Simi: I had the same thought. What efficiency does buy you is range and speed, the use case for FPB. Tradeoff is expense, both purchase and dockage due to skinny hull
George Buehler had a simple and efficient design philosophy - check Ellemaid . I think only one or two were actually built. One languished for sale for a very long time and apparently sold. They are relatively some construction so build time would be reduced.
https://georgebuehler.com/71-ellemaid/
Wife of a very good friend suffers from seasickness. So they bought a Horizon 52 Power Cat. Great at anchor. She still gets seasick underway and it's a problem. He's a very experienced sailor and in his opinion, the ride on a stabilized monohull trawler is more comfortable than his PC. But his PC52 boat bears little resemblance to Malcom Tenant designs such as Klee Wicks Domino. KW has owned full displacement trawlers for years and I'd be interested in his take on the comparison.
Hopefully, a TF member Hippocampus will find this thread. Like the OP, a lifelong Bluewater sailor converting to Trawlers. He's mentioned Artnautica several times as his dream boat (I had never heard of them prior). After almost two years of trying to find a long distance Bluewater trawler in decent condition within his budget, he punted and decided on Coastal passagemaking - a nicely appointed and stabilized (Seakeeper) Nordic Tug 42.
Sounds like OP has three issues that will drive to needle-haystack search. Wife's seasickness, desire for incredible fuel efficiency, and budget constraints. Not a good market for highly specific selection criteria. May want to consider a build. In the end, might be faster than finding the perfect used example.
Good luck
Peter
Thanks for the interesting prompt in your question directed at me above, Peter.
There are many of these questions/debates around the subject of boating and around long-range cruising/passagemaking specifically.
Our human nature makes us desire a simple and sure answer to these multifaceted subjects so that we can make the perfect choice. We can desire that certainty and let our decision making be paralyzed by that, or we can accept the reality that it is all a set of compromises and like Hippo's fine example, we look at the options, we make our own personal set of compromises, and we go boating. We can get excellence in meeting our needs, but we do not get perfection. Ever. No matter how much we agonize over it.
Yes, I drive heavy, round bilged, full displacement, single engine, monohulled boats designed for 'efficiency'. And yes, I have studied and begun to operate a multihull that is designed around the same concept as the FPB where we take advantage of the 'long, lean, fast (relatively speaking) hydrodynamics.
In terms of efficiency, here is my non-expert perception:
My two heavy displacement classic Beebe concept vessels could be very efficient, but personally I found that efficiency sweet spot to be BELOW hull speed and not AT hull speed as it is classically calculated. At hull speed, pretty hard to get these boats much over 2-3 nmpg but many of them over 4 at a knot or so below hull speed. It seems simple that when a bow wave or stern wave appears, you are consuming energy to move water in addition to the energy to move the boat. You cannot beat these physical laws of nature, I think.
So, in the end, if consumption is your only driver, you are tied directly to the length for how far you get in one day's time. Period.
When comparing the heavy monohull to the cat, it does appear that the 12+ length to beam pushes easier than the heavy 3:1 length to beam monohull. Plus, in this configuration you buy more length for the same money once you have set the constraint for how much fuel, water, and cargo/supplies you think you need to transport. Thus, you gain speed almost for free in the long lean versions.
To put this in more concise terms: for the same amount of fuel carrying the same amount of contents when making the crossing from the US to Hawaii for example, on the monohull I arrive in 17 days and in the cat I arrive in 12 days. Do you care?? Is it safer due to a shorter window?
Now, on the motion question: my wife and sailing partner has been known to spend some time at the rail. I have been in situations where I have thought that I might get there. That takes some fun out of it, right?
The gap in my ability to contribute to this discussion is around active or passive stabilization of a heavy monohull. Many of these things are not rational but I have taken the path of ballast and design to enhance stability in the monuhulls that I have owned and avoided the moving parts and expense of the more dynamic options. So, I can only compare a well-designed but non-stabilized monohull to a well-designed but non stabilized multihull. Here again, and I find myself not wanting to admit this even to myself, the cat appears to win. Do you care about this? Are you affected by motion either in terms of nausea or even just the exhaustion that motion creates even where 'sea sickness' is not part of it?
I sort of like the motion of the monohull on short to moderate cruise days, but I am less exhausted by long days on the cat. No question. My wife has not been to the rail on the cat under the same conditions where she clearly has been there on a motor sailing displacement monohull off the coast of Austrailia, where that motor sailor was quieter than either of my monohulls would have been. All vessels were sans fins or fish.
I like them both. I am excited by the cat. I am not selling the heavy monohull that would be the classic attempt at what was promoted as the ideal for passage making in the first edition of Voyaging Under Power.
However, some of you may have noticed that these ocean multihulls have made their way into the fourth edition of this same treatise on long range cruising, and there is even a discussion of my specific vessel, Domino, acknowledging that perhaps we should be thinking about this as a reasonable way to serve the mission.
There is no right answer, just the answer that is right for you, one that you can afford and enjoy. Go get it.