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I was standing on a floating dock on a Pacific-ocean inlet, a place where it’s obvious why motorboats are such an environmental disaster. Fortunately lots of other people have noticed too and it looks increasingly that more people will be able to enjoy Messing About In Boats without feeling like they’re making Greta Thunberg justifiably angry at them.

Hm, this piece got kind of long. Spoiler: I’m here mostly to talk about electric hydrofoil boats from Candela, in Sweden, which look like a genuinely new thing in the world. But I do spend a lot of words setting up (separately) the electric-boat and hydrofoil propositions, which you can skip over if you’d like.

Background · Last year I wrote about personal decarbonization, noting that our family works reasonably hard at reducing our carbon load, with the exception being that we still have a power boat that burns an absurd amount of fossil fuel for each km of the ocean that you cross.

Electric boats · Separately, back in 2019 I wrote a little survey of electric-boat options; my conclusion was that it shouldn’t be too long before they’re attractive for the “tugboat” flavor of pleasure boats. Which is perfectly OK unless you want to cover some distance and get there fast.

There’s been quite a bit of action in the electric-boat space. Here are some companies: VisionMarine Technologies (formerly the Canadian Electric Boat Company), Rand Boats, Greenline Yachts, Zin Boats, and then here’s Electrek’s electric-boats articles. If you like boats at all there’ll be pictures and videos in that collection that you’ll enjoy.

A lot of these are interesting, but (near as I can tell) none of them come close to combining the comfort, capacity, speed, and range that my family’s current Jeanneau NC 795 does.

But in the wake of Tesla, enough people are getting interested in this problem that it’s a space to watch.

That float · Here’s a picture of the float (and the boat). I was sitting down there on a lawn-chair enjoying the view, good company, and an adult beverage.

Floating dock on Howe Sound

What I noticed was that every time a motorboat went by, the wake really shook us up on the float. That float is a big honking chunk of wood, something like ten by twenty feet, and those powerboat wakes toss it around like a toy.

Which is to say, moving a boat of any size along at any speed throws a whole lot of water around. My impression is that most of the energy emitted by the burning fossil fuel goes into pushing water sideways, rather than fiberglass forward.

Let me quote from that Electric Boats piece: “There are two classes of recreational motorboat: Those that go fast by planing, and those that cruise at hull speed, which is much slower and smoother.”

Both of those processes involve pushing a lot of water sideways. And it turns out that my assertion is just wrong because there’s a third approach: the Hydrofoil. It’s not exactly a new idea either, the first patent was filed in 1869, and while they’re not common, you do see them around. In fact, here’s a picture of one I took in Hong Kong Harbour, of the fast ferry that takes high-rollers over to the casinos in Macau.

1994 picture of the fast hydrofoil Hong Kong-Macau ferry

If it looks a little odd that’s because I took it in 1994, with a film camera.

Hydrofoil sailing boats are a thing, including the AC75 design that was used in the most recent America’s Cup, probably the world’s highest-profile sailing race. These things are fast, coming close to 100 km/h. I strongly recommend this video report.

Then there’s the Vestas Sailrocket 2, which currently holds the world record for the highest sustained speed over 500m: 66.45 knots, which is 121.21 km/h. There’s a nice write-up in Wired.

Also check out the Persico 69F, something like the A75 only anyone can buy one. Here’s a story in Sailing World that has a lot of flavor.

Hydrofoil + electrons = Candela · I guess it’s pretty obvious where I’ve been heading: What about an electric hydrofoil motorboat? It turns out that there’s an outfit called Candela which is building exactly such a thing near Stockholm; their first boat is called the C-7. I reached out and got into an email dialog with Alexander Sifvert, their Chief Revenue Officer. It’s remarkably easy to strike up such a conversation when you open with “I’m a boater and an environmentalist and well-off.”

The idea is that you make an extremely light hull out of carbon fibre, give it an electrical drive-train, and put it on software-controlled hydrofoils that lift the hull out of the water and adjust continuously to waves and currents, to give you a smooth, silent, fast, ride. They claim that the foils experience only a quarter of the water drag compared to any conventional hull going fast — the typical cruising speed is 20kt or 37 km/h. So with a 40kWh battery pack like that in a BMW i3, they get 90+km of range at cruising speed.

Obviously there’s vastly less wake, and once you’re out at sea the operating cost is rounding error compared to what you pay to fill up the average motorboat’s huge fuel tank. Also, experience from the electric-car world suggests that the service costs on a setup like this should be a lot less over the years.

All this on top of the fact that your carbon load is slashed dramatically, more if your local electricity is green but still a lot. I also appreciate the low wake and silence — at our cabin, overpowered marine engines going too fast too close to shore are a real quality-of-life issue.

The Candela website is super-ultra-glossy and not terribly information-dense. Soak up some of the eye-candy then jump to the FAQ.

But there are terrific videos. The one that most spoke to me was this, of a C-7 and a conventional motorboat running side by side in rough water, which we experience a lot of up here in the Pacific Northwest. Here we have a famous powerboat racer (yes, there are such things) taking a C-7 out for a spin. And here we have a C-7 cruising along beside one of those insanely-fast hydrofoil sailboats from Persico.

I’m seriously wondering if this is the future of recreational motorboating.

Would I get one? · Well, it’s a good thing the C-7 doesn’t use much fuel, because it’s really freaking expensive, like three times the price of my nice little Jeanneau. Which should not be surprising in a product that is built out of carbon fibre, by hand, “serially” they say, in a nice neighborhood near Stockholm.

In any case, I wouldn’t buy the C-7 model because it’s built for joyriding and sunbathing, and we use our boat for commuting to the cottage and as Tim’s office. Mr Sifvert agreed, suggested they might have something more suitable in the pipeline and wondered if I’d like to sign an NDA (I declined, no point hearing about something I can’t buy or write about right now). Separately, I note that they’re also working on a municipal-ferry product.

I’ll take a close look when the product Mr Sifvert hinted at comes out. But at that price point, I’ll need to try it out — I gather Candela is happy to give you a sea trial if you’re willing to visit Stockholm. Which actually doesn’t sound terrible.

Independent testimony would be nice too. Which is a problem; as I noted in my Jeanneau review (while explaining why I posted it), boats are a small market with a tight-knit community and truly impartial product evaluations by experts are hard to come by.

Futures · The core ideas behind the Candela C-7 aren’t that complicated: Electric powertrain, battery, hydrofoils, software trim control. Because of electric cars there’s a lot of battery and electrical-engine expertise about. Hydrofoils aren’t a new technology either. So getting the software right is maybe the crucial secret sauce?

Thing is, as a citizen of the planet, I’d like to see the roads full of electric cars — this is definitely going to happen — and the waterways full of boats that look like what Candela is building. Which won’t happen at the current price point, but I’m not convinced that can’t be driven down to what the boating world sees as a “mass-market” level. I’ve no way to know whether that will happen. I sure hope so.


Comment feed for ongoing:Comments feed

From: Grahame Grieve (May 10 2021, at 21:23)

Looks kindof cool, though you could have many of the benefits and still burn fuel, right? Because it looks like you're still tied to the grid, and many good places to get in the water are far from the grid (at least in Australia)


From: Dave Pawson (May 11 2021, at 00:30)

"So getting the software right is maybe the crucial secret sauce?" Fail safe more important?

Salt and electronics don't mix Lauren / Tim? Enough juice to get back with the foils in 'worst' (safest) configuration?

What sort of sea-worthiness cert - if any, for the electronics.

Great idea, must admit.


From: Kevin Marks (May 11 2021, at 03:42)

Looking at the sailboat and the Candela side by side, it seems like combining them could be an idea - both sails and a motor for less windy days. I bet you could get a lot of solar cells on that amount of sail area too to recharge the batteries.


From: craig (May 11 2021, at 09:25)

I saw the candela when it came out and was pretty impressed as well. the surf guys like rush randle and laird hamilton have been riding foil boards for 20+ years but foiling has recently caught on in the surf world in a big way.

It is inevitable that it will also catch on in power boating. I agree that the control system both hardware and software to control the boat's pitch and roll via foil flaps or ailerons is going to be a major component, but like quadcopter drones it will eventually be ubiquitous.

There is so much woody debris floating in Howe sound it is bad enough to hit a log already but it could be pretty nasty to hit one when foiling.


From: Debi Butterfeld (May 11 2021, at 09:54)

Hydrofoils are inherently inefficient and can be shown to have a similar transport cost to airplanes. See the addendum to "Sustainable Energy Without the Hot Air" by David JC Mackay: https://www.withouthotair.com/cC/page_279.shtml

Rather than pushing water to the side, hydrofoils must throw enough water down to support their own weight which ends up using quite a bit of power.


From: Mark S (May 11 2021, at 12:22)

> I’d like to see the roads full of electric cars

Electric cars don't save the planet. They save the car, as Ran Prieur said.


We'd be better off if people just got a bike (electric or non-electric), and got rid of their car(s), if that's at all feasible.


From: Andrew Reilly (May 11 2021, at 22:57)

This sort of a thing is probably a bit lower price-point, (but doesn't have a galley or flybridge): https://youtu.be/J0K1F8bU4tY

People are exploring alternatives to carbon fiber too, with flax looking promising (and you can make epoxy from non-mined oils too): https://green-boats.de/projects/flax-27/?lang=en

Sailing foilers (probably) started in Moths, and are now something like this: https://youtu.be/z6xmTnXBd5Y

Do you really need to plane? Long, skinny boats traveling at displacement speed don't need to push much wake: ask any rower. I doubt that foiling is compatible with comfortable accommodation, water tanks and anchors. Would love to be proven wrong of course.


From: Dale (May 12 2021, at 04:22)

A slight digression:

Paul Larsen's Sail Rocket uses a foil for exactly the opposite effect of all the other foilers mentioned.

The foil offsets the vertical lift component (upwards) of the wing sail, by generating the same lift component downwards. So not a hydrofoil.

Instead, something so clever that no other sailing vessel has ever done. Hence the huge jump in the speed record. It's an amazing story on its own.


From: ForeverYoung (May 12 2021, at 05:54)

Presumably the advantage of hydrofoil boats is that you can justify going faster. Because normally when fighting resistance speed is the enemy. But this should change the equation quite significantly.

Still, I doubt leisure boats will ever be used enough to make it an effective way to combat climate change. Just the battery is likely worth orders of magnitude more in carbon offsets than you would save in CO2-e emissions.

Unfortunately I think Candela and many other Swedish startups are really just targeting those who have received a windfall in the Stockholm housing market. They can afford to drop a few hundred grand while retiring to the archipelago as the next generation pays the price.

I do recommend visiting the Stockholm archipelago though.


From: Randy Heath (Sep 08 2021, at 08:26)

"Messing About in Boats" - thank you! Those four words took me right down memory lane, to when my son was small and we read Wind in the Willows over and over. How he would laugh at the great battle with the Stoats and Weasels! Much appreciated having this fond memory prompted.


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