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Old 26-06-2014, 20:41   #61
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Re: You are setting your anchors badly and then blaming the anchors

Best thing I ever did was own a boat with a lousy anchor for a few years. I learned so much more about anchoring with that piece of junk than I ever did with well equipped boat. There is nothing like holding the rode on a small boat and "feeling" the bottom as the anchor skips along to let you know what a real hold is like. I always slept soundly (minus the few hard blows) but I did give a few hard tugs before being convinced it was set.

I see boaters that drop the anchor and forget about it. They simply don't know what they don't know. But I do since I check out their anchors while swimming. At one anchorage in St. Lucia I saw 9 out 10 anchors on their sides. Ignorance is bliss.
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Old 26-06-2014, 20:42   #62
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Re: You are setting your anchors badly and then blaming the anchors

I was warned.... coming back in the bus from Papeete tuther day a French lady who had been around these parts ( on a boat) warned me... lots of boats in the Taina anchorage sitting in 15 metres with only 25/30 metres of chain out.... and these aren't people on lunch hooks..
Shifted anchorage after bunkering 2 days ago... pick a big empty bit... stretch out 55 metres in a light southerly .. get the 'bitch wings' from a boat astern of me... chain takes up.. boat sitting nice and comfy.
Next morning wind goes north gusting to shock horror 17 knots... Bitch wing boy promptly drags down on my neighbour and departs for parts unknown... followed by another boat that had come from over the northern horizon with no sign of anyone on deck until it belted my neighbour ( who I think has a boat magnet on his bow)... 6 or seven others also dragged... makes one wonder how they got all the way to Tahiti without dragging ashore somewhere.
Me... I just want to get back to Patagonia muy pronto...
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Old 26-06-2014, 21:06   #63
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Re: You are setting your anchors badly and then blaming the anchors

Well there goes my theory on the South Pacific, LOL. Sure been crap weather the last while, winds/thunderstorms another big blow coming thru here Sunday/Monday. Might be normal who knows!
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Old 27-06-2014, 02:09   #64
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Re: You are setting your anchors badly and then blaming the anchors

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Originally Posted by avb3 View Post
One thing I've learned from this thread that I will be doing differently is letting the anchor settle. I've always dropped it, and then slowly backed up, and, on feeling it grab, applied full power for about a minute or so, doing what many have suggested, the transit check.

There are many threads on this. But anyway, for whatever it's worth -- if you can let the anchor settle for a bit before you start backing down on it, it seems to bite better. If you can pay out the chain while drifting back, rather than letting it pile up over the anchor, you will get a steadier pull when you do start backing down, which is more conducive to good setting. Then start backing down very, very gently -- watch SOG on your instruments and don't let the speed get up to even 1 knot. If you are moving too fast when the slack comes out of the chain, the anchor will slide across the seabed and won't bite. Then you should feel the anchor start to dig into the seabed -- very slowly increase revs and let it work its way down -- burying itself. SOG should hit 0.0, or you may see some SOG but the COG vector will be abeam, not astern, because you're swinging a little. The chart plotter is incredibly valuable here. You can see from your track on the plotter that you stopped moving back and are moving only a little back and forth as you swing. From this you know the anchor is set. After you've given it a decent period of time (a few minutes) to set and bury itself, then adjust scope. Then back down on it with full power for a couple of minutes (not 30 seconds). Watch SOG and COG vector line to be sure the anchor is not moving. You will clearly see if you depart the arc your track on the plotter makes; that would mean the anchor is not holding*. Snubber, then cocktail.

For whatever it's worth, that's my technique. I find the plotter to be much more useful than transits because it gives you much more information -- especially the COG vectors, and especially the tracks. I don't think millimeter position accuracy is needed for this to work extremely well (I now have a Glonass/EGNOS position sensor which is accurate to about 2 meters, but the technique worked equally well with simple GPS). Another bonus is that the plotter works equally well day or night.


Since I changed my anchor from Rocna to Spade three years ago, I have only had one failed set. I have not dragged an anchor in more than 10 years, not once, although I anchor in all kinds of weather. This technique takes time (15-20 minutes) and uses some diesel fuel, but it is extremely reliable.



* Again, you don't need millimeter position accuracy for this to work. A couple of minutes in astern at full power will move you far enough to see, if the anchor is not holding.
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Old 27-06-2014, 02:42   #65
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Re: You are setting your anchors badly and then blaming the anchors

OK that begs the question... why did you change anchors if you have never dragged in 10 years??
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Old 27-06-2014, 02:56   #66
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Re: You are setting your anchors badly and then blaming the anchors

A couple of things I would add to Dockheads technique when using the plotter. I always zoom in, place a waypoint when the anchor is dropped, and another while reversing at full revs. This shows the maximum swing circle pretty clearly and can be referred back to at anytime. Keep an eye on the second waypoing while reversing and its clear if you are dragging. Know where your anchor is by the first waypoint. If you think someone is over your anchor its easy to check with the radar anytime. When its time to weigh anchor you can motor directly to/over it.
We also use an anchor app on the iphone and usually walk forward to press the drop button directly over the anchor. This works well for setting the radius while backing down. Apps with google earth overlays are handy for seeing how close your swing will be to ..earth..
Like Ange we usually forget to turn it off when we are leaving the anchorage and they usually sound a loud alarm within a few seconds of being outside the safe zone. We have ours charging next to the bunk so anytime you can open one eye and get an idea of where you are, check for wind/tide shifts etc.
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Old 27-06-2014, 03:03   #67
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Re: You are setting your anchors badly and then blaming the anchors

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Originally Posted by El Pinguino View Post
makes one wonder how they got all the way to Tahiti without dragging ashore somewhere.
Me... I just want to get back to Patagonia muy pronto...
Cruisers in S Pacific get lulled into false sense of anchor security by calm weather - soon shattered when squalls in June-Sept trade wind season (maaramu season in Fr Polynesia) hit. El Pinguino's Papeete experience sounds v much like that.

And that's on top of ground failure (in contrast to anchor failure). Around some islands and atolls, ground is stratified: a thin layer of shell grit and coral sand, perhaps 30 cm only, above a thicker layer of tightly packed coral rubble and old coral heads. So anchor often can only penetrate top layer. And it offers little holding - what looks like sand is light (not dense) and resists anchor poorly.

Some anchorages in SE Asia offer different version of ground failure: recent forest clearing and overdevelopment produce fine unconsolidated silt. Near big urban centres on rivers, that also means silt has plastic bags and other urban trash embedded. Not helped by turbid water, rendering anchor invulnerable to inspection.

So anchoring failure sometimes ground failure, not anchor setting failure.

Al
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Old 27-06-2014, 03:09   #68
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Re: You are setting your anchors badly and then blaming the anchors

A good test of the ability of GPS to determine if your anchor is moving backwards, is to let out a bit more scope on a windy day and see what distance you need before you can reliably detect, by looking at the plotter, that you have moved backwards.

Try the same thing with transits and compare the two methods.

The distance taken to set does give you some information on the quality of the substrate. Modern concave anchors normally set remarkably quickly within a couple of metres. If the anchor has taken 5m to set I want to know about it if possible.
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Old 27-06-2014, 03:21   #69
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Re: You are setting your anchors badly and then blaming the anchors

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OK that begs the question... why did you change anchors if you have never dragged in 10 years??
Because not dragging is not the only thing you expect from an anchor!!!

My Rocna did not set very well in some types of seabed, especially soft mud. Besides that, it did not fit my bow roller very well (it was a little too big at 55kg or 121 pounds). The last straw was when the Rocna scandal broke and I found out it was made of out-of-spec material, so I exchanged it (through the nice people at Pipler's of Poole) for a slightly smaller (100 pounds) Spade.

Of course I had to add money, because the Spade was much more expensive. But very well worth it -- the difference is night and day. The Spade sets much, much, much better. And doesn't get clogged up like the Rocna did in softer seabeds -- the Rocna would turn into a ball of mud which didn't hold anything, and was hell to clean off after pulling up again out of soft seabed.

The Rocna was a good anchor -- once set, it would hold in any conditions without fail. And it usually set very well as long as the seabed wasn't too soft; certainly it set much better than the Delta it replaced. But the Spade is much better still, and to boot is much easier to handle without any rollbar getting in the way.

Besides that, the Spade is much better balanced (it has lead ballast) and comes up straight into the bow roller. I had to use a swivel with the Rocna, which liked to come up upside-down, and always had to horse it around with a boathook (fun on a bouncing foredeck with 121 pounds of anchor swinging around -- NOT!). The Spade, because of its better balance, comes up right side-up, and I was able to get rid of the swivel altogether, and rarely have to manipulate it with the boathook.
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Old 27-06-2014, 03:30   #70
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Re: You are setting your anchors badly and then blaming the anchors

Quote:
Originally Posted by noelex 77 View Post
A good test of the ability of GPS to determine if your anchor is moving backwards, is to let out a bit more scope on a windy day and see what distance you need before you can reliably detect, by looking at the plotter, that you have moved backwards.

Try the same thing with transits and compare the two methods.

The distance taken to set does give you some information on the quality of the substrate. Modern concave anchors normally set remarkably quickly within a couple of metres. If the anchor has taken 5m to set I want to know about it if possible.
Good point, and good methodology for understand the resolution of your GPS I have actually done just this, and find that I can see movement of less than a meter, although the theoretical accuracy of my position sensor is 2 meters (when it's receiving EGNOS).

If you have decent transits at a close enough distance, and you have daylight to see them in, there's no doubt you can see finer movements than you can with an ordinary GPS (maybe not than with a high precision GPS like mine).

This can be useful, for sure, but you are still only seeing one dimension. COG vector lines and tracks are giving you information you can't get from transits.

By the way, your post, and all the excellent anchoring photos you've posted, made me wonder -- some people might like to see video of their anchors setting, and this would surely not be very difficult technically. A waterproof camera hung a few meters up the chain from the anchor would do it. If small enough, you might even be able to figure out a way to rig it where it would run through your bow roller. Then you could see what your anchor is doing in real time, instead of guessing.
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Old 27-06-2014, 03:42   #71
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Re: You are setting your anchors badly and then blaming the anchors

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I have actually done just this, and find that I can see movement of less than a meter, although the theoretical accuracy of my position sensor is 2 meters (when it's receiving EGNOS).
A metre is great and that would make it as good, probably better than transits which explains your preference especially as you say it can be used in poor visability etc.
With my GPS units I would put the distance as much higher, perhaps 5m. I do get EGNOS, but I think I more on the limit of coverage of coverage than you are, which may effect the quality of the differential correction.
Also while some of my GPS units are new with modern chips they are all 1hz units. Is yours a high speed GPS and if so did that make a difference?
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Old 27-06-2014, 03:43   #72
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Re: You are setting your anchors badly and then blaming the anchors

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Originally Posted by monte View Post
A couple of things I would add to Dockheads technique when using the plotter. I always zoom in, place a waypoint when the anchor is dropped, and another while reversing at full revs. This shows the maximum swing circle pretty clearly and can be referred back to at anytime. Keep an eye on the second waypoing while reversing and its clear if you are dragging. Know where your anchor is by the first waypoint. If you think someone is over your anchor its easy to check with the radar anytime. When its time to weigh anchor you can motor directly to/over it.
We also use an anchor app on the iphone and usually walk forward to press the drop button directly over the anchor. This works well for setting the radius while backing down. Apps with google earth overlays are handy for seeing how close your swing will be to ..earth..
Like Ange we usually forget to turn it off when we are leaving the anchorage and they usually sound a loud alarm within a few seconds of being outside the safe zone. We have ours charging next to the bunk so anytime you can open one eye and get an idea of where you are, check for wind/tide shifts etc.
That's a great idea about setting the second waypoint

I'm going to try that!

I used to set waypoints where I dropped the anchor, but with my new plotter, for some reason, I see so clearly from the track (which I think is much higher resolution than the tracks on m old plotter) where the anchor went down, that I typically don't bother now.

The track makes a very hard arc on the plotter screen after you've been lying for a while. You can also recognize where the anchor is from that arc -- it's the center point of it.
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Old 27-06-2014, 03:46   #73
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Re: You are setting your anchors badly and then blaming the anchors

Well Dockhead I do agree with several of your points on the Rocna, we use one and it does like to hold mud and it also likes to come up backwards so I have a swivel on it. I too have found it less than sterling in soft mud but enough scope and a tender set and it does hold, so far anyways but in those conditions I would prefer to have something that really buries itself. Thanks for your feedback.
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Old 27-06-2014, 03:54   #74
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Re: You are setting your anchors badly and then blaming the anchors

Quote:
Originally Posted by noelex 77 View Post
A metre is great and that would make it as good, probably better than transits which explains your preference especially as you say it can be used in poor visability etc.
With my GPS units I would put the distance as much higher, perhaps 5m. I do get EGNOS, but I think I more on the limit of coverage of coverage than you are, which may effect the quality of the differential correction.
Also while some of my GPS units are new with modern chips they are all 1hz units. Is yours a high speed GPS and if so did that make a difference?
Mine is an inexpensive Simrad GS25. Nothing fancy; just the very last generation of these devices which incorporates a number of significant improvements in technology.

This one: GPS Antenna | SIMRAD GS25 | Marine Electronics - Simrad Marine Electronics

It is not 1hz, it is 10hz, and I suspect that the rate of update has a lot to do with its usefulness.

The spec calls for 5m horizontal position error, but observed typical EPE where I am sailing is 2m or less. The device receives the Russian GLONASS constellation as well as GPS, so it has about double the data points of a GPS-only device, which also improves the accuracy.

They only cost $199 in the U.S. I can bring you one back from the States in August if you want one.
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Old 27-06-2014, 04:03   #75
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Re: You are setting your anchors badly and then blaming the anchors

Wonder how long before we can add a gps or transmitter to the actual anchor.
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