Minimum anchors size, what’s the point?

[Dockhead]

Originally Posted by Panope

I do not have a pair of Spades (no pun intended), but I do have a pair of identically sized Sarca Excel # 5 anchors. One of galvanized steel (47lbs.) and the other aluminum (27lbs).

My testing indicated that the heavier steel version set faster and more reliably. However, once the toes started to penetrate, the performance appeared to be identical (they both dove in the seabed a similar amount).

Note: my test boat was not powerful enough to reach the ultimate holding power of either anchor.

Steve

Entirely consistent with all the reports I've seen.

[noelex 77]

Originally Posted by jkleins

Doesn’t Spade make an aluminum anchor in the same shape and fluke area of their steel anchor? Does anyone know what the difference in holding and setting is for that anchor. It seems a perfect proxy for what we are discussing/arguing about. I have never seen any data on it.

The alloy Spade is a good anchor, but in my view it does not have the excellent performance of the steel Spade. As well as my own observations, this has been verified in anchor tests. For example, in the large independent 2009 multi magazine test, the holding in hard sand for the steel Spade was 1905 kg. This dropped to 1050 kg for the aluminium version.

[jmh2002]

Originally Posted by Dockhead

I just cracked Dashew's "Cruising Encylopedia", and the very first chapter is on Ground Tackle. This is what he writes:

"You should carry the largest possible anchor and use it for everyday anchorages...

Steve dashew tends to go (what appears to be) over the top with most of his solutions.

Why? Why bother in fact, when a lesser solution will do, most of the time? Well, because it works, in all conditions, when the shxt is hitting the fan, and (in regards to anchoring) when everyone else has already dragged and is on the beach

A long time ago (20 years or so) when alternators were mostly crap I fitted one of the Electrodyne (Electrodyne | Brushless Automotive Alternators) models that Dashew mentions in that book. I dealt directly with the 'old man' there who, semi retired, enjoyed himself with the marine projects as opposed to the main business of battle tanks and rescue vehicles that their gear was mainly fitted to.

Again, why? It was more expensive, it was more difficult (not off the shelf), it needed a custom bracket, etc, and we even needed to convince the old man to approve the sale in the first place because they only sold 'stuff that works'!

But, in the same space (couldn't fit a bigger frame size in the engine box) it tripled the previous output, and continued to exceed it's own rated output even when running for hours and hours getting very hot (external regulator and diodes, massive heatsink and fan).

The 'over the top' solution ended up being cheap, and a godsend in the long run when other cruisers were either having constant problems and replacing alternators or simply not being able to produce enough amps in the first place.

Going back to the point of my first post in this thread ("for serious cruising it makes total sense to go significantly up in size and weight in terms of both the anchor and the chain"), as with quite a lot of serious cruising gear (or gear for professional/commercial use, where it gets even more of a workout - I have experience with both) there is often a significant benefit to going for 'more' rather than 'less'.

It normally ends up just simply better in the long run.

But hey, people can keep arguing here about smaller and lighter anchors and chain as much as they like. No doubt these are the same type of people that I was yelling at in the anchorage in the past to stay the hell away from my boat and go and anchor somewhere else... (far away from me...)

[jmh2002]

Originally Posted by 2big2small

I’m sorry but all you’re giving me is people howling with the wolves without factual base.

Huh? I didn't see any factual base for your posts? But I linked articles and numerous other cruisers confirmed the same experience.

I think they know who the howler is here...

Originally Posted by 2big2small

Dashew... He’s the irresponsible one, not me...

Most people here will no doubt be entertained by this comment. I had a good laugh too

Some even pulled out their copy of Dashew 'Offshore Cruising Encyclopedia'. Did you check yours? It is still useful reading and stands up there together with Jimmy Cornell's World Cruising Guides, and Nigel Calder's Boatowner's Mechanical and Electrical Manual. Essential for every cruiser, regardless of the size of their anchor.

[Dockhead]

Originally Posted by jmh2002

Steve dashew tends to go (what appears to be) over the top with most of his solutions.

Why? Why bother in fact, when a lesser solution will do, most of the time? Well, because it works, in all conditions, when the shxt is hitting the fan, and (in regards to anchoring) when everyone else has already dragged and is on the beach . . . .

Ha, ha, ha! Well formulated!


But there is wisdom at the heart of this. There is no such thing as overkill, when things are really bad. I think it goes back to what I was saying in an earlier post -- it is not right to size the anchor for the average case. It's not even right to size the anchor for the average bad case. The right size and capability of the anchor and the whole anchoring system, is the biggest and best you can afford and which you can handle. Because you just can't calculate a "worst case" -- you can't know what it will be. There are situations where no anchor will hold. The smaller the anchor, the greater number of situations there are, where the anchor won't be up to it, and the number of such situation increases in a non-linear fashion, as you choose a smaller anchor. By following Dashew's advice and oversizing the anchor as much as practical, you are reducing the number of potential disasters you may get into because you somehow got into a situation which your anchor was not capable of handling.


The decision to oversize the anchor is relatively easy because of the non-linear relationship between fluke area and weight. As Dashew says, a small increase in weight gives a large increase in holding. So if we agree that there is no such thing as an anchor which will hold in any conditions, then there is simply no such thing as an anchor which is too big, up to the point where we can no longer handle it well, or it's too expensive for our budget.

[double u]

"But hey, people can keep arguing here about smaller and lighter anchors and chain as much as they like. No doubt these are the same type of people that I was yelling at in the anchorage in the past to stay the hell away from my boat and go and anchor somewhere else... (far away from me...)"

GREAT!!! Absolutely GREAT! AGREE 250%!

[double u]

"There is no such thing as overkill, when things are really bad. "

words of wisdom!!!
Downsizers, small-is-beautiful-ers, goatchain-&-toy-anchor users:
do as you please, but stay the hell away from our boat!

[rognvald]

"This is the whole problem on smaller boats, and it is close enough to being unsolvable, that it becomes a good reason not to use a smaller boat at all for any kind of remote cruising. " Dockhead


The above quote is my vote for the most ridiculously absurd statement ever stated on this Forum. It is arrogant, uninformed and patently untrue. Have you, Dockhead, ever heard the following names?) Roger Taylor, the Pardeys, Robin Lee Graham, Joshua Slocum, the Hiscocks, John Guzwell, the Smeetons, Robin Knox Johnston, Tania Aebi, Matt Rutherford, Donna Lang, Edward Miles, Alain Girault, Harry Pigeon, Thomas Fleming Day . . . and countless other unnamed souls who have not attained notoriety and who are, perhaps, members of this Forum and have made voyages to remote places all over the world in small boats. It is not about size but competency in a well found vessel whether large or small. It is my observation in the last 30 years of sailing that there are more fools hiding behind big boats than small boats in the unfounded and absurd belief that size will save them from their lack of skills or competency. When the sh-t hits the fan . . . it's the sailor not the boat that will save the day. Geez . . . I think I need a Vodka Martini.

[jmh2002]

Originally Posted by double u

"But hey, people can keep arguing here about smaller and lighter anchors and chain as much as they like. No doubt these are the same type of people that I was yelling at in the anchorage in the past to stay the hell away from my boat and go and anchor somewhere else... (far away from me...)"

GREAT!!! Absolutely GREAT! AGREE 250%!

I am not embarrassed to say that whether it was:

'down island' on a 50 foot cruising boat and standing on the bow, rum drink already in hand, yelling at bareboat charter people that 'I'm a big heavy boat and I have 300ft of chain out (regardless of how much chain I actually had out ) so you can't anchor anywhere close to here... please foxtrot oscar'

or

in St Tropez on a 50 metre superyacht and sitting in the bridge, no rum drink in hand unfortunately, and instead having to send a crew member over in the tender to advise another boat (because of course they don't answer on the VHF) that they were already detected by our radar's ARPA as being inside the perimeter of our swinging circle and the Captain 'politely requests that you please re-anchor in another location'

the same applies regardless - stay far away from me with your BS anchoring

[Dockhead]

Originally Posted by rognvald

"This is the whole problem on smaller boats, and it is close enough to being unsolvable, that it becomes a good reason not to use a smaller boat at all for any kind of remote cruising. " Dockhead


The above quote is my vote for the most ridiculously absurd statement ever stated on this Forum. It is arrogant, uninformed and patently untrue. Have you, Dockhead, ever heard the following names?) Roger Taylor, the Pardeys, Robin Lee Graham, Joshua Slocum, the Hiscocks, John Guzwell, the Smeetons, Robin Knox Johnston, Tania Aebi, Matt Rutherford, Donna Lang, Edward Miles, Alain Girault, Harry Pigeon, Thomas Fleming Day . . . and countless other unnamed souls who have not attained notoriety and who are, perhaps, members of this Forum and have made voyages to remote places all over the world in small boats. It is not about size but competency in a well found vessel whether large or small. It is my observation in the last 30 years of sailing that there are more fools hiding behind big boats than small boats in the unfounded and absurd belief that size will save them from their lack of skills or competency. When the sh-t hits the fan . . . it's the sailor not the boat that will save the day. Geez . . . I think I need a Vodka Martini.

Ha, ha, ha! That's a good rant! Peace, my brother.



I certainly didn't say it's not possible, and I'm sorry for stepping on a nerve. I certainly agree that the competence of the mariner is key, and that neither size of boat nor size of anchor or size of hmm, whatever, can make up for it.



I was only saying that when you venture into very remote areas, especially in high latitudes, the difficulty of anchoring safely goes up very steeply, and a particular disadvantage of small boats is the inability to carry the kind of really large anchor which is really, really desirable in some conditions. I said "disadvantage", not "disqualification", and in my previous post, I said "good reason", not "imperative".



Is that, now, better formulated?


I hope so, because I'm running out of flowers

[jmh2002]

Originally Posted by rognvald

When the sh-t hits the fan . . . it's the sailor not the boat that will save the day. Geez . . . I think I need a Vodka Martini.

This part is certainly correct. Even about the Vodka Martini too

[Dockhead]

Originally Posted by jmh2002

This part is certainly correct. Even about the Vodka Martini too

I prefer gin!

[Mike OReilly]

Cheers folks. It's afternoon drinkies time here in NFLD.

[thinwater]

Originally Posted by Dockhead

On a catamaran, especially a small one, even more so a high performance one, you have a completely different set of priorities with regard to weight, than the rest of us. I don't envy you that, but then your use pattern must be completely different also. You're probably not cruising 3 or 4 months at time and thousands of miles from home base, either.

As to rules of thumb: I think we have to be careful how we use them. I think we all agree that there are multiple non-linear factors in anchor performance. Given that, does it really mean much, to say that an anchor is x% of displacement, so it must be ok?

Surely for this to be even approximately right, it will need to be scaled up for size -- x% up to 5 tonnes, y% from 5-10 tonnes, z% from 10 - 20 tonnes, etc.

And surely catamarans demand their own coefficients, since they are much lighter for a given amount of windage, no?

And then not every anchor performs the same per pound of weight, not so? The Bruces the Dashews used to use needed to be far bigger, for example.


My hundred pounds on my 20 metric tonnes light ship (so maybe 25 tons loaded) is marginal for my use case. Granted, my use case is at the extreme end, what concerns demands on the anchoring system. I would feel much better with an anchor two sizes bigger than this one, but I would need a different bow roller and a different windlass. I would like very much to have 30 meters more of chain, also, but I can't put any more weight in my bow without an unacceptable impact on sailing performance.

For more normal conditions -- say the English Channel, which is still somewhat demanding, but not like Greenland, the 100 pounds is probably enough, but is certainly not overkill. For Florida I could probably use a 25kg Spade with perfect results.

If I had a catamaran, I would be forced to push the anchoring system harder, and get more out of less.

So I find it really hard to apply any kind of rule of thumb.

Much of my experience comes from larger cruising cats in which I went farther and longer. I've been sailing for 35 years. Don't assume. But yes, nearly all of it in multihulls. However, I don't see this as a mono-multi debate. I may poke at people for weight, but it is less because a few pounds matter than because they can't relate the number to any basis.


I don't take stock in the % weight rule of thumb. It does not fit with either experience, standards, or the engineering science. % ABYC storm load, on the other hand, is based on both engineering and long experience, and is adjusted for boat size and type. However, I'm one of the first to say bottom variability is HUGE. As you point out, the Burce is a nice anchor, but it needs to be 30-100% larger to work in soft bottoms. That's not a bad thing, you just need to understand it.



Actually, multihulls can use the ABYC data to good accuracy if they simply add about 15% to the length. The correlation to load cell measurements is then good through the full range of windspeeds and boat sizes. I'm sure there are many factors, but they seem to average out if this approach is used. I've measure rode tension from 1200-14000 pounds, from light winds to gale conditions. The fit is astoundingly good through the full range.




Your 100-pound anchor makes perfect sense with the 3% of ABYC storm load rule. Slightly conservative and appropriate to the boat. I've used less, but for long-term cruising, I would have liked 3% (one size up from what I used).


I don't think we actually disagree.

[Dockhead]

Originally Posted by thinwater

Much of my experience comes from larger cruising cats in which I went farther and longer. I've been sailing for 35 years. Don't assume. But yes, nearly all of it in multihulls. However, I don't see this as a mono-multi debate. I may poke at people for weight, but it is less because a few pounds matter than because they can't relate the number to any basis.


I don't take stock in the % weight rule of thumb. It does not fit with either experience, standards, or the engineering science. % ABYC storm load, on the other hand, is based on both engineering and long experience, and is adjusted for boat size and type. However, I'm one of the first to say bottom variability is HUGE. As you point out, the Burce is a nice anchor, but it needs to be 30-100% larger to work in soft bottoms. That's not a bad thing, you just need to understand it.



Actually, multihulls can use the ABYC data to good accuracy if they simply add about 15% to the length. The correlation to load cell measurements is then good through the full range of windspeeds and boat sizes. I'm sure there are many factors, but they seem to average out if this approach is used. I've measure rode tension from 1200-14000 pounds, from light winds to gale conditions. The fit is astoundingly good through the full range.




Your 100-pound anchor makes perfect sense with the 3% of ABYC storm load rule. Slightly conservative and appropriate to the boat. I've used less, but for long-term cruising, I would have liked 3% (one size up from what I used).


I don't think we actually disagree.

We don't indeed, and there's lots of good information in this post


I remember your actual measurements of rode tension a few years ago -- can you give us a link please? This is also very useful information for this discussion. Observations are gold (theories are bronze etc.).