Re chain length, at least my comments on 200' being sufficient was in the confines of the US east coast. In some other areas, including the NA west coast up through Alaska, I'd be trying for 200m or as close as practical. I went from 400' on the last boat to 600' on this boat. I got by with 400', but there were a few times when I had it all out.
As a reference, my recollection is that Dashew had a 150kg on his 7801. His comment was that he wanted to carry a mooring, not an anchor. I like that thinking.
FWIW, add my vote to those who advocate going with "the biggest anchor, longest chain you can stand and then at least one size up" Club. While I appreciate that your NA will obviously need to know all the details of your ground tackle and incorporate this into their design decisions, just remember very few NA's have ever spent a night on anchor, let alone in a whale of a gale.
Ground tackle for me is all about SWAN and so I go with what will give me the most of that and then design around it. Keeping things in perspective relative to your use case for the boat, if you are going to be cruising the world then you will run into EVERY type of bottom there is and the full spectrum of pretty much every category. Factoring this into your primary anchor choice is key and this perspective will also dramatically change your reactions to the various tests and reviews that are out there. For example, I have huge respect for Steve Goodwin who now has more than 100 YouTube videos of his anchor testing but when you look over how different anchors have rated on the various categories he has for different bottoms and different conditions, the top rated anchors change accordingly. I read and watch Steve’s and many other examples of anchors working and not working and again my conclusion is that it always comes down to “it depends”. For example, I think that any anchor can fail to not reset quickly in certain bottom types, on certain boats in certain conditions and so there is once again no “best” anchor for all. This is just as you’d expect and makes perfect sense and this also means to me at least that if you and your boat intend to cruise the world then you have two ways to go: carry what you think is the best anchor for each of these bottom/condition categories OR carry one anchor that you think will give you a “mooring” every time you anchor.
On previous boats I used to go with the "carry multiple anchors so you have the best one for different bottoms and conditions" and I think I had up to 6 onboard at one point. However, after many years and nautical smiles of anchoring hundreds of times in most every condition and speaking with many other captains about their experiences, I reversed my thinking and my ground tackle along the lines of the quote that Peter attributed to Dashew about wanting to wanted to "carry a mooring, not an anchor" and ever since I have gone with one monster anchor and lots of big chain. My thinking is that every time I anchor I want to have THE best anchor I have down there so my main anchor is my only anchor and it goes down every time. To round out my overall ground tackle inventory onboard, I do carry a second anchor for kedging situations as well as shorefast equipment for situations that require it.
There is some truth to the concern some have expressed about the chain at the bottom of the locker not being used very often and turning into a pile of rust but this is easily solved with a well designed anchor bin that self drains and has a non metallic grid on the bottom. In my experience, doing this along with regular chain maintenance that would include reversing your chain ever 1-2 seasons has kept all of my chain in very good condition for at least 5-8 years.
Anchor choice borders on a religion for many it seems and so I won’t enter into that endless debate. However, I value first hand experience very highly and appreciate all who share what their choices have been and what works and what does not for them and their boats. In that same spirit, I will gladly share the choices that we made for ground tackle on our recently launched XPM78-01 mv Möbius which is a 24m/78’ all aluminium eXtreme eXploration Passage Maker that would be in the same family tree that includes boats such as Pilot Boats, FPB series, Circa 24, Arksen, etc.. Relative to ground tackle the dimensions at half load are: LWL 23.9m BWL 4.3m Displacement 40.5T The ground tackle we carry on Möbius is as follows: Main anchor 125kg/275lb Rocna with 125m 13mm G43 chain and 100m 15mm Dyneema rode, Kedging anchor Fortress FX125 (31Kg/70lbs) with 50m 10mm G43 chain. It was over two years ago when I was ordering these items and I considered many different choices for all of them and then made what was the just right, just for us choices above. In the case of the anchors themselves we ended up “go with what you know” and having had a lot of excellent experience with Rocna and Fortress for many years all over the world, this is what we decided was best for us.
As for the question that Salty Pelican posted about using a 55kg Rogna and 100m of chain (not sure what size or type?) my suggestion would echo the same suggestions from others here to upsize both of them substantially to provide the most robust and dependable ground tackle on a global passage maker. Hope this is of some value to Salty Pelican and others out there who are considering what is the just right choice of ground tackle for them and their use case.
-Wayne