Bigger is better, part 2

[JonJo]

[QUOTE=Blue Crab;1509050]

Originally Posted by JonJo

Even a DoubleWhisky?

Very Droll

And we only do SingleMaltWhisky - no ice

Jonathan

[Andrew Troup]

Originally Posted by noelex 77

I think this is generally true.

The ability to use many extra anchorages, or anchor locations which may otherwise be unsuitable because of poor holding, or the requirement to anchor on a short scope, is one of the underrated advantages of the BIB philosophy.

Occasionally this is convenience. The shorter distance you have to carry heavy items like gas bottles the better. More often it is about other factors such as aesthetics. Some of the most beautiful anchorages have been judged as unsuitable, or at least too dangerous to use overnight.

A good quality BIB anchor opens up the possibility of using these anchorage locations with a degree of safety.

There is nothing nicer than watching the sun go down in an anchorage that you now have by yourself because all the other boats have left in the afternoon because the holding was deemed inadequate for overnight anchoring.

It's a well recognised syndrome: the cruiser who spends the first half of their cruising lifetime religiously choosing anchorages from the cruising guide, often spends the second half studiously avoiding said anchorages.

Curmudgeonhood comes to us all, given sufficient time ...

[Blue Crab]

This thread may have tipped the scale, anchorwise, for me:

I have a new, never-been-wet-yet, Rocna 10 for my need-to-raise-the waterline 8500# vessel. However, using it is fast approaching. Perhaps I should trade up to the 15kg. The factory rep said the 10 was enough but what is enough?

I used to be indecisive, now I'm not so sure. Yesterday I was going to drop it into the mud and end this winter of discontent. Today, not so much.

Help me mighty Neptune! Help me mighty Poseidon! Some of youse lesser gods too!

[cfarrar]

so why do we not see more (people using G7 chain)?

One reason is that G7 lashing chain probably won't fit your gypsy (in the U.S.). Then there's the cost.

By the way, there was interesting, recent article in Practical Sailor about how smaller diameter chain allows the anchor to penetrate deeper....

[Pelagic]

Originally Posted by cfarrar

By the way, there was interesting, recent article in Practical Sailor about how smaller diameter chain allows the anchor to penetrate deeper....

Hmmmn! .... That's a new line I have to try.

[cfarrar]

Hmmmn! .... That's a new line I have to try.

I also thought this strange at first. However, it turns out that as the anchor fluke is setting into the bottom, the tip of the shack (where your shackle attaches) is also pulled into the substrate. As the anchor penetrates deeper the shank and several feet of chain are also pulled into the substrate. As an example, check out the beach anchor test on YouTube:

YouTube

.

Note: I've never used a Sarca Excel, but this video is for JonJo

Anyway, the PS testing suggested - all else being equal - that smaller chain "cuts" more easily into the substrate than larger chain, thereby allowing the entire anchor to set deeper and with the optimum geometry. A wire cable allows for still deeper penetration.

Obviously this doesn't mean we should switch to wire rode, or even the smallest diameter chain, since there are other things to consider! Still, it suggests that bigger chain isn't always better.

[JonJo]

Originally Posted by cfarrar

One reason is that G7 lashing chain probably won't fit your gypsy (in the U.S.). Then there's the cost.

By the way, there was interesting, recent article in Practical Sailor about how smaller diameter chain allows the anchor to penetrate deeper....

Gal G7 chain in America is produced to a size similar to, but not identical to, G43. The easiest way to check is to buy, you would think the chandler would have a piece to loan (on deposit) a 2' length and try it, or take your gypsy in.

Muirs of Oz sell their windlass in America and their Imperial gypsies (they tell me, I have not tested) are to a G43 size.

Jonathan

[JonJo]

Originally Posted by Pelagic

Hmmmn! .... That's a new line I have to try.

I did not want to copy the longer reply but

Many people on this forum will describe how their anchor has been set and when examined found to have disappeared completely, taking some of the chain with it.

Its logical that bigger chain would retard this diving and that Kryptonie piano wire is actually the way to go

During the 'remove the roll bar debate' (of one specific anchor) the anchor maker themselves pointed out that the roll bar actually hindered depth of set and removal meant the anchor would set more deeply (omitting to mention it might not set at all). Its the same principle. One reason we have thinner shanks, compared to the drop forged Danforth or CQR is because thicker shanks hinder penetration - but thinner means weaker - so we have had need to have anchors with stronger steels - which is why we went to ASTM 514a (the highest tensile steel that can be safely or easily galvanised). Manson's Boss takes this to new extremes - being a very thin shank. But beefy swivels, lots of shackles all play a role. Sometimes it is necessary to have this extra kit other times - maybe questionable, what we need is all the information so that we can make the decisions.

None of this is new - the oil rig anchor makers have this all documented, see the Vryhof manual.

But smaller G7 chain should help an anchor to set compared to thicker G3 or G43 chain (sticking to the same strength) - less resistance. The deeper you can get your anchor to set the better the holding. This will be more marked in harder seabeds (those where holding might be more difficult to achieve).

One reason a Fortress might set well is that it is all fluke, with sharp leading edges. Moreover its shank is tapered to ease penetration. It has that bar at the rear, which will retard penetration, but its quite thin (compared to a roll bar) and most of it is pulled through seabed already cut and weakened by the flukes. Finally it develops holding capacity before the shank has need to pull the shank (and chain) down - its an anchor where the shackle end penetrates last (contrary to most other anchors).

Jonathan

[Blue Crab]

The video lost me early on with the mention of Pearson using rolls of glass and epoxy in the late 50s.

Nah. Why waste more time on poor scholarship?

[downunder]

Originally Posted by DoubleWhisky

I'm afraid Beata (my Dearest Wife and Highest Authority) can oppose to the idea of me being shared....

I will drink a Wiskey to that. Na Double Wiskey

[mpatter894]

This comes from over 20years of merchant marine service as a deck officer and Captain with the largest shipping company in the world.

A Common Misconception Cleared

I would like to clear a common misconception at this stage that the weight of the anchor holds the ship in place. This is not correct because the main role of the anchor is to grip the sea bed. The role of securing the ship is performed mainly by the chain rather than the anchor, though the latter has a role to play in that as well.

Once the ship is anchored properly, it is bound to remain in a certain circular area which is defined by the length of loose chain. Of course there are several other factors which need to be considered to ensure that the ship is safe during anchor. The weight and length of the catenary takes the shock and holds the vessel as it swings or rises with the currents or tides if you have the right scope of rode out for the conditions it should have minimal pull on the anchor. a 22 ton sailboat is going to drag any reasonable size anchor for the size vessel if the conditions are bad and the rode is to short. It will drag or if it holds you will suffer some sort of casualty to the anchor, the rode or the vessel itself.

USCG Master any gross tonnage any oceans

[DoubleWhisky]

Originally Posted by mpatter894

This comes from over 20years of merchant marine service as a deck officer and Captain with the largest shipping company in the world.

A Common Misconception Cleared

I would like to clear a common misconception at this stage that the weight of the anchor holds the ship in place. This is not correct because the main role of the anchor is to grip the sea bed. The role of securing the ship is performed mainly by the chain rather than the anchor, though the latter has a role to play in that as well.

Once the ship is anchored properly, it is bound to remain in a certain circular area which is defined by the length of loose chain. Of course there are several other factors which need to be considered to ensure that the ship is safe during anchor. The weight and length of the catenary takes the shock and holds the vessel as it swings or rises with the currents or tides if you have the right scope of rode out for the conditions it should have minimal pull on the anchor. a 22 ton sailboat is going to drag any reasonable size anchor for the size vessel if the conditions are bad and the rode is to short. It will drag or if it holds you will suffer some sort of casualty to the anchor, the rode or the vessel itself.

USCG Master any gross tonnage any oceans

It looks we are all enlightened at least....

[mpatter894]

Originally Posted by DoubleWhisky

It looks we are all enlightened at least....

just thought I would mention it because there were some people debating the theory of getting a bigger anchor and using lighter chain, you of all people should know that's not a good idea or maybe you dont sailing around the coast of Poland around Gdansk where the wind can really howl

[Andrew Troup]

I would like to question the relevance of small chain in the context of how deeply an anchor can be encouraged to bury.

I think we need to beware of a modern reflex, obsessing about peak performance.

What really matters with an anchor is not the maximum figure it can be persuaded to notch up, ie the figure tests tend to focus on.

Given that in modern times we generally rely on the same anchor in all situations, what matters is the WORST holding figures, in the worst bottom.

Any bottom where a given anchor can dig deep enough to benefit from a slim chain or wire, and yet be solid enough for the chain diameter to materially affect depth of burial, will develop WAY more resistance than the same anchor in more challenging conditions (not involving burying).

Which by definition is way more than we will ever need, because otherwise our anchor is inadequate across the range of conditions we might encounter.

It's not a contest like a tractor pull, where the maximum figure wins. The interest is at the losing end: we're trying to finish as far from the tail of the pack as we can, in our worst event.

And in that context, it strikes me that slimming the chain is like shaving your legs for a marathon.

[JonJo]

Andrew,

If you look at how a modern anchor sets, and they all (except the Fortress) set the same way, then the toe and the shackle end of the shank bury together. This occurs, now depends on the anchor, until only the top of the shank is visible - then the whole thing disappears.

With this orientation the fluke is always at the same, or similar, angle to the seabed - with the toe (and fluke) pointing down - the whole thing is 'angled' to dive.

Now say we hold the shackle end of the shank on the seabed surface, but allow the toe to dive, with the fluke. As the fluke buries it will tend to flatten out (because the shackle end is being kept on the surface). it will 'rotate' until the fluke is parallel with the seabed. If we keep the shackle end on the surface then the fluke will eventually reach equilibrium and sit parallel to the seabed - no more diving.

So which is better:

An anchor such that the fluke is forced fairly early on in the piece to bottom out or one allowed to dive as deep as possible?

Hard seabed, big chain - how do you imagine the chain becomes buried. It is only buried because it is pulled down by the anchor. What sort of chain will bury more easily, big chain or smaller chain.

The differences might not be great but remove the roll bar from one specific anchor and it will set 25% more deeply. Think of the cross sectional area (along the length) of a 1/2 inch (or 13mm chain) and then of an 8mm or 5/16th chain. A 8mm G7 chain has a min break strength of 7,000kg, a 13mm G3 chain a min break strength of 8,000kg or an 11mm G3 has a WLL of 1,600kg but a 8mm G7 chain a WLL of 1,400kg. Put them side by side, what sort of difference is there in surface area (how does that difference compare to the surface area of a roll bar)

This is not to say roll bars should be cut off - they are there for a reason, in the same way a Spade has a big obstruction under the fluke (containing the lead) - its simply easier to visualise the roll bar and compare with a chain.

Which of the chains do you think might be more conducive to allowing the shackle end to be pulled below the seabed surface by and along with the toe - the 8mm chain or the 11mm/13mm chain. Then add the big shackle to the bigger chain etc.

The roll bar of an an anchor does not look much - but remove it and it makes an immense difference (even the anchor maker said so).

But you are correct - its the worst case scenario we should be looking at and if a smaller chain improves that worst case scenario then it might merit inclusion into the consideration.

Currently G7 chain seems to be the limit but potentially (and maybe sooner than we think) we could see G100 chain - much stronger and much greater opportunity for an even smaller size.

I'm not sure what worst case scenario is - hard seabed and difficult to penetrate or very soft soupy seabed with no hold (or even one with a lot of weed)?

Jonathan