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Comment by zknill | Hacker News Reader

The promo video has a perfectly flat body of water. I'd be interested to know what impact waves have on a hydrofoil.

Hydrofoiling boats have been in commercial use for quite some time. I've taken one[1] between Estonia and Finland a couple of times but these are sadly not operating anymore.

1. https://images.delfi.ee/media-api-image-cropper/v1/02cc3aa0-...

The Greek apparently still operate hydrofoil boats between islands on Mediterranean sea. Sea, not river.

Same in Italy. Both sea and lakes.

I recall a hydrofoil on Lake Garda -- obviously lots of power required -- it was much louder than the normal ferries on that lake.

Some hydrofoil ships are powered by turbines, which produce a high-pitch whine, much more noticeable at a distance than the low-frequency rumbling of a diesel.

jet foil in Japan https://www.youtube.com/watch?v=e_lKISuF5Y4

edit: shorter video

I think that's a Boeing 929 Jetfoil. They've been going since 1974 https://en.wikipedia.org/wiki/Boeing_929_Jetfoil

What are the economics of hydrofoils like? I recently watched a YouTube video covering the rise and fall of hovercraft ferries. Basically, the lower reliability of hovercraft eventually overwhelmed the utility of faster transit times. Is it the same for hydrofoil ferries?

I remember reading articles about the Silja Line ferries needing repairs all the time. But that might have been an issue with the specific models and not an indication of hydrofoil reliability in general.

They must be much more efficient than both boats and hovercraft - they don't need to keep the air cushion, and they don't need to push their full tonnage away from their path - lift losses excepted, they must be equivalent to much smaller boats.

I would expect to see more of these as recreational vehicles, as they must be much cheaper to operate and, with recreational boats having a much lower duty cycle than, say, BEVs, solar recharging becomes attainable, as long as you keep the boat docked or anchored and charging for much longer than you use its propulsion.

I saw a single person standup foil on a local lake. They look unreal, almost unbelievable in operation. Like someone is flying over the lake. Search for efoils on youtube

This does sound approachable. From my experience, people with lake front property and docks with boat "houses" are clear from any obstruction of direct sun. Line the roof of said boat "house" with solar, and in the typical weekender/vacationer use of a boat, seems pretty managable. However, when the sun is up to be charging is typically the time of the boat's use so it won't be on the charger. Use the solar to charge a powerwall type of solution, and then charge the boat at night?

Solar panels could be on the boat itself, but I am assuming solar won't be able to do much recharging while the engine is in use anyway. OTOH, very few boats are used, or moved, every day.

I imagine a boat would have a hefty battery pack anyway, to power a stove, fridge, air conditioning, plus essential bridge equipment.

I think we're talking different sized boat on a lake. Do house boats typically power from battery or from a generator? I have no familiarity with those.

Most houseboats are barges with no propulsion. They use shore power but often have a backup generator. Having some solar or a small wind turbine is relatively common too.

Yes. I was thinking "river boat with limited propulsion that is moved when the owner wants a change of scenery".

Boat houses are extremely heavy, for obvious reasons. Hydrofoil requires light construction, so these two are not compatible (plus it only works at speeds you would not want to have a house moving at).

A Boeing 929 Jetfoil with ~450km range, ~300 passengers, 2x Rolls-Royce Allison turboshafts is often quoted to be ~$60M. Tickets are $35-$120. Many routes operating it has been seeking government subsidization to build replacements as hulls near ends of life; so far, only one 929-117 has been built since the turn of the century.

IOW, not a lucrative business on its own, makes _some_ sense as a subsidized public transportation.

Hi there, Mikael at Candela here. Since the P-12 uses 80% less energy than a conventional vessel, the cost of operating it is far less than diesel vessels- overall around 50% percent lower including service, energy, salaries etc. This makes electrification desirable for operators for the first time. Usually, conventional (non-foiling) electric vessels are more costly to purchase than diesel vessels, and more costly to operate too, as they require MW charging infrastructure on land. The P-12 uses a DC style charger of up to 175 kW, which is pretty affordable to install.

I talked to the skipper of one. He said the boats (Linda Line) had been in service in the Black Sea.

On the Thames: https://www.londonreconnections.com/2020/soviet-fleet-on-the...

I took one from Tangier to Gibraltar, in the 1970s (Might even have been the 1960s).

Video of one of their smaller "speedboats": https://www.youtube.com/watch?v=2i2Zf9WVlNY

I guess they can operate in waves that don't reach the hull? At least sideways

EDIT: Their FAQ says the speedboat can handle 1.2M high waves: A Candela generally outperforms regular leisure boats in rough weather. The maximum wave height when foiling is approximately 1.2 meters from wave peak to valley.

https://candela.com/faq/

That video has the title "extreme weather". That's a very liberal use of the word "extreme"

It's extreme relative to the operating capabilities of the hydrofoil.

Now try the North Sea on a windy day: https://www.youtube.com/watch?v=TYzIWngs_T8

Watch the helicopter coming in to land 30 seconds into the movie. It lands at the end.

I doubt these small taxis are designed for the North Sea though.

No these are mostly meant for rivers and intercoastal waterways. They're not going to be used for intercontinental travel.

They would be perfect for the public boat transportation system in the Oslo fjord between the islands there.

Mikael at Candela here. Norway is indeed a target market for us!

Just in case anyone was ever wondering why the conditions of a SpaceX launch (specifically for the water landings), but also any launch with an at sea recovery zone can prevent a launch from occurring even if the weather is sunny at the launch site.

Wow that helicopter must be super light weight for the blade to rotate so slowly near the end. :-)

Fantastic example of stroboscopic effects in video.

And? It's a ferry designed to operate, like most ferries, in littoral waters. Harbors, bays, rivers, channels, and ocean areas close to shores. Not North Atlantic bluewater conditions.

This has as much relevancy as "nerrrrrr, dumb plane, why did they build it if it can't fly from NYC to Australia" while looking at a picture of a Dash-80, a regional commuter plane.

Now try Las Vegas. I can beat it on a bicycle by myself over any distance under 200 miles and if you have to return to the Luxor pyramid, I could beat it myself over any distance.

That's a well know problem for all of us that want to surf around Stockholm: the baltic sea us just too calm. You can go to Torö and hope for rhe best but in reality even with good wind, all you can do is wing or SUP foil, not even enough to try prone foiling...

(My comment may sound sarcastic but I am serious: the baltic sea has always seen other types of boats, both for leasure and commercial)

They have sensors that detects waves and adjusts the hydrofoils to avoid crashing into the water.

If one would like to use hype words I guess one could call them AI-driven hydrofoils or something

Control is the word you are looking for.

It is a _control_ system that takes sensor _inputs_ and _outputs_ hydrofoil tilt actuation.

It maybe controlled by undergraduate Control Theory or some secret sauce predictive model but making a claim in either direction is speculation.

Mikael at Candela here. Our C-8 can foil in wave heights of around 1.2m, which are pretty big waves for a 27-foot leisure boat. The P-12 is designed for much bigger waves, and can foil in 2 meter high waves, meaning it will be able to cover rough weather in archipelagos and littoral waters. The catamaran hull is also efficient at slower speeds up to 10 knots, if the weather would not permit foiling.

I foil and efoil as a hobby; Once on foil, surface waves have no impact as long as you keep the foils in the water -- this means observing and adjusting attitude. If you do it well, you can maintain full speed and only feel the attitude changes (no bumps). Though, if it is very windy and wavy on the ocean/lake it is more difficult to develop foiling speed to take off.

The reason why Candela is pioneering sub surface foils now is because it takes a reasonable amount of sensors and computation to avoid the foil breaching.

For the most part, you wouldn't want to take a sub surface foiling vessel flying out in a storm with significant swells, but that's not what most boating is anyway.

Navier boats in the bay area has a very high end luxury electric hydrofoiling boat, and this guy took a tour in much rougher waves, with a wife that is easily sea sick. they did fine, since you are no longer riding up and down the waves, more through them. Also, they use much, much less power once they are up on the hydrofoil, since they have much less resistance, just takes a bit to get up to speed first (which electric motors are great for)

https://www.youtube.com/watch?v=HQbT4pr5ylE&t=6s

https://www.navierboat.com/

I have taken a several hour hydrofoil ride in the Mediterranean in moderate swells.

The ride is deeply nauseating as the foils are positioned towards the outside corners and (on this 200+ passenger craft) catch the swells independently. The result a ride with similar pitch and roll as a traditionally-hulled ferry, with far more yaw and far less periodicity.

Mikael at Candela, the hydrofoil maker, here. Our P-12 uses submerged hydrofoils and emplys a digital Flight controller, which stabilizes the craft by adjusting the angle of attack of the foils 100 times per second. So the pitching and heaving you found nauseating in the old Soviet Raketa and Kometa hydrofoils don't exist in P-12 - it's smooth sailing even in. chippy weather. Watch this video: https://www.youtube.com/watch?v=xIp9OkMzZkM

I can speak to this a bit, having piloted a Candela (the speed boat version, I forget the number) on the Swedish west coast where seas can get notoriously choppy seemingly out of nowhere. This is a couple of years ago though so maybe they've improved things since.

The impact of any waves higher than maybe a meter is likely to make the software take you in for a rather rude landing, and quick stop.

It's unlike any boat of that size I've piloted, it was very heavy and it never felt like you were totally in control, with some small but quite noticeable latency between input and action. Felt more like piloting a larger ship than a small speed boat.

The fact that it felt like you were at the mercy of the controlling software meant it became a very anxious ride as soon as you ran into a bit of choppy waters.

When flying it was a very nice ride, but when you're not you have to go very slow or you quickly run out of battery. It was not particularly pleasant doing 3-4 knots in choppy waters, even if it did seem rather stable presumably due to the wide base, low height and deep rudders (foils).

Fine boat in calm seas for sure, but I wouldn't use it for anything else. Should do fine in fair weather in central Stockholm though.

There is another video on their channel that shows the technology in rougher weather and sea, seems to work fine.

Which video? None of the videos I see show in rough conditions - the worst is probably "better than average" from spending time on the ocean.

This one:

https://www.youtube.com/watch?v=2i2Zf9WVlNY

All vessels have limits on the sea state they can handle, particularly small vessels. Very large vessels can generally handle much more. You can see how much more the traditional small patrol vessel is bouncing out there, my spine hurts just watching. I could see this being used for pilot vessels and harbor patrol craft, for sure.

Cool, definitely a smoother ride than the adjacent boat.

That isn't rough.

According to another comment, the Candela can handle waves of up to 1.2 meters. But about half of waves in the open ocean are 2+ meters. So this boat can't handle a normal ocean sea.

This is Sweden. I've lived in the east coast of Sweden for 10 years, never seen a wave and there is water everywhere.

Now I'm from Portugal, so… no comparison really.

Yes. The east coast of Sweden is the Baltic Sea, which is not an open ocean. This boat may be perfectly usable there. But that's still not a rough sea. Other than temperature, that is water that I'd be perfectly comfortable swimming in.

I don't think the primary target for these boats is the ocean, they're mostly designed to operate on lakes, bays, rivers, etc

...so places where 5 knot speed limits are often enforced to prevent wakes.

Since they barely produce wakes when they are hydrofoiling, these rules can probably be changed.

But during the transition to the hydrofoil mode and back they produce a lot of waves and wake; seen this many times firsthand.

They have been given permission to drive at 12 knots because they produce much smaller wakes.

https://www.hamnen.se/varldens-snabbaste-elfartyg-far-kora-f...

Candela has been granted a waiver for the 12 knot speed limit in Stockholm, presumably because they make way less wake. Places like the San Francisco Bay are also clear examples of not-the-ocean but no-speed-limits.

https://candela.com/candela-p-12-enables-public-transport-fa...

Why do you need a ferry for a small lake? Anything you'd need a ferry for won't be much distinguishable from an ocean. https://www.youtube.com/watch?v=PebbX8uzyPI

The Great Lakes are not that choppy on average except during storms. But the primary use case would be along intercoastal waterways and rivers, which are also very calm except during storms.

I dunno, where there is boat traffic there will be chop as well. So it's intercoastal, low traffic areas.

> Why do you need a ferry for a small lake?

E.g.:

* https://en.wikipedia.org/wiki/Toronto_Island_ferries

* https://streetsoftoronto.com/guide-to-the-toronto-islands-fe...

How about Puget Sound (Seattle, Tacoma, Olympia...), where there are ferries all over. Several routes have "foot ferries" (no cars) offering rides with added speed to get the commuters to home or work across several miles of semi-open waters. Only rarely are waves a serious factor, and I don't know if that's even serious enough to affect this watercraft. Just one example of where this could really be useful and profitable. I can think of others.. Chesapeake Bay, Lake Champlain, Great Lakes...

What about between OAK and SFO terminals inside security, so that connecting flights (or East Bay passengers boarding and returning) could transfer to & from international gates at SFO?

With Google Maps I found a ferry on the Swedish lake Hjälmaren, between Vinön and Hampetorp.

https://sv-m-wikipedia-org.translate.goog/wiki/Vin%C3%B6lede... says the route is 5km long and takes about 16 minutes.

Wikipedia says the lake is 483 km², while Lake Champlain is about 3x bigger at 1,331 km².

From Google Street View it seems the mainland is visible for nearly every direction.

Oh! I found another ferry, a car ferry from "Boheden, 956 93" to "Sandudden, 956 93 Överkalix", according to Google Maps. The lake Djupträsket is 8.68km² and the ferry is a few hundred meters.

And one between Sund and Jarenleden, on the lake Stora Le, 131 km² but it's narrow and the ferry is only about 600m.

Sweden has a LOT of lakes, and most of them are narrow. I assume they were made by glaciers? I found those two ferries by looking for two roads ending on opposite sides of a lake.

The Stockholm area looks like this:

https://www.google.com/maps/@59.3284101,18.0369884,11.71z?au...

There are plenty of places where the water route is much, much, much faster than the land route, and there are plenty of islands that are only accessible by boat.

As you obviously have never been to Stockholm, feel free to pay us a visit. Its really nice in the summer! This is the ferry map for the archipelago: https://waxholmsbolaget.se/globalassets/kartor/hela-skargard... Note though that that doesn't include the line the P-12 will be in service on from next year as that is line 89 run by SL: https://sl.se/globalassets/linje-89.pdf

https://www.hamburg.com/visitors/hamburg-by/13965006/ferry/

There are plenty of places with large expanses of flat water where a fast electric ferry would be useful.

Yes, you get surface chop, but this craft is designed to keep foiling in up to 1.2 metres of chop. That’s heaps for many bays, estuaries, lakes etc.

I imagine one of the challenges would be getting up to foiling speed in rough waters. From the videos I've seen, once the hull of a foil boat is out of the water, the ride is much less affected by waves.

they take off at around 7-8 knots, so as long as you can get up to that you're good. the motors and wing stay well below the water, the candelas do wave detection as well IIRC.

The deeper the lifting surface the larger the waves can be. You need the waves to not have too much of an impact at their peak while the foil still being underwater at the trough. Unless the foils can extend and rectract[1], the depth of the lifting surface impacts minimum draft of the ship as well.

1: Or fold, though with folding foils, you need to transition from foiling to floating where the water is deep enough, then float into the shallower water.

In general, hydrofoils provide a smooth ride as the vessel is lifted out of the chop. But in more extreme conditions, the hull can nosedive or otherwise slam back down into the water, at which point it's lost its momentum required to stay in foiling mode.

Foiling sailboats deal with pretty substantial wave action, including open ocean storms. It’s all in the design.

What’s really shocking to me is how slow this ferry is compared with those foiling sailboats which can reach upwards of 90 km/h.

Here's old footage of the foilborne Canadian Navy hydrofoil HMCS Bras D'Or from the 1970s, with some rough sea action right at the start of the video. Doesn't look like a smooth ride, and must be a huge stress on the hydrofoil structure: https://www.youtube.com/watch?v=XVYSUWEi-WQ&ab_channel=imaxg...

I think that as a general rule, longer vessels tend to be more seaworthy, they don't get swallowed by waves.

Absolutely not true. Long vessels have different problems with waves, like having the bow AND stern lifted by waves at the same time, so you have a whole different set of failure modes.

Interesting, but I think many ocean-going vessels tend to be fairly long for good reason, with the bigger, longer ones also being faster and more capable in rough seas.

Offshore commercial fishing boats are an example of shorter ocean-going boats. I think they would normally prefer to avoid storm seas if possible. They have to head up and turn into the waves, they can't take them sideways.

One example of when people thought that a big, long boat would be more seaworthy, was the Titanic, which sank in 1912 after hitting an iceberg. But it wasn't the waves that did it.

I think big, long and strong boats are pretty great in rough seas. If I was crossing the Atlantic, I think I'd rather be in a bigger boat, provided that it doesn't break up or develop any leaks.

I think I'd rather be in a bigger boat, provided that it doesn't break up

This is a very high structural demand. Torpedoes work best, when they can effectively "lift" the keel, breaking the back of the ship. (Not exactly, but kind of, IIRC.) Very high sea swells apparently do the same thing! When there's far less buoyancy supporting one end of the ship than the other, the entire ship has to act as a cantilever. At the size of large ships, the square-cube law dominates, and the ship is far more fragile at that scale than a model boat would be. Even steel structures at that scale are flex-y.

Depends on the height of the waves relative to the height the foiling boat flies at. There's a reason those America's Cup boats and the big ocean going trimarans that use foils have quite different designs.

The biggest issue is that if the foiling fails the boat has a tendency to bury the bow quite violently. This killed an AC sailor a decade or so ago.

Foils make sense for inland waterways but making them work for the ocean proper is considerably more difficult.

I'm no naval architect but this boat is awfully narrow in beam which is probably its biggest limitation.

There are lots of videos on YouTube of the smaller C8 in choppy seas and crossing the wakes of other boats.

I happened to see one for real gliding over some waves big enough to give me a bumpy ride in a conventional motorboat.

So they do better than a conventional motorboat in the kind of normal rough sea.

There must be some wave height that starts to give it problems, but it’s up past where normal little motorboats become hampered too.

Can you link? I don't see anything that is more than "average" waves for the sea.

I think the video wood_spirit is referencing to is https://www.youtube.com/watch?v=2i2Zf9WVlNY

It's not extreme weather and the waves don't reach the length of the foil itself. I'm curious as well as to what happens on rough seas.

Also totally different boat eh. Those waves are probably a little bigger than they look, but yes, definitely "better than average" I would say.

A quick search for “candela c8 rough” finds some?

Boy do I want one. For those calm days though. The quietness is another big draw. I have a 4stroke and it’s so peace destroying.

It's intended for use in coastal waters in the Baltic Sea, around lots of islands and behind the Danish straits that significantly tame incoming winds & waves:

> P-12 [...] will halve commuting times in Stockholm from 2024.

In the waves hydrofoils can handle, they're more comfortable than traditional boats -- the waves don't move the boat around as much.

Wouldn't / Shouldn't they slow down out of hydrofoil speed when they enter rough seas? I would imagine that would be the prudent thing to do.

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