Anchor design and misnomers

[estarzinger]

Originally Posted by JonJo

possibly you need a new lifestyle. It happens.

Possibly . . . Or to learn to anchor as well as you and K.

Well I am untieing from the dock on Sunday, so I guess I will have to wait until the fall to get my anchoring lessons from you two. But the tip about backing on the anchor was really useful. I had never thought of that before.

[JonJo]

Originally Posted by estarzinger

Possibly . . . Or to learn to anchor as well as you and K.

Well I am untieing from the dock on Sunday, so I guess I will have to wait until the fall to get my anchoring lessons from you two. But the tip about backing on the anchor was really useful. I had never thought of that before.

Sarcasm does not become you!

I'm not an expert, which is why, when we are twitchy, I have a second anchor sitting ready for immediate deployment! its 'as good' as the anchor on the bow roller - but a different design.

[Kettlewell]

Well I am untieing from the dock on Sunday

Fair winds! Check out what those trawlers up in Greenland and Iceland are using for anchors and let us know.

[JonJo]

This is a bit of thread drift, back to BIB, but everyone seems to have migrated here.

Evan - you are implying that you find your choice of anchor can, in specific anchorages, be 'iffy'. I think you have also said that you prefer the Bruce to a Rocna, for good reasons. I suspect most anchors have a weakness in specific seabed (and prudently one should make the assumption they will have a weakness).

The 'small is adequate' minority, in smaller medium sized yachts, can manouvre their anchors around, I can change anchor on the bow roller within about 5 minutes single handed - what do the BIB majority do? Their anchors can be 40kg, instead of 25kg - a nightmare to manhandle, none actually seem to carry a second anchor.

So what happens when, in the scenario you paint, their main anchor (only anchor?) is not adequate - ie in the location where your Rocna proved a danger to you and itself?

Jonathan

[Andrew Troup]

Evans, you don't have an irony deficiency, do you!

(I think JonJo has a rare talent to needle, which he seems to save mainly for you: you don't seem particularly prone to online exasperation, but there are limits!)

Well, to answer your very pertinent and probing question: I'd take anchor B in a heartbeat, even if anchor R in good holding provided 4000kg or 8000kg, and all the other figures remained as quoted.

(largely for the reasons Evans gave, and because difficult bottoms are endemic in some very attractive cruising territories)

and if necessary I'd upgrade to a bigger size, so that B in bad holding bottoms would provide enough holding power for my boat.

Enough is enough*: if you never pull at 2000kg, you never need 2000kg. I don't see any advantage to anchor R, and am puzzled why anyone would in the stated scenario, because it seems to me anchor B behaves as an ideal anchor, whereas anchor R is a show pony.

*(contrary to the currently increasing tendency, since maybe 1980ish, to consider that too much is NEVER enough...)

.... And how hard you pull has nothing to do with the quality of the bottom.


But if the 'upgrade' decision meant my anchor B would have to be too big and heavy to be practical for anything but extraordinary circumstances, I'd relegate it to storm anchor status, try to reengineer it to be collapsible/telescopic/whatever, and possibly stow it in a scabbard/anchor well near the mast, for hoisting on a halyard and deploying and retrieval amidships in those extraordinary circumstances: ie when I couldn't get a satisfactory set on the main anchor.

Or when conditions were expected to deteriorate beyond what that anchor might be expected to endure.
　
I don't want to have to try to stagger towards the bow with such a weapon, and I don't want that weight stowed anywhere far from the CoM
　
- - - -

The last question Evans asks (How often do you want to pull another anchor out):

I think that depends greatly on how big your boat is (and consequently, the anchors) - a point made by someone recently on this very forum -- with a notional flipover of 40', above which the attractions of changing anchor rapidly diminish, which seems to me about right.

(I'm assuming for the purpose of this discussion that we're talking anchors of a size and weight which makes it unrealistic to carry more than one on the bow. I realise that's not everyone's view, but for me I would not want any of the sorts of boat I can think of which would not have a problem with that.)

OK: a big strong crew could push this flipover point towards a bigger boat (or more specifically, bigger anchors), and a feeble crew perhaps settle for a "one anchor to rule them all" policy, even on a smaller boat.

To illustrate the former by giving an extreme instance: My first ocean passage was on a boat with no concessions to anchoring: no bow roller or chock, no windlass, no spurling or navel pipe, no chain locker, nothing.

The main anchor was a big (110 or 130lb?) CQR, with 30m of 16mm chain. And, coincidentally, the boat had a 30m rig, with all the windage that entails.

But because there were fourteen crew, only one of whom was feeble (she turned two en route) and the skipper was a genius and highly experienced seaman, we were successfully able to anchor in the most god-awful situations, with no damage to the boat or to us.

[JonJo]

Snowpetrel,

Again I thought it was in the Vryhof manual, I have an older version, they do mention chain, wire and Dyneema.

All anchors reach a maximum diving depth for a given seabed. The ability of an anchor to dive is 'retarded' by the rode, chain being the worst culprit. But any anchor has need to drag down whatever the rode is and as the anchor gets deeper the rode, obviously gets longer and imposes increased resistance. Because chain imposes the higher resistance the oil industry went to cable and in some cases Dyneema.

Bigger anchors can pull chain down further, they have more diving power.

This is one reason why a, very, small anchor cannot be used to anchor a large vessel it simply does not have the 'power', diving ability to pull the chain down

Whether the size of chain has that much impact on 'our' anchors I do not know but one would certainly think a 12mm chain would have a quite considerable impact compared with an 8mm chain. None of this matters for an anchor that does not dive and probably not in the top few inches of seabed as it is commonly soft - the impact would be felt as the anchor dives into the denser lower levels.

It is in the denser lower levels that the roll bar, very important to right the anchor initially, becomes a further impediment to diving. It is simply another obstruction along with the chain that the anchor needs pull down. Reinforcing Evan's anchor choice - if a Bruce is in an environment, or is big enough (whatever it takes) then it is simply fluke and shank and should develop good holding (though whether the more vertical component of the fluke adds to holding, I'm not sure).

Jonathan

[JonJo]

I recall now the use of wire came up somewhere earlier.

It was posted that an anchor maker(?) supplied their anchor with a wire strop (was it Danforth?) to be used between chain and anchor. I'm guessing the wire was to reduce resistance to dragging. I think wire might have lost favour as an anchor maker would not desire responsibility for a wear component that possibly needs regular replacement?

Jonathan

[Snowpetrel]

The bruce anchor group site shows a clear small advantage to the wire leaders on its anchor holding graphs in soft mud. It would be interesting to know what the lifespan of wire rigged like this would be? Another idea would be to use a short high tensile leader a size down for the part between the anchor and the windlass. If like me you cant justify the cost of all high tensile chain.

[Andrew Troup]

JonJo, it was Danforth, IIRC.


SnowP: I can see the attraction, because wire in small sizes feels wrong to me, particularly if there's any chance of abrasion or sharp rocks ....

It seems to me even for chain, that the advantage might need to be more than slight, to make it worth introducing extra failure points. (like Small shackles)

You've got me thinking though, because I had toyed with the idea of a length of BIGGER chain between my windlass and bow... to further improve the hold when the boat's moving around and the bottom is rocky.

(For two reasons: rocky bottoms are the last place you want the shank oscillating sideways, and rocky bottoms provide a LOT of friction in combo with heavy bottom chains.)

But I have to confess that until your question, it hadn't fully sunk in that there might be a price to be paid when trying to get deep digging in soft holding...


Hmmm ... given that the weakest bottom for a Bruce (and I'm putting kelp to one side because it's not strictly a 'bottom'...) is greasy mud: in that case I don't think a heavy chain is disadvantageous, and may improve the prospects of setting, if the mud's deep... I'm not ruling it out.

As a rule, it seems to me that anyone intending to use one anchor for most of their anchoring, really ought to prioritise attending to the worst-case scenarios (ie lowest numerical holding power) for the chosen anchor, and find ways to mitigate those, rather than increase the holding power in bottoms where that particular anchor has a natural tendency to hold fairly well.

[Andrew Troup]

Originally Posted by JonJo

...
The 'small is adequate' minority, in smaller medium sized yachts, can manouvre their anchors around, I can change anchor on the bow roller within about 5 minutes single handed - what do the BIB majority do? Their anchors can be 40kg, instead of 25kg - a nightmare to manhandle, none actually seem to carry a second anchor.

So what happens when, in the scenario you paint, their main anchor (only anchor?) is not adequate....?

Jonathan

At least on a monohull, the anchor does not need to go over the bow; it's only the chain which needs to.

On big boats whose anchor of last resort is a big Luke or other fisherman-style storm pick, often weighing as much as a man, one method is to lift it over the side, on a halyard, at the chainplates. The snapshackle can be 'spiked' when the anchor is in the water. A retrieval line (ideally rigged as shown in a recent post by Jackdale, with a toggle at the inboard end of the pendant which can simply be poked through the chain when the anchor is launched) can be used to retrieve it back to the same location.

Such anchors are traditionally stored on deck or lashed to the mast, but a folding one (like the Nicolson Belfast) can be stowed in a compact vertical well, so the weight is lower, and the process is safer. Kind of like a scabbard with a sealing hatch.

Probably something you'd only see on a metal boat, where such things can more easily be arranged with the necessary strength.

[JonJo]

Thanks Andrew,

I was also thinking along the lines of Evan's experience when he found his Rocna less than satisfactory (or any other anchor so not appearing too critical of Rocna).

So if one has gone BIB and has a Bruce, Rocna, Delta

Do you anticipate a potential weakness in some substrates (not substrates that a Luke would be used in) or do you just cross your fingers?

And if you carry a second anchor (as big as the first, not the Luke) where do you store it.

I'm thinking that if you believe in BIB then any second anchor will be the same 'size' - so halyard deployment seems the only option but storing it must be an issue. When I asked the question on the BIB thread no-one responded which left me thinking maybe they just cross their fingers.

Storing on most multihulls is much simpler - commonly they have a bow locker under the mast, so central and on deck.


As an aside, there is another ocean race due to leave the UK this summer, Clipper Ocean Challenge (I think that's the name). 15 identical 70' yachts. They will be using 40kg Deltas + over 60kg of chain and lots of octaplait, stored below. Part of their training programme is how to deploy them, and they use a halyard (they also have big crews).

[Andrew Troup]

Hmmm...

re JonJo's << Do you anticipate a potential weakness in some substrates (not substrates that a Luke would be used in) or do you just cross your fingers? >>


I know this was not aimed particularly at anyone, but it's an interesting and highly pertinent question. Here's my take on that...

I do anticipate a potential weakness (apart from, as you say, Big Pick bottoms) - and for me, the one which for me is currently "top of mind" and applies to all anchors, would be that old chestnut: a thin stratum of sand or mud (or crushed coral) over a hard layer - too hard even for a Big Pick.

It seems to me that the single big anchor fails here: as I think I posted elsewhere: much of the fluke area will be standing above the sea floor. Hard to get much grip on seawater...

There are two stratagems I have thought about: the first relies on multiple smaller anchors, which can pile up enough of a mound to each give a half-decent contribution to holding the boat. If it needed four anchors, I'd set two tandems in V formation (tandems are notorious for being hard to get both anchors set in general, but in this type of bottom, probably relatively straightforward)

The second is pretty wacky, but it has occurred to me that (if the ecological impacts were modest, and time was not of the essence) one could theoretically dredge up a quite decent pile of bottom material with an improvised bucket (like a scallop dredge lined with locker lids?)

That's pretty fanciful, though.... more practicably, one could go diving (no flippers, strong bootees, and lots of weight on the belt) with a shovel. Weighted boots would be ideal - possibly one could improvise by strapping a dive weight under each arch?.

Any boat which sails in high latitudes will probably have a big snowshovel, and these work fine underwater, although the popular plastic ones, great on deck, might be annoyingly buoyant...

Then it's simply a matter of dragging the Single Big Anchor into the middle of the heap. But it would want to be a pretty decent heap...

Of course this would only be doable if you were not arriving later in the day, and not worthwhile unless you planned to spend quite a while.

And it would be only right and proper, on leaving, to put the bottom back as you found it.

The other specific bottom condition I dread is gloopy mud. It's a real weakness for a Bruce, in my experience.

Once again, I'd be inclined to use a multiple anchor rig, in this case preferably Fortress type, set to the mud angle, with the optional large deflectors fitted.


I've only got one Fortress, so that's something I'll be looking to rectify for long trips (for short trips, people often lend or borrow these, in this part of the world)

If I can't afford them, (unavoidable greasy gloop not being that common, in my experience) I'd knock up a few Danforth clones out of steel.

[downunder]

Originally Posted by Andrew Troup

Hmmm...

re JonJo's << Do you anticipate a potential weakness in some substrates (not substrates that a Luke would be used in) or do you just cross your fingers? >>


I know this was not aimed particularly at anyone, but it's an interesting and highly pertinent question. Here's my take on that...

,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,,,,,,,,,,,,,,,,,,,,,,,,,,,,

The second is pretty wacky, but it has occurred to me that (if the ecological impacts were modest, and time was not of the essence) one could theoretically dredge up a quite decent pile of bottom material with an improvised bucket (like a scallop dredge lined with locker lids?)

That's pretty fanciful, though.... more practicably, one could go diving (no flippers, strong bootees, and lots of weight on the belt) with a shovel. Weighted boots would be ideal - possibly one could improvise by strapping a dive weight under each arch?.

Any boat which sails in high latitudes will probably have a big snowshovel, and these work fine underwater, although the popular plastic ones, great on deck, might be annoyingly buoyant...

Then it's simply a matter of dragging the Single Big Anchor into the middle of the heap. But it would want to be a pretty decent heap...

Of course this would only be doable if you were not arriving later in the day, and not worthwhile unless you planned to spend quite a while.

And it would be only right and proper, on leaving, to put the bottom back as you found it.

The other specific bottom condition I dread is gloopy mud. It's a real weakness for a Bruce, in my experience.

Once again, I'd be inclined to use a multiple anchor rig, in this case preferably Fortress type, set to the mud angle, with the optional large deflectors fitted.


I've only got one Fortress, so that's something I'll be looking to rectify for long trips (for short trips, people often lend or borrow these, in this part of the world)

If I can't afford them, (unavoidable greasy gloop not being that common, in my experience) I'd knock up a few Danforth clones out of steel.

I just imagining you underwater digging up a big heap of bottom.
Know anybody thats tried it.

[Snowpetrel]

You might be pondering this a little more than needed Andrew. We used a CQR +shorelines in the beagle with a 100% sucess rate. In antarctica the old BIB CQR also worked Ok. It wasn't great in many spots but it worked, and if you were singlehanded you would be better to stay in the areas with good shore moorings and natural ice barriers anyway. I would never leave a boat alone for long with ice dangers. I Think your BIB bruce will do fine without resorting to underwater shovels. If not anchor someplace else.

[Andrew Troup]

Downunder

Sure thing, but not in this precise context.

I first struck the general idea a long time ago when a Nth Islander got washed over a river bar which wasn't as deep as the chart said (having touched coming up towards high tide - yikes!), he got pushed over sideways, long keel dragging, but of course it was too shallow to get back out when the boat was upright)

So he dug himself a trench, with a bunch of helpers. Of course, they did as much as they could at low tide, but coming up to high, he had a mate put on dive gear and clear it back out ('cause the trench filled up with loose stuff quite quickly, but it wasn't so hard to move). I think the guy was said to have wrapped a length of chain around each shin.