It always amazes me how often you see boats motor into an anchorage, choose a spot, seemingly at random, and then immediately drop the anchor with no more ado. And it’s not really surprising how often the same boats go through the whole anchoring process again because they ended up too close to the shore or another boat.
Over the years Phyllis and I have developed a method of anchoring that means that we just about (no one is perfect) always anchor so that we don’t have to move and so that we can sleep soundly without worrying about a nasty crunch from swinging into shallow water or another boat.
The Eye is Not Good Enough
It may come as a surprise, but even after years of anchoring, we have learned that our visual estimates of distance are very often way out, even though we use a visual trick of imagining our own boat’s size and then laying multiple Morgan’s Clouds out end to end in our mind’s eye.
There is a better way:
How Big a Circle
Our first step is to determine how much scope will be required by checking the water depth in the anchorage from the chart or with the sounder after making a rough guess of where the anchor will go. We then calculate the length of the rode by adding the height of the bow to the water depth at high tide and then multiplying the result, preferably by five but never less than four (we like to sleep well), to yield rode length.
Radar as an Anchoring Tool
We then set the result from the above calculation, plus a boat length, on the variable range marker (VRM) circle on our radar. When doing this it is helpful to know that 0.01 of a nautical mile is equal to about 60-feet (18.5 meters). In fact we have this marked on our radar with a labeller—if you can’t be smart, be methodical, we say.
The resulting radar display gives us a good idea of the relationship of our anchor circle to the shoreline and any fixed obstructions, such as an unoccupied mooring that won’t tend to move much with a wind shift. (Anchoring in harbours crowded with other boats is the subject for another post.)
If there is plenty of room, the radar display will enable us to position the anchor properly with no further ado. We just place the radar circle about in the middle, perhaps with a bit of bias away from the expected lee shore, well clear of other boats and the shallow areas that can be determined from the chart, and drop.
A Radar Example
In this case shown above we had determined that we needed at least 150-feet of rode plus 56-feet of boat so the VRM (dotted circle) is set to 0.04 nautical miles or 240-feet. We were just able to anchor in the middle since the shore was steep to. In making your calculations when things are this tight, you do need to take into account the position of the scanner when dropping the anchor. In our case, because our scanner is aft, we biased the drop point a little aft of the center of the anchorage. (Note that the above image was made after we had anchored and does not indicate where the anchor is laid.)
Difficult Anchorages
But suppose the anchorage is only barely big enough. And let’s make this really hard. Suppose the chart is not accurate or the datum is a bit out, which will displace our GPS position, or both. It’s amazing how often we find these conditions, even in supposedly well charted places. Or, suppose you are not blessed with radar.
In these cases we need to make our own chart—well, sort of. To do this we very carefully and slowly motor around the edges of the anchorage getting as close as we dare to areas that will be too shallow for us at low water. (Prior to coming into the anchorage, we look up the state of the tide and check what the maximum drop from the current level will be over the time we plan to stay.)
Counter Clockwise
We nearly always do this scan of the edges of an anchorage in a counter-clockwise direction. Why? Because Morgan’s Cloud has a right hand propeller and therefore if we reverse hard in the case of getting too close to a shallow patch, or even touching the bottom, the stern will kick to port, which will be the direction of deep water. Of course, it’s a lot better to play this game on a rising tide.
Clunk is Better Now Than Later
Sure there is a risk of touching bottom, but as long as we keep the speed below about a knot, we should be able to reverse off. And we would rather touch in daylight with everyone on deck and alert, than at zero-dark-thirty in a raging thunderstorm.
Sonar is Cool
We have a forward scan sonar, which makes this easier, although not as risk free as you might think since the machine only looks out about three times the water depth, so when we are getting close to grounding we are only really looking out 20-feet. The point being that you can still do this with a normal calibrated sounder—you did calibrate yours, right?—and someone on the foredeck to look for rocks.
Once we have made a full circle it is a simple matter to examine our track on our plotter and check that the total diameter is enough to accommodate our potential anchoring circle. Then, assuming that the anchorage is big enough, we just move to the center of our circle and drop, secure in the knowledge that as long as we don’t drag, there will be no bumps in the night.
“Charting” Example
In this case the datum was out, so that just trusting the chart and setting the anchor in the middle would have resulted in hitting the shore. Also the chart seems to indicate an anchoring area of nearly 500-feet across, but in fact the actual usable area is more like 450-feet. Note that although the diameter of our traversed circle is only about 350-feet, because we were using a forward scan sonar, we were looking out another 50-feet or so at the steep-to shore either side and were therefore able to determine that we would be just OK with 150-feet of chain out. A tight anchorage to be sure, but using this system, we knew we were safely anchored.
Comments
How do you determine where to anchor? Please leave a comment.
Steve July 24, 2012 at 8:26 pm
Thanks John for the tip on using the radar for anchoring, we will give it a try. Like you we always make a circle or two of the area we are going to anchor in, inspecting depth and any other thing that may indicate a not suitable anchoring place. We do use our chart plotter at the helm and its track lines once we to mark our circle. I’ve even used a way point to mark where we will drop anchor in crowded anchorages and make a circle back to that spot. That gives me more time to figure out that we are in the right spot. Also if I’m alone when anchoring I can check the number of feet from the way point I have out and make adjustments. Chart plotters are good for that.
Like many, crowded anchorages are the most nerving but after you get used to it not so bad. I might say that it is interesting watching boats from different countries anchor, all do it a bit differently. We ask when possible the crews of the boats around how much rhode they have out and I check for chain or rope anchor rhode on boats near by, also observe what type of boat before dropping the hook. Cats swing differently than a full keel boat. It will be interesting to see how the Boreal behaves at anchor, will we keep the centerboard down or up, a new experience for us.
Luckily we have never dragged but in Pogo Pogo harbor we had to set 3 times on bed rock. On the second go around I pulled up from the bottom a large plastic garbage bag, a pair of jeans and a pair of old welding chaps. Nice clean harbor that one is.
John July 25, 2012 at 9:14 am
Hi Steve,
All good information, thank you. Good point about cats.
My guess, and it is just that, is that the Boreal will behave best at anchor with the board up. And in that configuration, might lie quieter than a keel boat.
Jacques Landry July 24, 2012 at 9:53 pm
More thanks from me for this tip John. I was contemplating buying a radar in the next few months, and that will be one more use for it!
I am in the Windward Island at the moment, and the problem is rarely a tight anchoring spot due to the natural environment, but a tight fit due to crowded bays, more so in Martinique. Anchorage are always on the west side of the island, with winds mostly form the east. I normally try to find an “opening” in the crowd and move between two anchored boats, then drop the anchor at their level and motor back to 1:7, setting the anchor properly, and then bring back some chain to get a 1:5 scope as it is what everyone here uses. Normally I end up at an acceptable distance from the others, and never had a problem, even if wind shifts to some extent, as everyone seems to move in harmony. There is very little tide, winds are N-E to S-E and we anchor in 15-20 feet of water. If the weather is not that good, I anchor a little further out with 1:7 to 1:10, where it is not as comfortable but having more room and a lot more scope makes it feel safer. If the anchor was to drag at night, I would end up in the Caribbean ocean somewhere between Martinique and central America, hopefully awake before I hit land, thousands of miles away!
However I do understand that this approach might not be a proper way where there is an important tide, or where the prevailing winds might blow you ashore. But what if you don’t have a radar or GPS plotter ? Can this be an acceptable approach in some other places ?
John July 25, 2012 at 9:18 am
Hi Jacques,
We agree with you that it is often safer to anchor in a more exposed and deeper place to get away from other boats. The only anchor related damage we have had in the last 40 years of anchoring was sustained in hitting or being hit by other boats. In the first case when our old CQR dragged at Bequia, and the second detailed here.
Chris July 25, 2012 at 8:28 am
Our process is remarkably similar, but we only sleep well when we are the only boat in the anchorage. The technique, or lack thereof, employed by many folks we’ve seen is mostly drop (or toss) and let the insurance company sort it out.
The most egregious was the boat that came in at sunset and picked up our anchor buoy (25 cm soft poly ball) and tied off to it. When the boat had settled, the person in the cockpit complained loudly, with several short words, about how closely we had anchored to a mooring. When I explained, he wanted to know if he could just move in the morning.
John July 25, 2012 at 11:42 am
And you mean you did not let him stay? What’s wrong with you Chris?
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Seriously, this is one of the may reasons we don’t like trip lines. We are currently experimenting with an alternative.
Bill Balme July 30, 2012 at 11:05 am
Had an interesting experience last week with our trip line… Travelling along with another boat, we anchored fairly close together, but sensibly apart. An afternoon squall came through and I watched as our buoy floated between our friend’s boat and their dingy as they fishtailed during the high winds. If the rudder had caught our buoy, they’d have tripped our anchor and off we’d go!
Once the squall passed we upped anchor and redepolyed – without the buoy!
No more anchor buoys for me! Would love to hear your alternative!
richard s. July 25, 2012 at 9:02 am
after hundreds of anchoring events i have decided that anchoring is like lightning…never really sure what it’s going to do…can observe all the precautions and still be surprised…my most recent surprise this past spring in pelican bay nicely sheltered anchorage just inside boca grande on fl’s gulf coast south of tampa bay…wind forecast up to 25 knots overnight…no problem with my oversized danforth and plenty of scope in the lee of a nearby shoreline…winds at least up to forecast with higher gusts, but held firm in the bottom mud-sand mix…as designed the more strain on the anchor the deeper it penetrated…when i brought it in the next morning the shank was bent 90 degrees and i have the photo to prove it…this is an 18 lb danforth with the shank probably 3/8″ thick solid steel…beyond me how this could happen without the anchor breaking out first or the 5/8″ nylon rode breaking…the force required to make a bend like that must be huge…another time all seemed to be well until i noticed a bit of a drift…upon bringing up the anchor it had with it an old wire fish trap obviously preventing the anchor from doing its work…other similar experiences, but i believe these make my point…being on the hook can (will) lead to surprises despite best efforts to prevent…richard in tampa bay (m/v cavu’s skipper, formerly s/v sidra’s skipper)
John July 25, 2012 at 11:38 am
Hi Richard,
Interesting on bending the stock. However, having bent two Danforth type anchors myself over the years I’m not sure that the load required is that huge, certainly far less than the break load on 5/8″ nylon.
This one of the reasons that we now recommend the SPADE anchor: We have abused ours horribly in rocky bottoms and never done any damage.
David V July 25, 2012 at 10:31 am
Hi there John…
We like to add a little extra insurance by amending your recipe for anchouring to read… “the water depth @ HIGH TIDE”… esp. in The Whitsundays and North West coast of OZ.
Hehehe… fancy mistaking an anchor buoy for a mooring ball ! But we’ve seen many such foibles in the Charter Industry.
Cheers from DV
John July 25, 2012 at 11:28 am
Hi David,
Good point! I did mention looking up the tide later in the post, but I should have made that clear in the recipe. I will change it, thanks.
As you say, it really matters in some places like Down East Maine of western Nova Scotia. A lot of places in Europe too.
Tom Keffer July 25, 2012 at 10:43 am
I use a similar technique, but rather than use my radar, I use a golf rangefinder. Like this. http://is.gd/Ca6uVN . It has the advantage of being up in the cockpit and works well even with non-metallic targets.
John July 25, 2012 at 11:34 am
Hi Tom,
Wow, what a great idea, thanks. Sounds like a great substitute for those that don’t have radar.
BTW our radar, when properly tuned, will pick up a round plastic mooring ball easily, it does not need to be metal.
John
Scott Kuhner July 25, 2012 at 11:34 am
John,
Eileen Quin has the perfect description of trying to anchor in her song, “the Anchoring Dance” . Kitty and I love her songs about the cruising life. To read the beginning lyrics to that song go to:
http://www.eileenquinn.com/lyrics.htm
and then scroll down a few songs. You will see that she hits the nail on the head!!
Scott
Westbrook July 25, 2012 at 11:49 am
Agree with you John and David V about knowing the state of the tide when you anchor. Not much of a problem here in the Chesapeake Bay, where the average tidal range is <2 feet. But where the tidal range is 10 feet or more, the depth at low tide is (say) 10 feet, and the shore or other hazard is nearby, estimating the proper rode can get tricky and is impossible without knowing the tidal state.
And there is such a thing as too much rode. I once anchored in about 10 feet of water here in the Chesapeake several 100 feet away from the nearest boat. The crew and I went below while a little afternoon thunderstorm blew through. We we reemerged on deck after the storm, the boat that had been several 100 feet away now was within 15 feet. The skipper said that is anchor had not dragged, but that he had out 200 feet of anchor chain in our 10 foot anchorage. I upped anchor and moved.
Erik Snel August 17, 2012 at 11:05 am
We just came back from a nice trip to the English Channel including the Channel Islands. Especially in that area, taking tide into account is crucial. We anchored in a nice lee shore off Sark, where the tide changes at least 6/7 meters at neap tides and over 10 at spring tides. We came in at dusk at high tide. Therefore we anchored in 15 meters, with enough space around us (which was not that easy as we were the 20th boat in that particular bay). We used 1:5, so quite a lot of rode. At low tide we had drifted quit near some other boats with -apperently- a lot less rode. Luckily we did not hit any of them.
Your tip with the radar we are going to follow up, sounds like a good approach. Up till now we more or less estimate on the chart plotter in cooperation with the depth meter. But especially in remote places the charts may not be as accurate and would not be enough.
Erik
John August 17, 2012 at 11:49 am
Hi Erik,
Now there is a tricky anchoring situation: 7-10 meters of tide and a whole bunch of other boats around. That makes our current summer anchoring in mostly deserted anchorages (you gotta love Newfoundland) and only 1-2 meters of tide, look like a walk in the park.
Having cruised both Europe and North America, I always tell my friends from this side that we generally have things much easier than you east side of the Atlantic cruisers do, and this is just one more example.