Propping my boat up

David Sidbury, owner of the second N68, has been updating me on some research he has been doing.


Both David and I are interested in extending the range of the N68. I haven’t really put any serious effort into it, because the little testing I’ve done implies that I can safely run 2,000 miles at over 9 knots. This is enough to make virtually any passage in the world, except going non-stop to Hawaii. I can still run to Hawaii, but I’d have to slow down to somewhere around 7.25 knots. I had hoped for greater range with the boat, but knew, when I opted for twin engines, that this would cut range by 10 to 25%. No one yet, with an N68, has opted for a single engine boat, so it is impossible to know what penalty I am really paying. I have tried running my boat on a single engine, and did receive a “pickup” in range of over 10%. I’m crossing the Pacific next summer, but cheating, and running a route that requires no major passages, so it is irrelevant for me. Were it really an issue, I’d just load on some extra fuel in a bladder, and run with both engines, at 8 knots. I’d be fine.


David, on the other hand, has continued to explore other options. He has mentioned to me several times that he has thought there might be a way to repitch the props and get better range. He gave me several links to sites that have algorithms for computing the perfect prop pitch and size. I went to the sites, and always entered in numbers, but never really “got it.” I’m good at math, and very analytical, but not good enough or analytical enough. David must have also come to the conclusion that this is a job best designated to experts. David got some experts involved who crunched a bunch of numbers, and gave David a design for a new prop that could give as much as an 18% increase in range. That’s a lot of money saved, and a lot more distance between filling stations.




The downside is that it requires buying a new set of props, which are not cheap. And, David’s boat is presently in the water, so he can’t do the measuring required to know that the new props would fit. Until the next time he, or I, do a haul-out, we can’t really measure. I think David said we would need to switch to props that are about 4” greater in diameter (from 38.5” to 42.5”). Both of us think we have room, and the plans indicate we do .. but, until the boat’s out of the water, we can’t say with enough certitude to write the big check for larger props. And, then, of course, the new props may accomplish nothing. In my usual style I said “As soon as David makes the change, and reports success, I’ll jump on the bandwagon.” Unfortunately, Jeff Leishman, the designer of the N68 sent me an email saying that David’s and my boat’s are similar, but not identical (different main engines for one thing), so what works for David may or may not work for me. Darn. If David rolls the dice and wins, I may get my own chance to try.


And on a different topic…


I don’t know how many of the readers of my blog also follow the Passagemaking Under Power mailing list. It’s a great list, because it is all people like myself who have trawlers and want to do long distance cruising. However, for months, the list was inactive. No one could think of anything clever to say, until a couple months back when someone (I think it was Scott Bulger, a Nordhavn owner) suggested we pool our collective thinking and come up with ideas for what the Perfect Passagemaker might look like. Asking a bunch of captains what makes the perfect boat is bound to stir up some conversation, and it did. In July and August the list was averaging about 10 messages posted a month. For December, the list already has 65 messages posted in the first nine days.


From the beginning of the discussion I have found myself outside the mainstream of thinking, and can’t seem to rally anyone else to my position. Here’s an excerpt from an email I posted a few days ago:


“…Each buyer's Perfect Passagemaker is unique to that buyer. The best we can

do is to outline the options so that when each of us refit our boats, or

pick a new boat, we understand the full range of possibilities, so that we

get as close as possible to our Perfect Passagemaker on the first try. All

of us have bought a boat, and then wished we had done something differently.

That’s a lot of money wasted. If we educate ourselves on what the pros and

cons of each option are, and leave breadcrumbs for others, we’ll have done

something of value.


We’ve actually been doing that in an unstructured manner over the past

couple of months; discussions of house battery banks, charging systems, hull

types, stabilizers, length to width ratios etc.


My suggestion would be that we pick one system at a time, according to our

mood, and discuss it until we lose interest. I think I gave a list a few

months back of what the “systems” on a boat might be:


– Hull (wood, FRP, Steel, Aluminun, hull shapes, etc)

– Propulsion (engine brands, single vs twin, fuel efficiency, value of wing

engine, redundancy, engine controls, dripless shafts, prop selection, etc)

– Communications (internet, ssb, epirbs, fax, vhf, nets)

– Stabilization (active fins, paravanes, anti-roll tanks, etc)

– A/C (conventional, chilled water, soft starts, vfds, etc)

– Electrical (battery charging, inverters, diagnosing problems,

international power, isolation and step-up transformers, cables, etc)

– Entertainment systems (movie servers, sat radio, tv receivers, etc)

– International cruising special requirements (international power adapters,

passarelles, med mooring etc)

– Galley (gas vs electric, best barbecue, grey water tanks, refrigerators,

freezers, etc)

– Monitoring systems (what needs monitored, what is possible, etc)

– Cabins (Ventilation, port lights, mattresses, etc)

– Tenders (davits, inflatable vs hard bottom, water toys, fendering, etc)

– Ground tackle (snubbing, anchor selection, rode, winlasses, etc)

– Diving (hookahs, compressors, tanks, etc)

– Hydraulics (cooling, ??? – I’m a complete loss on hyrdraulics)

– Navigation Systems (nav software, radar, ais, sonar, gps)

– Fuel and oil (filters, cleaning, storing, transfer systems, filling,

bio-protection, alleged efficiency enhancers etc)

– Safety (rafts, flares, ditch bags, epirbs, sat radios, medical kits, life

rings, survival suits, etc)


I’m sure I forgot several systems in the list above, but you should see

where I’m going with this.


In short .. There are as many different “Perfect Passagemakers” as there are

buyers. The best we can do is to help buyers know what to ask for – so,

let’s focus there. Rather than saying “What do I think makes a perfect

boat?” we should say instead: “According to different cruising plans, and

budgets, what are the possibilities, and how does a buyer pick between them,

so they arrive at their Perfect Passagemaker?”….”


This was the third or fourth time I had argued that there wasn’t one particular perfect boat, and it was the third or fourth time that my argument fell on deaf ears. The dominant argument seems to be that the “perfect passagemaker” is a boat that is the cheapest boat that will safely, and VERY efficiently move you from point A to point B.


I absolutely think there is a market for such a boat, but I doubt it would be the right boat for everyone. Several people dumped on high-end boats, with many seeking euphemisms for “Nordhavn”. None have been willing to admit there is more than ONE Perfect Passagemaker. For instance, let’s take my boat, and the most obviously ridiculous thing; the hot tub. I’d be the first to say that it is silly for a boat to have a hot tub, but if it makes the boat more fun for me, why is it a bad thing? It certainly isn’t for everyone, but that’s my whole point. Would the perfect car be the one that has the fewest bells and whistles but reliably moves you from point A to B? Should a car automatically be considered imperfect for having a convertible top? Would the Perfect House be one that gives you a place to sleep, cook and go to the bathroom, but no extra space, no tv-room, and sure as heck no swimming pool? I think there is a perfect $10,000 boat, a perfect $1 million boat, a perfect $10 million boat, and yes – even a perfect $100 million boat, and everything in between – and, that there is a perfect owner for each of these boats.


Oh well .. excuse the rant… it’s irrelevant anyhow…


-Ken W

16 Responses

  1. Rudders look small in relation to the rest of the boat. I know single engine rudders much larger, but I wonder if these will really hold up in an agressive following sea. Best know how to use a drogue rather than incur high rudder stress.

  2. Oh….and Ken’s comment about when a diver goes under the boat, filling the tube with air would confirm my hypothesis of the tube, as it would mimic a level, with the air bubble sitting at the top of the tube, which would then require the propeller having to “re-prime” the tube with water before being effective again.

    – John

  3. I think the picture of the stern thruster is a little misleading, in that if you examine it closely, the tubes aren’t pointing down, but are in fact pointing to the sides of the boat. If you can picture slicing the top off of a circular tube, you would end up with the necessary tube for the stern thruster, with the thruster’s propeller mounted at the top of the sliced off section of that tube. At least that what I think its like….Ken can correct me if I’m wrong.

    – John S.

    (P.S. – I had to enter the verification code twice again…)

  4. When I first saw the stern thruster tubes, I thought “there is no way this can work” — but, running the boat, I can say that the stern thrusters are just as strong as the bow thrusters, and both have exceeded all expectations. They are MUCH stronger than what I had on my N62. Don’t ask me how… – Ken W

  5. That isn’t for lateral thrust. Ken decided he wanted hovercraft capabilities if he ever wanted to enjoy the hot tub in the Everglades 🙂

  6. Ron – Those are the stern thruster tubes! It’s tough to imagine they can have much power like that, but they do a great job.

    One bizarre thing about the stern thruster…

    Because of the way they sit, if a diver is beneath the boat, they fill up with air. The first time it happened I thought I had major thruster problems. Now, I know what to expect. I have to give it extra thruster, and hear a horrible noise, for a few minutes to force the air out of the tubes.. then all is fine.

    -Ken W

  7. Ken,

    What are the “crop circles” above the rudders? Prop circles.

    The props in the photo look like props manufactured by an East Coast custom prop manufacturer located in southern Virginia.


  8. Ken,

    Since most engine failure results from fuel problems, do you have your engines drawing on separate tanks? It seems like, in the event one died because of fuel, the other would two.

  9. Buying the perfect boat of any type is like buying the perfect plane. “Mission” may be the most important consideration. I believe budget comes second and is highly variable depending on “want” versus “need”. Finally risk needs to be considered and that is a very personal decision. If your mission is to fly cross country on a regular basis, a Cessna 172 is not the best choice…possible but impractical becasue as soon as you get there you must return. The plane simply isn’t fast enough, doesn’t carry enough fuel, isn’t capabile of handling an array of weather etc. Doesn’t make the Cessna a bad plane, just a bad choice for that mission

    Need is a very basic level. If you want to cross a 2000 mile expanse of ocean, you NEED to be able to carry enough fuel if you are a trawler. You may want to have a hot tub and if you hve the budget to satisfy the want…then rock on!

    We can’t also ignor the emotional componant of boat ownership. If all people were coldly rational in their purchases, there would not be much of a market for high end anything. Some people want to project an image and feel like they can “go anywhere”, “cast off the lines and be self sufficient.” many of these people who will spend mightly on very capable boats won’t get very far from shore and even fewer have the practical navigation and seamanship skills necessary to safely pilot their boat across an ocean.

    I do think however that we all benefit from dicussions on categories and choices. Education is never a bad thing.

  10. Chuck: That’s a fun question, and the answer is YES. However, it is usually attached to the end of either the wing engine, or the second main engine. I doubt many boats carry spares tucked away onboard. These things are REALLY big and heavy. Finding a place to put them would be difficult, whereas I can always have a new prop flown into anywhere in the world.

    -Ken W

  11. I agree that there is no such thing as a “perfect boat,” even for a single buyer. This is particularly true of a Passagemaker I believe. In order for a boat to make long ocean passages it must meet certain basic design requirements. Typically they have a fairly deep draft, go slowly, are heavy, have relatively small windows, etc…

    All of these traits, and many more, are required to safely cross oceans, but aren’t necessarily desirable once you get to your destination. If you are cruising in the Bahamas or along the Intracoastal it isn’t desirable to have a deep draft. Sometimes you want to be able to go faster. Sometimes you want to have big windows and lots of visibility to see the scenery. Once you get to your destination you may not need all of the tankage and redundancy in a passagemaker.

    There has been a lot of discussion about the Dashew’s unsailboat. While this is a great boat for crossing oceans, it doesn’t make a lot of sense for coastal cruising. For it’s length (high moorage costs, if available) it is very small inside and it isn’t a very pretty boat and it is expensive to built. But for long ocean passages it is tough to beat.

    Nordhavn has tried, quite successfully, to create boats that are a good compromise between capable ocean crossers and good coastal cruisers, but they are the best at neither. I think that with the more modern boats they have tended to go for more interior volume and greater amenities which makes sense since the vast majority of the time the boat is coastal cruising, not ocean crossing. Really, people cross oceans so that they can cruise coastally in other areas. Would it be ideal if you could optimize each boat for each cruising area? Absolutely, but you can’t. Each boat is a compromise depending on what the owner needs. The ideal boat for cruising the Inside Passage is different from the ideal boat for cruising the ICW, but it isn’t practical for people to have different boats for every place they cruise, so they must compromise.

  12. “Would the perfect car be the one that has the fewest bells and whistles but reliably moves you from point A to B? Should a car automatically be considered imperfect for having a convertible top? Would the Perfect House be one that gives you a place to sleep, cook and go to the bathroom, but no extra space, no tv-room, and sure as heck no swimming pool? I think there is a perfect $10,000 boat, a perfect $1 million boat, a perfect $10 million boat, and yes – even a perfect $100 million boat, and everything in between – and, that there is a perfect owner for each of these boats.”

    This is a very persuasive argument, it’s a shame that it fell on deaf ears.

    Every design decision on a boat is a tradeoff. You would think a list full of experienced boaters would understand this fundamental fact of boating.

    I find the idea that efficiency is the only metric for perfection ridiculous coming from the PUP list. If efficiency is all that matters, shouldn’t they all be on sailboats?

  13. The perfect boat doesnt and never will exist, there are just too many comprimises and trade-offs. How much space, weight, expense is too much and if given over to one item is this going to exclude another?
    My choices in building my passage-maker are made for my own reasons which may not be the same as yours. Example 1. I have chosen a single engine but with hydraulic power driven off the genset engine able to turn the main prop shaft through a BAT get home system. Obvious advantages here are the usual single engine effeciency and simplicity. No wing engine to take up space, need maintaining, and no wing eng folding prop hassles etc. Dissadvantage maybe manouvability but with a powerful hydraulic bowthruster not really a issue. Everyone will see some of these points as being important or not to them. The point is that we each place a different level of importance on things that matter or not to us. I guess in this respect the perfect boat is what works for you. I have yet to fine tune my vessel (now building #4)to the perfect spec and probably never will because my priorities have changed a bit over the years. Ken, I enjoy your perspective, most recently on the topic of how complicated is too much, and this also showed how different we all are in our priorities.
    Regards from Steve, New Zealand.

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