Anchors - Bigger is Better ?

[Andrew Troup]

Evans

It's intriguing to speculate whether your experiences with the Rocna would show up on the Rocna "Knowledge Base" website, were you to submit them !

Interestingly, according to the same "Uniform Shipping Laws" chart which suggests that your 50kg anchor is the right size for your boat (assuming for the sake of the exercise that Bruce anchors do not qualify for the "high holding power" discount, IOW they cannot be relied on to develop a holding power in excess of six times their own weight), my 30kg Bruce is 4kg overweight for my projected 11m, low-freeboard sailboat, whereas Jedi's much-vaunted 70kg Bruce is at least 10kg underweight for his Sundeer 64

[Cotemar]

Wouldn't it be a better idea to use the surface area of the anchor instead of the weight to judge how good the anchor will hold.

You’re all looking at the wrong numbers. Think Area of the flukes in square inches.

When you talk about your sails, don't you talk about the area of the sails in square feet? The area of the sail is more important than its weight.

Anchors are the same. The square inches of area a fluke has is more important than the anchor weight.

[sabray]

The great unknown is what the other anchor would have done? It's really not good form dying this or that anchor failed this time. I have heard the same story for every anchor made. From fisherman to cqr to Danforth to next gen.
My Bruce held well all over. It once skidded on hard pan.
The story is my Bruce failed in a sandy bottom. It would grab and then the chain would vibrate and the boat slid tword shore. Demise was sure. I rowed out the fortress and set it saving the day.
Meaningless or better anchor?

[Cotemar]

Originally Posted by sabray

The story is my Bruce failed in a sandy bottom. It would grab and then the chain would vibrate and the boat slid tword shore. Demise was sure. I rowed out the fortress and set it saving the day.
Meaningless or better anchor?

No, it simple math. you just put out a light weight Fortress anchor with much more area of the flukes.

Anchor fluke Area will win over anchor weight almost every time

[Andrew Troup]

One serious question, Evans: did you ever get to test a Spade? I guess it's the obvious candidate, for a reputable new-Gen design with no roll bar...

It doesn't offer the multipoint purchase of a Bruce in rocky bottoms, admittedly, but who knows?

IIRC, you did one Patagonian season with a close copy of a Manson Supreme, and since then at least one season with the genuine Rocna?

(PS: strikes me it's really unfortunate timing that your Bruce came back damaged from the galv process the very same year that Bruce pulled out of the small anchor market!)

[Andrew Troup]

Cotemar

Strikes me that single-figure 'measures of excellence' are notoriously unreliable. Very popular, though, particularly in some cultures, and/or among neophytes...

You're suggesting replacing one single figure measure with another: I'm not convinced it's a great improvement.

Furthermore, (and I realise your comment was not just aimed at me, but I can't speak for others) I was careful in the comparison to select three boats which all used the same design of anchor, so that weight and area are both proxies for the 'size' of the anchor.

Think: megapixels as the measure of performance for a digital cameral; BMI as a measure of obesity (according to which Michael Jordan was seriously obese); GDP as the measure of the health of an economy (a good earthquake is marvellous for increasing it, but lacking that, you can just go round breaking windows to jack it up!).

Young people are notorious for choosing rock music based on the decibel measure of merit...

So while you qualified your post with "ALMOST" every time, I think you need to also say "all else being equal"

And even then, some anchors probably scale up in area only (without increasing weight) with better results than others.
Anchors which work their way down into soft bottoms over time just with jiggling and little load (the Bruce is the obvious example, but this is the primary mode for many big-ship anchors) would be unlikely to do so if they were the same size, but much lighter. And while this is not an important benefit, it could well be that other, more important behaviours, do not scale either.

Fisherman (and other 'pick' style) anchors for use in mudstone or kelp are another example: if they're not heavy enough for their fluke area, you can forget about getting them to dig.

[Cotemar]

All things being equal.
The issue with Bruce anchors, is that it has the lease fluke area of most every anchor made. This is why every cruiser that has a Bruce is also in the Bigger is Better camp as they are compensating for small surface area, so hence add on the weight.

[Andrew Troup]

Originally Posted by Cotemar

All things being equal.
The issue with Bruce anchors, is that it has the lease fluke area of most every anchor made. This is why ever cruiser that has a Bruce is also in the Bigger is Better camp as they are compensating for small surface area, so hence add on the weight.

Hmm - it's an appealing theory, and your conclusion certainly tallies with real life practice, but I think you're guessing or inferring rather than using real data.

The Bruce's fluke is 85% of the area of a Rocna but it's 95% of a Supreme (in the large sizes, around 50kg), and bigger area (per unit weight) than a Bugel
I'm guessing it's similar to the (steel) Spade and CQR ... and WAY bigger than an sort of pick, even a Northill....

So the aluminium anchors are the only commonly used ones which support your claim, it seems to me.

[JonJo]

Andrew and Cotemar,

It is possible to compare, of the same surface area, Danforth, Fortress and Guardian. I suspect if you bury all of them to the same depth they probably have a similar holding capacity - I'm guessing. But the key is - how easy is it to bury each of them when loaded with a chain. I'd guess the Fortress would set more quickly. its of little value having high surface area if the anchor does not set easily.

Equally it is possible to buy a Mantus and Spade of the same surface area, once set they possibly have the same holding capacity - but I might guess they perform differently when setting and perform differently again in different seabeds, they possibly perform differently when you try to break them out.

In some seabeds a Mantus might be better (at setting) than a Spade and in other seabeds the opposite.

Spade has an enviable reputation but some of its weight is in 'ballast' and they seem to have the balance between ballast and surface area about right - otherwise it would not be such a respected design.

Its not only surface area but design.

[SailFastTri]

Originally Posted by Dockhead

Well, a few comments:

snip
I have never personally seen a Fortress release unexpectedly.
snip.

I have seen seen a Fortress release unexpectedly -- and it was in only about 5 knots of wind:

The wind in the anchorage was blowing from the SW for about 3 days, then died to dead calm, and boats were meandering with the current and little wisps of air. Nothing more than cats paws on the water. Then the wind came up from the opposite direction, at about 5 knots, and the boat on the Fortress just started drifting into others.

People were near in dinghies and got it under control when they saw what was happening (I was one of them). When the anchor came up it was the typical Danforth/Fortress problem of weeds and mud and rocks/shells jammed between fluke and shaft, so when the anchor flipped over the flukes were pointed upward and couldn't set.

I think those types of anchors do tend to rotate in the sea bed and stay set when there is a constant pull while the wind veers. But in this case the boat had likely drifted over the anchor until it flipped with a ball of stuff jamming the works.

BTW I too carry a Fortress as backup/secondary because if its light weight and high holding. It's great for what it is, and everything involves trade-offs.

[estarzinger]

Originally Posted by Cotemar

The square inches of area a fluke has is more important than the anchor weight.

As a single number metric for holding ability in sand and mud that's certainly true. Side note: fluke surface area is important for holding power in sand and mud, but is relatively less important to holding power in other 'non-penetrating' bottom types (rocks and coral etc). Tip contact is the more important aspect for holding in these sorts of bottoms.

However, as a single number metric for setting ability, weight (more specifically tip weight) is the best metric. And setting/resetting ability is at least as important (for me) as holding power. The Bruce happens to have quite high tip weight (we measured/tested this in the test that has been posted elsewhere in the thread I think).

Alain (of Spade) was the first to make a big deal of tip weight. And the Spade is carefully designed to maximize it. The roll bar anchors copied his concave flukes but did not match his tip weight - probably because it was an expensive feature that does not help in the simple raw holding power tests that get so much press and which the roll bar guys used to sell their concept.

Originally Posted by sabray

The great unknown is what the other anchor would have done?

Agreed thats always a problem with dragging stories.

Of the four incidents I mention above, in only one of them dud we later returned to the same harbour. We anchored in a different spot, however another cruising boat tried to anchor (with a cqr) in the spot our rocna failed at, and the cqr had no chance. They tried about a dozen times. It was getting dark and blowing quite hard (harder than when the rocna failed) and was a tricky anchorage to get in and out of so that other boat really wanted to stay. We chatted with them on the radio and offered them our Bruce, which they accepted, so we pulled it out and dinghied it over, and they shackled it on to their chain and dropped it . . . . . And It set and held first time. This was certainly no rigorous scientific test and I am not claiming it was, but a small affirmation of our experience that the Bruce does hold (better) in these sorts of bottoms.

[SailFastTri]

Originally Posted by estarzinger

As a single number metric for holding ability in sand and mud that's certainly true. But fluke surface area has less to do with holding power in other bottoms (rocks) And as a single number metric for setting ability, weight (more specifically tip weight) is the best metric. And setting/resetting ability is at least as important (for me) as holding power. The Bruce happens to have quite high tip weight (we measured/tested this in the test that has been posted elsewhere in the thread I think).

Alain (of Spade) was the first to make a big deal of tip weight. And the Spade is carefully designed to maximize it. The roll bar anchors copied his concave flukes but did not match his tip weight - probably because it was an expensive feature that does not help in the simple raw holding power tests that get so much press and which the roll bar guys used to sell their concept.

snip

Evans, would not "pounds per square inch" of tip pressure be a better measure of penetrating (setting) ability than tip weight?

A smaller (sharper) cross-section would penetrate the bottom better than a bigger (blunt) one. It's only common sense.

I used to own an aluminum Spade and found that with it's triangular cross-section it did not penetrate hard-packed bottoms as well as the Manson Supreme, which has a very sharp tip that being flat has a much smaller cross-section (in three dimensions).

For this reason, and recognizing the drawbacks imposed by a hoop, I'm interested in finding out how the Manson Boss will perform in the real world.

[Cotemar]

Originally Posted by JonJo

Its not only surface area but design.

Absolutely. If I had to prioritize anchor attributes, I would start with design
1) Design
2) Material
3) Fluke surface area
4) Shank thickness
5) Weight

This thread has concentrated on the last element more than some of the more important anchor aspects.

Most Anchors are made from a flat pattern of material. Then put some bends in the flat pattern to either concentrate the loads (Concave design) or cut the loads and push seabed to the sides (Convex plow design).

As an anchor designer, you can start with a blank canvas (flat pattern) and make a great anchor or a paper weight depending on how you bend it. As I showed earlier that the Convex plow anchor has one bend on the spine of the fluke that compromises its design by putting a pointed bend facing and cutting the seabed into two and pushing it to the sides, basically cutting the load you wanted holding your boat.

Fortress is one of the few manufactures to use Extruded aluminum to add strength or taper the material to be thicker just where they need it. It works well for them as they have cornered the 2nd anchor/Storm anchor market. Some here would say it has a few issues, but fortress is the best by far in there 2nd anchor/Storm anchor market. They happen to get the Design, Fluke surface area and Weight all right with their design.

[Kettlewell]

The overall design of the anchor is the most important part, rather than focusing on one particular feature or dimension. For example, Spade and other anchors focus a lot on tip weight, yet many here have noted the extreme holding power developed by Fortress anchors that have very little tip weight. Yet the Fortress design with its correct angles and sharp points often slices right into the bottom where other anchors have a tough time getting hooked up. At the opposite end of the spectrum, I was on a boat that went aground up in Labrador on solid rocks--no visible mud or what you would call "holding ground," yet we were able to hook up with a heavy Luke Herreshoff-style anchor that wedged in allowing us to put significant pull on the line.

But, I would argue that most cruisers, most of the time, seek out and anchor in decent holding ground, so that is what most anchor companies logically build their anchors for. There wouldn't be much of a market for anchors designed to hold perfectly in hard shale bottoms like Evans was showing in his big anchor test in Chile. It is more by chance that the big Bruce works well there, because in reality the design was meant to do well in ordinary mud where most people anchor. So in his case a BIB Bruce makes perfect sense, but it is hard to read much into that for the 99% of cruisers that won't be anchoring in those conditions. And a significant chunk of those 99% seem quite happy with their Rocnas, Mansons, Spades, Mantus, Fortress, etc. anchors.

[sailorboy1]

What has the group decided? Is bigger better for a given design/anchor ( a 40 lb CQR is better than a 30 lb CQR, a 60 b Delta is better than a 45 lb Delta, etc ignoring differences between types).

- yes it is
- no it is just a waste of money

Is it time for a poll?