Anchors - Bigger is Better ?

[Bash]

Originally Posted by JonJo

As far as I can make out the jury has returned a verdict - but the verdict seems based on 'feel' rather than any technical basis.

At the risk of branding myself a heretic, I don't run with the "bigger is better" herd.

Using the Rocna sizing chart, my anchor is the one recommended for my boat's size and weight. I've spent considerable time hanging from it, often in a strong breeze (22-27 knots, which is the average summer wind here in SF Bay) without ever once dragging. In my home waters I find that it digs itself exceptionally deep in an all-night blow, and although I have a large horizontal windlass I sometimes have to use the engine to break it out.

When it next occurs to me to spend money on ground tackle, I will invest in an upgrade from the current BBB rode to G4. I'm hoping to get a few more years out of the current chain before making that move. Otherwise, I'm happy with my selection of anchors.

This is not in any way a criticism of the "bigger is better" mentality. If a bigger anchor helps you sleep, get one. If painting it white helps you sleep, paint it white. I'd rather share a cove with a boat with oversize tackle than with a boat with inadequate gear.

The one area I will disagree with claims being made on this thread is in terms of an anchor being a permanent piece of gear. In my years as a scuba instructor I've recovered way too many anchors to believe such a claim, and I've had to abandon at least one anchor that, fortunately, I was able to retrieve later. Should I ever need to abandon another anchor, it's going to be a lot easier to do so knowing I didn't purchase one twice as large as I needed.

[s/v Jedi]

at 22 knots I can anchor with my winch handle

[Kettlewell]

I'm sort of in between. I generally go by the old adage that you should have a pound of anchor weight per foot of boat, and then when in doubt go one size up. I think it was Eric Hiscock who said that for some reason any anchor less than 35 lb. was ineffective, and I think that is basically true except for Danforths and Fortresses. Sometimes it just takes weight to penetrate the bottom, and I don't think there is any argument that additional weight aids initial penetration. Therefore, the proponents of extreme weight are on to something--weight increases initial penetration, which promotes the anchor reaching its potential holding power. In other words, if the anchor doesn't bite into the bottom, it won't provide enough holding for higher wind speeds unless it is something like a 4000 lb. mooring block, which is quite common in New England--no mechanical holding power, but decent holding due to sheer weight and some friction on the bottom. In any case, back to the OP, yes something like a FX-23 Fortress will hold until something breaks if you get it properly dug in, but Nick's 176 lb. Bruce is just about sure to hit the bottom and penetrate and then dig in once the wind builds. The Fortress will be harder to get started, but it is effective if you can get it to penetrate.

[JonJo]

Originally Posted by Cotemar

Kenomac,
That Ultra Anchor looks like a sweet anchor. A real piece of art. Had seen a few at the boat shows
The $1,965.00 for the 21 KG / 46 Lbs model may hold some cruisers back. Maybe someday they will make it in galvanized alloy steel

You cannot galvanise a sealed hollow shanked 'steel' anchor (or a hollow fluke). They would need to perforate the shank (otherwise it blows up) and once perforated there would be doubts of inadequate interior galvanising (because you cannot see it) and thus corrosion would be an issue. 316 Stainless steel from which the Ultra is made has a tensile strength lower than marine grade aluminium alloy and maybe 25% the strength of the steel used in the Supreme or Excel. No-one has tested the strength of the Ultra shank, at 90 degrees to its length. Testing does not show the Ultra to perform any better in a seabed than say a Spade, Excel or Supreme - seems a lot of money to invest when you can buy as good more cheaply and that has been tested.

I would exclude it from my list on the basis its a bit, very, expensive and though I am sure the manufacturers say the shank is strong enough I'd like an independent comment (tested at 90 degrees).

But it is beautiful, stunning (as Cotemar says: its almost art!) and other than the strength issue works well - but does tend to look less beautiful once its been used. I'd exclude the Stainless Spade on much the same grounds (but include the alloy Spade because it has unique positive attributes, its light)

[Bash]

Originally Posted by s/v Jedi

at 22 knots I can anchor with my winch handle

That reminds me of a story....

[Panope]

Originally Posted by JonJo

Why do we need to upsize the new gen, when our fathers and grandfathers all survived with old gen?

A difference between today and years past is that (in general) the cruisers of today have more money and can afford any sized anchor they choose. They can also afford the (now readily available and reliable) powered anchor windlasses to retrieve oversize anchors.

My father "survived" with normal sized, old gen anchors. Nowadays, people want to do more than just survive. They want more comfort and relaxation. The technology is readily available and they can afford it.

Steve

[JonJo]

Originally Posted by Kettlewell

I'm sort of in between. I generally go by the old adage that you should have a pound of anchor weight per foot of boat, and then when in doubt go one size up. I think it was Eric Hiscock who said that for some reason any anchor less than 35 lb. was ineffective, and I think that is basically true except for Danforths and Fortresses.

If I translate this; a 40' yacht should carry a 40lb anchor (just above the 35lb limit) but a 40lb (18kg) anchor is hardly over size (and the next size up might be 25kg or 55lb) and certainly not 2 sizes up which might be 33kg. And that adage - which seems to fit the USL codes was on the basis of 'old fashioned' anchors. I might agree with Hiscock that small anchors were ineffective - they had blunt toes and simply did not engage for example Bruce, CQR. Today the toe of a Supreme or Excel look like weapons of war, which is why they engage and set so quickly (even in smaller sizes).

[klem]

I tend to like new generation anchors that are between the recommended size and 2 sizes up depending on the use. In most parts of the world, there are thunderstorms or squalls that roll through at least occasionally and it is my opinion that everyone should be capable on anchoring through them in reasonable conditions (fetch, holding bottom). For most people, this means buying a new gen of the recommended size. We end up anchored out in storm force conditions from time to time and named storms occasionally so I want my primary anchor to hold reliably through those. We like to choose places with good protection and holding bottom but we end up riding out a lot of nor'easters on the coast of Maine where the mud provides decent holding but is certainly not nearly as good as sand. What really scares me is that the forces go up very quickly as the wind speed increases so people that boast about being anchored in 35 knots have no idea what it is like to be in 50 knots and I can't imagine what it would be like to have been on Jedi's boat during the hurricane. Everytime we survive a big blow, it adds to my confidence but also makes me nervous because of the loads that we saw.

From an analytical perspective, one of the major flaws of the anchor tests is that they give you the average holding power. They really should run a lot of tests and establish a distribution for the given conditions. I would say that the reliable holding power and holding power are wildly different. I would define the reliable holding power using a 99% confidence interval which is way lower than what the tests would lead you to believe. For example, in the West Marine anchor tests, the Delta averaged 1925 lbs of "holding power" but the standard deviation of this is 1384 lbs which is rather alarming. Part of this may have been the small sample size but it shows just how much variability in the set there is even with the same bottom. My guess is that if you applied my reliable holding power rule and did 20 trials each, you would find that the holding powers were decreased by 50% on most anchors. Unless you can deal with the variabilities that cause this, the only other way to ensure you won't drag is to apply a large safety factor.

JonJo's concern about a partially set anchor not remaining embedded in the bottom in a veering situation is a real concern but I don't know of any evidence that this is truly a problem. Playing around with anchors on the beach, I have not observed this to be true except with a danforth which seemed to be more roll stable when deeply buried. The new generation anchors seem to be good enough that this simply isn't a problem but I have not rigorously tested this.

[foggysail]

Guys-- CarlF said it all!!! Quote from his post--



"No one lying in their berth at 2AM during a sudden squall thinks 'I should have bought a smaller anchor' "

[Jim Cate]

The argument that our fathers (and Eric H too) survived on old design anchors so they must be ok is specious IMO. Those same fathers survived on cloth covered airfoils in their aircraft, tires which blew out regularly, non-safety glass in auto windows, no seat belts and so many other things and practices that we now view as outmoded or dangerous.

Those same fathers cruised in different times, times where most anchorages were uncrowded and there was room for all to use 7+:1 scope, where huge mooring fields didn't occupy the best anchoring spots and when keeping all night vigils (anchor watches) was a normal practice. My view as a long term cruiser is that I am willing to pay the weight and fiscal penalties for the larger anchor because I find that I often need to anchor in less than ideal circumstances. While it may at times be necessary, standing anchor watches as a normal practice is hard on short handed cruisers and I'll do my best to avoid the requirement.

Finally, JonJo, could you post a link to the USL code that you refer to so often? I've not found one that seems to work, and I would like to see the numbers for myself.

Cheers,

Jim

[Kenomac]

Originally Posted by s/v Jedi

The stainless anchor is -not- quality stuff.

My father is a metallurgist who specialized in stainless steel.... his opinion is the opposite of your's. I'll go with the expert's choice for quality 316L stainless, not hearsay.

Lot's of myths out there regarding the strength of various metals under load, although there's one certainty... if you buy a Chinese made anchor, you won't know for sure what you're getting.

[s/v Jedi]

Originally Posted by Kenomac

My father is a metallurgist who specialized in stainless steel.... his opinion is the opposite of your's. I'll go with the expert's choice for quality 316L stainless, not hearsay.

Lot's of myths out there regarding the strength of various metals under load, although there's one certainty... if you buy a Chinese made anchor, you won't know for sure what you're getting.

So your father tells you that 316L anchors are stronger than same size and weight alloy steel versions? Or is he telling that it looks prettier?

[JonJo]

316 stainless has a yield strength of about 205 MPa, min

5083 alloy ('common' marine grade aluminium alloy) has a yield stress of 240 MPa min - (there is better and it is used)

ASTM 514 (High tensile steel) (same as Excel and Supreme) has a yield stress of 690 MPa min (typ 750 MPa)


There are a number of steels described as mild steel

but yield stress of 250-350 MPa would be about right.

Tensile strength of 316 stainless is quite high, at 515 MPa, but that is not actually relevant - we want to know how easily it will bend, hence yield strength.


You can engineer strength by building a box section, Spade and Ultra - but you depend on the manufacturer getting it right - and no-one has tested an Ultra shank. With a shank made from plate, what you see is what you get - and you can make a rough calculation of strength. Spade's box section, you can actually see the wall thickness, Ultra - no idea.

[JonJo]

Originally Posted by Jim Cate

Finally, JonJo, could you post a link to the USL code that you refer to so often? I've not found one that seems to work, and I would like to see the numbers for myself.

Cheers,

Jim

Jim,

USL codes I'm working on it!

Most of the anchor makers, Lewmar, Rocna, Manson, Anchor Right etc base their recommendations on the USL codes.

I'm not sure how Fortress (and maybe Danforth) derived their recommendations.

I hope you have better weather at Bruny than we are getting in Sydney - its rained for days.

[Cotemar]

USL code as in (Uniform Shipping Laws)?