How to Test Anchors?

[SaucySailoress]

Originally Posted by Kettlewell

What would you like to see in an anchor test?

This:

[doug86]

What's the point? Are you looking for a guarantee? Anchoring has inherent risks. There is no such thing as an anchor that will never drag, or will always reset.

Each type of anchor can be shown to be "the best" under a certain set of test parameters. So, the most comprehensive test will reveal that each one is "the best" for the conditions it excels in, while the others fill a spectrum of "suitable" all the way to "fail". The results of such a test really doesn't answer anything, other than different anchors work better in different conditions.

US charts list 24 basic bottom qualities, including: mud, ooze, shale, clay, sand, gravel, broken shell, rocks, pebbles, ash, coral, grass, weed, hard sand, soft sand, silt, oysters.... how can you possibly test for all?

The combined experience of the past century of boaters provides overwhelming evidence of what gives the mariner the best chance for successful anchoring: the weight of the anchor (heavier is better), the length of the rode (longer is better), the composition of the bottom (firm, but not too firm), and the wind protection afforded by the place chosen to anchor (more protection is better).

There is an anchor on a boat on my dock that I know has never failed. It has never been deployed.

[cal40john]

If there's no point in looking for a better anchor then I expect that you have either a traditional Yachtsmans, or better yet a big rock with a hole drilled in it to tie the rode to. Every anchor we have now comes from someone saying there has to be a better way, making something and trying it out. There has always been someone there to tell them what's the point.

Many carry different anchor types for different bottoms. It would be nice to know which work in which bottom. You can say that everyone knows from experience which is best, but how many times has traditional knowledge been improved on by scientific testing.

No guarantees, no perfection, hopefully improvement though.

John

Originally Posted by doug86

What's the point? Are you looking for a guarantee? Anchoring has inherent risks. There is no such thing as an anchor that will never drag, or will always reset.

Each type of anchor can be shown to be "the best" under a certain set of test parameters. So, the most comprehensive test will reveal that each one is "the best" for the conditions it excels in, while the others fill a spectrum of "suitable" all the way to "fail". The results of such a test really doesn't answer anything, other than different anchors work better in different conditions.

US charts list 24 basic bottom qualities, including: mud, ooze, shale, clay, sand, gravel, broken shell, rocks, pebbles, ash, coral, grass, weed, hard sand, soft sand, silt, oysters.... how can you possibly test for all?

The combined experience of the past century of boaters provides overwhelming evidence of what gives the mariner the best chance for successful anchoring: the weight of the anchor (heavier is better), the length of the rode (longer is better), the composition of the bottom (firm, but not too firm), and the wind protection afforded by the place chosen to anchor (more protection is better).

There is an anchor on a boat on my dock that I know has never failed. It has never been deployed.

[S/V Alchemy]

Originally Posted by Saucy Sailoress

This:

Ah, yes. Look at the Hydrobubbles on that anchor.

[doug86]

I love innovation and new ideas, and I'm not opposed to looking for improvement. But the OP was about coming up with another way to test existing anchors. Anchors have been tested ad nasuem by magazines, by yacht clubs, by manufacturers and boating associations for decades. From what I have read, the results are just more fodder for the debate.

I spend every summer on a mushroom mooring, which is really not much more technically advance than the hypothetical rock with a hole drilled in it. Lots of folks have tried to improve on that, but it's tough to improve on Big Dumb and Heavy when it comes to keeping a boat in one place.

[GordMay]

Originally Posted by doug86

... rock with a hole drilled in it. Lots of folks have tried to improve on that, but it's tough to improve on Big Dumb and Heavy when it comes to keeping a boat in one place.

Actually, it's very easy to conceptualize a huge improvement on the deadweight. Consider the screw-in helical mooring.
The mushroom, itself, is an improvement on the simple deadweight.

[doug86]

Gord, the helical system has some drawbacks, including a practical depth limit imposed by the way it needs to be installed from a fixed platform on the surface (a spud barge. A barge large enough to set a helical in 40' of water makes the entire endeavor far too costly compared to the ease of dumping a mushroom and chain overboard). To inspect the screws, they must be unscrewed which requires a diver with some understanding of how the helical system is assembled. The chains still rust and wear out with the same regularity as a mushroom's tackle would, but again, inspecting and changing the chain requires a diver. They do offer some swing room advantages in a tight mooring field, but not much. Finally, a mushroom can be moved quite easily to a new location with a small winch on a small boat. If you have to move a helix, you're in for a long day. So, I don't think they are a "huge improvement" over heavy mushrooms.

I work for the mooring service provider on Block Island, and we rejected the helix moorings after careful consideration of all the factors. They are an alternative to mushrooms, but not necessarily an improvement.

As to the rock vs mushroom, I did admit it was a small an improvement.

[Therapy]

Originally Posted by Saucy Sailoress

This:

Ya.

All the same questions though.

How deep is the penetration?

How long to get it there?

What happens when there is a 180º change?


PS you started it.

[Hydra]

Originally Posted by doug86

US charts list 24 basic bottom qualities, including: mud, ooze, shale, clay, sand, gravel, broken shell, rocks, pebbles, ash, coral, grass, weed, hard sand, soft sand, silt, oysters.... how can you possibly test for all?

Without testing for all types of bottom, it would be interesting to compare the holding strength of anchors in good to marginal conditions that are frequently encountered: mud, hard and soft sand, broken shell, pebbles, grass...

I don't expect any anchor to be the best in all conditions but I would like to know if my ground tackle is sufficiently versatile for the ground where I intend to drop anchor.

Another task would be to measure the force exerted by a yacht on an anchoring rode (all chain or rope+chain), in relation to the current and wind speed and direction, and the wave height, direction and period. This would require accurate measurements on a long duration to reach reliable conclusions. It would probably exceed the capability of any yachting association.

Alain

[sarafina]

Originally Posted by Therapy

Ya.

All the same questions though.

How deep is the penetration?

How long to get it there?

What happens when there is a 180º change?


PS you started it.

So.... Succinct...

[klem]

I agree that the scientific method needs to be applied a bit more rigorously to anchor testing. Things like a well designed experiment to test different factors like anchor size, scope, bottom type etc.

My biggest complaint and one that could potentially be solved without tons of extra testing time is how they report the results (okay this takes a lot of extra web space or paper but it is certainly doable). I would want to see a graph of force readout and a video of what the anchor is actually doing. In addition, I want to know the number of trials and the standard deviation. If an anchor holds 5,000 lbs, that isn't any good if the standard deviation is 3,000 lbs.

My other complaint is that they have only tested half of what we need to know. The other half is what the expected forces are at given windspeeds and wave heights of different boat types and sizes. To my knowledge, there isn't that much better data out there than the ABYC guidelines which a lot of people claim are too high. Again, I would want to know the force versus time, not the average although the peak alone would suffice. I was very happy to see that Maine Sail bought a force meter and am hoping that he gets some data, especially of storm type conditions.

[markpierce]

You need to know your bottom. Start there when choosing an anchor.

[Kettlewell]

My other complaint is that they have only tested half of what we need to know. The other half is what the expected forces are at given windspeeds and wave heights of different boat types and sizes. To my knowledge, there isn't that much better data out there than the ABYC guidelines which a lot of people claim are too high. Again, I would want to know the force versus time, not the average although the peak alone would suffice.

Good point, brought up by several in this thread. Several problems I see with this. One is that there is a wide variation in forces based on the type of boat and even within specific types different models. I have observed many boats at anchor and in the same wind condition some are pulling their rode bar taught while others have a nice curve in the rode, in the same anchorage and the same wind. In any case, I suspect the ABYC guidelines are way too high for many boats, based upon my own very crude observations.

[klem]

Kettlewell,

I agree completely that it would be impossible to figure out the loads for each boat but if someone were to set up a test using several different boats representing many types and give the data, one could get a good idea of what their boat should see. If you had a bunch of force sensors, it shouldn't be too hard to install them on a variety of boats in a harbor before a storm and then install one wind gauge and as long as you sync the time on all of them, you would get somewhat representative data. It would also be great to put an accelerometer on the bow of each boat to measure pitch and yaw. There are all sorts of other pieces of data that I would like to see but this would give a pretty decent picture in my opinion. I just hate using a formula and having no hard data to back it up.

[Kettlewell]

It is rather amazing that so much to do with anchoring is based on no, or very little, scientific data at all. I believe the ABYC guidelines for anchoring forces, which are quoted everywhere, are totally theoretical--not based on any actual measurements. Interestingly, Danforth used to conduct quite a bit of anchor testing, partly because of all their work with the military. I have some old Danforth brochures that have some of the most detailed discussions and data on loads, etc. I've seen anywhere. I wonder where all of their testing data and information is these days?