TEST Anchor, chain, line. The whole truth about the anchor line


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I finally did it. I now know how far a boat’s anchor holds depending on the strength of the wind. That way I won’t have to argue with the one on the bow, yelling at him to give some more chain or line because the one he gave is not enough.
Most importantly, I won’t spend nights in the cockpit with the wind creeping into my bones (I’m not a kid anymore) with my eyes on the bow, worried that the anchor will start plowing and I’ll have to scramble to start the engine. So as not to risk disaster.

schermata-2016-11-10-a-15-02-49DOES IT HOLD OR DOES IT NOT HOLD?
For those who haven’t figured it out yet, I’m talking about the essential topic for every boater: does it or does it not hold my anchorage in the bay? Who is right, the one who pontificates that a heavier anchor and lighter chain is better or the one who says the reverse is better. Or, but is it really true that I have to carry a hundred kilos in the bow with the “all-chain” option that make me bang like hell when I have a wave in the bow and make me lose my boat trim? Continuing, is it not wrong for those who instead theorize about the “light” option with a good last generation anchor of the right weight combined with an adequate dose of chain and then a nice top? Years and years of discussions that frankly, had broken my back. But I wasn’t able to give a definitive answer that would relieve me of those tedious sailor discussions and, most importantly, put me at ease when I drop anchor in a bay and the weather says the wind will pick up overnight.

The solution to my problems materialized at the end of last September when, browsing through the French magazine Voiles et Voiliers, I read an article where a test of an anchor’s tensile strength before it shipped was carried out, comparing three types of anchor lines: all chain, chain and top, and all top. Interesting but theoretical. It was not explained, in reality, up to what wind strength, in relation to the size of the boat, the anchoring systems resisted before “giving up.” Now I’m going to take this test and complete it to make the results useful to me and everyone else who has anchor anxiety, I said to myself. And I did.

schermata-2016-11-10-a-15-02-05WHAT I DID.
I look at the weather forecast and on Friday night I am on the ferry to North Sardinia. There is my son’s boat there, which has exactly the two anchor lines I need, and they just happen to be practically the same as the ones in the test done by the French magazine. That way, I tell myself, I can have a verification if the data I am going to detect is correct. Let me explain well what I did. I called a friend of mine who has a motor boat, an old fishing boat that he has also adapted to a cruising boat, equipped with two powerful, low-torque engines capable of strong pull even at low rpm. Perfect for testing. What I need. I purchased, and brought it with me from the mainland, a dynamometer (MCWN Ninja with measurement up to 6,000 kg). The person who sold it to me assured me that if I treat it well then he will buy it back at a small discount. The rest of the materials to carry out the test I already have, they are the two anchor lines that are aboard my son’s boat.

I know them well because I gave them to him. He has two because he uses his boat for both cruising and racing. Aboard his 11-meter Rodman 42, which weighs only 6,500 kilos, he embarks on an anchor line with a 12-kg Kobra 2 anchor paired for cruising with 50 meters of 8-mm diameter chain and a second line, which he uses when he goes racing because it is lighter, with 10 meters of the same chain combined with a 16-mm three-strand line. There is also the tender that I will need for visual detection of anchor behavior. All I need is a top, identical to the one that is already there. I will buy it in the port store (it is very common). I am accompanied by my son who, in exchange for assistance, will force me to help him do some shipboard work. I do so gladly.

ultra_anchor_white_backgroundTHE CONDITIONS OF THE TEST
On Saturday morning, we embark the three anchor lines planned for the test on the pleasure fishing boat. The first is “all chain,” the second is 10 meters of chain, and the third is “top only”. We will try these three options combined with the Kobra 2 anchor on the four-meter “all sand” seabed in front of the beach, which is just off the harbor. We will test them with three different calumo (length between the sunken anchor and the bow of the boat) options. The first will be 3 times the height of the seabed (12 meters of calumain) which we call the “short” option, the one used when the roadstead is crowded and there is no room to give the correct calumain. The second option will be what we call “right” with six times the height of the bottom (24 meters). We call the third one “long,” the one you give when you decide to stand at anchor in a roadstead when the wind is blowing hard and you want to be safe without having to give the second anchor. Test begins.

Let’s start with the simplest the “all top” option. The fishing boat begins to push its engines. With the tender we observe-the water is transparent as only in Sardinia can be found-and see everything that is happening underwater. With three 12-meter lengths (three times the bottom) the line-only option is totally ineffective; as soon as from gas the boat, the anchor sends out inexorably. Zero holding. Let’s try to give top by arriving at the “right” solution (six times the bottom), which is what is normally used for proper anchoring in the bay. The anchor holds up to a pull of 270 kg, then gives up. With my son’s 12-meter boat he would quit in less than 20 knots of wind intensity. With the “long” solution (10 times the bottom) it can withstand up to 350 kg. At about 30 knots the “target” boat would spend big.

Better situation with the second option, the one with 10 meters of chain and the rest rope. With the “short” solution the hold is again nil, but with the “right” one it plows a little with a 450 kg pull but then the anchor plants well up to 600 kg and then gives up. The “test” boat would stand still up to more than 30 knots of wind. With the “long” solution after plowing for about a meter with 600 kg stabilizes and up to 800 kg holds. It means that the boat would remain in place up to 40 knots of wind.

With the “all-chain” option, the results are excellent. It plows a little, but does not let up, with three lengths “short” solution up 210 kg, that is, in wind up to just over 15 knots of wind. At the “right” solution of six lengths it resists with a pull of 920 kg i.e. as if there were more than 40 knots of wind. With the “long,” 10-length, spring with 1,230 kg, or about 50 knots of theoretical wind.

schermata-2016-11-10-a-15-01-16 schermata-2016-11-10-a-15-01-37

What happened in our truth test is well summarized in the data in the tables above. All you need to do is compare the tensile strength of the three different anchor lines in the three different lengths, measured in kilograms (table above left) and compare them with the 11-meter option. We tell you to compare the “11-meter” length data because the materials used for the test (anchor/chain/rope) are the correct ones to use for a boat of this size.
is’ obvious that in case your boat has different sizes, the materials used will be of different diameter and weight, but the sealing result as wind conditions change will not vary much. Because one thing is certain, it is not true that a much heavier anchor will allow you to increase the tightness. All anchors, but especially new generation anchors such as our Kobra 2, do not increase performance as a function of weight, but of the angle of pull they can maintain. From the visual detection of our test, the situation was crystal clear. When the pull angle of the anchor line was more than 10 to 15 degrees to the bottom, the anchor would rise relative to the bottom and begin to drift or drop off suddenly.

The practical lessons from this test? Here they are: always give as much length as possible relative to the bottom; never use the “top only” option, it doesn’t work. Check the expected wind strength because your anchor line may not always hold, even if the anchor is well sunk into the ground. And we repeat, stretch your anchor line as far as you can. Tightness will increase exponentially.




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