Kilowatts and Horsepower

I’m as concerned about climate change as anyone, and maybe more than most, but obfuscation and pretengineering does not help us get to a sustainable future.

A good example is the way that electric-drive vendors use horsepower when talking about the diesel engine they want to replace and kilowatts when talking about their offerings.

You see, horsepower and watts measure the same thing: power.


It’s that simple,

I was triggered to write this by an electric-drive company claiming that installing their serial-hybrid drive—diesel generator driving an electric motor—in a long thin efficient motorboat would save 30% in fuel burn over the standard diesel engine that comes with the boat.

But here’s the smoking gun, they promised 8.5 knots top speed with the generator driving the electric motor, but with the standard diesel that boat can do 18 knots and cruises efficiently at 10.

Yup, all they have done is decrease the power, probably by more than half. Of course that will save fuel.

But here’s the thing, in most usage profiles for cruising boats, simply putting in a right-sized diesel engine and settling for say 9 knots cruise and about 11 knots wide open—still faster than the electric—instead of 18, would almost certainly save more fuel as well as costing way less (think less than half), and weighing less, than an electric motor, generator, and a huge lithium battery bank.

The latter to run silent for an hour or so…and then have to be charged with…the diesel generator, in most cases.

Wait, it gets worse, weight is a killer on a boat like this, making the hybrid setup an even sillier idea since it will weigh way more than the right-sized diesel and so make her even less fuel efficient and take up more space.

What fevered mind came up with the idea that burning diesel to create rotation (generator engine), and then turning that into electricity (generator alternator), and then turning that back into rotation (electric motor), is more efficient than burning diesel to make rotation (diesel engine) in the first place—conversion losses are a bitch (they compound)—one conversion always beats three.

Sure, electric is great, as long as we stay close to a source of renewable produced power, but staying close to the dock is not what people will use this boat for—and no, a practical amount of solar panels are not going to help much.

Which brings us a full circle.

It’s always a danger signal when a sales person talks HP one moment and kW the next. They are probably trying to hide something, and now you know what that is.

And no, there is nothing magical about a horsepower or a watt just because it was produced by an electric motor. The whole torque thing is most-all BS too when applied to cruising boats—great though if you want to get a heavy train moving from a standing start.

More about all this here, including a very cool calculator, which will let you see if your usage profile will benefit from an electric drive. It’s a bit out of date but the basic physics does not change…conversion losses are a bitch…wait, I already said that.


Cool Motorboat

A few years ago I got interested in efficient motorboats and wrote several articles on the subject. At the time there were almost none around, with the exception of the FPBs from our friends Steve and Linda Dashew that cost millions, and a first try from a budding designer in New Zealand that still cost more than most of us can afford, and since then his boats have got bigger and way more expensive.

Other than that the market was, and mostly is, all huge barge-like trawlers so inefficient that some 47-foot examples have 300 HP engines, and even with that power and horrendous fuel burn can’t get out of their own way.

But at last that seems to be changing, with two new efficient motorboat offerings. I will write about the other in another Tip, but check out the 32-footer from Pogo that can cruise all day at 10 knots and top out at 15 knots, driven by just 50 HP!

And all of this brand new for €130,000 (US$138,672).

Of course this is not an offshore boat, but totally fit for coastal cruising and staying aboard for a week or so while doing it.

They also make an outboard version and are promising a 40 footer.

While the mission is very different, the idea of focusing on doing one thing really well, while stripping away all unnecessary complication, is very like the Adventure 40—love it.

We need more of this kind of thinking.

Thanks to member Richard for the heads-up.


Twin Rudders Have No Place In The High Latitudes or Maybe Cruising

We just got an interesting question from Françoise and Jean-Michel who are looking at buying a new boat.


Boreal’s daggerboards can be broken as you can see on the n° 42 ep ” Bushpoint ” on You tube. It was last year on a Boreal 55 in the north of Norway. Even if it was not a great issue , it can happen. The owner fix it himself.

My wife and I are looking to build a new boat to change our Ovni 43 and we ask Patrick Lenormand, the yard manager of NYS ( Caen France) to build it .

We have chosen a Cordova 45 ( design of Jean-François André , well known french architect ) . His choice of a twin rudder system concern me .

He said that he put two strong skegs welded on the hull to prevent any damage. My worry is also about the drag of these skegs in front of the rudders.
I know that a boat is always a trade-off but I don’t want to make a mistake.


You are right to worry about the twin rudders and that’s a great question because it exposes something we are often told: that we can fix a basic design problem by just making it stronger.

I used to believe this, too, until the engineers that comment here helped me understand it better.

Sure the boards on the Boréals can break. Boréal themselves talk about this.

But that’s a a good thing, not a bad thing. It’s a feature, not a bug.

A key thing to understand about boat engineering is that saying we will just make it stronger, is actually bad engineering.

There is no way to build a skeg strong enough to withstand even a six-knot impact from ice, a rock, or a big log (big problem in many places). The key point is that something must flex and bend to absorb force.

So if we make the skeg super strong and it does not flex, then maybe it rips right out of the hull and the boat sinks. The force must go somewhere.

So based on that, here are the key points that I think about:

  • When a Boréal board gets damaged, it breaks and the hull is fine. With skeg-hung twin rudders, a bad collision with a rock or ice can hole the boat and the stronger we make the skeg the worse that problem gets.
  • A Boréal can operate fine with no boards (I have sailed one that way). You could even sail all the way home with no boards. Bend a twin rudder and skeg and the steering is jammed until we can haul the boat and then we need skilled metal workers to fix it.
  • When in tricky waters (rocks or ice) on a Boréal, we can pull up the boards and the rudder is protected by the huge keel box. We can never pull up twin rudders, they are always down there ready to get damaged.

For me, based on some 30 years of cruising, particularly in the north, I would never do so in a twin-rudder boat. Heck, I would not own a twin-rudder boat for cruising, but that’s me.

And by the way, the reason Boréals will never have twin rudders is because the chief designer, Jean-Francois Delvoye, went to Chile in a twin-rudder boat and broke a rudder on a rock.

After that he sold the twin-rudder boat, and designed and built a boat with a single rudder and keel box for himself. That was the first Boréal.

A good example that will help to explain this point about the force being absorbed by bending is the A40 keel.


Good Boat Review—Leadership 44

Practical Sailor just reminded me in an email of an excellent review, written by editor Darrell Nicholson, of the U.S. Coast Guard Academy Leadership 44, designed by David Pedrick (one of my favourite designers) and built by Morris Yachts.

Darrell also compares the Coast Guard boat to the Navy 44 Mk II, also by Pedrick, which adds even more useful information to his excellent review.

Both boats can teach us a lot about what really matters when we go offshore. A highly recommended read, and it’s outside the PS paywall, too.

Adventure 40 Learnings

And those of you who have been involved in the Adventure 40 discussions will note many things in common between all three projects, mainly around elegant simplicity and sailing performance offshore.

Lots of differences, too, given that the Navy 44 and Leadership 44 mission is fully crewed and the Adventure 40 primarily a two-person boat. Different budgets, too!


Mono- or Multihull?

As I have said many times before, I’m agnostic about the number of hulls a cruising boat should have. There are benefits and drawbacks to one, two, or three.

That said, I do have a soft spot for some boats with three hulls, but that’s another post.

Anyway, I came across this good article comparing the options that’s worth a read.

I think the author does a very good job of pointing out that condo-cats are great for hanging out on, particularly in rolly anchorages, but if we want a cat or tri that sails well, we gotta keep her light, and if we are not willing to do that, the overloaded multi will have a hard time keeping up with a similarly loaded mono.

That was certainly our experience over the years we sailed our McCurdy and Rhodes 56, and is also why our friends Steve and Linda Dashew turned away from cats (their first love) in favour of long thin monos.

Real selection criteria to think about, instead of engaging in the silly which-is-best argument.

Much more about how to cut through all the noise and blather to end up with the right boat for our needs.


The Best Cruising Boat

The photo shows our new-to-us J/109 and AAC member Frank’s Ovni 435 hanging out together in the workshop at East River Shipyard here in Nova Scotia.

It would be hard to imagine two more different boats, and yet I like both boats a lot.

Which is best? Wrong question. They are designed for different purposes.

Sure, this is a radical example, but it does serve to illustrate how silly the all too common “best boat” meme is.


Wing Keel Craze

I will bet this keel was designed shortly after Australia II won the America’s Cup.

It’s a dead ringer for Ben Lexcen’s revolutionary keel.

But here’s the thing, while end plates are good and bulbs can make shallower keels more efficient than they would be otherwise, Australia II‘s keel was designed to get around or fool the 12-meter rule, not because there is anything intrinsically good about this design.

And yet a bunch of cruising boats at the time ended up with keels like this that will catch any piece of floating debris and have large vulnerable wings, just because it was fashionable.

Watch out for the results of trends like this when buying a boat.


Don’t Overload Catamarans

People often think that I must be a multihull hater, just because I own a monohull.

Not true, I love well-designed catamarans (and tris, too) like this way-cool Chris White 42.

But here’s the key point:

To be safe, and deliver on their speed potential, cats must not be overloaded.

Check out how thin the hull of this same cat is. It won’t take a lot of weight to push this hull dangerously low in the water.

Overload this boat, and she won’t be much faster than a mono, and, counterintuitively, will be much more likely to end up upside-down than if kept light.

So to have a safe cruising cat, and to be able to carry a reasonable load of cruising comforts, we will often need a bigger cat than we might at first expect.


Water Likes Fair Curves

One of the things I look for when looking at boats out of the water is a nice fair curve of the bottom of the hull from bow to stern.

Contrast our J/109 (above) with the boat below.

The knuckle at the bow does not bother me, but check out the lump in the line just forward of the prop strut. I’m guessing that’s there to provide the buoyancy missing from the pinched stern.

I always prefer boats where the designer has focused on keeping the water happy, not the rating.


Where Bulb Keels Don’t Belong

At first glance, you could be forgiven for thinking you are looking at the keel of a full on racing boat, but in fact this is a new boat sold as a cruiser.

Who on earth thought it was a good idea to fit the boat with a bulb extending forward creating a setup to catch every stray piece of gear floating around our oceans, never mind the risk of snagging her own anchor rode or mooring chain?

You gotta seriously wonder.


The IOR Rule Has a Lot To Answer For

Here’s a nice looking vintage Nautor Swan.

But look at the strange distortion of the stern.

You think this looks weird? Check out the next shot taken from off the quarter.

When shopping for boats, it’s worth looking for this result of designers cheating the station measurements of the IOR racing rule.

Such distortions don’t necessarily ruin a boat, but they sure as heck don’t help, particularly with tracking when sailing downwind in big breeze, just what we cruisers want to do.

Generally, boat design got better under the influence of rules that imaged the whole boat, starting in the early 90s with the MHS that became the IMS and then the ORC, still used today.

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