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Old 14-08-2010, 12:14   #1
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Tandem Anchors - a Thought

I'm getting my head round tandem anchoring with a view to a voyage to a part of the world (Patagonia) where it seems to be a necessary practice.

My reading suggests that the second anchor over the bow is the 'main' anchor, and so I was wondering if I made that anchor the heavy one (I have Rocna in mind) could the first anchor over the bow be something like a lightweight but large Fortress?

It would certainly make the recovery easier.
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Old 14-08-2010, 12:25   #2
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Originally Posted by oldvarnish View Post
tandem anchoring . . . a part of the world (Patagonia) where it seems to be a necessary practice.

Only if your main anchor is not heavy enough. A lot of cruisers get to Patagonia with ground tackle that is good sized for tropical cruising but not adequate for Chile/South Georgia/Antarctic. In that case, tandoms works (if properly rigged its not too difficult to handle) and is a good solution for them (or at least better than trying to get a new bigger anchor shipped in) . . .but its even better to go down there with a main anchor that's properly sized for the possible extreme conditions - eg you will almost certantly see +60kts sustained at anchor.

second anchor over the bow is the 'main' anchor, and so I was wondering if I made that anchor the heavy one (I have Rocna in mind) could the first anchor over the bow be something like a lightweight but large Fortress?

Yes, that works fine. When we have done it we usually use a 40lb steel danforth as the 'first anchor' but we have used our fortress and it works also.
attched is a photo from patagonia - this is an Oyster 72. Its in a quite protected anchored with good holding just north of the horn. You can tell the wind is about 60kts by the 'smoke' - water surface being vaporized. They dragged and had a hell of a time getting restuck.
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Old 14-08-2010, 12:59   #3
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One advantage with the Rocna is that it has a dedicated attachment point for a tandem anchor in the first place, a point I'm sure you haven't missed. The easier you can make these things, the more likely you're to use them, before (not after) you need to.

But I'd really like to support the main point that Evans makes - go large in the first place. Too many people opt for what seems about OK, and in out of the way places with dubious holding that ain't enough.
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Old 14-08-2010, 13:47   #4
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Hey, Evans, did you take that photo?

How was your boat?

What do you have as an anchor?

It looks seriously like I never want to be there
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Old 14-08-2010, 14:45   #5
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Mark,

We carry two 55kg anchors (a manson ray and a rocna). We had them both out (in a "V" . . . yes yes I know that's not optimum but it's practical). As I said the bottom was good sand/gravel, so if your anchors were proper for the (extreme) conditions you were fine, and Hawk was fine.

A good friend of ours was the captain aboard this boat. They were using an 80kg CQR. This was always fine in the tropics but they had trouble with it both in Chile and in the Falklands. They had a second anchor (100lb danfoth) but it was too clumsy/impractical to handle and set once the weather got bad.

This sort of wind went on for about 24 hrs. It's one of the few times I have gone to sleep wondering about chain breaking strength.

Down there, when its bad it can be absolutely terrible, but when its good it can be equally marvelous.
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Old 14-08-2010, 15:12   #6
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So, I'm baffled what would have been more practical? If not V then Tandem? Double Tandem?
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Old 14-08-2010, 18:48   #7
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So, I'm baffled what would have been more practical? If not V then Tandem? Double Tandem?
I think you mis-read my post. I said the V was the most practical, but not the theoretical best holding, solution.

Usually down there the answer is a long line (or two) ashore to a boulder or a tree, put in place before the wind gets to hard . . . but this is one of the anchorages where that is not a possibility. There is a ship mooring bouy in this anchorage, but it is quite far out from shore and thus less well protected and is uncomfortable.
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Old 14-08-2010, 20:47   #8
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Sorry estarzinger...a mental typo on my part...I meant "optimum"

Thanks!
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Old 15-08-2010, 05:41   #9
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Sorry estarzinger...a mental typo on my part...I meant "optimum"

Thanks!
Well, we all agree that a single big anchor is the 'optimum' . . . but if you have to deploy two anchors my understanding is that the (theoretical) optimum holding configuration is a (properly set up) tandem.

But with a tandem you do have a single catastrophic point of failure (the rode and aft anchor attachment point). With the V set-up you do have redundant rodes . . . so it's not all about holding . . . there are other failure modes that are on my mind as I go to sleep.

My 'hurricane' arrangement is V tandoms (4 anchors out on two tandem rodes). But I have only gone to that trouble once. One of my anchors has sufficient holding for pretty much any possible situation.
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Old 15-08-2010, 05:50   #10
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Thanks, Evans. I was the original poster and a handful of experience is worth many hours of speculation - I'm grateful. And the picture is deeply unsettling!

I'm starting from Europe, and if I want to get to the Pacific I can do it the easy way and head for the canal. But although those southern waters are a challenge, I guess the rewards are huge.

I see you headed north up the Chilean coast to Peurto Montt - my plan too. Where did you go after that?
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Old 15-08-2010, 06:57   #11
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Originally Posted by oldvarnish View Post
And the picture is deeply unsettling!

Yes, the conditions can be very tough and you need to be prepared and cautious. It s very unlike tropical cruising, a completely different game. But it is very doable. In most of the anchorages you can tuck out of the wind very close to the shore in tiny little coves with multiple lines ashore are are safe as houses.

those southern waters are a challenge, I guess the rewards are huge.

Again yes, I have to say that we did not completely enjoy our first trip up the channels because I found it pretty stressful, but Beth then forced me to make two other transits of the channels which we completely enjoyed because we knew how the game was played. It is one of our most favorite cruising grounds.

I see you headed north up the Chilean coast to Peurto Montt - my plan too. Where did you go after that?

We went up the channels and then turned around and went back down, then went round the world eastward (59 days non-stop from the horn to fremantle) and returned for a third southbound down the channels from the west. Unfortunately for you, going down (south) the channels is more pleasant than going up (north) because the wind is predominantly from the North (and west).
There is quite a bit of information on cruising Chile scatter around our website. But a big main anchor, two long shore lines and a decent cabin heater and some prudence/caution are the main points.
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Old 15-08-2010, 07:13   #12
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I don't know that this will add anything to Evans' comments, but ...

My wife and I cruised (we called it "adventure sailing") for 6 weeks in the Falklands and 2 months in Patagonia including the islands around Cape Horn during the 1980s -- e.g. pre-the new generation of anchors. We also cruised southern New Zealand (Stewart Island) and the Arctic using these same techniques. Our boat was a 45' classic S&S design; 10.5' beam, 31' on the water, just under 7' draft, 15 tons, fiberglass. Some observations (that obviously are from one data point only):

1) As has been said, and can't be emphasized enough, whatever anchor you use, make it big. This isn't a place to scrimp on either weight or $$.

In Patagonia, we used two anchors every night. The primary was a 150lb Luke Fisherman. I believe that it is an old Herreshoff design that Paul Luke, a well known builder in Maine, made for a number of years back then. It disassembled into 3 pieces to aid storage. We added an eye bolt threaded into the crown (e.g. in the end, in-line with the shank) to which we added a trip line. This was really a lifting line, as we only had a hand cranked windlass, which was useless, so we used a halyard to raise the anchor off the deck by the lifting line and pushed it out over the lifelines. When the anchor hit the bottom (not unusual to see 50 to 75 feet), we would release the snap shackle. We would recover it by driving up to the buoy, reconnecting to the lifting line, and using a nice halyard winch to raise the anchor. The rode was chain and nylon.

The Fisherman is a good anchor for the kelp, rock and sand that you can see in these anchorages. It clearly doesn't have the pound for pound holding power of the new generation anchors -- hence the really heavy size -- on the other hand, it penetrates well, which is a plus.

Our secondary was either a 45# Bruce (the "new generation" anchor of the time, which we happily used as our primary elsewhere on our trip around the world) or a 75# Luke Fisherman. The rode was all chain over the bow roller and we endlessly cranked our Simpson Lawrence windlass to retrieve it (or I would pull some by hand until I couldn't get any more -- it helped in those days to be young and strong).

2) As Evans did, typically we would use two anchors in a V configuration and two stern lines ashore. His picture is a great one and, while not an every day occurence by any means, should be expected and planned for. We holed up in the kelp behind land during one blow which the Chilean Navy described as the worst they had seen in the 3 years prior to our visit (over 100 knots at Puerto Williams). In other words, we were protected. Nevertheless, the boat was heeling 45 degrees to either side just through rigging drag and we couldn't keep our diesel heater lit for the life of us.

3) If we didn't tie ashore, we still used a V configuration for ease of deployment. This is a relative comment as it often took us an hour and a half to get settled in at night or cleared out in the morning. We never dragged and the effort was well worth it. It wasn't unusual to change the line lengths to allow for wind shifts.

4) For what it is worth, we had a 45' CQR aboard that we ultimately sold. I mean no disrespect to those who love this anchor. Our experiences with this anchor and diving on this anchor used by others, convinced us that it wasn't for us.

5) We had a Danforth on board, but I wouldn't use it in these conditions, unless I knew that I was in sand or mud. So ... I wouldn't use a Fortress for this.

Today, things might be a little easier. We use an 88 lb Rocna on our 15 ton, 55' catamaran with a wonderful electric windlass. It stows beautifully on our forward roller and we have another roller for a secondary. While this would be considered a large anchor for our sized boat, if I was headed to Cape Horn, I would go even larger.

We have two "flat line" reels on our stern pushpits, one with 280' of nylon and the other with 400' of dyneema -- these are terrific and we have used them extensively when cruising in Nova Scotia where we often tie ashore too. And ... our dinghy (a RIB) is much more forgiving than the wobbly, oar-driven dink that we had then. These would have made our trips ashore MUCH easier.

This all without getting started on all the other great devices that we can put on our boats today.

As I said, I am not sure that this adds anything new, but perhaps it reinforces the excellent earlier comments.
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Old 15-08-2010, 08:40   #13
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Originally Posted by estarzinger View Post
There is quite a bit of information on cruising Chile scatter around our website. But a big main anchor, two long shore lines and a decent cabin heater and some prudence/caution are the main points.
How long is (likely) sufficient for shore lines?

My thought is that we would probably get 4 150' warps of something like Olectec, for use as Panama Canal lines and if needed, shore lines....or if 150' isn't enough (which seems likely) tie two together?

I see some high-latitude boats set up with multiple (or at least dual) 600' spools on deck for shore lines....is that much line advisable?
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Old 15-08-2010, 09:01   #14
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From our experience lines of 150' to 200' should be plenty for "regular" tying ashore. You may want more for other purposes. Ours currently are 280' and 400', which would have been sufficient in Patagonia.

We now use heavy duty lifting straps for going around trees and rocks ashore. They have loops to which we connect with a large shackle. They are much easier to use than the chain lengths that we dragged ashore in the past.

You might want to consider flatlines, as I mentioned above. They work well and roll into a small space. Nylon, of course, is stretchy and Dyneema floats. We use both. This was much easier for us to use than huge coils of rope. Ours were from Quicklines -- they are expensive, so there might be a better source.

Personally, I would rather rent "the package" for the Panama Canal (e.g. cover tires and long, heavy lines) and let it get beat up instead of carrying fenders and lines specifically for that, relatively rare, transit.
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Old 15-08-2010, 09:18   #15
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I want to make sure I understand the terminology, I assume by tandem anchoring we mean one anchor attached to the rear of the first. If that is the case I had always assumed that practice was not advised since the holding power only multiplies if on a straight pull and in fact reduced on an angular pull. I had believed that 2 anchors on 2 rodes of differing length to be the most effective method. I look to this forum for real world advise as opposed to the armchair info I often get in publications. Dave
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