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.