"Surfing anchor"

[ulferlingsson]

With my newly purchased boat came an anchor. An aluminum danforth One the maiden trip I decided to test it, since I like testing different anchors and see what I can learn. A squall came on Biscayne Bay, we threw it, took down the sails, and off we went. I swam to the bottom to see what was going on, and the anchor was "surfing" over the bottom in about one knot.

I wouldn't follow rules when getting gear but base my decisions on experience and knowledge of what makes for seaworthiness, but just for fun, is there a rule in your jurisdiction that says that a boat must have an anchor aboard? And if so, does that rule say anything about what constitutes an "anchor"?

For instance, if I made an anchor out of styrofoam, would that qualify? You see, the underlying problem with the aluminium anchor is that it's density on water is too low, just about the same as the density of the bottom, not more. It should be more than the density of the sediment under the sea, IMHO.

Rules that are blindly obeyed don't create safety. Safety is created when an informed skipper takes full responsibility for having his vessel seaworthy. Which means not buying inferior equipment just because someone certified them. Right?

[speciald]

Aluminum "Danforth" is probably a Fortress anchor. Try adding about 10 feet of chain to the rode to help the anchor get set.

[ulferlingsson]

I can't believe they still sell that. It defeats its own purpose.

Mine has some chain, not enough. If one has about 70 m of galvanized anchor chain one needs no anchor up to gale or so (15 m/s, 30 knot). So at some point this so-called "anchor" just becomes a way to throw money in the sea.

FYI, the only anchor type that I have found to get a reasonable grip on all types of bottoms (clay, mud, sand, gravel, stones, boulders, rock) is the plough. I prefer without a hinge. Bruce and mushroom styles are my second choice.

[scottyt]

well anchor weight as long as the anchor is denser than water should not matter. the weight of an anchor does not really matter once it digs in, the holding force is a matter of design and surface area as well as bottom composition.

if you had set the anchor properly it would not have sailed

edit

small mushroom anchors are one of the worse anchors out, they need lots of time to dig to hold at all. they are basicly just a weight sitting on the bottom

dansorth anchors have some of the highest holding forces of any anchor they just suck at reseting

bruce anchors dig in pretty well

if you ask me plows are the worse idea for anchors, plows are designed to move thru the dirt, they dont dig in they move the dirt off to the side

as for you 70 meter chain anchor, it sure as heck better be a 1 inch chain and weigh hundreds of pounds

[Craig Smith]

Originally Posted by ulferlingsson

With my newly purchased boat came an anchor. An aluminum danforth One the maiden trip I decided to test it, since I like testing different anchors and see what I can learn. A squall came on Biscayne Bay, we threw it, took down the sails, and off we went. I swam to the bottom to see what was going on, and the anchor was "surfing" over the bottom in about one knot.

All Danforths are liable to behave like this, they have high holding power when set but their setting behavior is unreliable and shouldn't be used as general purpose anchors.

Originally Posted by ulferlingsson

For instance, if I made an anchor out of styrofoam, would that qualify? You see, the underlying problem with the aluminium anchor is that it's density on water is too low, just about the same as the density of the bottom, not more. It should be more than the density of the sediment under the sea, IMHO.

A styrofoam anchor would float and therefore obviously not meet even the most basic definition of an "anchor". Aluminium anchors on the other hand are fairly well recognized. However, most rules that you are talking about are very broad and lax in their scope.

Classification society rules or local regs that more or less parrot classification rules, which apply to larger vessels or commercial boats, will require classified anchors, which will be type approved and pull tested to 'normal', HHP (2x normal), or SHHP (4x normal) ratings. Such certification is fairly useful and eliminates the real junk, but is not required on private yachts anywhere that I'm aware of, and still doesn't bar the sort of Danforth behavior you witnessed.

Originally Posted by ulferlingsson

Rules that are blindly obeyed don't create safety. Safety is created when an informed skipper takes full responsibility for having his vessel seaworthy. Which means not buying inferior equipment just because someone certified them. Right?

Right.

[ulferlingsson]

Thanks, Craig, that was an insightful comment. I can share some experience with you. I first had a Danforth 12 or 15 kg (forgot which) on a 22 ft 1.5 ton motorboat, with 70 m 6 mm chain. When hauling in the anchor at a depth of some 12 m with sand bottom, a wave lifted the boat when the chain was taught, and the anchor broke. More holding power than strength, thus. Switched to a plough, about same weight. It held on any bottom I dropped it; never dragged. I anchored on sand, mud, clay, even rock. The sharp tip has an amazing ability to find something to hold on to on rock, and if it is designed correctly, it won't twitch off. In soft sediment it will not drag if it is the correct size for the boat, and you have enough chain that the force is parallel to the bottom. I anchored for diving in the open sea, at up to 40 m depth, and in each case I checked the anchor for holding the first thing on the dive, that's why I got all this first hand experience. And that's why I know that even a chain is remarkably able to hold the boat; often the chain was just lying in a pile next to the anchor. It required close to gale or large waves, and deep water, for the anchor to be put into action. (Extreme case: We anchored at 35 m depth on loose volcanic sand in the Atlantic Ocean south of Iceland, without problem - but it was of course a calm day.) As for mushroom, the kind I had for dinner anchor was a stainless bowl half filled with lead. It was surprisingly efficient as anchor, contrary to its reputation. But what you said about Danforths matches exactly my experience.

[sailingdog]

Ulf—

The behavior you saw is one of the primary reasons I dislike Danforths for use as a primary anchor. This is especially true on a multihull, which can accelerate a lot fast than a monohull and has far greater potential for "kiting" a fluke-type anchor.

[pdqaltair]

Save your money, you have a fine anchor. You just need to learn how to set it. Comments from the seller and groupies ( ) aside, it probably has twice the holding power per pound of anything you can buy--it does have limitations and a learning curve.

* Learn to set an anchor. You don't just drop it and hope.
* Fortress anchors do not re-set well, so set them deep. With a 20-foot boat it should hold well even in a shift, with a good bottom.
* Guardian anchors. I had a small Guardian, and it was too light to work well.
* Size. Anything smaller than the FX-11 is too light to get down, in my opinion.

And much of what Craig and SD said was true. IF you want drop and forget, sell the anchor. I learned to like them while cruising on a very light (1200-pound) catamaran--100-200 pounds of ground tackle in the bow would have been quite absurd. Now I only use a Fortress as a secondary and kedging anchor, which it does well.

[sailingdog]

Danforths and other fluke-type anchors are great for kedging or stern/secondary anchors. But a primary anchor needs to be able to reset reliably—which is something that fluke-type anchors just don't do well. A Delta FastSet, Rocna, Manson Supreme, etc. are all going to be better as a primary anchor IMHO>