Hacker News Reader

>Another interesting startup is Candela (https://candela.com/) who is taking on the problem from a similar angle; they use hydrofoils and a complex controls system to keep the hull foiling which is very low drag.

Candela is what I immediately thought of when I saw this, and looks like a much more interesting approach that I like both for boats and aircraft. There is no getting around present disadvantage in energy density for batteries vs fuel, even if efficiency helps make it a bit less bad than it'd look like on the tin. But electric drive trains have their own fundamental advantages too in terms of motor power for a given volume, lack of plumbing required, torque, etc. So the more interesting designs seem to be leaning into that to do things that just plain wouldn't be feasible with ICE/turbines. Like with aircraft NASA's X-57 concept [0], electric allows simply having a ton of little motors all over so rather then needing a large wing to try to prevent stalling (inefficient at high speed) they can simply actively force air over a thin wing then shut them all down. Or with Candela they can do interesting things with motors on small foils with the boat fully out of the water.

I'm not expert, but attacking the entire problem space from a different angle rather then just swapping engine for electric and fuel tanks for batteries seems like an interesting way to go long term. Though of course probably makes for more challenging engineering.

----

0: https://www.nasa.gov/specials/X57/

Absolutely agree, couldn't have said it better myself. It's a systems engineering problem and requires rethinking of nearly every component, from the propeller design to the architecture of motors and controls.

Torqeedo is an interesting example, they've been very successful with low-power electric outboards because in contrast with other companies they've invested heavily in rethinking propeller designs to be suitable for electric motors. The result looks nothing like a gas motor: They have huge, slow-rotating propellers that peak at <1200rpm and a high-speed brushless motor that gets geared down so it operates at the top of its RPM and efficiency range.

Getting on plane requires a high peak power output

Could a capacitor bank be used to deliver a burst of power to plane out? Or does the weight and volume of capacitors still exceed what's practical? Also seems like it wouldn't work for wakeboarding, where the goal is to generate a big, inefficient wake all the time.

The power required to plane in a boat looks a bit like a normal curve -- Power consumption scales upwards exponentially with speed until you either 1) Get going fast enough to hydroplane and reach a high efficiency regime 2) Hit the peak power of the drivetrain and fail to accelerate further

A capacitor bank wouldn't really help here, since that power has to come from somewhere. The issue isn't that the batteries aren't capable of outputting that peak power -- Even small battery systems are more than capable of outputting the 50kw+ it might take to get on plane. The real issue is that doing that repeatedly requires you to scale up your battery capacity and weight, which is a positive feedback loop.

Boats are not just getting on/off plane once on a tank of gas, they're doing it 10-20 times depending on driving conditions, surroundings, no wake zones. This might happen 100s of times for watersports like wakeboarding. So a big part of the equation is finding a way to save weight elsewhere that can then be used to insert more batteries.

Okay, so I've looked more into the stats based on their marketing material, and I just don't see how the math works out...

They're claiming a 200kWh battery which seems a bit high for the size of the boat.

An equivalent battery system for marine environments that exists today is the Deep Blue BMW i3 (https://www.torqeedo.com/us/en-us/technology-and-environment...) which is a Torqeedo-BMW collaboration. That battery is 40kWh and 278kg.

Now, obviously there is a BMS and other parts that don't need to be replicated 5x, but scaling that up to a 200kWh pack gives 1390kg. That is absolutely ridiculous. Candela's entire C-7 boat weighs 1300kg, and it's only able to maintain a good range by utilizing hydroplaning extensively.

I'm not sure how a conventional planing hull that might weigh well over 2000kg with interior components, passengers, etc will get any reasonable range, and I suspect they don't show average range or loaded weight in the stats because it just doesn't look great compared to their competitors.

One advantage is you could put your battery bank at the very bottom of the hull, making your otherwise pretty lightweight ship more stable.

However the sum of my boat knowledge comes from this amazing post...

https://ciechanow.ski/naval-architecture/

Since it seems like a bit of a cool toy more than anything, I don't quite understand why they wouldn't go for carbon fibre at that price point?