Chesapeake Bay Anchor Holding Power Test

[FrankZ]

You should try the mud over at the hammock in Bodkin creek. That can be a right soupy mess to get a grip on.

[Fortress]

Originally Posted by kmacdonald

Brian, why dont you use a 40 foot sailboat to test with? The big powerful research boat is not what we cruise in and will skew results. With enough power it could bury a fortress to China but our sailboats cant do that. Dont forget to try it on an oyster bed.

I guess since you are paying for the tests you can taylor it for best results. By the way I have a guardian that I use in silt or soft mud, works great. It has fouled with oyster shells and failed to reset so I don't use it in oyster areas.

Dont do the 180 degree swing test after setting it with a tug boat or straight line pull. Maybe set it with 200 or 300 pounds and then test for reset after180 degree swing. Our boats dont even have cleats that will hold the forces exerted by the research vessel.

Kmacdonald,

We will not be pulling with the research vessel: it is too big, the bottoms are too soft, and the anchors are too small to be able to get consistent results.

We will be using the aft winch to do the pulling, and we have rented a running line tensiometer that will be installed on the wire rope and is capable of measuring & logging the payout, tension, and pull speed.

The research vessel will be held in place during the pulling by its "state of the art" Dynamic Positioning System.

200 or 300 lbs of load, which is about a 15-knot breeze against a 35-40 ft boat, is not much of a deep set in this soft mud bottom, and I'd expect that all of the anchors will be able to turn and maintain a grip after a minimal load.

We will experiment and see.

Thanks,
Brian

[nigel1]

Originally Posted by Fortress

Kmacdonald,


The research vessel will be held in place during the pulling by its "state of the art" Dynamic Positioning System.

200 or 300 lbs of load, which is about a 15-knot breeze against a 35-40 ft boat, is not much of a deep set in this soft mud bottom, and I'd expect that all of the anchors will be able to turn and maintain a grip after a minimal load.

We will experiment and see.

Thanks,
Brian

Hi Brian

Hope the DP system has been properly configured for the testing.
To work properly, the DP system will need an input from the tension meter.
Without a tension meter, the test winch will pull the boat ahead or astern depending on where the winch is placed, and the boats engines/prop pitch will adjust to get the boat back into position. Without the tension meter input to the DP computer, the boat most likley will tend to yo yo ahead and astern.

[Snowpetrel]

I am looking forward to seeing the results. Even if the fortress comes out best, and I think it stands a good chance, being a damn good anchor. It will also be interesting to see how the the other anchors go in very soft mud. Good on you fortress for organising the tests.

It would be interesting to see the effects of a wire leader on the UHC and depth of set. Or more practically lighter g70 chain vs heavier normal chain.

And also settling time on UHC. If an anchor is left overnight does its UHC increase by any meaningful amount? Leave all the test anchors sitting overnight and then test again the next day.

I would love to get some sort of data on depth of set vs surface area vs UHC, but getting depth of set accurately might be tricky. Maybe a tripping line pulled tight and marked before setting and again after setting? Good luck with the boat and weather.

Cheers

Ben

[Waterway Guide]

Hi Brian,

Do you have a list of the specific anchors that will be tested, and the details of the specific tests?

[Fortress]

MikeA,

Please see image below for the anchors to be tested.

Brian

[Waterway Guide]

Thanks, Brian. I reread the thread and didn't get a complete picture on what tests you'll be performing. The distance to reset after a strong 180º direction shift is probably the only test my readers would have much interest in.

[Fortress]

Originally Posted by Waterway Guide

Thanks, Brian. I reread the thread and didn't get a complete picture on what tests you'll be performing. The distance to reset after a strong 180º direction shift is probably the only test my readers would have much interest in.

Thanks for your comments, and anchor re-setting capability is certainly a key performance factor. However, if an anchor cannot handle much of a load in a soft mud bottom during a straight line pull and it drags, then you can obviously expect this anchor to drag as well during a 180° wind shift.

With that said, we have to first establish what loads an anchor can handle in soft mud when pulled in a straight line, which should be when it performs optimally.

Brian

[barnakiel]

What I would like to see in an anchor test:

break down per:
- comparable fluke area,
- comparable weight,

then:
- straight pull results,
- drag rate,
- break out point,
- angle pull results,
- resetting results,

- info on bottom type,
- info on depth,
- info on rod,

Have a great testing day. Looking forward to reading your results and findings. Thanks for your effort and for sharing!

b.

[nigel1]

Hi Brian

When do you expect to make the test results public, and where will be able to see the results.
You have a couple of my anchors in the mix, including the Fortress, I'd be interested to see the results.

[Fortress]

Originally Posted by nigel1

Hi Brian

When do you expect to make the test results public, and where will be able to see the results.
You have a couple of my anchors in the mix, including the Fortress, I'd be interested to see the results.

Nigel1,

The testing will be conducted over a 3 day period (Tuesday-Thursday) and possibly Friday as well. I hope to publish the results after each day.

Brian

[Auspicious]

Good choice of anchors.

I'd like to see bottom samples collected and tested for viscosity and shear strength.

You probably won't have time, but it would be nice to have a statistically significant number of pulls for each anchor - assuming a normal distribution that means 30 pulls per anchor. Any statistician or experimental scientist can provide the rationale.

[noelex 77]

I presume the bottom is soft enough to justify the 45 degree fluke angle on the Fortress. Do you plan to do any tests at 32 degrees?
It would be interesting to see the difference. I would imagine it would be considerable, but I have never seen any figures.

A lot of cruising sailors that own Fortress anchors are not aware of the adjustable fluke angle and it is quite common to see it never adjusted, or incorrectly set (I even think one magazine anchor test conducted in soft mud managed to get it wrong).

There are also instances where the bottom type is not accurately known and the conventional 32 degree setting is used as the safer alternative where there is some doubt.

I can imagine it is a bit late in the day to modify the test schedule to incorporate this so I understand if it is not possible, but I think it would be useful practical information for Fortress users like myself.

[Fortress]

Originally Posted by Auspicious

I'd like to see bottom samples collected and tested for viscosity and shear strength.

Auspicious,

Bob Taylor, a retired US Navy anchor design and soil mechanics expert is consulting for us on this project, advised but us that "a typical mud has a shear strength profile equivalent to about 9-12 psf / ft of depth."

We will certainly take soil samples, which I expect will be coming up with the anchors, as per the below image.

Originally Posted by noelex 77

I presume the bottom is soft enough to justify the 45 degree fluke angle on the Fortress. Do you plan to do any tests at 32 degrees?
It would be interesting to see the difference. I would imagine it would be considerable, but I have never seen any figures.

A lot of cruising sailors that own Fortress anchors are not aware of the adjustable fluke angle and it is quite common to see it never adjusted, or incorrectly set (I even think one magazine anchor test conducted in soft mud managed to get it wrong).

There are also instances where the bottom type is not accurately known and the conventional 32 degree setting is used as the safer alternative where there is some doubt.

I can imagine it is a bit late in the day to modify the test schedule to incorporate this so I understand if it is not possible, but I think it would be useful practical information for Fortress users like myself.

Noelex,

Thanks for the input. We plan on testing the Fortress anchor at both the 32° and 45° angle settings, although this is obviously a soft mud bottom for which the 45° angle was intended.

I will send you a copy of the results from the 1990 San Francisco Bay soft mud tests which show the holding power of the three Fortress anchors which were tested at both angles, and there was a dramatic difference between the two angles.

[noelex 77]

Originally Posted by Fortress

I will send you a copy of the results from the 1990 San Francisco Bay soft mud tests which show the holding power of the three Fortress anchors which were tested at both angles, and there was a dramatic difference between the two angles.

Thanks