There have been many interesting anchor tests published, usually concentrating on ultimate holding power in one bottom type or another; however, none of these can test for the many variables found in real-world anchoring situations.
Anchoring technique can make a huge difference in holding, regardless of the anchor type or the composition of the rode. In fact, I would venture to say that anchor setting is the single-most critical factor assuming an anchor of adequate size and a rode of adequate strength.
No matter what you’re dropping over the side, the first step is to let out an adequate amount of scope — say, anywhere from 5:1 to 7:1 — then use your boat’s engine to back down on the anchor. Let the wind take the boat back, then gradually apply power until it feels like the anchor is holding well. If it begins to drag, you might be able to get a bite by letting out more scope and/or dragging it back a few feet.
If the initial application of power indicates good holding, it’s time to try some horizontal bungee jumping. Get a bit of a running start in reverse and really bounce against the rode. Two or three bounces, and you’ll have a good idea if the anchor is going to pop out or drag. Caution: Don’t try this with all chain rode without a substantial nylon snubber in place. I’ve found that if I do this successfully, my set is good for at least gale-force winds when anchored in mud or soft sand.
If the bottom is covered with thick weed, anchors may have a tough time penetrating to good holding ground. If the wind isn’t too strong when you anchor, wait a while before backing down. This gives the anchor time to sink through the weeds to the bottom. Sometimes several short bursts of power help the anchor work its way down. The same technique often works if the mud is very soft — give the anchor plenty of time to sink before applying significant power.
Unfortunately, tropical bottoms consisting of hard sand and/or chunks of coral sometimes can be misleading. The point of your plow or one of the flukes of another type of anchor might be hooked neatly into a rocky crevice while most of the anchor remains unburied. Even a strong pull in reverse might not budge the anchor, while a calm evening drifting about might be just the thing to send you sailing away through a crowded anchorage.
Luckily, areas likely to have this sort of bottom are often ideal for snorkeling to check the anchor. When in places with warm and clear waters, always check your anchor set by snorkeling out and/or diving on the anchor.
There will be times when your anchor set is not confidence inspiring. I remember dragging anchors up and down Nassau Harbour trying to find some sort of holding, only to fetch up with a satisfying tug. A quick dip over the side revealed the anchor entangled in the remains of a large Junkanoo costume (Junkanoo is a Mardi Gras-like festival on Boxing Day, the day after Christmas) on the bottom of the harbor! The combination of anchor and costume held our boat for several days, though I knew not to trust it if the wind picked up.
If at all possible, try to find bottoms with good holding. When the approach of a storm requires maximum holding, many techniques can be used. You can search anchorages for depressions or slopes that allow the anchor to be set so it is an uphill pull. Fighting gravity greatly increases holding power &mdash the steeper the slope, in general, the better the holding.
One time in Annapolis, I inadvertently dropped the hook into a deep pit dug in the middle of the harbor. As I sailed in, my depth sounder was reading in the teens and 20s, but my anchor didn’t touch bottom until I had let out 50 feet of chain. A severe blow hit, and the fleet dragged all around, while I didn’t budge &mdash a case of superior anchoring luck, not skill. When I mentioned this to a local, he laughed and said the Navy had dredged that spot for some reason and everyone in the know avoided it because it was so deep.
In some places it might be an option to put the anchor in much shallower water than the boat is in. You can anchor in the Bahamas with your anchors set on the shallow banks of narrow strips of deep water. With the anchor placed about as deep as the waterline, the angle of pull is greatly reduced, mimicking the effect of increased scope.
However, keep in mind several disadvantages of this technique. If an anchor does drag from the flats around your boat toward deep water, the scope and holding power of your anchor will decrease suddenly when the anchor reaches deep water. Also, a downward slope between your anchor and your boat results in an increased angle of pull, reducing holding power.
It also can be very difficult to set and retrieve anchors in water too shallow to float your boat. You won’t be able to use your windlass to break the anchor free, and you’ll be very close to going aground when you’re over the anchor. This technique works best when you can set and pull the anchors from a dinghy, or even while walking around with the anchors.
A great way to decrease the angle of pull on your anchor rode is to rig your boat with a snubber line attached somewhere near the waterline (my catamaran has twin eyebolts set close to the waterlines). You should always include your boat’s freeboard in your scope calculation; a 5:1 ratio means about 80 feet of rode if you’re in 10 feet of water and have 6 feet of freeboard. Drop that anchor rode down to the waterline, and you reduce your scope requirement by 30 feet &mdash or more importantly, you increase the scope ratio to 8:1 with the same 80 feet of rode out. An added advantage is this technique keeps more of your rode well below the water’s surface, which damps out side-to-side drifting and can help prevent passing boats from snagging your line.
Once your anchor is set, keep a close eye on changes that can alter the effectiveness of what you’ve carefully set up. Other boats can anchor too close, the wind can shift, and the weather report may change.
It is wise to be pessimistic about what may come. Don’t just set it and forget it &mdash adjust to your best estimate of what the anchoring situation will be like if the wind shifts at 2 a.m., your neighbor’s anchor begins to drag or a thunderstorm pops up.
These are all techniques for your arsenal that can maximize available holding power, no matter what type of anchoring gear you happen to own. The most important thing you can do is trust your senses, not your equipment. In other words, observe the bottom, know where the anchors are placed and why, test your system’s holding power, and monitor the situation for changes in the weather, your neighbors, and other factors.
John Kettlewell is sailor and freelance writer in Saratoga Springs, N.Y.