How do anchors work?

[Captain Spod]

If it was just the weight, dragging along the seabed, then they wouldn't all have that, well, anchor shape. If the shape is important in somehow clinging to the seabed, how does the ship simply raise it (avoiding the temptation to use weigh) and not snag it on the bottom when it's time to sail the Spanish main?

[Buenchico]

The anchor starts to grip the seabed but it needs a great deal more weight to hold a ship in place. The rest of the weight is provided by continuing to let out more of the massive steel cable to which the ship is attached. So it's really the weight of cable which fixes the ship to the seabed.

Hauling in the cable gradually removes that big weight from the seabed, so it's then fairly easy to disengage the anchor (which is relatively light when compared to the cable) from anything which it might loosely be caught upon.

Chris

[Captain Spod]

And now it all makes sense. Thanks Chris.

[scotman]

http://en.wikipedia.org/wiki/Anchor

[jake-the-peg]

Hmm not quite sure on that answer Chris.

most anchors work like a plough
http://www.tstiger.or.../anchors/anchor05.png

The chains pull down to make sure they dig in at the right angle - to release it's best to sail over them in the opposite direction.

Or failing that when I was diving - yank on them for ages swear a lot and finally send down a diver to untangle a the mess

the chain on the rope pulls it at the right orientation so it digs ito sand or gravel

[heathfield]

In the main, Chris is right. For example, working offshore, and as a normal procedure, we test-tensioned a particular oil rig's anchor chains to a pull of 400 kips, (i.e. 400,000lbs). To our later surprise, an ROV visual inspection of the anchor chains showed more than one was lying in an 'S' curve near the anchor. Even that pull hadn't been sufficient to straighten the chain fully and have the anchors dig in - the mere weight of the chains was successfully holding the rig in position.
But rope lacks the weight. Archaeologists in the Middle East found evidence of wooden anchors being used !! It seems weight had been added by tying stones to these anchors. Along with the anchors they were puzzled to find objects, made from clay, that looked like the pins used in ten-pin bowling. It turns out that these were used as weights, and were attached along the anchor rope to help provide a more horizontal pull on the anchor, hopefully making it dig in to the seabed.

[Captain Spod]

Hmmm.. more to this than I thought. I'm very glad I asked though!

[Skids]

Interestingly, submarines have anchors too.

[mollykins]

There's different anchors for different bed materials. Plus if you have partly or all chain, it helps to weigh it down .

[betterman]

Imagine Jonathan Woss asking this question.

[McMouse]

Sounds a bit flukey to me.