The Green Samba – the first viable electric Personal Water Craft
By Mike Hanlon
May 19, 2010
You're looking at the first exclusive images of what we expect to become the Personal Water Craft V 3.0 – it's the Green Samba. It has the same straight line 65 mph performance of the fastest 260 bhp sit-down PWCs, combined with handling and agility far beyond those of a stand-up PWC. The biggest benefit though, is that the Green Samba uses twin direct drive electric propulsion pods (unit pictured bottom left), so it doesn't directly deliver any hydrocarbons, CO2 or NO2 into delicate marine environments. Equally as important as the lack of noxious gases, the Green Samba is also completely silent, removing one of the greatest causes for complaint against PWCs and no doubt offering respite for those creatures with extremely delicate hearing which live on and under the water. A working prototype of the carbon fiber construction Green Samba will be on the water for testing purposes in Q3, 2010. The pictured action shots (bottom center and bottom right) of the Samba are the most recent development of the internal combustion Carbon Samba we first wrote up this time last year.
Things have been extremely busy at Ohio-based Silveira Group, a design and composites company founded by Rodrigo and Kristen Silveira that specializes in carbon fiber components for high performance applications ranging from race car parts and sulkies for horse racing (trotting) through to high end consumer products such as lightweight suitcases. Silveira Group has been working for five years on a tiny stingray-shaped PWC named the Samba. We first reported on the development of the Samba this time last year and that article should be read in conjunction with this one for the full picture. The Samba looks like a stingray and is ridden in a motorcycle-like crouch and was developed with the specific intent of creating the PWC V 3.0.
The basic premise was that existing PWCs began in a different era – when the now familiar form factors of the sit-down and stand-up PWC were penned, gasoline was far more plentiful and much cheaper, and environmental concerns were the domain of tree-huggers and ecological extremists. From the outset, Silveira's aim was to create a small and lightweight craft capable of changing direction easily, of offering extreme performance from a modest power output because it had less mass to accelerate.
When we wrote up the Samba in April 2009, it had already been through four prototypes, and several more have seen the water since then. The latest iteration has seen the shape and construction refined to such an extent that according to Rodrigo Silveira, just 65 bhp is now required to match the performance of the biggest 240-260 bhp Sea-Doo, Kawasaki and Yamaha designs. But the aim had also been to eventually replace the 800cc twin-cylinder internal combustion engines the company was using in the development process with electric propulsion.
In the last twelve months, the company almost gave up on that process. “I can tell you that making a green watercraft is not easy,” Silveira told Gizmag.
“Our experiments were becoming more discouraging. We knew that the public would not accept lesser performance to go green – being a good citizen does not compensate for being ten mph slower than your friends on their internal combustion skis.
"We wanted to use an electric motor but the amount of energy required to get a jet ski on the plane was so large that it was using too much of the battery capacity. Combustion engines give you the torque you need to get to planing very quickly, without using too much of the available stored energy. We refined everything we could but to get the engine performance we wanted, and sufficient range, we would have needed 150 pounds of batteries which would have impinged on the weight and hence maneuverability too much. We had some sleepless nights wondering if our objectives were achievable with the current state of battery technology."
As the man who split the atom is oft quoted, “we didn't have any money, so we had to think” and it was in going back to the objective and rethinking it that the breakthrough came for Rodrigo. With limited resources and the high burn-rate of funds associated with intensive R&D;, Silveira acknowledges that he was on the verge of giving up when the breakthrough came.
“We realized that we had been focusing on the motor, not the pump. In the same way that automotive electric propulsion is just about to go through a revolution of design because it doesn't require the same centrally located ICE we have had for the last 100 years, we began exploring what could be achieved with different propulsion methods.”
“Once we began looking, we came across a propulsion technology originally developed for military applications that had not been previously used in watercraft and we have now acquired an exclusive license for using the technology on watercraft. After testing, we are now confident it makes our objectives possible both weight and price wise.
“With twin electric shaft-less drives of far less modest horsepower output, we are expecting about the same top speed as with the 65 bhp gas engine, which will give us 65 mph. In some ways the US Coast Guard's limit of 65 mph for watercraft has worked to our advantage as otherwise we'd probably be seeing 80 mph watercraft by now. Aiming at a non-moving target of 65 mph has been a huge advantage.
“The PWC is a huge water pump and the existing manufacturers have ignored the inefficiencies of the jet drive system currently in use by pouring horsepower and fuel on it. The inefficiencies in the horsepower-thrust conversion are quite obscene and that's were we've been focusing our energy.
"The propulsion pods we're using have an electric motor self contained within them. Each one has one moving part on the internal wall of the thrust pod, so it's a direct drive and it has eliminated many of the losses and made the system extremely efficient. What started out as a 6 horsepower motor became two 12 horsepower pods that are far more efficient.
"Our tank tests have proven to us that we can achieve between 34.9 and 36.5 pounds of thrust per horsepower compared to 28 pounds of thrust from a gasoline engine. By going electric and having a self contained pod that isn't connected to anything else other than a power source and a controller, we have achieved a similar freedom of design as automotive designers are now experiencing with electric motors. It means we don't need a big fat motor and a drive train in line with the motor.
"We started out with a single, centrally-located propulsion unit, but along the way, we realized if we made it into a dual pod system we would gain maneuverability by being able to get far more angle on the thrust pods than by using the traditional centrally-located nozzle steering. Then to take full advantage of turning the propulsion units, we had to completely different hull configuration.
“The redesign allowed us to put the pods below the planing line, which allows a more efficient intake and even better performance. With traditional design you can overload the pump, so you have a limitation on the amount of water going into the intake tunnel, but with these pumps we realized that the more we feed the pump, the better the performance.”
One of the benefits from using a lightweight, low-powered craft with such efficient drives is that the range of the unit has now skyrocketed and Rodrigo expects to get more than three hours usage from a full charge – well in excess of the 250 horsepower sit-down PWCs.
"Our testing so far shows that by getting the two pods on either side of the center line, you can get amazing turning ability. The first tests showed it was a bit too sensitive – it'd tip you off too easily because you just couldn't hold on. The prototype we have planned for August brings all the strengths into focus and… we're confident now we have a viable next generation PWC in every respect, the most important being that we've stemmed the flow of harmful emissions into what should be a sacrosanct pristine environment.
"The world's waterways have been absorbing a disproportionate amount of emissions since the diesel engine became routinely used in watercraft. Most of Europe's lakes and waterways now restrict recreational usage for the very reasons we expect to overcome with the Green Samba.
“We can fix that, and we very excited about the prospects!
We're now prototyping this unit and it'll be ready by the end of August at which time we'll have a working unit and enough costing information to project a ballpark retail price. By the beginning of the fall we'll have that information available and a demonstration unit that'll do all the talking.”
The aim of the Silveira Group is not just to offer a consumer PWC but to be able to deliver customized units for marine research, environmental and other groups with particular needs. Quite obviously, not only environmental and research groups will find the Green Samba's capabilities compelling. Special Forces and other military groups will no doubt find application for a completely silent watercraft with a top speed of 65 mph and a range of more than three hours.
It looks like a winner on paper - we can't wait for the prototype.