Anchors - Bigger is Better ?

[Andrew Troup]

[QUOTE=Panope;1179079]

Originally Posted by JonJo

...

JonJo, will you please direct me to a person article or post that claimed that their anchor dragged because it was to big. ....

Steve

I once resorted to a 30kg (66lb) Bruce on 16mm (5/8") chain to anchor a 7m (23'), 1850kg (4000lb) sailboat. I was unable to set the anchor well enough to get it to hold.

The circumstances were (as you might expect) unusual. I was anchoring in very shallow water in soupy/greasy mud* , to get inside a mooring field in front of a house I was minding for friends for a month.

*(principally loess falling out of suspension, redistributed from continual dredging of a shipping channel in the lee deposition zone of a massive foehn-plain, supplied in turn with glacier-ground greywacke rock dust by the most rapidly eroding mountain chain on the planet)

The boat's own anchor - which is normally entirely satisfactory under normal circumstances - was dragging at the rate of about 1.2 to 1.5m per 24 hours, when the winds got above about 25 knots

I took a road trip and got my big Bruce and chain out of storage, and set it as well as I was able: the 7m boat has a 1GM swinging a 16" prop, but in the shallow water (the boat has a swing keel, so I was in only about 2m of water at mid tide) I was stirring up the mud so much I was reluctant to apply full urge for the time it would take (saltwater cooled engine).

I tried laying the boat's own 7.5kg Bruce as a stern anchor in order to carry out a winch assisted set, but (as you'd expect) it didn't hold well enough to do the job properly. Even dragging that massive chain through the deep mud to straighen it out required almost as much resistance as the small anchor could muster, given the crappy bottom.

I kicked myself for not fetching my big Fortress out of storage to use in lieu of the baby Bruce, but I figured the sheer weight of the big Bruce and the considerable drag of the chain would effectively serve as a mooring, and I was going to be close at hand. (The front lawn of the house I was minding ran right down to the beach I was anchored in front of)

That anchor dragged for the next two weeks - at an imperceptible rate, over any 24 hour period, but the aggregate over that time was probably at least 3m (10').

At the end of that time, it still wasn't properly "Set" in the way it would have been with a decent, judicious pull or three from a big-enough boat.

I think there's possibly a moral here for people with big anchors and small (or no) engines.

I'm as sure as I can be that I would have done just fine in this situation with an intermediate sized anchor, one I could set properly.

(And to be fair, such an anchor would, by any normal standards, still be considered overkill for such a small boat)

[GordMay]

Originally Posted by Exile

What's the natural regeneration time of this purported damage to the seabed? A lifetime, 10 years, the day after tomorrow?

Ads little as 6 months for the quickest, to decades (or NEVER) for the slowest growing species.

* “... Sometimes the loss of seagrass can lead to irreversible changes in the nature of the environment and habitat, rendering the site no longer suitable for seagrass survival (e.g. West et al. 1990) ...”

➥ http://www.globalrestorationnetwork....bilitation.pdf

[Kettlewell]

Any relation to Bob Griffiths ?

Brain fart--of course the guy I was referring to was Bob Griffiths, not Maurice. Bob wrote Blue Water, the book I was referring to where he lists all the rather small anchors he uses. Maurice was the Magic of the Swatchways author and the editor of Yachting Monthly for years.

[Dockhead]

Originally Posted by Hydra

It seems to be proven that anchoring frequently in "Posidonia Oceanica" meadows ruins thems. See for example:
ScienceDirect.com - Journal of Experimental Marine Biology and Ecology - Boat anchoring on Posidonia oceanica beds in a marine protected area (Italy, western Mediterranean): effect of anchor types in different anchoring stages

Of course, this refers to anchorages where thousands of yachts drop anchor every day.

Alain

Maybe, but that's a specific Mediterranean type. We don't have it in yours or in our cruising area (actually it's the same cruising area -- La Manche ). Even if it's true, that frequent anchoring damages this specific plant Posidonia Oceanica, this may not be relevant to cruising areas outside of the Mediterranean.

[Dockhead]

Originally Posted by Bash

I share your curiosity about this. When I hear some of our bigger-is-better members talking about backing down at full throttle for 30 seconds to set an anchor, I wonder what makes them feel this is necessary. On my just-right anchor I back down just enough to straighten the chain and take out the catenary. That's nowhere near full throttle! All I'm trying to do at that point is make certain the anchor sets. Then the wind can do the rest of the work diggin it in, as necessary. I've never yet dragged using this technique with my just-right Rocna, and every once in a while it sets so deep that the windlass struggles to break it out. (In those situations, as I mentioned before, I generally prefer to use the engine to break the anchor out.)

Well, first of all, you never know for sure really, do you, how well your anchor is set unless you dive on it. So why wouldn't you use everything you've got? Can't hurt anything.

Second, why wouldn't you test the holding of your anchor with as much force as you have? The wind force equivalency of full throttle in reverse will be different with different boats (different horsepower, different props, different windage), but I doubt that many sailboats can generate more force in reverse than would be provided by a 30 knot, say, wind. I would do it just out of principle (and do do it). If your anchor won't hold at full throttle reverse, then you shouldn't by lying to it.

Last good reason to do it is that it is good for your engine to run it hard at full throttle and preferably near redline, for a few minutes at least every few hours (unless it smokes under those conditions; in which case back off until the exhaust is clear-ish, and make a note to yourself to have your prop cleaned and/or repitched). Running it hard like that while setting your anchor blows out the cobwebs, helps to keep the rings seated, and helps to get rid of carbon buildup from futzing around at low RPM. If you have a turbo, then be sure to let that cool down before shutdown (but you know that).

[GordMay]

Originally Posted by Dockhead

... The wind force equivalency of full throttle in reverse will be different with different boats (different horsepower, different props, different windage), but I doubt that many sailboats can generate more force in reverse than would be provided by a 30 knot, say, wind ...

Indeed.

[Kettlewell]

I prefer to give the anchor the bounce test. As I lower the anchor and let out chain as the boat drifts back with the wind I snub it periodically along the way, in order to nudge the anchor into the correct orientation and begin the process of digging it in. Once at the proper scope and with the snubber hooked up I I give it a burst of throttle and then ease off and let the momentum of the boat test the anchor. If you feel a good solid jerk you know it is set. If you are uncertain after one bounce, try again. Too much powering in reverse stirs up the bottom and I don't like to suck up all that mud, at least in the shallow anchorages I like to frequent.

[Hydra]

I believe this is just plain old bull poop!!! I wish the weeds in my front lawn were as fragile as the whackies claim ocean bottom is.

This is the mooring north of Hugh Town in St Mary (Isles of Scilly). It's perfectly clear that the friction of chain on the bottom has removed all weeds around each mooring block.

Alain

[DumnMad]

Its only perfectly clear to me if you provide a similar shot from before the moorings were placed. The field of larger moorings has more sand inshore of it and seaward of it. For all I know the moorings may have stimulated growth in the area.

[JonJo]

This one came across my screen, and for Cotemar's benefit, I'm still independent, I do not work for Manson nor any other anchor maker - no matter what you are encouraged to post.

Noelex,

This is a 15kg anchor withstanding a load of 4,200kg. Can you explain why this anchor will drag when holding a, say, 45' yacht and/or why anyone would want to buy a 25kg version of the same anchor to hold the same yacht.


In Seabed Test, Manson Boss Anchor
Sets Faster With More Holding Power
35lb Boss holds 4200kg, bends 5/8” shackles
HENDERSON, NEW ZEALAND – Manson Anchors recently completed seabed testing on its Boss anchor, producing results that even surprised the company’s testing team.
A 35lb Boss 2 held 4200kg (9260lbs) - and bent 5/8” shackles in the process.
Testing began with 40ft of 5/16 chain and 3/8 shackles and a scope of 5:1 using a 90 ton tug boat. “We pulled up to 2000kg (4500lb) but bent all the shackles. We returned to the dock, went to a chandlery and bought 5/8 shackles and 60ft of half inch chain. Back out testing on the tug again, and pulling on the 35lb Manson Boss. This time testing had to stop at 4200kg (9250lb) because the 5/8 shackles were all bending,” said Ned Wood, Manson Vice President of Sales and Marketing.

[Kettlewell]

I mentioned this before in another thread--Manson needs to get some of those Crosby high-test shackles.

[robert sailor]

Marketing hype, oh my god we are bending shackles! Lousy shackles I'd say.

[Kettlewell]

I saw an interesting marketing tactic today. Stickers on some shackles I was looking at covered most of the wording except for the "C" at what I assumed was the beginning of the name Crosby, which is seen on their very good quality shackles. However, upon peeling back the label I see the word is instead "CHINA" using the same font as the CROSBY shackles do. Even the size and the working load looked almost the same as on the Crosby ones.

[barnakiel]

Originally Posted by DumnMad

Its only perfectly clear to me if you provide a similar shot from before the moorings were placed. The field of larger moorings has more sand inshore of it and seaward of it. For all I know the moorings may have stimulated growth in the area.

And if you drive your tractor on your lawn, what do you get?

I think if the chains do not touch the bottom, you could be right. But it is very tidal there (I believe) and so part of the tide the chains may be sweeping the bottom killing all and sea life.

Moorings can do more or less damage than anchors, all depends on how and where they are employed.

Mooring blocks (if they are blocks), attract all sorts of sea life indeed.

b.

[sabray]

The market guys are not that smart. China however has flooded us with garbage products.Shackles being one of them.