[_jbcv]

Engine lost compression in two cylinders on my 5.7 GL Volvo Penta. ~ 300 HP, leaky exhaust riser. Took the opportunity to look into an electric option that can bring a 4,700 lb boat on plane, comparable power that is in production and available.

- Evoy hurricane inboard, 600 kW: NOK 1.497.000

- Battery pack: medium range, 252 kWh: NOK 1.476.000

In US dollars, that's $360,000 and I'd have to ship it from Norway. Closest second option was about half that price using BMW i3 batteries, at half power. Meanwhile, a new marine engine was $10,000 by comparison, or to repair exhaust and rebuild to last another 17 years, $5,000.

Boating is a luxury and I can't excuse it in environmental terms, same as I can't excuse electing not to walk 2 hours to my local starbucks for a consistent grande pike I enjoy in favor of brewing my own. But marine electric is currently nowhere near being a practical solution, and you cannot hydrofoil in all boating conditions, especially in choppy waters, or where there are seasonal floating obstructions.

Boats do have notoriously small efficiencies (1-4 mpg) in both displacement and planing modes, but consider that for an automobile to have its 25 mpg average we pour approximately 124,000 gallons of crude oil per mile every 5-10 years for a two lane asphalt road, a coarse byproduct of refined petroleum.

My whole point here is not to equivocate in any terms, but that it's easy to overlook externalized costs. Moving an object anywhere is a difficult problem.

[LeifCarrotson]

I'm not sure what you're putting that in, but there's been some increasing noise in the ski boat world for electrics (eg. [1] and [2]).

Electric power density in either volume or weight is OK in a car, where once you've accelerated you're rolling on low resistance tires on a smooth surface and the weight is less important. But in a boat you're fighting the equivalent of the rocket equation where the force on your planing hull has to have more batteries to lift more batteries to go farther.

It's fine, though, for a lot of watersports uses, where you want to put out hundreds of kW for a few seconds to pop a skier up, do a set, talk to your skier without asphyxiating them in exhaust fumes and without shouting over engine noise, and then plug it back at the dock. Less fine for cruising, where you want a tank of fuel to last you whole day. You only need enough energy storage to outlast human quads and forearms, not more to outlast human bowels!

[1] http://www.ltsmarine.com/english/lts-water-ski-boat/

[2] https://nautique.com/models/super-air-nautique-gs22e/overvie...

[timbray]

Note that the Candela people have videos of their boats running smoothly in waves up to 1.2m.

People used to say that electric cars were "nowhere near being a practical solution" until suddenly they were.

[0xbadcafebee]

> People used to say that electric cars were "nowhere near being a practical solution" until suddenly they were.

FWIW they were the most common automobile type at the turn of the 20th century. The naysayers were just internal-combustion apologists.

[aidenn0]

The spec sheet for the C-7 says "Wave height 5 cm when foiling[1]."

The C-7 is a toy. I have no doubt that they can make a non-toy at some point in the future, but the future isn't here yet.

1: https://candelaspeedboat.com/candela-c-7/

[Candelaboat]

Hi, I work for Candela in Sweden. 5cm is not the wave height the boat can handle. 5 cm is the height of the wake the boat produces, so almost no wake. You can go foiling in 1,2 meter high waves in 30 knots - check out this video: https://www.youtube.com/watch?v=m7I0pVpnytM&t=8s

[aidenn0]

Thanks for the clarification. Could you maybe update your product page? As someone who lives on the open ocean (rather than a bay), the first thing I look for is maximum swell or wave height a boat can handle.

[Candelaboat]

Update: it's done. Thanks!

[Candelaboat]

Good suggestion - thanks!

[inetsee]

I have to say that I think the Spec Sheet may be in error. I looked at the videos on Candelas website, and it looks to me like there's significantly more than 5 cm between the water surface and the bottom of the hull.

[Candelaboat]

Mikael at Candela here. It's supposed to be "wake", not "wave" - sorry for this. The wake behind the boat is only 5cm, so no wake damage here:) The boat handles waves nicely, we can fly in up to 1,2 meter high waves - watch this:

https://www.youtube.com/watch?v=m7I0pVpnytM

[_jbcv]

Water under all those videos on their homepage is what we'd basically call smooth as glass. That's definitely a calm +/- 5 cm wave range.

Here is what a 1.2 meter one looks like, just exiting an inlet: https://www.youtube.com/watch?v=rV41E9PQwiU

[Scene_Cast2]

Wait, don't foils handle fine as long as the chop is within reason? And if the waves are higher than the foil clearance, it's not like regular boats would do that well either.

Worst case, couldn't you go slower and just act like a regular boat?

[_jbcv]

Imagine cruising at 30-40 mph, angled so you cut through waves perpendicularly. Mostly you head straight, but you do need to lazily avoid some crests and troughs, aiming for that sweet middle. You then see a mostly submerged log 30 feet ahead, just barely under the surface.

You now have two choices, steer to the left or right of it. Those split-second decisions have consequences, depending on which way the prevailing waves are headed. Say if you turn toward port, you might be parallel to the waves which you never want to do: they can capsize you. So you don't turn to port.

Heading toward starboard might be a better choice, but it's still not perfect - you might head toward a crest that will definitely slam into your bow violently. Or there is another boat wake you now have to deal with that wasn't a problem seconds ago. In either case, you need to alter your speed to either avoid it or cut through it more gently. You start dropping off plane, cut through a favorable section, and then angle yourself and go wide open throttles to miss a trough. Maybe you rise back on plane before you avoid it, or just slightly afterwards but on most V hull powerboats doing all this is not a problem. In normal traffic, this might happen a few times a minute.

But hydrofoils have two things going against them right there. They have massive drag at lower speeds and thus maneuver poorly in an emergency, taking more time to accelerate on plane or change direction. Then the weight ratio is a challenge: they need a lot of power for cruising speed, so they weigh more than you'd expect and then weight management is one of the primary design concerns. That all means the propeller is optimized for power over acceleration, and that means that these three congruent design choices have painted you into a corner, limiting collision maneuverability. Hydrofoils handle rough seas far worse than any conventional hull shape and more importantly, colliding with anything underway is far less forgiving than striking an object on the bow or outdrive.

Emergencies notwithstanding, being normally outside a propeller's designed operating range and you have cavitation and ventilation problems, which then erode the propellers. And that weight constraint means fewer seats, fewer people to carry, so less efficient per capita.

[Candelaboat]

Mikael at Candela, the maker of C-7, here. This post is inaccurate and frankly makes no sense. First, the waves will never capsize the boat. Due to low cog, it's virtually impossible to do - we've tried. You can manoeuvre just fine at all speeds, but at high speeds it's correct that you might not be able to avoid running over a log or other submerged objects. Same goes for regular planing boats at high speeds. If you hit something, the foil will withstand smaller objects - branches, debris - but is designed to come off should you hit a bigger object, such as a log. While the foil breaks off, the hull will stay intact and avoid damage. Now, on the other hand, if you hit a log with a conventional boat, there's a risk the hull is pierced and the boat sinks. Regarding the "weight ratio": hydrofoil boats are super energy efficient and need very little power at cruise speed compared to a traditional hull, which is why we use them for C-7. At 22 knots, the C-7 uses about 25 hp, which is pretty remarkable for a 25-foot boat. We have a passenger capacity of six persons, but have actually taken off with 10 persons on board - using a motor rated at 65 kW!

[_jbcv]

Mikael, my hats off to you and your fine product and sweat you poured into it. My apologies if in any way I seemed to criticize performance of your craft, far from it. I know nothing of it, and electric is going to be the only way in the near future. The context got shifted toward it somehow.

My general skepticism regarding hydrofoils comes from, quite frankly, not seeing that much damage with them because they don't exist 'in the wild' so much here to establish a conventional sense for most U.S. east coast watermen. Plenty of other issues that everyone I know is familiar with, most commonly groundings and striking objects, and occasionally catching cage lines on props. The petrol-era weight bias sticks around and this is where I hope you show us very wrong. I'd love to see some rough water videos of your C-7.

My original response from where everything else stemmed from is that right now this isn't a practical conversion for a common man with something like a 27' cabin cruiser, certainly not in the pocketbook. I do not know how much the C-7 costs, but was my sticker shock that far off?

[Candelaboat]

Hi, no problem, just wanted to clarify. The price is 250 00 euros, which indeed is expensive for a 25 foot boat, but still about 100 000 euros less expensive than conventional electric boats that can go fast - but not that far.

The price stems from a high production cost, the whole boat is built like an aircraft, in carbon fiber (the designer used to work at Eurocopter) to be as light as possible. The weight of the hull and deck is about 240 kg. So our main goal for the future is to reduce the costs - by a lot. But think about C-7 as the Tesla Roadster. But our foiling ferry for the city of Stockholm will be launched next year, and then people using the Stockholm public transport system can go foiling for 2€.

[SigmundA]

How much does it cost to replace the foils should you tear them off? Because honestly on a pleasure boat say in Florida where I am your not going to hit a log but you will drag bottom at some point due to shallow waters and tides. Most outboards have some sort of skeg damage due to dragging bottom or strikes. Replacing props and lower units or repairing the skeg is very common.

[lstodd]

Total loss. Even on an alumunium hull, not to mention composite.

Besides, it might not sink, but the collision will throw people around, and it's not like boats have seat belts or people accustomized to using them.

[timbray]

It is really not obvious that it would be worse experience than sitting it with your fiberglass hull. (Clearly worse than an aluminum hull though.) This happens all the time in the Pacific Northwest where I boat, floating logs. Worst are the deadheads, waterlogged so they float vertically just below the surface. Never known anyone to actually sink, but there've been a few destroyed propellers and thousands of bucks worth of hull repair.

[karmicthreat]

My guess would be treat it like when you pull the chute on a Cirrus GA aircraft. Total loss, but you didn't die!

[Candelaboat]

Mikael at Candela here. The cost of replacing the foils vary, but considerably less than the lower unit of an outboard on 25 foot boats. I actually ran over a submerged chain and broke the foil once - the only time that has happened in Sweden. Took us an hour to replace it, so no big deal You hoist the foil/struts down completely and insert a new one.

[Candelaboat]

Mikael at Candela, the maker of C-7 here. Yes: The hydrofoils reduce slamming by about 95% in waves that are up to 1,2 meters. If they're higher than that, you can always go slow. The boat has a 40 kWh battery pack in the keel, so it's a very stable craft even at slow speeds. Check out Candela.com.

[acdha]

Is biodiesel getting much interest in boating? Given the cost disparities I wonder whether it’d make more sense to explore emissions controls with a non-fossil fuel until a better battery technology emerges.

[bosswipe]

If the goAl is reduction of emissions or generic environment friendliness biodiesel is not a solution. Especially if the biodiesel comes from palm oil.

[acdha]

It very much depends on the source - palm oil is a disaster but if there are alternatives it seems like it would be a net win for CO2 if you could avoid additional fossil fuel extraction. I’m thinking of a guy I knew who used to process oil from a local restaurant’s deep fryer – that would be problematic getting the formulation right for an advanced car engine but my (possibly completely incorrect) understanding is that marine Diesel engines are a lot simpler and there isn’t an obvious path for short-term replacement the way there is for an EV.

[magsnus]

~840 HP (1.4*600) to bring it up to plane with an electric motor but just ~300 HP to do it with a diesel engine? It's obviously more expensive but not that much more expensive.

[_jbcv]

Check out the electric co's site, and maybe it'll explain it better than I could have at a broad pass. But that inboard was their entry-level motor that actually existed.

I suspect their power declaration is marketing language claiming burst power, and that its nominal cruising range is well under it but regardless of any of that, the batteries costing $180,000 is still an issue.

Edit: forgot one important thing for that power matching, the weight. Replacing an engine and full gas tank -- the electric motor + mid-range battery pack overall adds about 2,500 lbs to the boat, so it'd be a 7,200 lb boat at that point and I'm not sure I could trailer it anymore.