Hydrofoiling(tbray.org)
tbray.org
Hydrofoiling
https://www.tbray.org/ongoing/When/202x/2021/05/10/Hydrofoiling
90 comments
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...
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...
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.
People used to say that electric cars were "nowhere near being a practical solution" until suddenly they were.
> 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.
FWIW they were the most common automobile type at the turn of the 20th century. The naysayers were just internal-combustion apologists.
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/
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/
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
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.
Update: it's done. Thanks!
Good suggestion - thanks!
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.
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
https://www.youtube.com/watch?v=m7I0pVpnytM
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
Here is what a 1.2 meter one looks like, just exiting an inlet: https://www.youtube.com/watch?v=rV41E9PQwiU
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?
Worst case, couldn't you go slower and just act like a regular boat?
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.
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.
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!
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?
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?
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€.
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€.
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.
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.
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.
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.
Again here in FL dragging sandy bottom is pretty common and most of the time no big deal, maybe scuffing your skeg. Many times what happens is you're out of the channel on a plane no problem, then you slow down come off a plane and oops the water is too shallow and your lower unit /prop hits being the lowest part of the boat.
Hitting a rock might bend your prop and you might need to replace, many carry a spare prop on board as it can be replaced relatively easy even out on the water with an outboard.
That same situation with a foil boat would be disastrous, again just one very expensive and dangerous mistake.
Hitting a rock might bend your prop and you might need to replace, many carry a spare prop on board as it can be replaced relatively easy even out on the water with an outboard.
That same situation with a foil boat would be disastrous, again just one very expensive and dangerous mistake.
My guess would be treat it like when you pull the chute on a Cirrus GA aircraft. Total loss, but you didn't die!
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.
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.
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.
If the goAl is reduction of emissions or generic environment friendliness biodiesel is not a solution. Especially if the biodiesel comes from palm oil.
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.
~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.
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.
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.
Hydrofoiling seems to be having something of a grassroots style renaissance, with incredible interest across all of boating, sailing, windsurfing, kitesurfing, surfing and pretty much any other board/boat water sport.
I find this peculiar because hydrofoils were seemingly much more common in the 80-90's in industrial applications such as ferries, but now suddenly have become hugely popular in recreational space, and rapid innovation in the design and construction of foils across all of the domains. Very interesting if you are interested in boats and water sports.
I find this peculiar because hydrofoils were seemingly much more common in the 80-90's in industrial applications such as ferries, but now suddenly have become hugely popular in recreational space, and rapid innovation in the design and construction of foils across all of the domains. Very interesting if you are interested in boats and water sports.
Mikael at Candela, the C-7 maker, here. Hydrofoils have a number of benefits, among them are: less slamming (up to a certain sea state), less drag and better fuel economy, and smaller wake. Boeing 929 Jetfoiler from the 1970's onwards and the Russian hydrofoils that were produced in large numbers during the 1950's-1980's largely used hydrofoils because they made smaller wakes (Russian river rockets) or handled choppy water well (Boeing, in Hong Kong and Japan).
At Candela, we use hydrofoils to reduce the energy usage, to be able to make an electric boat that has long range at high speeds, above 20 knots. Conventional hulls are hard to electrify since they need so much power. However, we use a new type of hydrofoil: fully submerged hydrofoils, that are more efficient but needs active stabilization from computers and software. The on-board Flight controller adjusts the hydrofoils at 100 hZ, or 100 times per second, which makes for a craft that won't pitch or heave. This tech was available in the 1970's - it's basically a very similar Flight controller as in an inherently unstable jet fighter like F-16 - but thanks to drones and smartphones, the price reduction of sensors makes it possible for us to offer this tech in a leisure boat.
And - we're scaling our electric hydrofoil tech to commercial ships. Right now, we're starting the construction of the world's first foiling electric shuttle ship for the city of Stockholm. At its launch next year, Candela P-30 will be the fastest electric ship ever at 30 knots, as well as most energy-efficient ship ever built. Energy usage is 1/10th of conventional diesel ships. Check it out here:
https://candelaspeedboat.com/public-transport/
At Candela, we use hydrofoils to reduce the energy usage, to be able to make an electric boat that has long range at high speeds, above 20 knots. Conventional hulls are hard to electrify since they need so much power. However, we use a new type of hydrofoil: fully submerged hydrofoils, that are more efficient but needs active stabilization from computers and software. The on-board Flight controller adjusts the hydrofoils at 100 hZ, or 100 times per second, which makes for a craft that won't pitch or heave. This tech was available in the 1970's - it's basically a very similar Flight controller as in an inherently unstable jet fighter like F-16 - but thanks to drones and smartphones, the price reduction of sensors makes it possible for us to offer this tech in a leisure boat.
And - we're scaling our electric hydrofoil tech to commercial ships. Right now, we're starting the construction of the world's first foiling electric shuttle ship for the city of Stockholm. At its launch next year, Candela P-30 will be the fastest electric ship ever at 30 knots, as well as most energy-efficient ship ever built. Energy usage is 1/10th of conventional diesel ships. Check it out here:
https://candelaspeedboat.com/public-transport/
Very cool, I've been following your products for a while, hoping to see them in the UK soon!
Yep
I've been hydrofoil windsurfing (and have tried wingsurfing/wingfoiling as well).
Hydrofoiling has extended the lower range of wind speeds that I can go fast in. For instance, around 10kts wind I can pump the board and sail to get on the foil and go about 20mph. Pros push this even lower, to about 7kts wind speed.
I can also go upwind much higher and downwind deeper, at speed, than I could with just regular windsurfing on a fin. Control is a bit difficult downwind for me, still, but it's fun.
Paris Olympics in 2024 will have hydrofoil windsurfing. There was also a race this weekend around Lanzarote, which was almost 10hrs of racing and 130 something miles traveled on windsurf foils.
I've been hydrofoil windsurfing (and have tried wingsurfing/wingfoiling as well).
Hydrofoiling has extended the lower range of wind speeds that I can go fast in. For instance, around 10kts wind I can pump the board and sail to get on the foil and go about 20mph. Pros push this even lower, to about 7kts wind speed.
I can also go upwind much higher and downwind deeper, at speed, than I could with just regular windsurfing on a fin. Control is a bit difficult downwind for me, still, but it's fun.
Paris Olympics in 2024 will have hydrofoil windsurfing. There was also a race this weekend around Lanzarote, which was almost 10hrs of racing and 130 something miles traveled on windsurf foils.
The 1980ies did not have foil sailing which is just incredibly inspiring. And that in turn is most likely enabled by carbon fiber manufacturing having become somewhat mainstream (and much better), even if it may not be entirely impossible to do in steel.
Also, for industrial applications (and for recreational without self-imposed restrictions), high frequency automated active servo control is now very much in the realm of practicality. Back then it was all self-stabilizing, which led to some very bumpy rides.
Also, for industrial applications (and for recreational without self-imposed restrictions), high frequency automated active servo control is now very much in the realm of practicality. Back then it was all self-stabilizing, which led to some very bumpy rides.
Well, there was the Hobie Trifoiler.
http://trifoiler.info/media/index.php?title=Main_Page
https://www.youtube.com/watch?v=zXSgZCDVWOM
I don't know if modern consumer-level designs are sophisticated enough to be using much CFD, but it definitely seems like the easy availability of CAD should be playing a role.
http://trifoiler.info/media/index.php?title=Main_Page
https://www.youtube.com/watch?v=zXSgZCDVWOM
I don't know if modern consumer-level designs are sophisticated enough to be using much CFD, but it definitely seems like the easy availability of CAD should be playing a role.
Maybe carbon fiber technology has improved and has become more affordable?
I'm in the proces of learning to use a kitesurf hydrofoil, it's funny to see the gps tracks from a smartwatch on strava, very messy, like a child scribbling.
I'm in the proces of learning to use a kitesurf hydrofoil, it's funny to see the gps tracks from a smartwatch on strava, very messy, like a child scribbling.
Hydrofoiling might be old but lithium batteries and electric motors have spawned a bunch of eFoils companies (electric hydrofoils):
https://fliteboard.com/
https://liftfoils.com/
I get friends who aren't into surfing sharing links to these things just because they look so fun.
They're not quite Gravity Industries[1] cool but they have an “Iron Man on water” feel to them, and they're an interesting entry point into watersports for people who can afford to buy or hire the things.
[1]: https://gravity.co/
https://fliteboard.com/
https://liftfoils.com/
I get friends who aren't into surfing sharing links to these things just because they look so fun.
They're not quite Gravity Industries[1] cool but they have an “Iron Man on water” feel to them, and they're an interesting entry point into watersports for people who can afford to buy or hire the things.
[1]: https://gravity.co/
I've been wanting one of those electric foil boards for a while. There are patents involved which is why the market hasn't exploded yet, but some folks have been making their own DIY versions with pretty great success:
https://foil.zone/t/filips-budget-3d-printed-hydrofoil/1968
I saw one of these electric hydrofoil surfboards in the distance off the beach last thursday.
It looked like a landspeeder, and felt like watching a fake youtube video.
It looked like a landspeeder, and felt like watching a fake youtube video.
Land Speeder and Speeder Bike eFoils are crying out to be made.
The closest thing I found was the “HydroFlyer”:
https://www.thehydroflyer.com/
The riding position is somewhat different to an efoil Speeder Bike, though, where your legs would presumably start in the water like with this design:
https://foil.zone/t/efoil-motorcycle/6432
The closest thing I found was the “HydroFlyer”:
https://www.thehydroflyer.com/
The riding position is somewhat different to an efoil Speeder Bike, though, where your legs would presumably start in the water like with this design:
https://foil.zone/t/efoil-motorcycle/6432
Wow that looks like fun. And while $13k isn't pocket change, it's about the same as a new motorcycle or high-end (e-)MTB. IOW not totally inaccesible pricewise. hmm...
Foiling has made it possible to do all of these sports with less power. I can now go windsurfing in 12kts on the same size sail that I would use for 20kts.
I remember seeing foils in the late 90s and early 2000s but they weren't available to purchase. I wonder why. Maybe it's because the construction process hadn't been commercialized yet.
I remember seeing foils in the late 90s and early 2000s but they weren't available to purchase. I wonder why. Maybe it's because the construction process hadn't been commercialized yet.
There's a YC company that's building hydrofoil container ships to lower the GHG emissions from shipping.
https://www.boundarylayer.tech/
https://www.boundarylayer.tech/
Interesting, and the video is informative (though a bit short) but we always want to know the caveats
- Why hasn't this been built before? Yes, minor hydrofoil ships have been built but why not cargo ones? (Constructor conservatism? Some issues that others have run into? Lack of technology before that)
- How does this fare in a marine thunderstorm?
- How many customers are time sensitive (but not much) so as to fit their window?
- What kind of problems can going 4x the speed on an open ocean can create?
- Is the actual cost 4x less once you factor everything in?
My bet is that this makes sense for shorter routes (like multiple ferry routes in Europe), maaaybe for "shorter" cargo routes, not so sure for the longer routes (though China-LA is not "too long")
- Why hasn't this been built before? Yes, minor hydrofoil ships have been built but why not cargo ones? (Constructor conservatism? Some issues that others have run into? Lack of technology before that)
- How does this fare in a marine thunderstorm?
- How many customers are time sensitive (but not much) so as to fit their window?
- What kind of problems can going 4x the speed on an open ocean can create?
- Is the actual cost 4x less once you factor everything in?
My bet is that this makes sense for shorter routes (like multiple ferry routes in Europe), maaaybe for "shorter" cargo routes, not so sure for the longer routes (though China-LA is not "too long")
There's a lot of vaporware out there, but this foiling ferry has been paid for by the City of Stockholm and will launch next year:
https://candelaspeedboat.com/public-transport/
https://candelaspeedboat.com/public-transport/
> Yes, minor hydrofoil ships have been built but why not cargo ones?
I'm assuming that the additional of the weight of the cargo means that you would need to go much faster in order to lift the ship up on the hydrofoils, and this makes it infeasable.
I'm assuming that the additional of the weight of the cargo means that you would need to go much faster in order to lift the ship up on the hydrofoils, and this makes it infeasable.
Also you need to lift your fuel and you might get into a rocket equation type problem. Fuel is less dense than water so one might imagine it contributes a little to buoyancy but aloft, you're paying to lift it along with the cargo.
Fuel means range so that all might get back to the mission: ferry or transoceanic.
Fuel means range so that all might get back to the mission: ferry or transoceanic.
Airplanes also have to lift their own fuel, yet are not, in practice, hostage to the rocket equation (though early, grossly inefficient jets may have experienced something like it.) Three things that make the rocket equation a problem for orbital launches are, firstly, you have to take along the oxidizer as well; secondly, you have to do much more lifting (and, considerably more significantlty, accelerating) than an airplane; and thirdly, without dynamic lift, all the lifting and accelerating has to be done directly by engine thrust.
Also, while fuel oil is buoyant, it still has mass and weight, and the fuel in a ship contributes its own weight's worth of displacement. Displacement, in turn, causes wave resistance.
The larger a ship gets, the less significant, proportionally, both wave and friction drag become, reducing the incentive for foiling. It seems significant that the YC company mentioned elsewhere in these comments (Boundary Layer Technologies) positions itself as competing with air freight rather than shipping (and, as flying in the thin air of the tropopause is pretty efficient compared with generating lift in water, I would guess part of their calculation involves building much larger-capacity vessels than current and projected air freighters.)
Also, while fuel oil is buoyant, it still has mass and weight, and the fuel in a ship contributes its own weight's worth of displacement. Displacement, in turn, causes wave resistance.
The larger a ship gets, the less significant, proportionally, both wave and friction drag become, reducing the incentive for foiling. It seems significant that the YC company mentioned elsewhere in these comments (Boundary Layer Technologies) positions itself as competing with air freight rather than shipping (and, as flying in the thin air of the tropopause is pretty efficient compared with generating lift in water, I would guess part of their calculation involves building much larger-capacity vessels than current and projected air freighters.)
Fairly large hydrofoil ships have been built before so it will probably work from an engineering standpoint. But the economics are questionable. They're betting on finding customers who want a middle option between slow, cheap container ships and fast, expensive air freight. I'm skeptical that many such customers exist.
Hydrofoils obviously can't operate safely in heavy sea states. When a storm comes up they'll have to delay sailing, or route around. That will add some unpredictability to delivery schedules.
Hydrofoils obviously can't operate safely in heavy sea states. When a storm comes up they'll have to delay sailing, or route around. That will add some unpredictability to delivery schedules.
Hadn't seen those, really interesting, thanks!
Also can't help smiling at their use of "BLT" as an abbreviation for the company name, I guess we know what their Official Company Lunch is going to be [1]. :)
I wonder if there has been any progress, the site is kind of ... light on the details. The prototype single-container ship was cute, though.
[1]: https://en.wikipedia.org/wiki/BLT
Also can't help smiling at their use of "BLT" as an abbreviation for the company name, I guess we know what their Official Company Lunch is going to be [1]. :)
I wonder if there has been any progress, the site is kind of ... light on the details. The prototype single-container ship was cute, though.
[1]: https://en.wikipedia.org/wiki/BLT
Check out our foiling ferry P-30 that already is paid for by the city of Stockholm and will be launched Q4 2022:
https://candelaspeedboat.com/public-transport/
https://candelaspeedboat.com/public-transport/
It is interesting that the illustrations use traditional looking props rather than ducted or shaft-less rim-driven thrusters.
https://www.researchgate.net/project/RIM-DRIVEN-THRUSTER
https://www.researchgate.net/project/RIM-DRIVEN-THRUSTER
A similar company: https://freightfish.io/
> The core ideas behind the Candela C-7 aren’t that complicated: Electric powertrain, battery, hydrofoils, software trim control.
I enjoyed the article, so I'm not trying to pick on the author too much, but I always find it funny when technical people say this about engineered things. Each of those things is literally an entire discipline and you could still spend a career (or at least many years) only working on one of them. I think we have a tendency to think that because we can understand something and have taken some of the magic out of it that it isn't complex.
I enjoyed the article, so I'm not trying to pick on the author too much, but I always find it funny when technical people say this about engineered things. Each of those things is literally an entire discipline and you could still spend a career (or at least many years) only working on one of them. I think we have a tendency to think that because we can understand something and have taken some of the magic out of it that it isn't complex.
Sailing has pushed Hydrofoiling to the next level there are 100m boats coming out that claim to be able to do 2.2x wind speed downwind. One of the things I miss the most living in Central Texas is sailing on trapeze and foiling. If I were back near the coast I'd buy one of these: https://iflysail.com/
For a cruiser a hybrid electric system has a lot of benefits. Basically it uses the conventional diesel engine, prop, gearbox, and adds an electric motor that bolts on. So if something goes wrong, all of those parts can be serviced worldwide. The electric motor is a form of redundancy, and can also be used as a starter if the starter fails, and the diesel motor can function even if the electric motor fails. At low speeds the electric motor only is used. The electric can be used at the same time for some extra power. For short trips with shore power you can get around without using any fuel. And you can recharge while cruising with the electric motor working as an alternator, allowing you to spend most of the time on only electric, extending your range.
Some boats charge batteries via shaft while on sail. Otherwise diesel generators aren't mechanically connected.
What I do wonder is whether automotive range extenders can be retrofitted instead of marine gensets. Seems way cheaper.
What I do wonder is whether automotive range extenders can be retrofitted instead of marine gensets. Seems way cheaper.
I take it the author hasn't heard of E-Foils or jetfoils?
Maybe not a family transport option, but we're talking a surfboard filled with 18650 cells (or similar) riding on a underwater wing driven by a jet or small propeller.
They are relatively old with companies building competition models at least five years ago.
The technology at heart is an outgrowth of the portable electric vehicle industry and hydrofoil development in the windsurfing commnity.
If you think this article is neat, I would check out the technology. You can build a performance board yourself for sub 3 grand US (possibly less if you are willing to vacuum mold the board yourself).
Good resources are available from the portable electric vehicle or electric skateboard communities. Board building has been covered in depth by generations of surfers.
Maybe not a family transport option, but we're talking a surfboard filled with 18650 cells (or similar) riding on a underwater wing driven by a jet or small propeller.
They are relatively old with companies building competition models at least five years ago.
The technology at heart is an outgrowth of the portable electric vehicle industry and hydrofoil development in the windsurfing commnity.
If you think this article is neat, I would check out the technology. You can build a performance board yourself for sub 3 grand US (possibly less if you are willing to vacuum mold the board yourself).
Good resources are available from the portable electric vehicle or electric skateboard communities. Board building has been covered in depth by generations of surfers.
Candela will also provide boats for a trial with the Stockholm Public Transport system, which currently employs quite a few traditional boats for transport around the city.
https://www.mynewsdesk.com/candela-speedboat-ab/pressrelease...
https://candelaspeedboat.com/public-transport/
https://www.mynewsdesk.com/candela-speedboat-ab/pressrelease...
https://candelaspeedboat.com/public-transport/
Am I correct in saying the key difficulty of a hydrofoil is making sure the boat never gets too high (and the hydrofoil leaving the water, causing massive mechanical stresses on the supports and failure) or too low (and the boat slamming into a wave at high speed, causing a very sudden stop and injured passengers)?
Mikael at Candela, the hydrofoil boat maker, here. Yes, that's a key difficulty that has to be solved by using sensors that detect flight height, and distance to the waves, among other things. If the foil leaves the water, you ventilate and come down. We use a flight controller, a kind of computer, to perform these calculations. Some sailing boats have wands, ie a mechanical stick that detects waves in front of the boat,, but using ultrasonic sensors and adjustable hydrofoils is a way more accurate solution. Check us out here: candela.com
This is explained on wikipedia: https://en.wikipedia.org/wiki/Hydrofoil#Foil_configurations
Basically, yes, for fully submerged hydrofoils you need to make sure you don't get too high or low. For surface-piercing you don't, they self-stabilize.
Basically, yes, for fully submerged hydrofoils you need to make sure you don't get too high or low. For surface-piercing you don't, they self-stabilize.
Charging these by marinas with solar shade seems obvious fit - it protects the boat from weather plus their batteries can balance grid as they are only used like 0.01% of time.
Question I have - do hydrofoils use ground effect to generate extra lift?
Question I have - do hydrofoils use ground effect to generate extra lift?
I’m guessing no because you have to travel pretty fast for an air wing to have an effect (~50-200mph), but you travel relatively slower for the hydrofoil to perform well (10-30mph). (These are very approximate numbers I made up from experience riding on different types of boats. They are not physical limits or anything like that!)
I think TeamNZ were talking about supercavitation for next foils so speeds can go well over 100km/h in next few years.
Water is considerably different to air and there is no analogous effect for ground effect in water.
Edit: I realise now that you mean hydrofoil as in the boat rather than the submerged wing (it's confusing that they both have the same name). I don't think the ground effect from the boat's hull contributes much to the lift but it is something that the designers of the AC75 boats take into consideration https://www.sailmagazine.com/racing/36th-americas-cup-differ...
Edit: I realise now that you mean hydrofoil as in the boat rather than the submerged wing (it's confusing that they both have the same name). I don't think the ground effect from the boat's hull contributes much to the lift but it is something that the designers of the AC75 boats take into consideration https://www.sailmagazine.com/racing/36th-americas-cup-differ...
I think the OP is referring to ground effect above the water surface, as employed by for example eraknoplans (https://en.wikipedia.org/wiki/Lun-class_ekranoplan)
I would speculate no, as it seems a trade off between inherently stable and inefficient (standard v shaped hull) and inherently unstable, but more efficient (inverted v).
Ekranoplans have wings and aerodynamic control surfaces.
I also wonder (this may be the primary reason) if the speeds a hydroplane achieves are sufficient to generate much lift in air from something the size of a boat hull.
Ekranoplans have wings and aerodynamic control surfaces.
I also wonder (this may be the primary reason) if the speeds a hydroplane achieves are sufficient to generate much lift in air from something the size of a boat hull.
Another solution that increases efficiency is to travel slower and design the hull for that. Non planing boats look like sailboats or retro motorboats.
Most boat owners can't afford a hydroplaning boat.
Most boat owners can't afford a hydroplaning boat.
Isn't that a bit of a tautology? Most boat owners can't afford a boat. (Talking about recreational of course)
No. Hydroplaning boats cost multiples of regular boats.
Three kinds.
Regular planing boat. Cheap and fast but very inefficient and thus can't be electric.
Hydroplaning boat. Fast, efficient so can be made electric. But very expensive.
Non planing boat. Cheap, efficient. Can be made electric. But is slow.
Three kinds.
Regular planing boat. Cheap and fast but very inefficient and thus can't be electric.
Hydroplaning boat. Fast, efficient so can be made electric. But very expensive.
Non planing boat. Cheap, efficient. Can be made electric. But is slow.
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TFA cites speed as a constraining factor for their particular needs: "attractive for the “tugboat” flavor of pleasure boats. Which is perfectly OK unless you want to cover some distance and get there fast."
A sailboat is the original "carbon free" way of propulsion for boats and ships. No, it is not as fast as a hydrofoil, but it also won't run out of power except under rare weather conditions (utterly becalmed).
Not that boats don't do a lot of environmental damage in other ways. Bilge tanks, anti-fouling paint flaking off, etc.
Not that boats don't do a lot of environmental damage in other ways. Bilge tanks, anti-fouling paint flaking off, etc.
Anti fouling is the only thing I can think of that’s really bad about boats. The rest seems ok/not worse than living on land.
The Candela boats he links to were discussed here[1] a while back, in case anyone is interested in that discussion.
1: https://news.ycombinator.com/item?id=24222208
1: https://news.ycombinator.com/item?id=24222208
Has anyone seen hybrid propeller / jet-pump boats or foils?
It seems like it would make sense to have a gas engine and propeller to get the foil on-plane from stopped, then when "gliding" switch to a battery powered jet pump to keep it at speed.
It seems like it would make sense to have a gas engine and propeller to get the foil on-plane from stopped, then when "gliding" switch to a battery powered jet pump to keep it at speed.
So why aren’t hydrofoils used almost everywhere? Who wouldn’t want less drag?
Mikael at Candela here. Because it's super hard to make the control system for an inherently unstable boat. It took five years of R&D to make it work in all manners of situations, banked turns etc. Conventional boat builders don't have access to software and control systems engineers, and tech companies seldom invest in the marien sector. But once we got it working, there are no real drawbacks, only benefits. Smooth, quiet, and fun to drive. Check out candela.com for more videos.
This is anecdotal but in the past ~5 years I've noticed foils popping up in more and more places (in Oahu).
One mistake going too shallow and you will probably rip the foils off doing significant damage to boat. Thats my theory why they aren't more popular except in specific applications. Fuel costs are always an issue with boats and foils are well known to reduce them along with smoother ride.
Most normal pleasure boats regularly go in shallow waters and pull up on the beach etc. If you look at the skegs of any of these boats you will see where they have dragged or struck something and a normal outboard doesn't stick down anywhere near as far.
It's cool the the Candela can retract the foils, but again forget to do it one time and those foils looks very expensive and what do they do to the hull as they are being ripped off.
Most normal pleasure boats regularly go in shallow waters and pull up on the beach etc. If you look at the skegs of any of these boats you will see where they have dragged or struck something and a normal outboard doesn't stick down anywhere near as far.
It's cool the the Candela can retract the foils, but again forget to do it one time and those foils looks very expensive and what do they do to the hull as they are being ripped off.
Big waves and high winds will cause your vessel to go unstable and crash. Ocean-crossing cargo vessels have to handle all weather conditions.
Hydrofoils significantly increase draft and nobody wants to dredge their ports and canals 20 feet deeper.
Also drag is proportional to velocity squared, so you can save a ton of fuel just by slowing down a bit. Much easier than designing a hydrofoil cargo ship.
Hydrofoils significantly increase draft and nobody wants to dredge their ports and canals 20 feet deeper.
Also drag is proportional to velocity squared, so you can save a ton of fuel just by slowing down a bit. Much easier than designing a hydrofoil cargo ship.
My friends also have this electric propulsion startup:- https://www.radpropulsion.com/
Skiing or wakeboarding behind this would be pretty rough except on really smooth water. What else do people use a little boat like this for?
Waterskiing behind a Candela C-7 here: https://www.youtube.com/watch?v=pAMlAcSEI1I&t=10s
I don't think you -could- wakeboard behind this, right? The whole point of wakeboard boats is to displace as much water as possible in a controlled way. Skiing would be interesting though.
You could wakeboard, it would just be kinda boring without the wake :-)
The obvious solution here is the world's first green transportation, a regular old sail boat.
- 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.