Active Anchoring

[belizesailor]

Originally Posted by Andrew Troup

Hmmm -- you did well, I reckon, it's damn tricky getting a good hold in that strength of wind in such shallow water (contrary to intuition), and your heavy chain is not much help in that specific situation.

(Although in the general case I'm a big fan of heavy chain ... and I applaud you for carrying it, on a cat)

I guess the relatively short fetch was a help. If you snatch an anchor in such shallow water, you can drag a really big anchor in anything but great holding, I've found.

If there had been a prospect of it blowing another 20 or 30 knots, and you had a bit or warning, I reckon (in the specific case of an offshore foehn wind, which is not going to shift direction without a major reduction in strength) a Fortress on another rode, set in a V, would be the way to go. In shallow water, it wouldn't need much chain: the more rope, the better the snubbing absorption.

Two anchors in a V is not popular these days on sailing forums because of perceived problems with crossing rodes, but in our part of the world where it regularly blows a hoolie from a single direction, I reckon it still has a place, especially for shallow water or bad holding. (Pray you don't have to anchor in both!)

People say the load won't be shared, but in soft sand, the anchor under the most load will simply creep downwind until it's no longer under that much load.

I have a theory which I have not dared to promote; I'm not in any way confident about it. But here goes:

The mere fact of 'taking turns' may help each anchor to set deeper than it would as a single in the same wind strength.

I have a suspicion many anchors dive slightly, early in each drag sequence, effectively they're simply digging in further ... until the resistance to burying of the shank, and the inability of the soil to provide enough resistance, causes them to start to 'porpoise' upwards.

So if there's another anchor which will progressively take the strain as the first anchor digs (because at the same time it's moving towards the vessel, de-stretching the rode) I can see how both anchors would help the other to dig deeper.

It does rely on the wind strength staying remarkably true, though, (which in this part of the world does happen, with foehn and katabatic winds particularly)

Another technique which addresses some of the issues above is two anchors in line on the same rode. One is connected to the head of the other. Dramatic increase in holding power and no dual rodes to worry about. If I am expecting a big blow I often use this set up.

[colemj]

Originally Posted by JonJo

This seems in stark contrast to the Bigger is Better concensus. In fact almost contradictory, small anchor, for the size (windage) of yacht; (seriously) larger chain.

80m of 12mm chain deployed is 264kg, that's like an extra 3 reasonably fit crew. That really is a lot of chain.

And Ann and Andrew - again your joint suggestions seems to contradict the consensus - you are suggesting there is real merit in setting 2 anchors in a 'V'.

Jonathan

With enough chain, one doesn't need an anchor. The whole point of anchoring is increasing friction higher than windage. The only reason an anchor is used is for convenience. It then becomes a matter of best balancing for the given boat/crew/handling equipment the size of the anchor with the size and length of the chain.

Mark

[Polux]

Originally Posted by colemj

With enough chain, one doesn't need an anchor. The whole point of anchoring is increasing friction higher than windage. The only reason an anchor is used is for convenience. It then becomes a matter of best balancing for the given boat/crew/handling equipment the size of the anchor with the size and length of the chain.

Mark

I don't understand if you are joking or really meant it. That is certainly true, I mean you don't need an anchor if you are using on a saillboat a chain from a ship. The sheer weight of it will provided the needed friction to keep the boat without dragging.

Just to put it straight a top 20kg anchor on a perfect sand bottom with the adequate scope (to have it pulled at the right angle) can hold between 1500 to 2000kg. How much weight you would have on a chain to equate that holding power?

Remember that the chain in the water weights less on account on that Arquimedes thing. You would need to have the better part of the load ability of a 40ft boat to carry enough chain for that and off course you could not have it all on the bow otherwise your boat would sail in a funny position.

And if you use ship chain it will be impossible to pull it aboard, if you used normal grade chain for a given size of sailboat your rode would be huge making anchoring impossible in any small bay and creating havoc with the neighbors on a "normal" rode.

It seems to me that one needs a good anchor, unless he has a fixed mooring set up and that limits the boat to a single anchorage.

[goboatingnow]

Originally Posted by colemj

With enough chain, one doesn't need an anchor. The whole point of anchoring is increasing friction higher than windage. The only reason an anchor is used is for convenience. It then becomes a matter of best balancing for the given boat/crew/handling equipment the size of the anchor with the size and length of the chain.

Mark

hmmm..... I don't think thats true at all. Hinz certainly doesn't agree.

dave

[goboatingnow]

Originally Posted by belizesailor

Another technique which addresses some of the issues above is two anchors in line on the same rode. One is connected to the head of the other. Dramatic increase in holding power and no dual rodes to worry about. If I am expecting a big blow I often use this set up.

Ive tried that once or twice, I find it so hard to set and retrieve that I don't rate it at all and confine it to the "anchoring theory". Better a bigger anchor me thinks.

Im also not sure that the forces distribute between the anchors correctly , resulting in one becoming a lazy anchor and not doing any useful work.


dave

[colemj]

Originally Posted by Polux

I don't understand if you are joking or really meant it. That is certainly true, I mean you don't need an anchor if you are using on a saillboat a chain from a ship. The sheer weight of it will provided the needed friction to keep the boat without dragging.

Just to put it straight a top 20kg anchor on a perfect sand bottom with the adequate scope (to have it pulled at the right angle) can hold between 1500 to 2000kg. How much weight you would have on a chain to equate that holding power?

Remember that the chain in the water weights less on account on that Arquimedes thing. You would need to have the better part of the load ability of a 40ft boat to carry enough chain for that and off course you could not have it all on the bow otherwise your boat would sail in a funny position.

And if you use ship chain it will be impossible to pull it aboard, if you used normal grade chain for a given size of sailboat your rode would be huge making anchoring impossible in any small bay and creating havoc with the neighbors on a "normal" rode.

It seems to me that one needs a good anchor, unless he has a fixed mooring set up and that limits the boat to a single anchorage.

No, I wasn't joking, and the rest of your post proved my point. Of course, using all chain and no anchor is not practical for all the reasons you mention. I could have equally made the point that no rode is necessary with a large enough anchor and a strong attachment of it to the boat. That isn't practical either.

My point was directed toward the seeming surprise that someone had good holding with a relatively small anchor and large chain. In other threads, surprise is shown regarding relatively large anchors and small chain. And everyone seems surprised when non-chain rodes are used.

Practically speaking, the answers lay somewhere in between those extreme (but equally valid) anchoring setups I mention. This is where the anchor wars are - the design of the anchor, the setting method, what is the best rode, etc.

And in defense of my examples, I regularly see unset anchors with boats being held in place perfectly fine (check out any charter anchorage in the BVI's) - in those calmer conditions, the chain is providing all the holding power necessary. It is a short conceptual leap to imagine an all-chain anchoring. But not a practical one. Likewise, a dead-weight mooring works very well, but not practical.

Mark

[tomfl]

Originally Posted by colemj

SNIP

And in defense of my examples, I regularly see unset anchors with boats being held in place perfectly fine (check out any charter anchorage in the BVI's) - in those calmer conditions, the chain is providing all the holding power necessary. It is a short conceptual leap to imagine an all-chain anchoring. But not a practical one. Likewise, a dead-weight mooring works very well, but not practical.

Mark

Those of us who dive our anchors on a regular basis have probably seen this. Unless there is some real wind or current the chain is seldom in a straight line. It is common to see the chain caught on a medium/small rock on the bottom. Even a five knot breeze would probably break it lose.

After enough of these small rocks or what ever the chain is using to increase the friction are disconnected the boat will finally be secured by the anchor.

[JPA Cate]

Originally Posted by JonJo

This seems in stark contrast to the Bigger is Better concensus. In fact almost contradictory, small anchor, for the size (windage) of yacht; (seriously) larger chain.

80m of 12mm chain deployed is 264kg, that's like an extra 3 reasonably fit crew. That really is a lot of chain.

And Ann and Andrew - again your joint suggestions seems to contradict the consensus - you are suggesting there is real merit in setting 2 anchors in a 'V'.

Jonathan

Jonathan,

I am not suggesting anyone at all use such a tiny anchor on a boat our size for its primary anchor. We brought it with us from our S&S 30 to our Insatiables (1 & 2)for a kedge. We use it as a stern anchor (pull is only in one direction) and in the abovementioned "V", and have used it off the stern to keep from swinging into a reef.

One of the benefits for the "V" for us is that we have little boat in the water and much windage forward, due to the two furlers, so the bow on our boat is likely to get blown around, and the "V" quiets that somewhat. If we have enough warning before a big blow, we have taken down the staysail (which we can deck-fold small enough to put belowdecks), and that eases the bow dancing, as well.

The way most cats seem to anchor, with a bridle to the hulls that goes to the chain, seems to make a "V" to me, as well, but it's upside down.

In the case above, of Ila Bay, we actually found a different bit of bottom with our Danforth. What I think that demonstrates is that even in one given anchorage, the bottom suitability for good holding may vary considerably. We sat out 50's there this year, in a different part of the bay, closer to where the stream comes in, on one hook (the Manson 60#), and all was well.

To me, it's just another facet of anchoring that in a known good anchorage you can still find bits of it that don't hold well. That's one reason we always set the hook carefully, in the hope that if we really pull hard on it, and the bottom's a bit weird, we find it out at the time we anchor, not by dragging later. I hope it continues so, I hate dragging.

Ann

[Pelagic]

Originally Posted by colemj

With enough chain, one doesn't need an anchor.
Mark

I think that is called "a self-fullfilling prophecy"

[belizesailor]

Originally Posted by tomfl

Those of us who dive our anchors on a regular basis have probably seen this. Unless there is some real wind or current the chain is seldom in a straight line. ....

Just "set" my chain today. Dropped anchor in about 25' onto nice fine clear sand bottom as a mild squall was passing so laid out chain in a wide arc as breeze shifted (Near Yansaldup, San Blas). Laid down about 200' of chain. Backed down to set and noticed boat was creeping a bit at 1500 RPM (that's about 40% throttle, +15-20 knot breeze, so I suspected loaded like 30 knots). Did not like that so dove to check it out....chain was "set" in a nice wide arc just below the sand...anchor was at the far end, not yet set (nor moved an inch from where I dropped it), with a small amount of very slack chain showing. So, it had not even loaded up the hook yet and chain only was holding fine in just the 15-20 knot breeze.

Returned to boat, backed down till the Bruce dissappeared in the sand...just a chain trail to nowhere...will sleep very well tonight.

[Neptune's Gear]

Hey Dave, nice bid. Ain't castle point great!!

Sent from my Nexus 7 using Cruisers Sailing Forum mobile app

[DavefromNZ]

Matt, pity you couldn't make it down south. Stewart Island and the fiords were certainly a trip of a lifetime! Cheers, Dave

[Neptune's Gear]

Yeah, maybe next time. How did the tricolor/anchor light work out for you?

Sent from my Nexus 7 using Cruisers Sailing Forum mobile app

[belizesailor]

Whole new definition of "active anchoring" recently. Several days of unsettled weather here in San Blas, no really strong winds, but from every direction. We've actively danced around in a nearly full circle a few times now.

[Atalantia]

Hello the people,
this is my first post. I don't have a boat yet but if I can effort once one it will be a Lagoon 620.
I'm always wondering about anchoring so I decide to jump in to discussion here. How do they make sure, that the boat doesn't move and finally crush on the rocks? I would sleep always on needles and jump up every 15 minute to be sure the boat didn't move towards the shore. Not to speak about going sightseeing on shore a leave my boat alone. Then I came to my landlubber conclusion:
I would always drill a whole into a rock unter water and dowel a ring hook into it. But as a meant before... I'm a landlubber only. So it is not really representative. But what you think about my newbe idea?