Recently I have gotten quite a few questions around the topic of speed and range of planing electrical boats. Can you build a planing electrical boat with both speed and decent range? Now we don’t build planing boats at Candela so we are no experts in the area (so pls correct me if anything is wrong below). The subject is however well researched, and some quite simple equations have been established. Already back in 1964, Daniel Savitsky published a paper laying out the foundations for calculating the power needed to push a boat forward. Refinements have been done since then but the original article still holds pretty well. And it turns out that you cannot do much to make one planing boat more efficient than the other. You want to have a certain ratio between weight and length and when that is set the only thing to do is to flatten out the hull. Hence, the most efficient planing boat is a dining table turned upside down. But such a vessel would be pretty bad in waves so some V-shape is typically preferable. Therefore, whenever you are told that a certain hull is very efficient, it is fair to assume it is BS. For example, adding steps can give a few %, but only in very high speed. Not pleasure boats. Such steps will only increase the drag at non planing speed which, arguably, is a bad idea for electrical boats especially.
To answer the question on range and speed of electrical boats, let us make an example. Assume a 8m boat, 2400kg plus 200kg passengers, 25kn cruise speed and 40kn top speed, and a V-hull with 18% angle. First step is to calculate the speed/length ratio –as the speed in knots divided by the sqr of the length in feet. That gives us 4,9. Then we need to check a Savitsky table, like depicted, to find the drag to lift ratio. In our case it is 0,18. Since the mass is 2400+200 we get a hull drag of 468kg or 4600N. To this we need to add drag of appendages and air. Savitsky recommends 20%. Then we are at 5520N in total drag. To get the power we multiply with the speed, 12,9 m/s, and get 71kW. To get to the electrical power we need to compensate of losses in propeller, transmission and motor. So we divide the power with 0,6 and get 118kW (the same operation for 40kn would yield 280kW - like a V8 big block). Now it is easy to calculate the range. If you have a 40kWh battery you can run at 25kn in 40/118h = 20min. After 20 min in 25 knots you have reached 8 nautical miles. If you can afford it, the battery size can be increased. If you put in 3 times a Candela battery, i.e. 120kW, the weight would increase with 400kg so you end up with a range of 22kn. With the same huge battery you get 16NM at 40 knots (not accounting for the mass of the electrical version of a V8).
Now if we allow a bit lower speed – say 20 knots, how much batteries do you need to put in to get a decent range of say 50NM (which happens to be the Candela range). Since a light battery is some 5kg/kWh (ours is heavier) it gets harder and harder to get the boat to plane. With an optimistic calculation you end up with a 400kWh battery (10 times Candela, 4 times a large Tesla) and a battery mass of 2 tons. Then, with the wind in the back, you get 50NM of range.
So yes, you can build an electrical boat with both speed and decent range. But if some tanned salesman gives you numbers that do not match with established knowledge, ask for a test protocol and make sure it is not done by Volkswagen 🙂 ... See MoreSee Less
“Ludicrous mode”. To celebrate that I this week, finally, will become the owner of a Tesla, Ludicrous mode feels like the right name for our new approach for handling ludicrous sea. Or at least a bit ludicrous sea. We have put a considerable amount of brain power into getting what may be the best wave handling ever made for a foiling boat. The new mode is achieved with three main changes: First we have redesigned the beam of the forward foil. The new one has a more refined shape to bend and twist in the right fashion under load and it is made in high modulus unidirectional carbon fiber baked in a 20 ton press. Despite being only 20mm thick, it can take 6+6 tons of tip load before collapsing. Secondly we have changed the height control algorithm in a number of ways resulting in a firmer response to waves of the size we want to follow and a lesser response to smaller waves. Third, we have beefed up the power to the hydraulic system allowing for faster foil movements. In the video you get a glimpse of the experience on board. Maybe more interesting is the attached graph showing the height measured from one of the two ultrasonic sensors when running over some larger wakes today. The first wakes are like 1 meter from top to valley and the last is approaching 1,5m. Since the height sensor sits at the boat which partly follows the wave, the real wave height is even higher. With the new Ludicrous mode, the forward foil is moving from some 12 degrees AoA to -4 in less than 400ms. In flat water such a change in wing angle would be painful. First you would feel 1,5 times heavier than you are and a second later you would feel the boat leaving under you with pretty high speed. The reason for this fast and large change in wing angle is that the water molecules move fast up and down in waves. So instead of +/-1,5g in horizontal acceleration, we get +/- 0,2-0,25g i.e. a reasonably smooth ride. And we feel pretty proud! ... See MoreSee Less
1 month ago
Föreslår Flying High Again med Ozzy Osbourne som soundtrack
Supper wonderful 🎬🎬
4 months ago
The team is getting larger. With 16 super talents we have more than doubled in a year. It is exciting to build a company! ... See MoreSee Less
Two days of temperatures above zero and a bit of wind opened up for a day at the water. ... See MoreSee Less
It was pretty easy to make a simple calculation and conclude: "they are all wrong. A kid can reduce the energy consumption of a boat with 75% and so kill the global warming impact from all planing water transport.
To move that claim into reality is challenging. We have to make basically everything from scratch. In many areas there is nobody to ask. It has never been done before. Doing something new can feel exciting. But when you fail - despite having pushed your mental focus and cognitive capacity to their limits - the doubt drips in and the mood gets dark.
Then a day like this is helpful. While now focusing hard on getting the first serial boats into water, we continue the R&D efforts where efficiency is one of the focus areas. The 75% efficiency gain has been reached since a while but some new insights into electromechanics and hydrodynamics suggest that there is more to be done. Since six months we have been working on some of the potential gains. For us it meant to move the power consumption down from the current level with 11%. Involving three hydrodynamic changes. Before we were at 16,5kW at 20 knots. The calculations on the new solution said 14,5kW. After many weeks of calculations, computer simulations, CAD drawings, CNC milling, part production and assembly we today went into water. Seeing the 14 kW showing up on the screen was a large relief. A crack in the feeling of doubt. Maybe we are onto something! ... See MoreSee Less
What will be the cost?
Impressive! What was the weight of the craft and the crew?
It's an honor to announce that Claes Bonde is joining Candela as Senior Mechanical Engineer.
With his experience from transmission development at both Scania and Volvo VCE combined with all the mechanics in the robot vacuum cleaner at Electrolux and a whole lot more, Cleas represents a talent that is hard to find. This will help us to enhance current technologies and, above all, continue pushing the boundaries of fossil free boating.
You are warmly welcome to the team Claes! ... See MoreSee Less
I am happy and proud to announce that we have been able to get Alexander Sifvert to join Candela as Chief Revenue Officer. In this role Alexander will lead all Market and Sales activities within the company.
After studies at the Royal Institute of Technology in Stockholm, Alexander has spent most of his career in the software industry. Most recently as Sales & Marketing Director at one of Swedens leading IT consultancies - Valtech.
The recruitment of such a high profile talent as Alexander is an important milestone for us. Now we are getting ready to lead the global transformation towards fossil free boating! Welcome Alexander! ... See MoreSee Less
The message is reaching outside Sweden. Here in the British tabloid Daily Mail.
It feels kind of unreal that we have moved from a crazy idea in a powerpoint presentation to now be in serial production and discussion colors and configurations with customers. Here is one of the boats sold and in production. The coolest boat in the archipelago? ... See MoreSee Less
Just back from a beautiful weekend in the archipelago of Stockholm. Hours of flying through a cold silent nature. It’s electric! ... See MoreSee Less
Erik Kårlin, Mauri Matikainen
Emil Andersson Robert Eriksson går som Hulken med Cresenten på 😎
Una buona soluzione. Silenziosa ed ecologica..... unico problema le batterie ! Quelle al litio sono ancora molto costose e hanno alti costi di smaltimento. Il futuro è però vicino....
Man skulle ju vilja se hur den klarar grov sjö också
Silenziosa???... Con il motoscafo?😳😳😳
Hann du ens se något ?
Kommer ni ihåg bärplansbåten Sirena som trafikerade Stockholm-Mariehamn T/R i slutet av 1950-talet, början av 1960-talet?
Två och en halv timme tog färden.
Samma princip som ovan Candela!
Sovjetunionen nyttjade denna teknik väldigt mycket.
Bellissimo ,questa è nord ....
Ping Theo Martins !
Kostnad för båt med styrhytt?
Botond Gáspár !
Ser fint ut i lugna vatten men hur tar den svall och grov sjö?
On our way to the outer archipelago of Stockholm. Minus 3 in the air. Plus 7 in the water. Creating a beautiful low floating mist. Grateful is probably the best description. ... See MoreSee Less
Important milestone today when the deck was glued to the hull on the first serial boat. 289kg in total plus 40kg gelcoat and 14kg glue. But rigid like a block of concrete. ... See MoreSee Less
Have I ever said that this bot is fun to run? It is insanely fun! In todays mist. ... See MoreSee Less
This was a fun day. As written about previously we have changed our model for dealing with waves. And today we got some wind and waves to test in. 30kn wind speed in the gusts and 30kn boat speed against the wind meant more than 100 km/h in apparent wind. And pretty choppy waves. The lift in the wing increases when there is more water above it. And the water molecules make a circular movement in the waves. Both phenomenons cause lateral accelerations at pretty high frequency. Aka a shaky ride (still 10 times better than a planing boat). If not managed. Then it is so cool when the thinking starts to pay off. Wind and waves. Not perfect yet. But decent. ... See MoreSee Less
When starting Candela I had this vision of getting the control system so good that you can take off, turn hard and land with a glass of water not falling. Since a foiling boat is above the shaky water surface it must be possible. Today we made it. Thanks to an extraordinary smart and dedicated team. ... See MoreSee Less