Anchoring in Soft Mud

[carstenb]

Dockhead, I had the same experience in the Swedish archipelago this past summer. Nothing, i repeat nothing I could do could get my Bruce to hold firm. It was fine up to about 2500 rpm then we moved ever so slowly backwards.

I tried 4 different places in that bay and got the same result. I'm pretty sure it was because the bottom was sheer rock overlaid with some mud. The mud just wasn't deep enough for the anchor to grab.

I normally carry a F-55 for just this type of crap - but I'd left it home. I now know better for next year.

[Dockhead]

Originally Posted by ranger42c

I take it you've seen the Fortress testing results -- here and in the much longer version on trawlerforum -- in soft mud?

-Chris

Hi, no, I haven't seen test results, or don't remember them. But I've been a Fortress owner for many years, and know from my own experience that the Fortress holds really well in soft mud.

I hesitated to throw it out, however, because it's near springs, and I'm anchored in the tidal stream, which reversed in the middle of the night. I've actually never had any Fortress pull out and fail to set on me, but this problem is well enough known, that I wouldn't want to take chances.

Besides that, it's a mess to use in mud, as I have to haul it in by hand. It means stinky mud on my hands and all over the deck.

[Dockhead]

Originally Posted by HopCar

My limited experience with anchoring in soft mud has led me to conclude that you want an anchor with as much fluke area as possible.


There are three common types of anchors in favor now, the weighted tip (Spade and Delta), the roll bar (Rocna and Mantus) and the Danforth (Danforth and Fortress).


If you had one of each of these and they all weighed the same (pretend the Fortress was steel) The weighted tip anchor would have the least fluke area because so much of their weight is in the form of ballast in the tip. The roll bar anchors would be next in fluke area. The Danforth style would have the most fluke area.


This is why I think Danforth style anchors do so well in tests in soft mud. It's simple, bigger flukes are harder to pull through the mud.


If I had to anchor in soft mud, and I'd rather not, my first choice would be a Fortress with it's flukes set for mud.


78 deg. F in Miami now. Probably go into the eighties tomorrow.

That's all logical enough, but my smaller (44 kg) Spade definitely works better in soft mud (and everywhere else) than my former larger 55kg Rocna.

I think besides having enough fluke area, an anchor needs to be dense enough to penetrate -- two criteria which might be in conflict with many anchors.

Which begs the question: how does the Fortress penetrate so well, without any weight? It's just aluminum. I really don't know -- maybe it's the particular geometry of the flukes. Very sharp, flat fluke, and nothing else -- just cuts right in like a knife blade. All I know is that my Rocna was harder to set than the Spade -- never budged once set (not once), but in some situations would skip across the surface of the seabed without digging in, especially in soft mud. The Spade cuts in better -- which I guess is from the sharper fluke and lead ballast. But I'm also guessing that differences in geometry probably play a role as well.

[ranger58sb]

Originally Posted by Dockhead

Hi, no, I haven't seen test results, or don't remember them. But I've been a Fortress owner for many years, and know from my own experience that the Fortress holds really well in soft mud.

I hesitated to throw it out, however, because it's near springs, and I'm anchored in the tidal stream, which reversed in the middle of the night. I've actually never had any Fortress pull out and fail to set on me, but this problem is well enough known, that I wouldn't want to take chances.

Besides that, it's a mess to use in mud, as I have to haul it in by hand. It means stinky mud on my hands and all over the deck.

The two recent threads about the recent testing in soft mud in the Chesapeake, one on each forum, have bazillions of posts...

FWIW, I begin to suspect the well-known problem... isn't one, really. I suspect when a Fortress is well-set -- meaning pretty much buried at least up to the shackle -- it doesn't actually suffer from reversing tides/currents. Just theory, though.

The only time I've had our Fortress maybe fail was when we were only lightly set in a well-protected creek... and a downburst came through and spun the boat in a 360° over the course of about a minute. I assumed (but don't know) that we'd have to reset, but we were so close to our home dock that we just brought it all up an motored home before the main part of the storm arrived.

I do very much know what you mean about stinky mud all over the deck. This around here is stuff where you can get knee deep without even thinking about it. Hence the raw water washdown we installed at the bow, etc. It still takes us 20-30 minutes to bring the anchor/rode all back aboard without making too much of a mess...


Our Fortress is not our main anchor either, though...

Originally Posted by Dockhead

I think besides having enough fluke area, an anchor needs to be dense enough to penetrate -- two criteria which might be in conflict with many anchors.

Which begs the question: how does the Fortress penetrate so well, without any weight? It's just aluminum. I really don't know -- maybe it's the particular geometry of the flukes. ... But I'm also guessing that differences in geometry probably play a role as well.

If left to its own devices, mass is likely critical to penetration. But with anchors, I'd expect the vector forces applied by some combination of fluke shape/orientation and tension on the rode likely either replace, augment, or mimic mass to a certain extent.


-Chris

[Dockhead]

Originally Posted by ranger42c

The two recent threads about the recent testing in soft mud in the Chesapeake, one on each forum, have bazillions of posts...

FWIW, I begin to suspect the well-known problem... isn't one, really. I suspect when a Fortress is well-set -- meaning pretty much buried at least up to the shackle -- it doesn't actually suffer from reversing tides/currents. Just theory, though.

The only time I've had our Fortress maybe fail was when we were only lightly set in a well-protected creek... and a downburst came through and spun the boat in a 360° over the course of about a minute. I assumed (but don't know) that we'd have to reset, but we were so close to our home dock that we just brought it all up an motored home before the main part of the storm arrived.

I do very much know what you mean about stinky mud all over the deck. This around here is stuff where you can get knee deep without even thinking about it. Hence the raw water washdown we installed at the bow, etc. It still takes us 20-30 minutes to bring the anchor/rode all back aboard without making too much of a mess...


Our Fortress is not our main anchor either, though...


If left to its own devices, mass is likely critical to penetration. But with anchors, I'd expect the vector forces applied by some combination of fluke shape/orientation and tension on the rode likely either replace, augment, or mimic mass to a certain extent.


-Chris

That all sounds quite reasonable to me. Nothing really to add. I also suspect that the Fortress would probably not release once well buried. I've just not been much inclined to test it. Especially since I would be hauling it in by hand. It's easier to use the main bower anchor, about which we have less doubt about releasing anyway.

I bought an (expensive) raw water washdown and have never gotten around to installing it. I really need it for these "muddy" situations; and also it would be a Godsend for keeping the teak decks moistened with salt water. I'll bump it up the winter refit list; thanks for the reminder.

[Dockhead]

When I pulled the anchor up in the morning, I could immediately see the problem -- I was anchored right in the plume of silt coming from the River Meon. I wasn't able to see that when I came in because it was already dark. Must avoid river mouths in future!

Today was an absolutely gorgeous day -- barometer off the chart; bell clear sky and sunshine. Almost no wind. So I sailed down to Yarmouth on the spring tide. Motorsailing lazily at 4 or 5 knots, but being swept along by 3 and 4 knots of tidal stream. I love days like this! Shame I have no principle headsail - my yankee jib was shredded in a storm in the Baltic in August, and don't have my new sails yet. So I was under main alone and needed to motorsail. I would normally put up all plain sail and just drift along at 3 knots if necessary -- as long as there's enough way on for steerage, you don't care, when the tide is taking you right to your destination.

But as it was motorsailing was also pleasant -- 1200 rpm.

It's going to be cold tonight, but I'm plugged into shore power, so I won't need to burn diesel all night in the Espar. Yarmouth is the most gorgeous little town, just like going back in time (much of the Isle of Wight has that kind of atmosphere). I'm going to finish my work and then walk into to town and have a nice pub dinner sitting next to the fire. Ah, life sucks!

[Fortress]

Dockhead,

As proven by the Chesapeake Bay tests, the 45° shank / fluke angle of the Fortress will offer a dramatic difference in holding capacity in soft mud, and you are right, once it is buried, retrieval can be difficult and messy.

This was evidenced by the fact that we broke a wire cable at 3,500 lbs (about 1,600 kg) trying to pull out the 21 lb (10 kg) FX-37 while directly above it and pulling at a 1:1 scope. The winch operator calculated that the anchor was buried at least 13 feet (4 m) into the mud, and the thought that this anchor would pull out easier at a normal or shorter scope and with a change of pull direction during a wind or tidal shift is unimaginable.

Fortunately we had a good strong power washer aboard the 81-ft Rachel Carson research vessel which served as the test platform. See images below.


At the end of 4 full days of testing and after all 11 anchors had been tested 5x (the Fortress at both the 32° and 45° angles) for a total of 60 tests, we tested the 10 lb (4.5 kg) FX-16 at the 45° angle, and it held far more than all of the 44-46 lb (20-21 kg) steel anchors....new and old generation anchors alike....and as much as the 35 lb (16 kg) Danforth and the FX-37 at the 32° angle.

Below is an image of this anchor after we were finally able to pull it out. A video from Day 4 is also below, and the segment with the FX-16 is just after the 8:00 minute mark.

https://www.youtube.com/watch?v=4Ga1...g&spfreload=10

This test obviously highlighted the importance of the wider shank / fluke angle for soft mud anchoring, which is no secret to Fortress, as Baldt, Bruce, the US Navy, and Vryhoff all make anchors with this configuration capability for this type of bottom.

[model 10]

I added an FX-27 in tandem to our Rocna once. When the chain came tight the Rocna lifted right out of the mud and the chain when tight to the FX-27.
I've seen several people dive on their Fortress to get loose in a soft bottom.

[Dockhead]

Originally Posted by Fortress

Dockhead,

As proven by the Chesapeake Bay tests, the 45° shank / fluke angle of the Fortress will offer a dramatic difference in holding capacity in soft mud, and you are right, once it is buried, retrieval can be difficult and messy.

This was evidenced by the fact that we broke a wire cable at 3,500 lbs (about 1,600 kg) trying to pull out the 21 lb (10 kg) FX-37 while directly above it and pulling at a 1:1 scope. The winch operator calculated that the anchor was buried at least 13 feet (4 m) into the mud, and the thought that this anchor would pull out easier at a normal or shorter scope and with a change of pull direction during a wind or tidal shift is unimaginable.

Fortunately we had a good strong power washer aboard the 81-ft Rachel Carson research vessel which served as the test platform. See images below.


At the end of 4 full days of testing and after all 11 anchors had been tested 5x (the Fortress at both the 32° and 45° angles) for a total of 60 tests, we tested the 10 lb (4.5 kg) FX-16 at the 45° angle, and it held far more than all of the 44-46 lb (20-21 kg) steel anchors....new and old generation anchors alike....and as much as the 35 lb (16 kg) Danforth and the FX-37 at the 32° angle.

Below is an image of this anchor after we were finally able to pull it out. A video from Day 4 is also below, and the segment with the FX-16 is just after the 8:00 minute mark.

This test obviously highlighted the importance of the wider shank / fluke angle for soft mud anchoring, which is no secret to Fortress, as Baldt, Bruce, the US Navy, and Vryhoff all make anchors with this configuration capability for this type of bottom.

Cool. That seems pretty convincing.

I guess I could disconnect the Spade from the main anchor rode and use it on that with the windlass, but that's a real PITA since I'm using the concealed pin Wichard shackle which needs the pin Loctited in place.

I don't really know of any other way to use the windlass with a different anchor. Maybe I could add some kind of connector which is easier to disconnect.

Otherwise, I'm left with using the Fortress on a nylon rope rode which has to be hauled in by hand.

[avb3]

Originally Posted by Dockhead

Cool. That seems pretty convincing.

I guess I could disconnect the Spade from the main anchor rode and use it on that with the windlass, but that's a real PITA since I'm using the concealed pin Wichard shackle which needs the pin Loctited in place.

I don't really know of any other way to use the windlass with a different anchor. Maybe I could add some kind of connector which is easier to disconnect.

Otherwise, I'm left with using the Fortress on a nylon rope rode which has to be hauled in by hand.

Just a silly thinking out of the box idea, (which I have not tried nor know if it would work), have you thought of using what I call a pikeral jig (from fishing) setup?

The idea is both anchors on the rode, separated by a significant amount of space. It would have to involve a lot of scope, but with the Fortress being the lead anchor, setting it, and if the Spade sets, great, if not it is there as a potential backup. Then you could use your windlass.

Something like this:

[Dockhead]

Originally Posted by avb3

Just a silly thinking out of the box idea, (which I have not tried nor know if it would work), have you thought of using what I call a pikeral jig (from fishing) setup?

The idea is both anchors on the rode, separated by a significant amount of space. It would have to involve a lot of scope, but with the Fortress being the lead anchor, setting it, and if the Spade sets, great, if not it is there as a potential backup. Then you could use your windlass.

Something like this:

Attachment 92274

Great picture!

It seems like a great idea in theory, but I am allergic to multiple anchor setups. I admit that I have very little experience, but that experience was so negative -- a tangle every time I tried it . . . .

[transmitterdan]

Dockhead,

We have a capstan on our windless (horizontal Lighthouse1501) to help pull up the FX-37 which is on about 5M chain then 5/8 nylon. Still messy but saves the back muscles.

[Dockhead]

Originally Posted by transmitterdan

Dockhead,

We have a capstan on our windless (horizontal Lighthouse1501) to help pull up the FX-37 which is on about 5M chain then 5/8 nylon. Still messy but saves the back muscles.

A Lighthouse horizontal windlass is one of my wet dreams.

Unfortunately I have much more mundane vertical Lewmar Ocean windlass.

[Fortress]

Dockhead,

To be very frank, without mechanical help I don't think that you would be able to get your 32 lb (15 kg) FX-55 anchor out of the soft mud after a heavy blow if you set it at the 45° angle.

During preliminary testing, it held to over 4,000 lbs (1,800 kg) several times and tripped the aft winch in the process, so if you don't need storm-condition holding power, then I would leave it at the 32° angle.

And your sailing grounds sound quite idyllic.

Enjoy,
Brian

[Dockhead]

Originally Posted by Fortress

Dockhead,

To be very frank, without mechanical help I don't think that you would be able to get your 32 lb (15 kg) FX-55 anchor out of the soft mud after a heavy blow if you set it at the 45° angle.

During preliminary testing, it held to over 4,000 lbs (1,800 kg) several times and tripped the aft winch in the process, so if you don't need storm-condition holding power, then I would leave it at the 32° angle.

And your sailing grounds sound quite idyllic.

Enjoy,
Brian

Well, believe it or not, I've used my Fortress a few times

That force does not exceed the SWL of the rode I'm using. I generally run it over a bow roller, tie it off securely to a bow cleat, then power it out with the main engine (100 hp Yanmar). Then, haul it up by hand (or use the giant electric Lewmar sheet winches ).

The main problem is the stinky mud.