Anchor Geekdom

Panope

Super Anarchist
1,425
569
Port Townsend, WA
I think you are correct, cje. Too much curve in the fluke.

In the past, I have read many persons hypothesis, that the roll-bar is the source of the Manson (and Rocna) fouling issue. I am now convinced that this is not the case, at least here in this seabed.

Steve

 

valis

Super Anarchist
3,773
597
Friday Harbor, WA
I think we all have to remember that the seabed characteristics are critical factors in anchor performance. However, I doubt that the perforations will make an anchor perform any worse in non-sticky-mud situations. Of course I wouldn't have guessed that they would make the difference we see in the last video, so obviously my assumptions could wrong.

 

py26129

Super Anarchist
2,802
160
Montreal
I will add my voice to the appreciative chorus here. I am currently in the process of upgrading form a cheap Bruce clone to either a Rocna or a Mantus and your videos have been most helpful.

Many thanks

 

IStream

Super Anarchist
10,715
2,921
I'm hypothesizing that during the reset process, the hydraulic pressure of the mud forcing itself up through the holes from the underside of the fluke dislodges the mud stuck on the top, clearing it for a reset.

 

Alex W

Super Anarchist
3,300
292
Seattle, WA
That's a great find. I would be curious to try it on my 10kg Bruce (real, not knockoff), but don't have a good way to test holding power. I cruised with an undersized anchor this year and using the Bruce reminded me of how much I like them. I just have fewer problems with initial set on the Bruce than I did with the Manson, especially in areas with weeds.

Do you think that reshaping the point on the Manson did much? It always seemed like it could be sharper.

 
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psychosailing

Anarchist
549
0
This is a very interesting battery of testing. It's amazing to see the behavior of anchors underwater, while the boat pulls.

I think the methodology used (the torture) gives information about the extremes at when every single design would fail. That helps find minimum scope per power, but not necessarily tell if a design is unsufficient when safety parameter (not choosing a dumb anchorage, enough scope, etc.) are respected.

why one would want to anchor on a 2:1 scope and face strong winds?

 

Panope

Super Anarchist
1,425
569
Port Townsend, WA
I'm hypothesizing that during the reset process, the hydraulic pressure of the mud forcing itself up through the holes from the underside of the fluke dislodges the mud stuck on the top, clearing it for a reset.
The pressure on the upper surface of the fluke is most certainly greater than on the underside, thus making it hard to imagine how mud could travel from below to above.

My theory, is that the holes allow the compacted seabed to remain wet and perhaps better lubricated.

Steve

 
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Panope

Super Anarchist
1,425
569
Port Townsend, WA
That's a great find. I would be curious to try it on my 10kg Bruce (real, not knockoff), but don't have a good way to test holding power. I cruised with an undersized anchor this year and using the Bruce reminded me of how much I like them. I just have fewer problems with initial set on the Bruce than I did with the Manson, especially in areas with weeds.

Do you think that reshaping the point on the Manson did much? It always seemed like it could be sharper.
Alex, hold off on drilling your Bruce as I MIGHT be doing the same. We will know right away if it has a positive effect as my 'side-view' camera shows very accurately how well (or poorly) the anchor will dive.

My belief is that ALL of my tip reshaping was useless. If I could do it all over again, I would not fuck with the tip of the anchor.

My Manson Supreme is at least 5 years old and I have since learned that newer 45 pound Supremes have a thinner shank. I removed part of my shank (.62 inch thick) as I felt the extra weight was causing a balance problem. The new anchors probably have the right amount of metal right out of the box.

Steve

 

Alex W

Super Anarchist
3,300
292
Seattle, WA
This is a very interesting battery of testing. It's amazing to see the behavior of anchors underwater, while the boat pulls. I think the methodology used (the torture) gives information about the extremes at when every single design would fail. That helps find minimum scope per power, but not necessarily tell if a design is unsufficient when safety parameter (not choosing a dumb anchorage, enough scope, etc.) are respected. why one would want to anchor on a 2:1 scope and face strong winds?
In my own experience it is rare to get to anchor with more than 4:1 in the PNW, often 3:1, because of the depths of anchorages. If you are in a busy anchorage with a lot of boats and the depth is 40' then 3:1 still puts you on a fairly large swing radius. The 7:1 that lots of experts suggest would take up the whole anchorage. I'd never anchor with 2:1 (at least not for long), but it does demonstrate worst case. He's done testing at a variety of scopes and seems to concentrate at 3:1 or 4:1.

The 10' deep anchorages common elsewhere (where 7:1 is practical) aren't even possible here with an average 6' draft sailboat since the tidal range is almost always >10'.

Panope has answered this before as well (in this thread), and I think his response is similar.

 

Panope

Super Anarchist
1,425
569
Port Townsend, WA
This is a very interesting battery of testing. It's amazing to see the behavior of anchors underwater, while the boat pulls. I think the methodology used (the torture) gives information about the extremes at when every single design would fail. That helps find minimum scope per power, but not necessarily tell if a design is unsufficient when safety parameter (not choosing a dumb anchorage, enough scope, etc.) are respected. why one would want to anchor on a 2:1 scope and face strong winds?
Thanks, psycho

My limit for sleeping at anchor is 3 to 1. If the wind pipes up and gets all the nearby boats settled into order, I add scope as able.

I executed some tests at extremely short scopes for research purposes only.

Steve

On Edit: what Alex W said above also.

 
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Panope

Super Anarchist
1,425
569
Port Townsend, WA
Jake,

I was disappointed to not be out on your vessel in that glorious wind, but I had family in town and wanted to stay with the group. We did take Panope out after the race for some wanking. I had nine people aboard (mostly lubbers).

Steve

 

valis

Super Anarchist
3,773
597
Friday Harbor, WA
Generally, "wanking" means what you probably think it means. But here in Cruising Anarchy it also means sailing around with just the jib up. Just taking it easy, not worried about optimum sail trim or anything much else.

 

Panope

Super Anarchist
1,425
569
Port Townsend, WA
WetSnail,

I wont mention to 'root' meaning as this is a family forum.

Let's just say that the sailing version only requires the use of one hand.

Steve

 

kinardly

Super Anarchist
Steve, as I think about this, one piece of info I'd like to have is how much wind does it take to make 3:1 inadvisable with all chain rode? I think it must vary from boat to boat and I wish I could think of a good way to experiment. Is there a way to equate pounds of pulling force to wind force and maybe throw in a little simulated surge action as well? Basically, most anywhere here on the West Coast you're going to have to anchor in deep water sometime and 150' of chain is probably the minimum for contingency purposes.

 

Panope

Super Anarchist
1,425
569
Port Townsend, WA
Kindardly,

With a short rode length of say, 100 feet of 3/8" inch chain, I have noticed that nearly all catenary is lost with less than 750 lbs of force. The better anchors are capable of holding much more than this even at the short scope of 3 to 1. Therefore, I see little correlation between ultimate holding power and rode type at SHORTER rode lengths.

However, when anchoring in very deep water (like 100 feet +) with VERY LONG rodes (like 300 feet +), the force required to remove catenary will be much much greater. Therefore, a heavy rode may very well increase the ultimate holding power of an anchor.

Many variables need to be considered (primarily, anchor type and bottom type) to answer your question: "how much wind does it take to make 3:1 inadvisable with all chain rode?". If I ever have any doubt about increasing wind load on the anchor, I just fire up the engine and pull has hard as I can in reverse. That tells me that I am probably good until the next increase in wind, at which point I do it again. Surge is easy to simulate with the engine - just motor ahead a bit and then get the boat going backward a knot or two. Just make sure your rode is belayed to something strong.

Steve

 
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