I’m not a mariner either, but for a ship that large, you don’t want to anchor if you can avoid it. Think about how big the anchors would have to be for that large a ship. Dropping them and raising them would not be trivial tasks. So best just to avoid doing it.
ETA: As far as fuel use goes, think about how much fuel it would take to raise the anchors. Lots of it.
Might be too deep for anchors anyway.
).Think of it in terms of gyroscopes and push bikes. The vessel is much more controllable when in motion. It’s also much cheaper, albeit “wasted” fuel.
Thanks for the replies, makes more sense now. I guess they are just trolling around at just enough speed to maintain steerage, i.e. pretty slow, so not using much more fuel than they would otherwise, anyway.
Yeah. The rule of thumb is to pay out anchor chain five times the depth is at, so if you’re in 10 fathoms, you let out 100 fathoms. This results in a great deal of chain lying on the bottom and it’s the weight of the chain keeping the ship in place, not the flukes of the anchor digging in.
Your math is not quite right
Thanks for saying something, I was wondering if my brain had shut off early and I was drastically misreading.
You’re right. I was thinking 20 fathoms because 10 is not deep at all for a ship that size, then my fingers misspoke.
I don’t know about big ships, but definitely not true for smaller boats, and I can hardly imagine it’s true for big ships either. Smaller boats use a heavy rope as the anchor rode, typically with a short length of chain at the anchor end. The only purpose of the segment of chain is to help hold the anchor in a horizontal position so that it does, in fact, dig in to the bottom and/or catch on rocks or whatever else. In fact standard practice after dropping anchor was to reverse the boat while playing out the necessary length of anchor rode, and then fixing it to a bow cleat and confirming that the boat stopped moving under reverse thrust. Weight alone ain’t gonna keep anything in place if you don’t have a good anchor-worthy bottom. Ask me how I know! 
If you watch this video, you will see that for big ships, it is indeed the catenary length of chain that holds the vessel in place
I disagree. I watched the video and it emphasizes many times that the anchor getting a grip on the seabed is absolutely essential. It even describes the situations where an unfavourable seabed – like one comprised of smooth rock or excessive seaweed – will cause the anchor to drag.
My specific objection was to the comment that “a great deal of chain lying on the bottom and it’s the weight of the chain keeping the ship in place, not the flukes of the anchor digging in”. This is not true as the ship will move and drag anchor if winds or currents push it when the anchor is not dug in. There’s a reason that anchors are built like giant hooks.
It’s true that when winds or currents push on a ship, the anchor chain lifts off the sea bottom and its own weight helps to hold the ship in place, but that’s rather a pedantic point since it wouldn’t have that effect if the anchor were not providing a corresponding resistive force. It’s like pulling a cable taut between two posts: the weight of the cable certainly contributes to the pulling force you must exert, but that opposing force only exists because the cable is firmly attached on the other end.
It seems to me that both the length of chain and the anchor itself are required to hold the ship in place. Lack of either one means the ship will drift.
And now the backlog of ships has been cleared.
In a month, this will all be forgotten the way we’ve pretty much forgotten how a volcano in Iceland shut down transatlantic air travel for a week in 2010.
That’s a good thing, isn’t it? It means that the long term impact was negligible.
We have a volcano erupting in Iceland right now but being a small one, it barely made a blip on this board.
It’s about 2-1/2 miles from the site I worked at when I was at Kef, closed a generation ago.
Honestly, the last event I remember that captured world attention the way this one did was the soccer team that was trapped in that cave.
Forgotten the pandemic already, have we?
Well, the last thing that only happened to a small group.
Can we all stop hoarding TP again?