How do ships anchor in the middle of the sea?
Clever, marine engineer with 50 years of experience at work.
Fair leading around and pairing up winches is one way, the other way, which I know was used on a ship not long ago, is to drag the anchor into shallow water and then recover.
We are 4+ tons/shackle (shot) and anchor is 8 tons, 10 shots out would be 40 tons plus anchor is 48 tons, no way a single windlass is going to haul that.
Some ship routinely anchor in 100 meters, off Fujairah for example. Some ships with worn out gear or gear that is at min specs even 100 meters might be an issue.
Seattle has anchorages over 100 meters.
Seriously - few vessels anchor in the “middle of the sea”, but I do have a buddy that was on a research ship that has a tremendously long stainless cable anchor rode that is thousands of feet long. I would think DP would have taken over most of that duty by now.
Another method might be to lower a workboat, tie a steel wire fed through the hawse pipe to the anchor chain at the water line and use, if available, deck winches to pull the chain about up to the pipe. I suppose it will require at least 1 1/4 or 1 3/8 inch wire to pull up that weight. Then take out the slack with the anchor windlass, tie another wire to the chain at water level etc. However, it will take some time… Or am I fantasizing too much now…
Are you sure that was a mooring anchor and not a taut-wire position reference system?
This would have been a ship back in the early 90s or late 80s. I am pretty sure they had a long stainless anchor cable for deep water, but not 100% sure.
Off the top of my head I’d say over 30 meters is deep water. Meaning it’s not a routine anchoring, the precautions used for deep-water anchoring would be in effect.
The first two post are ships that, in error, had all the anchor chain paid out.
Deep Water Anchoring - Washington State DOE.
Puget Sound ports are naturally deep water ports which contain anchorages in excess of 40 meters depth. Designated anchorages in Commencement and Elliott Bays, the respective gateways to the Ports of Tacoma and Seattle, can exceed 100 meters in depth. When designated anchorages are full, ships may have to anchor in depths approaching 125 meters.
I served in HMNZS Tui which had previously been the USNS Charles H Davis one of nine Conrad class ships. The vessel carried out oceanographic research both classified and unclassified.
There were two take up drums below deck, one for coring and the other containing about 10,000 metres of tapered wire. The traction winch was on deck and the wire came up through a riser and around two wheels of the traction winch about 5 times from memory.
The deepest we anchored was in about 5000 metres , the anchoring was by the stern.
Quite rightly anchoring at this depth has been made unnecessary by DP and GPS.
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I recall hearing about research vessels anchoring in very deep water with tapered wire. The explanation for the tapered wire being that ordinary wire would break due to its own weight.
I believe about 100 meters (4 shackles) is the maximum advisable depth to anchor with normal equipment. It is possible to assist with a second windlass to heave, but that should be in emergency only.
The problem with 100 meter anchoring are the depths around, if it´s all 100 meters not so big problem, but if its 2-300 meters or more you must be very careful where you lower your anchor. At 100 meters, it can be hard to see if you anchored well, and often you only get to know when you try to heave up the anchor.
Bringing the ship to more shallow water to retrieve the anchor is often not an option, and the reason why we anchor at deep water in the first place. I have done many anchoring at 100 meters, off the territorial waters of Morocco where the depths around are much greater, never a problem.