What is the purpose of anchor chain?

[P51D]

In another recent post people mentioned anchor chain to reduce chafing. Chafing of what upon what? The anchor line on a rocky bottom? <br /><br />Besides chafing, does the chain serve any other purpose? Someone mentioned it increases holding power. How does that work?

 

[RubberFrog]

Re: What is the purpose of anchor chain?

Chafing, as you mentioned, is one very important reason. Another important reason is to maintain the anchor line in an oblique manner while setting the anchor.

 

[Boatist]

Re: What is the purpose of anchor chain?

Anchor chain will stop the line from getting cut on rock as you said.<br /><br />Also most people do not use normal scope of 7 to 1. Distance from where you tie your anchor on the boat to the bottom times 7 is normal scope. Example you anchor in water 20 foot deep and tie to a bow cleat 2 feet above the water so 22 times 7 = 154 feet of line required for normal scope.<br /><br />Many people will use a scope of 3 to 1 and in 20 feet of water only let out 66 feet of line. At first that may seem like plenty of line but it is not. With a danforth anchor as the line gets tight you will see that the line angles up to the boat. As the boat starts to pull on the line it will lift the shank of the anchore up off the bottom to also point at the boat. When the shank lift up to point at the boat it also lift the flutes up to point upward. So now the anchor flutes are not pointed down into the mud but slightly upward and the anchore pulls right out of the mud and just slides along the bottom. <br /><br />Now adding a heavy chain to the front of the anchor the line will go strighter down and the chain will lay on the bottom so when you lightly pull the anchor shank stayes on the bottom and the flutes point down and the anchor digs in and holds. So adding chain held the shank of the anchor down and allowed the flutes to dig in.<br /><br />As current, wind and waves pick up and the pull on the line increases even the chain will lift up and again pull the shank of the anchor up and cause the flutes to angle up and the anchor to slide along the bottom. At this point the only thing that will help is letting out more line. This will reduce the angle of the line pointed at the boat and allow the flutes to dig in. This is normal scope or 7 to 1 and requires 154 feet of line to anchor in 20 feet of water.

 

[craze1cars]

Re: What is the purpose of anchor chain?

I think preventing chafing has little to do with why you must use a chain, but I'm sure it's a small side benefit. The main reason for chain is that anchors are not heavy enough without the added weight of the chain. They're designed this way, and often the length of chain is actually heavier than the anchor itself. As was just mentioned, that chain weight keeps the flutes of the anchor pointing down so they dig into the bottom. If you don't have a chain on your anchor, AND you don't put enough line out, your anchor will be standing up at the bottom, or will be forced to stand up with every tiny little wave. So you're basically trying to hold your boat with the equivalent of a light bowling ball at the end of a rope...it just slides along the bottom because the biting parts of the anchor never get a chance to hold.

 

[P51D]

Re: What is the purpose of anchor chain?

Thanks for the great explanation, Boatist.<br /><br />P51D