Arc One – Electric Boat
arcboats.com
arcboats.com
Electrification of boats is uniquely challenging because it's a delicately balanced optimization problem -- You need to keep the boat up on plane to get a reasonable range and compete in the same class as other recreational motorboats. Getting on plane requires a high peak power output, but that in turn requires a heavier battery pack, making it harder to get up to speed...
Battery energy density is not quite at the point where you can just stick a battery and electric motor in an existing boat hull and expect it to perform, so the theme of all these companies is using a custom lightweight hull or hydrofoil to reduce drag/weight enough to avoid the energy density problem. 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.
That said, I'm not sure Arc has done their research on the market fit for aluminum hulls. Based on their concepts it will take a lot of work to convince the recreational boating scene to buy a $300k aluminum boat with an inboard motor; typically aluminum hulls are used for fishing and shallow waters, and in those use cases an inboard doesn't make sense -- it might be better equipped in that case with a jet drive but would hit power issues there.
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.
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.
However the sum of my boat knowledge comes from this amazing post...
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.
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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.
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.
Also my understanding is that there are very people in the US who are naval architects.
What market segment is it trying to play in? I don't think I've ever really seen a 24 foot closed-bow boat.
This’s is not for fishing
It’s been a long time since I’ve seen a boat at that size that’s not a bowrider.
This feels like it’s designed and marketed for electric vehicle lovers rather than boat users
This seems like a boat designed by people who don't get boating, for an audience that doesn't really care about boats.
Unsophisticated investors.
I'm a complete layman though, so could be wrong. Can anyone answer whether modern hydrofoils are a game changer?
Though what is needed is an easy drop-in solution for existing boats. That's the breaker and charging.
Most composite boat hulls are way too heavy to stick an electric motor in and expect reasonable performance.
Electrification is cool, but dont make so many changes at once. I dont need nor want a new metal or carbon hull. Fiberglass hulls are perfectly good. Give me batteries and a standard electric outboard I can mount on my current boat. And i just dont like the idea of mixing a conductive hull, salt water, and a small tesla's worth of battery power. I dont know how it will short but i know i dont want to be anywhere near it when it does. Fiberglass please.
Hmm, I'm reminded on how Google Wave had a launch-date feature of custom scroll bars. Because that was somehow important.
>$300k
That makes it $2.5k/ft! For a recreational, non-competition, Class I boat, that's absolutely incredible to me.
That is, electrification is a bigger step then "the next generation", it's really a radical break.
Honest question.
Looks neat, but insane price given that the even the first-year Tesla S's were in the $50-70K range.
Why does a boat need "over-the-air updates"?