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Design Parameters For an Ideal Sailor’s Motorboat

Artnautica LRC58 01_small

In the last chapter I wrote about a fundamental problem for an aging voyaging sailor looking to transition to a motorboat:

For many of us, the sailboats we already have are better offshore motorboats than anything readily available out there on either the used or new boat market: safer, more comfortable at sea, dramatically more fuel efficient, and in many cases faster.

What We Aging Sailors Need

What we aging sailors really need, or at least want, is a simple, high quality, live aboard, production motorboat that can cross oceans as well, or maybe even better, than our sailboat and that also is cheaper to own and easier to maintain.

The Need for Speed

But, at least for Phyllis and me, there are other vital criteria that would govern the decision to transition to a motorboat:

We want to go at least as fast as we do now and preferably even faster, and we want to do that without increasing our current fuel burn or environmental footprint on a per mile basis.

And it is this last criterion that gives us a problem.

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More Articles From Artnautica 58:

  1. Design Parameters For an Ideal Sailor’s Motorboat
  2. Artnautica 58—Design Analysis
  3. A Real Sailor’s Motorboat Launched
  4. The Artnautica LRC 58 Adventure Edition Offshore Motorboat
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Dick Stevenson

John, It is really very nice to have someone keeping a finger on the pulse of things relevant to what we do now and might do in the future. Much appreciated. Dick Stevenson, s/v Alchemy, Gauda, The Netherlands

Jean-Claude GUILLOT

Do you have any comments about the Greenline hybrid motorboats ? I find the concept interesting.
Jean-Claude GUILLOT – SV Bauhinia

Matt Marsh

From what I’ve seen of the Greenlines, I’d consider them to be first and foremost an early-adopter’s technology showcase. An awful lot of design and engineering expertise went into those boats and their highly complex systems.

That’s great for showing off. It’s great for cruising between yacht clubs, taking friends and colleagues on tours, and exploring well-developed coastal areas. It’s a show boat, meant to say “this is the cutting edge of all the technology we could throw at it”, and in the right market, that is Very Cool Indeed.

For going beyond reach of help, or for voyaging without a VP’s budget, I’d have a harder time recommending this kind of technology. Long range cruising is a mission for which reliability, cost effectiveness and robustness are high priorities- hence something like the big Artnautica, which is well placed to score highly on these points.

Eric Klem


I find this series very interesting although hopefully I am many years away from even thinking about the switch. With your first post, I couldn’t help but think of the Shannon 53 and 58 HPS. In many senses, they don’t meet your requirements just like the Dashew’s boats don’t because they are too expensive. They are still very interesting boats to think about from a design perspective.

Recently, I was in a severe thunderstorm near one and they were zooming around under power at probably 12 knots doing circles around me (I don’t know why). The way that the boat moved easily through the chop and stayed level was very refreshing to watch. They are certainly not my type of boat, at least at this point in life, but I can appreciate them.



Which post are you referring to in the following paragraph:
“… there is a strong argument that this course of action is actually cheaper than keeping the sailboat since the annual cost of ownership on the motor boat could be as little as half that of the sailboat, depending on usage profile. (See my previous post for information that supports this rather startling assertion.)”

scott flanders

OK, I’ll rise to the bait. Speed isn’t necessarily a matter of need, it is a matter of want. I consider speed as voyage made good, not speed thru the water on a screaming reach. There are only 5 times in 12 years of long distance powerboat cruising we had to change course to a more comfortable heading. Also, a few or more hours difference in a passage from Labrador to Greenland for example, really doesn’t matter in the big picture because choosing a proper weather window is easy these days. What if’s are just that.

What does matter when you are financially challenged like ourselves and want to live large is the cost per nautical mile over the years with that particular boat. Cost per nautical mile includes everything from purchase price, operating costs and resale. That’s the bottom line. Maintenance on a simple system powerboat is minimal if it is built properly and not a hull #1 as custom boats tend to be.

Weight is your friend at sea. We are powerboaters but take a look at a lightweight charter type sailboat vs a proper sea boat loaded with cruising gear, spares and provisions. The difference at sea is huge as you know. Its the same with power; you can go fast for less with a super light boat that is flat aft but you will pound. A heavy boat is slower but you don’t get tired and tired sailors or powerboaters are more dangerous to themselves than any big seas.


Matt Marsh

Let’s say we want perfect seakeeping in any conditions, and we don’t care about an upper limit on weight.
We’ll end up with a submarine. And, despite many years of trying by many salesmen, those just can’t get past a tiny niche market. Heavy-weather seakeeping is just one of many criteria that buyers use, and emphasizing it at the expense of other features will turn off some customers.

If I had to get caught out in bad weather, I’d want to do it in a fairly substantial vessel that’s designed to take this kind of a beating, like a McCurdy-Rhodes or a Dashew.

I would, however, prefer to have enough speed on tap to get away from the bad weather before it hits. I’m a wimp that way, and I’ll sacrifice a bit of comfort in a Force 9 if it means the odds of getting caught in a Force 9 are cut in half.

Jim Johnson

Oh boy let’s get all excited about buying a powerboat. I thought you might be gone since you now talk instead of cruise. A powerboat would be perfect for you. You could have an office and, and……


I guess that the debate between motor cruising-boat & sail cruising boat (ease of use, environmental impact….) depends very much on which motor-cruising-boat and which sail-cruising-boats we are speaking of.
Are they:
– existing boats,
– custom-designed-boats-not-too-far-from-mainstream-technologies-and-design-practices
– or boats corresponding to radical technology or design changes

Considering sail-cruising-boats. Maintream technologies of those boat as they are built today give higher than commonly expected environmental impact (when compared to similar pure-diesel motor-cruising-boats…), because of the environment costs of fabricating, and replacing when needed, its “wind engine” components (sails, rigging, mast…), as generally fabricated today.

This might look a bit surprising, because most people tend to believe that sailboats have lower environmental impacts than equivalent motorboats, and because looking back at the days of commercial sailing ships, it seems obvious that, in the 1860′, a sailing cargo ship had a much lower environmental impact than the equivalent steamer cargo, including life-cycle environmental costs,

So I guess that the point is that using the technologies developped for (competition) sailing boats in the last 50 or 80 years, (dacron cloth, stainless steel rigging, high tension shrouds and stays etc…) the high environmental production costs and limited life-time of wind-machine components tend to make corresponding sailing-boat environmentally ineficients. I guess other technologies could be developped, perhaps inspired from 1860′ practices which might give much better environmental results.

Considering ease-of-use of sailboats vs mototboats, I understant that current sailboats are pretty much constrained to technical solutions tied to competition sailing-boats of the 1930′ to 2000′, with limited consideration for eease-of-use ou small crew, while motorboats use technical solution evolved from commercial trawlers ou tugboat, where ease of use has always bee a very serious issue.

—> I guess that if we get more critic on mainstream sailboat technologies, it should be quite possible to build much easier to use and much more environmentaly friendly sail cruising boats, those boats could use much more elastic riggings, spars and sailcloth (to limit constrains, allowing weaker scantlings and longer equipment lifes….). Ease of use could be much improved using simpler halyards and sheets configuration with rugged mechanical assistance (hydraulics…) etc.

Also, the sail cargo ships from the 1860′ generally didn’t have aux. engines, which looks somewhat unrealistic in 2013. Some of the last sail cargo ships from the 1900′ had aux. engine (like Prentout-Leblond “France 2” of 1913…) but seem to have made a very limited use of them, so its looks like their environmental impact was not much higher than pure sailing ships and still much lower that equivalent motor cargo ships.

Extrapolating figures from1860 or 1900 and taking some liberties with current sail-boat technologies (which might be beyond the scope of this forum….), it seems strange that sail-boat are supposed to be environmentally less-friendly than Dashew or equivalent motor-boats. I understand that in John’s long range cruising program, sail only average speed of a modern 40 ‘ or 50’ sail boat is not satisfactory, and motor-sailing or motoring does make a substancial part of the trips, but, if you consider some green energy harvesting during sail-only periods (solar panels, water-turbines, wind turbines….), it looks like such aux. sailboats should obtain substancially better environmental impacts than “adapted” motor boats (Dashew etc…). Of course this demands some radical reconsideration of current sailboat technologies (looking bak at the past ?…), and environmentaly well though aux prop. systems. It looks very obvious that first adopters of this kind of boats might have to pay some premiums for the pleasure of beeing first adopters. I guess that this has very often been the case, and I don’t think that this should be a very big problem, provided they understand this point.


George lewis

Hi John: had a 55 ft alum sailboat with a 54 ft water line built in 1999 . With a displacement of 32,000 lb at a cost of under $300,000. Beam 14ft water line beam 11 ft. Draft 10 ft. Lifting keel to 6 ft 6 in. Does 200 miles days sailing . Four wt compartments aft cockpit with a fully enclosed pilot house. Keel weight 12,000 lb. it can be done!

scott flanders

John, I never mentioned a case for the N46, just that weight was your friend. For a long narrow boat to go quickly it has to have a flat bottom and be light. Its simply horsepower to weight.
This mans it pounds to weather because to have a full keel it would be to bouyant. It may not pound like a canoe bottom race boat but it will pound.

We have very little relatively high latitude North Atlantic experience. In fact, just this summer´s trip to Iceland via Greenland. However, we have spent some time in the Southern Hemisphere high latitudes and the long distances along the coasts guarantee weather, particularly in Argentina. Speed would be nice like everywhere but it still doesn´t help move between systems because there is no place to hide.

However, except for that coast there are some myths that can be put to rest if you are on a smart recreationalschedule and not a schedule. For example: Hobart to Fremantle including Cape Leuwin, no spray on the pilothouse glass. Same for the trip from Richards Bay, SA to near Cape Town, same for Cape Town to Namibia, same for Namibia to St Helena and so on.

We have on occasion pushed it up to 7.5 knots for a nmber of reasons even though the fuel burn went up. 7 3/4 knots is in the realm of folks who aren´t financially challenged.

In any case, there isn´t any right or wrong. We are all different and in the end if we have fun and keep water out of the boat and the keel off the rocks its all good.


Rick Salsman

Hi John:
Another great piece! I sometimes think you are reading my mind. Your researched and well thought out articles on jacklines, miles per day issues and when or should we sailors go to power are concepts that seem to be occupying me and others lately. When Bonnie asks me why I might want a new to me boat, it fundamentally comes down to travelling further and faster in a day. The last Passage of the ARC by Steve Dashew in his FPB was a real eye opener to what is possible. Your search for something that will mirror those concepts at a more affordable price are keeping me glued to your screen! Keep up the great work, maybe if the stars align we can get a volume discount on the Artnautica series. 🙂 I will follow that build process closely. Thanks and Regards to you and Phyllis from Sicily

Danny Blake

Hi John
As you know I have been following Dennis’s progress with this great boat, when I emailed him a month back or so he spoke of a possibility that he may find a yard in the UK to build under licence, this would be a great help to me living in the channel Islands. I love watching this boat come together and all the details he is sharing with us all.

Annibale Orsi

I finished the read…interesting. It makes me think of a boat I saw last year that made a lot of sense. One could buy today a 56 foot Fountaine Pajot (cat) in good shape for under $350,000. Then sell off all the sailing rig, i.e. mast, boom, all the sails, all the standing rigging, all the sheets, etc. That would reduce the weight considerably and any future expense. Now take the money that you made from selling the things you do not need or want and a little from the cookie jar and outfit the interior with anything that might be missing that you want. I’ll bet, that for a total price of about $400,000 you would have a near new boat that is light and fast. I would add extra water and fuel tanks; not a problem. Fact, my cat (46 foot) cruises on one motor (2,000RPM, 40HP) at 6 knots. The converted F&P would be a stable platform, not expensive, fast and very efficient. Just a thought because I saw one recently just this way. Any comments?

Annibale Orsi

I forgot to mention that at 2,000RPM I am using less than 1.7 liters per hour.


Hi John,

A frequently overlooked but essential factor in the design of production or even custom displacement offshore motorboats is propulsive efficiency. High propulsive efficiency is achieved through fixed pitch large diameter, slow turning props and that requires deep draft. CPP are less efficient given the same speed and diameter due to their large central hub creating excessive drag. CPP make sense in variable load condition such as when motor sailing, in tug boats, trawlers etc.

My understanding is that motorboats should be designed from the propeller to the engine and then everything else added around them.

There is great book about propellers by Dave Gerr ‘Propeller handbook’ giving empirical and mathematical methods of estimating propulsive efficiency.

I have no affiliation or connection with them but in the recent past I have done a great deal of research on displacement boats, and their articles seem to be on-line with general accepted engineering calculations and methods as found in technical boat books.

Annibale Orsi

I was talking to my wife about the cat conversion for older sailor who wish to continue cruising without the work that goes into actual sailing. I said that if I was fifty again I would buy an older cat, fix it up, just like people do with older homes, and then cruise with it while having it up for sale. When it sells, do it again. Because older cat are still cheap, I will bet the one could do this and possibly make money. Just I though for you younger sailers who might wish to start cruising early in life.

Michel VAES

Back to your post October 2, 2013,
A Sailor’s Motor Boat-Part 2, here some interesting designs ( and his Foxtrott 65, MagicTroll, EcoTroll 49, Foxtrott 45 )


Would love to see your follow up of another approach.. at the end of the article. I’m convinced that a multihull is the ideal platform for a perfect sailors motorboat. I might be biased though as I trying to create just that myselff with our MP52- Trawler. Would love to get some feedback from John and the team. Like Dennis with the Artnautica 58, i put my money where my mouth is and took the build it and they will come approach. 🙂 Being a sailor at heart, I’d like to think that I’m on the right track but it’s certainly a different approach than these long waterline length cruisers.
Hope I’m not stirring the pot too much bringing a cat to a dog fight..:)

Douglas Nelson

To add to the powercat discussion the most interesting design i’ve seen is that of Aspen.
As the founder of Glacier Bay he found himself running his boats on one engine most of the time without much hit to speed….. so his new design is not a cat put a proa. Aspen’s are not really ocean yachts but I think this approach could prove to be the most efficient design yet.


George Buehler has designed a few boats which are efficient and avoid costly design.

Bill Parlatore

In Fall 1996 issue of PassageMaker, I did an article on Traveller, a 52-foot aluminum boat quite similar to what this discussion is all about. Designed and built by Jim Millett (of Millett Gun Sight Co. in So Cal), it proved the concept of a slender hull shape motorboat displacing 44,000 lbs. Very efficient and comfortable. Don’t know if the magazine sells back issues or articles, but perhaps I could post some images of scanned images if there is a way to do that.


Sailor’s motorboat being built.

Carl E.

Hi John,

Just curious: although not all details of this project seem to have been posted on their blog, in what way is the Mobius design too complex for you? Personally I could only mention their desire to reduce the boat’s height when visiting inland waters, and perhaps the CPP? They’re going without active stabilisation (for now) and a generator, for example.


I enjoy all the conversations. AS for speed, the best advantage with speed is safety- getting somewhere sooner rather than later, or getting somewhere period. I mean, for instance, that the tide swing off the coast of France from Cherbourg to Guernsey can run 6 to 8 knots. If you’re running against it, ON a sailboat doing 6 knots, you can watch the scenery not change. or go backwards to revisit where you’ve been. If you’re running with it, you have to be going 8 or 9 knots over ground to keep steerage, and a slow poke in front of you in the channel is going to cause a problem if you can’t pass him. Point is, there are times when speed can make you or break you. And when it comes to your spouse’s happiness , getting there with comfort prevails.
So, we’ve done our thing with sailing. I want more comfort, less physical work, and am now content with coastal cruising and , yes, inland , and up the East coast. We want a big boat, comfort, room for guests, that can cruise economically at 8 to 9 knots, but can get up to 20 knots if wanted for whatever reason. We need to be able to short hand her.
These new large semi-displacement cruisers ( trawlers?) , with a shallow draft and speed can easily get under the bridges , offer great accommodations, and do the speed when you need it, but I will not be doing any major crossings with the boat. I would want a dependable ocean sailboat for a crossing.