Anchors - Bigger is Better ?

[Dennis.G]

Originally Posted by Andrew Troup

... I fall in the camp where "two sizes too big" is not big enough...

I guess this was you shopping for your next anchor?

[downunder]

Originally Posted by estarzinger

.................................................. .................................................. ..................................

I have recently been wondering if a screw anchor (as is now often used in moorings) could be useful. They are not that hard to set, especially with dive gear or in shallow water. And are really and truly secure when properly set. And would not be that hard to stow and easier to unstow than a huge BIB anchor.

Interesting concept particually if you have diving gear on board. Apparently is what they use for moorings in the Whitsunday Islands, here.

[Andrew Troup]

Originally Posted by Dennis.G

I guess this was you shopping for your next anchor?

No, I'm a Bruce man....

Rather than have the agonising process of 'outing' me prolonged by leaking photos, I decided to make a voluntary disclosure my new BiB anchor prior to galvanising, and my vfBiB chain being delivered

[Snowpetrel]

Originally Posted by Andrew Troup

Rather than have the agonising process of 'outing' me prolonged by leaking photos, I decided to make a voluntary disclosure my new BiB anchor prior to galvanising, and my vfBiB chain being delivered

I see.. Very cunning, Andrews patented anchor centreboard. I dreamed up a boat like that as a kid. It had a big ships style dreadnought anchor that slotted into the keel. It was after sitting out a nasty blow. And bending our danforth yet again...
You have improved on my idea with a winged keel, I knew there had to be a reason for an anchor that shape.

[Andrew Troup]

Originally Posted by Snowpetrel

I see.. Very cunning, Andrews patented anchor centreboard. I dreamed up a boat like that as a kid. It had a big ships style dreadnought anchor that slotted into the keel. It was after sitting out a nasty blow. And bending our danforth yet again...
You have improved on my idea with a winged keel, I knew there had to be a reason for an anchor that shape.

Mmm - some keel... Given it weights 6850kg, I'd have to shave the rest of the boat down to about 400kg to meet my target weight. I think the motion might be a bit cranky, with a 95% ballast ratio....

I couldn't even get the keel case down to 400kg for a lifting keel that big!

Not a train of thought with absolutely no destination, though. Given the right valving, there are those who have found a hydraulic lifting keel can be used in some circumstances to supplement or even replace the anchor.

At least if you don't mind being called a 'stick-in-the-mud' ! (Certainly solves any problems of 'sailing about' at anchor)

[nigel1]

Originally Posted by Andrew Troup

No, I'm a Bruce man....

Rather than have the agonising process of 'outing' me prolonged by leaking photos, I decided to make a voluntary disclosure my new BiB anchor prior to galvanising, and my vfBiB chain being delivered

The Bruce anchor in the picture is for use as a "piggy back" anchor, used by rigs in poor holding conditions. It is connected to the main anchor via 100 to 200m of wire/chain.
In the background you can see the main anchor, which is a Vryhof Stevpris in its dismantled state. The flukes are behind the Bruce in the foreground and the shank is over to the right in the picture.

[Andrew Troup]

Thanks for that, Nigel. Great information. Any chance of a description of how the anchor is connected (does the main anchor have a competely separate chain? Where does the piggyback anchor connect in the system, and how are the two anchors set?)

On the face of it, the photo appears to refute a couple of points made by the people who (ironically enough) posted that photo, designers and promoters of a rival anchor (and in the case of one point, by the designer of another competing anchor as well)

See here, relating to the question of whether our anchors bear any resemblance to oil rig anchors:
http://www.cruisersforum.com/forums/...tml#post127834

further up the page, he contradicts the other point from nigel1's post when he writes

<<That the Bruce was designed for tandem rigging is nonsense. .... The angles of force transfer are critical, and had Bruce intended for this technique, a dedicated attachment point would certainly have been provided as with the (dot dot dot) >>

This point is made on their own website, with similar force but more self-servingly:

<<Anchors which cannot have tandems attached directly to them include the CQR, Bruce, Delta, Spade, and Danforth types.
The only anchor which has a tandem attachment point, designed and tested specifically for this purpose, is the (dot dot dot)>>

The designer of the other anchor can be seen here:
http://forum.ssca.org/viewtopic.php?f=4&t=253&start=60
saying
<<Sorry Gmac if I have to correct you This is one of the old beliefs that are not true..

The Bruce anchor we know on the bow roller of our yachts, has only one common point with the Bruce's anchors used for oil rigs.. the name of the designer: Peter Bruce, but the Bruce anchors used for oil rigs are completely different models.. (see the photo below.) >>


I'm not carrying out a jihad or vendetta here, I just thought it was worth making this point: we have to beware of the power such people have already demonstrated, to reshape conventional wisdom on the topic of anchoring.

These people are essentially sailors like us, except more enterprising than most, who happen to have got disillusioned enough with what's on offer and done some testing and designed successful anchors (rightly successful, in both cases) but that does not actually mean they have comprehensive access to knowledge which is denied to us.


A great many sacred cows have been deflated in recent years to do with anchoring, and, undoubtedly some needed to be.

However I believe it's important to fully understand the deepest thrusts and most delicate nuances of conventional wisdom before discarding it, and I think that, by and large, the anchor testing and anchor designing communities (which overlap) have not tended to do that.

I realise they would dispute this energetically and convincingly, so I offered a couple of examples above of claims which could easily have been verified, and would have been, by people with truly inquiring and open minds, but were instead mistakenly inferred, using faulty logic or wishful thinking, and then asserted authoritatively.

It doesn't mean their anchors don't work (they do !) but to me it suggests that their wider claims about anchoring practice should not be taken on faith, based solely on the reputation of their anchors.

[nigel1]

For a basic introduction into anchors used on rigs, the Vryhof Manual is available on line
http://www.vryhof.com/anchor_manual.pdf
Good section on anchor theory in the first part.
For an explanation on piggy backing anchors, see page 87.
It used to be that the secondary anchor was buoyed off, and the buoy pennant used to recover the anchors when the time came. However, with a number of incidents involving ships ignoring nav warnings and radio calls, and running over the buoys, todays practice is to lay the pennant wire on the seabed, and to recover using a grapnel.

[Snowpetrel]

Originally Posted by nigel1

For a basic introduction into anchors used on rigs, the Vryhof Manual is available on line
http://www.vryhof.com/anchor_manual.pdf
Good section on anchor theory in the first part.
For an explanation on piggy backing anchors, see page 87.

Very very interesting anchor manual, thanks Nigel.

Some bookmarks I found interesting:

Pg 17 Danforth types rated at 8-15 as opposed to bruce anchors 17-25. probably a cast danforth with poor weight/area ratio?

Pg 27 and Pg 50 fig 2-07 effect of chain on holding in soft mud and the reverse catenary making 3:1 scope efficient.

Pg 31 rule of thumb for bottom types

Pg 33 fig 2-11 great diagram of fluke angle and depth of set

Pg 41 set up (settling) increasing anchor holding by up to 1.5x

Pg 42 sudden shocks vs steady pull, Sudden jerks can take 1.1-1.3 more load.

Pg 47 anchor test curves what they mean

Pg 90 VLA anchors, are these the ultimate hurricane anchor. maybe stash a big aluminium one flat in the V berth.

Pg 125-126 Concave vs convex anchors see graph on pg 186 as well. the mk 6 is convex and seems to have more surface area from the dimensions?

Pg 186 the convex mk 6 has much better holding than the concave mk5. without surface area comparison this doesnt mean much but it is interesting anyway.

[Kettlewell]

Pg 17 Danforth types rated at 8-15 as opposed to bruce anchors 17-25. probably a cast danforth with poor weight/area ratio?

I have no idea where they got those numbers from, but they certainly don't correlate to what we see in yacht anchoring tests, where holding is up in the 45-50 range on the better anchors (more in sand). Some old tests I have put both the Bruce and the CQR right around 20-25, and I think that may be about right.

[Sabbatical II]

In buying anchors for my new boat 8 months ago, I chose to follow what some old salts on CF were doing. (Thanks Evans). How did it work out? Well recommended size for my 42' boat was about 25kg depending on which chart you read. So my #2 anchor is a 25 kg Rocna. It has yet to be used. My #1 is a Manson Ray which seems to be styled on the Bruce anchor and is 2 sizes to big at 40kg. One of its main advantages is that it sits neatly under my bow roller and doesn'y look as ungainly as the roll bar anchors on the bow. It has never failed to set first go and it has never dragged an inch. I use it at 3:1 in a crowded anchorage but prefer 5:1 and will put more chain out if there's swing room because I can see it's much use in the locker. I have tried it at 1.5:1 in light winds over lunch one day just to see if it would hold and it did. I can see many advantages and few drawbacks of having a heavy anchor.

[foggysail]

Originally Posted by JonJo

I think Manson would be most upset if you had not found that a 60lb Supreme was better than a 45lb Delta. Your experience is typical, upgrade from an HHP anchor to a SHHP anchor (of larger size than the HHP anchor). I'm not surprised you are happy, you are comparing Quince with a Granny Smith What would be interesting would be someone who upgraded from a Delta to a slightly smaller Supreme (in line with HHP and SHHP differences), found the smaller Supreme still wanting and then upgraded to the larger Supreme which then was found adequate. This si not to suggest a smaller Supreme might not work - its the principal to which I refer, the Supreme is just the example quoted.

Jonathan

Well of course Jonathan. But and I always seem to see buts. I went the Delta path, from a 55 to an 88#. Neither anchor would hold my 40" Silverton. But back to the buts---the 80# Manson that I purchased to replace the Deltas always seemed to get a death grip on the ocean floor.

[JonJo]

Lots of information seems to be turning up.

Sabbatical - one of the conflicts in the posts is that the BIB premise is based on what we are loosely calling 'new gen' anchors. My definition of 'new gen' covers SHHP rated anchors and those that appear from a variety of tests to be roughly equal to the SHHP models, Kettlewell produced a list with which I concur, Spade, Fortress, Rocna, Supreme, Excel SARCA, and I'm guessing Boss and Mantus will join the ranks. Anchors like Bruce, Bugel, Delta, CQR have about half the holding capacity (and commonly take longer to set). These are 'sweeping' sentences - I'm just setting the scene.

The BIB question arises as we now have better anchors, but despite their being better (and Evan would dispute that, and I have no problem - its his anchor, his yacht) we find people are buying anchors 2 sizes bigger than the size recommended for the older style. I can see why people might buy a Bruce 2 sizes bigger, it probably makes it about equal with a modern new gen anchor of the 'right' size. So the fact you have success with a Bruce 2 sizes bigger and Evan has the same experience - does not to me support BIB - it just means you gone bigger because that anchor is only half as good as say a Rocna or Spade. Again a sweeping statement - I'm simply extrapolating what your, and Evan's, experience is to a wider cross section of yachtsmen/women and generalising that most people find a Spade, say, better than a Bruce.

So the BIB is really focussed toward new gen anchors.

One of the central themes of small is more than adequate is that the few adherents all mention, I think without fail, that they all carry a quite large armoury of anchors and are prepared to deploy at least one of them (in addition to the primary anchor) whenever necessary. The armoury usually is of similar sized anchors, often of different styles, and commonly (always?) includes a Fortress. One advantage of this policy is that in the event one loses an anchor (or it needs abandoned for later retrieval) there is a second anchor, as good as the one currently unavailable, which can be deployed immediately. The select members of this cabal are aufait with use of second anchors and though losing an anchor is a major upset the deployment of the second anchor is second nature.

Its does not come through for the adherents to BIB, or the little that comes through is that second anchors are very much an afterthought. So for the BIB, what do you do if you lose an anchor? Where do you keep your second anchor how do you physically manage it? Or is experience such that it is simply not needed?

I ask as being stuck in Labrador, or Patagonia with you anchor wedged in a rock at 2 am and you must move and your second anchor (do you have one?) weighs 40kg and having deployed the second anchor - do you have a 3rd? that will allow you to continue your cruise in the same comfort and relaxed style as previous.

Jonathan

[Andrew Troup]

Originally Posted by nigel1

...the Vryhof Manual is available on line
http://www.vryhof.com/anchor_manual.pdf
Good section on anchor theory in the first part.
For an explanation on piggy backing anchors, see page 87.
...

Thanks a LOT for that, Nigel, you're a champ !
It's very interesting to learn how our big cousins make their living on the deep briny....

And intriguing to speculate whether and how the various underlying concepts scale to our practice.

For instance, it's instructive and thought provoking to learn a bit about piggybacking, and compare it with tandem anchoring at our scale.

I was off-beam, it seems, inferring that the 6350kg Bruce in the foreground was rigged as the main anchor, perhaps to piggyback behind the other (orange) Bruce immediately beside it.

I led my thoughts in that direction by assuming that the heavy chain shackled to the crown of the main anchor would be led to the shank end of the secondary anchor.

What do you infer to be the purpose of using a chain of that calibre for a pendant / tripping line? Would it become wire further up, and if so, it this common practice?

Sorry about all the questions. I've got dozens more, but I'm not going to trespass further on your goodwill. (Not yet, anyway ;-)

[nigel1]

Originally Posted by Andrew Troup

I was off-beam, it seems, inferring that the 6350kg Bruce in the foreground was rigged as the main anchor, perhaps to piggyback behind the other (orange) Bruce immediately beside it.


What do you infer to be the purpose of using a chain of that calibre for a pendant / tripping line? Would it become wire further up, and if so, it this common practice?

Sorry about all the questions. I've got dozens more, but I'm not going to trespass further on your goodwill. (Not yet, anyway ;-)

The Bruce anchors in your picture are rigged to be used as secondary's to the main Stevpris anchors.

for the chain fitted at the anchor crown. It is commonly known as a thrash chain. When the anchors are close to the anchor handlers stern roller, the pennant wire is more likely to move laterally across the roller, and also to higher loads. The chain reduces wear on the pennant (tripping line).