Is anyone aware of general guidelines for sizing an anchor to use as a semi-permanent mooring? Lots of info out there for sizing concrete blocks, Dor-Mor, augers, etc., but not necessarily anchors. I'm thinking along the lines of a HHP stockless which could be lowered into the hold and relocated when needed. I've checked IACS but they seem to only address working anchors.
Using an anchor as a mooring
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Nomad Willy
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This guy spent a lot of time in Craig Alaska but actually lived on an island not too far west of town. He had no permanant mooring. He anchored in front of his house/cabin using this 500# Navy anchor. The old saying is we have "50 knot gales in the summer and 60 knot gales in the winter." Don't know where that comes from. SE Alaska has 50 knot gales in the summer and tales of higher winds can, I'm sure be found but I've not heard them. I anchored in a 50 knot gale in northern coastal Canada but I had nothing to measure with. There were gusts beyond that I'm very sure but It's just my senses doing the measuring. Winter gales get much stronger that 50 knots so the saying about 60 knot gales in the winter should read "60+" knots. Perhaps 80 ... or so.
Well this guy didn't want his boat going anywhere. I remember hearing something about it but can't remember why he didn't install a mooring buoy. So he mounted this 500 pound Navy to keep his boat secure. It probably did. I'm guessing he probably did'nt need that big of an anchor. A member of the "bigger is better club to be sure.
Well this guy didn't want his boat going anywhere. I remember hearing something about it but can't remember why he didn't install a mooring buoy. So he mounted this 500 pound Navy to keep his boat secure. It probably did. I'm guessing he probably did'nt need that big of an anchor. A member of the "bigger is better club to be sure.
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eyschulman
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I have used an anchor system as a mooring following a practice used in a crowded anchorage in NY by the local harbor master. This is a versatile system very well tested. The idea was to have a strong reliable system use less room and have easy set up and serviceability. The system uses three Danforth anchors chain and a float with rode. The anchors are set at 60 degrees with about 60 foot of chain and linked to a central ring then another section of chain maybe 2X greatest tidal depth with a heavy road at approx. the greatest tidal depth hooked to the float. The end result is no mater where the boat is or turns a very secure very high holding power. The chain stays on bottom away from where it deteriorates faster and the chain and joining ring can be pulled up for inspection without heavy equipment.
I used this type mooring for years, I found it in Chapman's. I used 22 lbs Danforth anchors and 3/8" chain. The mooring held through winds up to 60 knots. As mentioned, easy to pull up the center and do maintenance on the three rodes. The 60 degree anchor settings allowed two of the anchors to take the strain from any wind direction.
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eyschulman
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Thank you for the correction. I don't deserve any points for being half right.
Nomad Willy
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I thought about that too but what you meant was obvious.
Your example may be more like a permanent mooring rig. Mako said "semi permanant" but really was'nt very clear about his needs.
Your example may be more like a permanent mooring rig. Mako said "semi permanant" but really was'nt very clear about his needs.
Mine became permanent as far as the 22 lb Danforth because the only wear on the chains was at the center. If you don't pull up the whole rode occasionally the anchors will bury to a depth that hand retrieval becomes impossible. I would pull the center and cut out about 5' of wear caused by the center rodes moving around in the sand/mud bottom. I used 50' rodes, once the anchor and about 45' of the chain buries there is little wear. I used this type mooring for about 12 years.
FF
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"If you don't pull up the whole rode occasionally the anchors will bury to a depth that hand retrieval becomes impossible."
IF you are in a tidal area , and have the time , the slow pull of an incoming tide works wonders.
Have used the 3 Danforth technique , and recovering 60 lb anchors that have been down a while is usually far beyond even a Hyd windlass.
But Time and Tides do fine.
IF you are in a tidal area , and have the time , the slow pull of an incoming tide works wonders.
Have used the 3 Danforth technique , and recovering 60 lb anchors that have been down a while is usually far beyond even a Hyd windlass.
But Time and Tides do fine.
The harbor is tight here with little swing room due to all the fishing dhows so the three anchor system would be best, except for the hassle of crossing lines. I'm thinking along the lines of just a single anchor but perhaps doubling the weight (400-500lbs) with a leader of heavy chain like 3/4" stud link. I suppose there are no calculations or guidelines so it's just a matter of estimating or guesstimating.
FF
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Anchors work best if pull is in only one direction . even a 500lb can flip over if the load gets severe.
Two big anchors would be a bare minimum.
If they will be delivered , have the delivery boat set them for you.
Two big anchors would be a bare minimum.
If they will be delivered , have the delivery boat set them for you.
FF
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Mushroom anchors seem to work OK as single anchors , but 1000 lbs might be required .
There is no fetch and winds generally don't exceed 30-35 knots so I might get away with a smaller mooring. I will need to have it fabricated anyway. I suppose we drop it and dive down there with the hose from a trash pump to bury it deep. Thanks for the input
caltexflanc
Guru
I have had the opposite experience with three Danforths. Years ago our club had a mooring field for 15-20' sailboats that were mostly based on 100-150# mushrooms and one triple Danforth setup.
Hurricane Floyd came through and most of us pulled our boats beforehand but a half dozen stayed through it. A couple of the mushrooms dragged ashore as well as the triple Danforth. These moorings were in 6' MLW off of Westport in Connecticut. The triple Danforth setup used 20# real Danforths.
One problem with the triple Danforth rig: once it starts dragging it is all over. But maybe the same can be said for a mushroom. I would prefer a big block of granite myself.
David
Hurricane Floyd came through and most of us pulled our boats beforehand but a half dozen stayed through it. A couple of the mushrooms dragged ashore as well as the triple Danforth. These moorings were in 6' MLW off of Westport in Connecticut. The triple Danforth setup used 20# real Danforths.
One problem with the triple Danforth rig: once it starts dragging it is all over. But maybe the same can be said for a mushroom. I would prefer a big block of granite myself.
David
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22 pounds. As deep as a Cape Dory 25D being pushed by 135 mph winds could bury it in mud!
Nomad Willy
Guru
I'm thinking one should think of what kind of security is most desirable.
With the anchors we use for general anchoring we choose burying anchors. I know Danforth anchors aren't really burying anchors unless the bottom is very loose mud. But we should consider them burying anchors because their performance is like the burying types.
Burying types set w their flukes well submerged. With their flukes buryed they have excellent holding power .. until they break out. They may reset. But they may drag. There's a wide range of predictability or unpredictability depending on the anchor and the bottom. But a near total loss of holding power is possible to very likely.
Non burying anchors like a Navy or Dreadnought fail by draging. They generally do'nt break out and become useless. They reach their maximum holding power and then drag. But they drag w/o loosing much or any holding power. Their dragging may be very slow. Slow enough to hold a boat off the beach or away from danger. Ships use non-burying anchors like the Navy anchor and for many good reasons I'm sure.
It occured to me that for a semi-permanant mooring the non-burrying stockless anchors may be better than the burying anchors we commonly use.
I'm not making a case for this as I do'nt know enough about stockless anchors. I am saying it may be worth thinking about.
I do think, however that one big stockless anchor w heavy chain may likely be good for the OP.
With the anchors we use for general anchoring we choose burying anchors. I know Danforth anchors aren't really burying anchors unless the bottom is very loose mud. But we should consider them burying anchors because their performance is like the burying types.
Burying types set w their flukes well submerged. With their flukes buryed they have excellent holding power .. until they break out. They may reset. But they may drag. There's a wide range of predictability or unpredictability depending on the anchor and the bottom. But a near total loss of holding power is possible to very likely.
Non burying anchors like a Navy or Dreadnought fail by draging. They generally do'nt break out and become useless. They reach their maximum holding power and then drag. But they drag w/o loosing much or any holding power. Their dragging may be very slow. Slow enough to hold a boat off the beach or away from danger. Ships use non-burying anchors like the Navy anchor and for many good reasons I'm sure.
It occured to me that for a semi-permanant mooring the non-burrying stockless anchors may be better than the burying anchors we commonly use.
I'm not making a case for this as I do'nt know enough about stockless anchors. I am saying it may be worth thinking about.
I do think, however that one big stockless anchor w heavy chain may likely be good for the OP.
markpierce
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A heavy mushroom should work in thick mud. Leastwise it worked with this lightship formerly anchored off the exposed SF Golden Gate:
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