So I was watching something about huge nuclear-powered supercarriers on tv last night, and they briefly showed the ship’s impressively huge anchors (this huge Nimitz class carrier has two of them, each link in the chain weighs over 300 pounds, I forget how many dozens of tons each anchor is - but huge).
That got me thinking… when and under what circumstances would a huge ship like that supercarrier or an even bigger post panamax/ULCV container ship actually use an anchor? Seems they go directly from port to port, at which point they’re tied up to the dock with ropes.
I know small fishing boats operating in shallow water drop anchors when they want to stay in the same spot (i’ve done that before out on a lake). I know old 18th century ships of the line would drop anchor offshore and the crew would disembark the ship via smaller boats to come ashore. I can imagine large modern cruise ships using anchors to ‘park’ offshore in shallow waters to let passengers jet-ski, scuba dive, and take boat trips to shore - that makes perfect sense.
But when would a modern, HUGE vessel like a nuclear powered supercarrier or Ultra Large container ship need to drop its anchor(s)? I figure the vast majority of the time such vessels are operating in water too deep to even use anchors.
This feels like a stupid question, but I just can’t come up with a reasonable situation in my mind where a huge ship like that would ever need to drop its anchor(s). Please enlighten me. I’d hate to think they’re just there for decoration and “nautical tradition” - that would be a ludicrous waste of money… plus based on what I saw on TV, they’re clearly functional (though it looked brand new like it had never been used - not a speck of rust, perfectly shiny freshly painted chain not a scratch on it… looked like it had never touched water).
Theoretically, a super-carrier might have to base is a lagoon somewhere during a shooting war. But given the speed and range of the ships, I really don’t think there is any practical need for anchors these days. But it’s the Navy. They still teach celestial navigation and how to use a sextant. Also handy theoretical skills to have.
A lot of ports are not deep enough for a carrier, so they do “anchor out.” It’s more common in the med than you might think. They use the anchors much more than you think. And it’s the anchor chain that holds it in place, not the anchor itself.
Surely the anchor has to touch the ground… are you saying an anchor with 1000’ of chain just hanging there in 5000’ of water would do anything? Might cause some additional drag… but not much, certainly not enough to keep the ship in place. Yes, the chain is vital to the operation of the anchor, if that’s what your saying. But as far as I know and logic dictates, you can only use an anchor in water as shallow or shallower than the length of the anchor’s chain.
I think what Spifflog was talking about was the chain lying on the seabed. People tend to see the shape of an anchor and assume it hooks onto something (It would have to be a really big something…and if it was big enough to hold, how would you get loose?).
That’s exactly what I meant. The anchor doesn’t hold the ship in place. The weight of the anchor chain on the sea bed is what holds the ships in place.
Slight highjack: why is the anchor shaped this way if it’s not meant to hook onto anything? If only the weight matters, shouldn’t it be a blunt shape to avoid any undesired, uh, hookings?
I doubt that they would risk this with a carrier, but the captain of a smaller craft might throw out an anchor if the ship needed to ride out a storm while in shallow water.
The anchor sits on the bottom. If it is dragged the Fluks will dig into the bottom increasing the force required to move the anchor. The anchor chain sitting on the bottom will also increase the force necessary to drag the anchor.
If a ship is going to anchor out in a harbor the captian will take into account the speed of the currents, the force of the wind on the ship, and the tides. If these forces are going to be strong and there is room he may let out more chain. one thing the captian has to consider is the swing of ship on the anchor chain.
Navy ships anchor out in many ports of call because of the expence of docking. Container ships would have a hard time unloading with out docking. Jumbo tankers anchor in the San Francisco Bay, they pump oil to baby super tankers that the oil up to the refinerys.
If the captian does not want to swing on the anchor then both the bow and stern anchors are put out.
I thought anchors were shaped the way they are to dig into the seabed. Not hook onto something, per se, but to get more of a grip into the seabed than, say, a heavy round ball (like a wrecking ball) would. I’m sure the weight of the chain laying on the seabed surely helps create a log of drag too. But if it were 100% chain doing the job, why have anything at the end of the chain at all? Surely the chain is heavy enough to sink to the bottom without a weight on the end.
But are you saying if you had 100’ of chain (assume the size of the anchor itself is included in that 100’) and you were in, say, 99’ of water (also assume the anchor is released at sea level, just for convenience of this hypothetical) the anchor wouldn’t accomplish anything?
cornflakes: I would think using an anchor during a heavy storm would be a horrible idea, especially for a small boat. might pull the boat under if there were a high wave, and it might rip the boat apart. But what do I know… i’m no nautical expert. It just sounds like a bad idea to me.
I’d love to hear from someone who actually worked on a modern supercarrier or panamax or larger container vessel and hear when, if ever, the anchors were used on their ships.
When the anchor is played out it lays flat on the bottom and the hook (fluks) will move on the anchor shaft and dig into the bottom. While at anchor the anchor is out infront of the ship some distance. When the anchor is pulled back in the shihp will move to the anchor, as chain is pulled in the chain is lifted off the bottom and anchor shaft will also begin to lift off the bottom. The anchor is no longer being pulled across the bottom of the sea floor, but up at an increasing angle until it will begin to come free.
In a Heavy storm a small boat can really move fast one way then another being tossed each way and not necessary bow or stern on to the waves. A wave broardside can capsize or swamp a boat. Because the wind will change directions often it can turn a boat. But the waves do not change direction much or fast. Dropping an anchor will cause a drag on the boat keeping the stern or bow pointed in the directions of the waves.
The anchor does not hook onto any particular “thing.” It is designed to dig into the soil. In this application, the ship rides up to the anchor point, drops the hook, then backs away to set the flukes into the soil, the chains extending out from the ship at an angle that curves to rest on the bottom near the anchor. The anchor holds the end of the chain in place, but, as spifflog noted, it is the chain that holds the ship in place.
When the anchor needs to be retrieved, the ship moves up to a point vertically above the anchor and reels it in, (weighs it), after the vertical position of the chain, pulling on the shaft, pulls the flukes out of the seabed.
I haven’t sailed on commercial ships, but I have been an underway Officer of the Deck (OOD) on a carrier (Coral Sea). As I mentioned up thread, in most ports that we stopped at in the Mediterranean Sea, we anchored out. Meaning we didn’t pull into port, but rather anchored out 1/2 to one mile out, and took water taxies into port. This was part security, but more so due to depth of the port, and lack of a pier that could handle the carrier.
Other than that, we wouldn’t use the anchor. Certainly not in poor weather.
I’d think the friction of the anchor digging into the soil would cause more drag than the chain just lying on the seabed. I’m sure the latter contributes drag too, but I’d think the majority, if not vast majority of the drag force keeping the vessel in place would be from the anchor flukes having dug into the seabed.
If the principle is the same for huge ships as for smaller boats (yachts, maybe): the chain needs to be long enough to to angle down to where part of it lies flat on the harbor seabed. No, there’s no anchoring in water that’s a mile deep. The anchor is at the very end (duh) and it too lies flat on the seabed. The hook ends (flukes) dig in to the seabed, and work fine as long as the boat is pulling back on the anchor - itself known often enough as a ‘hook’. Pulling back on a single hook is not that difficult to arrange as long as the wind is reliably blowing in one direction for the duration of the anchorage. Otherwise, maybe more than one anchor is needed.
Which is to say, setting anchor is a skill.
To raise the anchor, start engines and cruise slowly up to where the anchor is, cruising at the speed the chain is being winched up. When the boat is over the anchor, the anchor chain is near vertical, the anchor has been flipped up, the hooks are no longer hooking, and aside from the weight of the whole thing, it come up easily. Mostly. Sailor cursing also assists with raising anchor if the proper curses are used, those powerful enough to raise anchors all by themselves. (Whooshh…)
The harbor might not be set up to receive a given ship, or might not have dock space available immediately. The alternative to anchoring is to keep the engines running and keep manoeuvring the vessel in place until the dock space (if any) is ready - not a good use of fuel and not easy at all in tight harbor quarters.