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Old 18-07-2022, 20:16   #1
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How do you size a stern anchor?

I'm going to be replacing our CQR with a shiny new 65# mantus for our Moody 425. I figured as long as I'm going this I might as well pick up a stern anchor in case we find need of one. However, I have no idea how to size them. We are on the great lakes right now but will be making the tip up the st lawrence and down to the caribbean next year. Is there a rule of thumb for sizing?
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Old 18-07-2022, 20:29   #2
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Re: How do you size a stern anchor?

It appears that given your wide cruising range you kinda need to define "stern hook." The use of it will define it's type and weight. I anchored fore and aft on a river. I also dropped a small anchor off my stern to minimize sailing at anchor. I used a second anchor to kedge us off a sandbar.


All completely different loads, all need to be factored into choice, which sometimes leads to two different choices.


Choose wisely.
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Old 18-07-2022, 20:31   #3
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Re: How do you size a stern anchor?

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It appears that given your wide cruising range you kinda need to define "stern hook." The use of it will define it's type and weight. I anchored fore and aft on a river. I also dropped a small anchor off my stern to minimize sailing at anchor. I used a second anchor to kedge us off a sandbar.


All completely different loads, all need to be factored into choice, which sometimes leads to two different choices.


Choose wisely.

I figure it will most likely be used to prevent swing in weird anchorages.
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Old 18-07-2022, 21:24   #4
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Re: How do you size a stern anchor?

A stern anchor should have the same holding power as the bower, IMO. But due to the general lack of stern-mounted anchor rollers, you want it to be lighter. So, a properly sized Fortress with 15-20 feet of chain and a few hundred feet of appropriate sized 3-strand rode should suffice. Carry a third “lunch hook” if you wish to prevent swinging during temporary anchoring.
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Old 19-07-2022, 03:49   #5
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Re: How do you size a stern anchor?

Congratulations on your new Rocna. Your life is about to change vs. that CQR.
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Old 19-07-2022, 04:28   #6
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Re: How do you size a stern anchor?

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I figure it will most likely be used to prevent swing in weird anchorages.
keep the CQR as a secondary- I do not know what version you have- but with the wide range of cruising you suggest-
Or buy a fortress rated for the boat.

For that distance/diverse areas, and seaworthiness it would be prudent to have two different anchors and equivalent strength rodes. This permits various uses that covers all conditions.

Do not confuse stern anchors and lunch anchors- lunch are a short time excursion monitored anchoring- and are used whatever way is convenient.

The CQR uses weight but could be on bow roller or a stern roller, with a proper sized nylon anchor line stowed below or out of UV. Makes it easy to handle.
Fortress costs money and is even easier to handle, disassembles, etc. but again, your real intended uses are?

So many options, so few answers.
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Old 19-07-2022, 05:20   #7
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Re: How do you size a stern anchor?

Iíve never used a stern anchor in decades of cruising.
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Old 19-07-2022, 05:27   #8
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Re: How do you size a stern anchor?

Quote:
Originally Posted by nuru05 View Post
I'm going to be replacing our CQR with a shiny new 65# mantus for our Moody 425. I figured as long as I'm going this I might as well pick up a stern anchor in case we find need of one. However, I have no idea how to size them. We are on the great lakes right now but will be making the tip up the st lawrence and down to the caribbean next year. Is there a rule of thumb for sizing?
Our main use of a stern anchor has been to limit swing in crowded anchorages or in narrow rivers. Found the fortress invaluable as is easy to row out and drop / retrieve. Have 2 different chain lengths to hook up to it and choice of rope rode lengths. Have a 30kg Sarca Excel as primary anchor, 15 kg plough as back up and 10kg Fortress.
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Old 19-07-2022, 05:50   #9
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Re: How do you size a stern anchor?

I often anchor from the stern cleat in quiet anchorages to get a better breeze through the boat/avoiding bugs.
I also anchor some ingenuity ideas- drag the anchor rode (soft nylon) just under mast and with snubber lock it at bottom of front of keel. Allows (to 20knts) ability to current swing on anchor acting like a vessel half my size.
Stern anchor when in a cut hole twice my beam. Back in , drop anchor, ease out to position, lock all down. No dingy.
Also, mentioning multiple uses of two types but proper sized anchors- the Danforth shackles into back of CQR (type 2) which is then appropriate short chain to nylon rode. Worked extremely well in four storms each with excess 70knots wind. grass, clay, and rocky bottom. Sail/swinging was reduced in one weather pattern by a long scope nylon rode on the Danforth and a short scope rode on the CQR. This created a "Hammerhead mooring" which allowed the 40 degree gusts of wind to drag the CQR along the arc and meanwhile reduce the loads on the Danforth and avoid breaking it out.


The Mantis, etc anchors are good, but no less prone to breaking out in certain conditions. The advantage is they fit bow rollers- so if one does not have that type system restriction, then the success discussion begins to become far less restrictive.
Bottom line- what makes your vessel seaworthy in the anticipated conditions-
and having choice justifies two different type anchors that individually can hold the vessel in anticipated normal conditions (<45kts and moderate seas).
Beyond those winds one needs to invest in a decent weather source locally and motivate to some more sheltered location.
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Old 19-07-2022, 06:09   #10
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Re: How do you size a stern anchor?

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I’ve never used a stern anchor in decades of cruising.
Skilled use of stern anchors permits more anchoring options than with a single hook only. Fox example, if you wished to anchor in a “tight” location such as a small cove of an island or mainland coast, hardly more than a few boat lengths (say 200 ft across or less) with rocks about, you want to constrain movement with any changes of wind directions and of course tidal flow. The gunkholers make regular use of them. Cruisers should carry a minimum of two, three better, sets of ground tackle for the variety of anchoring options.
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Old 19-07-2022, 06:20   #11
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Re: How do you size a stern anchor?

Kind of a counterculture view on this. On our trip up the coast into the Bay of Sunday last year, we had more than a few anchorages that were inadequately protected from the ocean swell. In lighr wind, the boat would turn sideways to the swells and roll horribly. We found a stern anchor to pull the boat into the waves was a solution.

We carry a big Fortress, but it is kind of buried. However, we found that the 4.5 lb Danforth from the dinghy was up to the task. Our boat is 43 ft and 25,000 lb, but the loads were light.

Hardly a real stern anchor! Certainly not equivalent to the 55 lb Rocna in primary or the 65 lb Bruce in secondary on the bow. If I were to actually buy one for the purpose, I might go for an 8 lb. Still super easy and light to handle, but a little bit more powerful. I would also equip it with a 3 mm dyneema rode.

Like I said, counterculture. While I've had opportunities in my life to put two anchors off the bow, I have yet to find a need for a serious stern anchor. But we have definitely found value in an easy to deploy lightweight stern anchor.
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Old 19-07-2022, 06:21   #12
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Re: How do you size a stern anchor?

Quote:
Originally Posted by boat driver View Post
Sail/swinging was reduced in one weather pattern by a long scope nylon rode on the Danforth and a short scope rode on the CQR. This created a "Hammerhead mooring" which allowed the 40 degree gusts of wind to drag the CQR along the arc and meanwhile reduce the loads on the Danforth…
I believe you are referring to a Hammerlock Mooring.
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Old 19-07-2022, 06:23   #13
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Re: How do you size a stern anchor?

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Originally Posted by sailingharry View Post
Kind of a counterculture view on this. On our trip up the coast into the Bay of Sunday last year, we had more than a few anchorages that were inadequately protected from the ocean swell. In lighr wind, the boat would turn sideways to the swells and roll horribly. We found a stern anchor to pull the boat into the waves was a solution.

I think that still follows the general view on the matter. Stern anchor only when it's determined to be needed and there's not a better alternative available.
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Old 19-07-2022, 06:46   #14
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Re: How do you size a stern anchor?

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Originally Posted by sailingharry View Post
Kind of a counterculture view on this. On our trip up the coast into the Bay of Sunday last year, we had more than a few anchorages that were inadequately protected from the ocean swell. In lighr wind, the boat would turn sideways to the swells and roll horribly. We found a stern anchor to pull the boat into the waves was a solution.

We carry a big Fortress, but it is kind of buried. However, we found that the 4.5 lb Danforth from the dinghy was up to the task. Our boat is 43 ft and 25,000 lb, but the loads were light.

Hardly a real stern anchor! Certainly not equivalent to the 55 lb Rocna in primary or the 65 lb Bruce in secondary on the bow. If I were to actually buy one for the purpose, I might go for an 8 lb. Still super easy and light to handle, but a little bit more powerful. I would also equip it with a 3 mm dyneema rode.

Like I said, counterculture. While I've had opportunities in my life to put two anchors off the bow, I have yet to find a need for a serious stern anchor. But we have definitely found value in an easy to deploy lightweight stern anchor.
Here in CA sailors frequently anchor in coves of the offshore islands. In strong conditions a skipper might wish to lay at anchor under the lee of a sheltering rock cliff. You get more shelter the closer to it (cliff) that you are able to lay. If the bower is set close (to bring the vessel close) you need a stern anchor to prevent swinging into the cliff with a unexpected change of wind direction. You certainly would not want it to break out in a gust from astern. Winds gusts near islands may come from a variety of directions, and of variable strengths, guided by the island’s topography. Alternatively, the skipper might wish to lay “parallel” to a cliff instead of perpendicular to it. Need two anchors to maintain attitude. Maybe a third set abeam away from the cliff.

In short, if the purpose of a stern anchor is to hold you away from rocks, cliffs, or other structures/vessels, then it had better hold, etc. Each skipper decides the required holding power in a given situation, of course. I choose to carry one of equivalent holding power of the bower, although it is of a different type with a different rode for ease of deployment and recovery. So, I can get about the same scope for each.
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Old 19-07-2022, 10:10   #15
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Re: How do you size a stern anchor?

Is there a 'rule of thumb' for selecting a stern anchor? Yes. Definitely. The same rule of thumb that applies to all anchor selections. " Get the biggest anchor that you can reasonably manage" factoring in weight, size, shape, and space available. When the **** hits the fan, you will never wish you had set a smaller anchor. AND don't assume that just because an anchor was designed by a computer in the 21st century, that it is superior to an anchored developed over centuries of experience, trial, and error.
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