse conditions at night at anchor was a rare event. Being gently rocked to sleep by the boat in a sheltered anchorage is a pleasant experience.

 

[B27]

The anchor alarm on our 'boat tablet' allows setting different drift limits in different direction sectors. It's not going to keep you out of trouble in a crowded anchorage, but it's not hard to set limits which keep you off the beach. Just give it an allowed distance of more than twice the rode in the general direction of 'beyond the anchor'.
I think it's 'Anchor Lite'?

I've also anchored on a short scope, set the anchor alarm, then let more string out.

Instances of anchored boats ending up stranded are pretty rare, but AIUI 2 of the last 3 I'm aware of could have been prevented by rough and ready use of an anchor alarm on Android. It's free and gives a bit of extra re-assurance, if it wakes me up when the tide turns one day, I'll live with that.

 

[14K478]

The better you know your boat the more confident and relaxed you become.

 

[B27]

The better you know your boat the more confident and relaxed you become.

AKA 'complacent'?

 

[srm]

AKA 'complacent'?

Perhaps in your case.
Personally, I prefer competent, relaxed, and confident to paranoid, but then I have worked at sea on survey vessels and sailed commercially as a charter skipper and YM Instructor.
For me the interesting and fun thing with sailing is that there is always something new to find, and possibly catch you out. Even in waters you think you know like the back of your hand.