<h4><span style="font-family: tahoma, arial, helvetica, sans-serif;"><strong>In favor of one main electric motor</strong></span></h4>
<p><span style="font-family: tahoma, arial, helvetica, sans-serif;"><strong><img src="/sites/default/files/inline-images/MM199-62-01-Jan%20(1).jpg" alt="" width="536" height="720" /></strong></span></p>
<p><span style="font-family: tahoma, arial, helvetica, sans-serif;"><strong>By Jan Rouzeau</strong></span></p>
<p><span style="font-family: tahoma, arial, helvetica, sans-serif;"><em>Jan is a recent multihull convert, and having owned a Mahé 36 on board which he joyfully toured the Mediterranean, he parted with it to undertake the home-build of a superb Vik 140 to an Erik Lerouge design. The quality of his practical approach deserves a wide audience.</em></span></p>
<p><span style="font-family: tahoma, arial, helvetica, sans-serif;">Amateur construction of multihulls might seem somewhat outdated these days, but it is nevertheless the only option if you want to be able to integrate all the latest energy solutions. In the search for maximum autonomy to limit our dependence on diesel, we pushed forward our thinking on the ideal long-distance catamaran with naval architect Erik Lerouge, and looked at adapting one of his designs to new hybrid solutions. In the long run, diesel can be difficult to find and sometimes of poor quality – the same goes for gas for the outboard and for propane. The principle is therefore to limit its use. The diesel stove which shares fuel with the diesel engine is one alternative: no more need for propane tanks. And with an electric outboard for the dinghy that recharges along with the batteries, there’s no more flammable fuel on board. Our VIK 140 <em>Sono 2</em> is a 14 m x 7.80 m (46’ x 25’7”) catamaran with a laden weight of 8 tons. The powertrain: a 20 kW electric motor and a 40 kW bank of traction batteries for principal power, plus a 30 horsepower diesel engine - useful if we had a man-overboard situation, working our way up a channel, maneuvering in port, and as last resort as a generator. The engines will be centered to limit pitching.</span></p>
<p><span style="font-family: tahoma, arial, helvetica, sans-serif;">Two electric motors and a large generator, or one electric motor and one internal combustion engine? Solution 1 allows hydrogenation capacity under sail, as both electric motors are able to recharge together, but an ad hoc generator is heavy - 280 kilos (620 lbs) for a 1.5 liter diesel - and consumes more. It delivers more 220 volts AC, but is less reliable over time than a standard propulsion engine. Paradoxically, with the same quantity of diesel on board and use, the all-electric solution will limit range. And solution 2? Two completely independent systems mean you’re not putting all your eggs in the same basket: it would be rare for a serious power failure to be accompanied by an engine failure. Another benefit is that you’ve got a lighter motor (132 kilos/290 lbs for a shaft-driven model), that is more reliable and easier to maintain than a generator. It is therefore this simpler, less expensive solution that we have chosen. With an air-cooled 48-volt electric motor, a 24-volt house bank, solar panels and two wind generators, the entire electrical propulsion and domestic installation, their interconnection, peripherals, conversion problems, cost and maintenance are greatly simplified. In addition to the well-managed weight of the boat, the objective remains performance under sail.</span></p>
<p><span style="font-family: tahoma, arial, helvetica, sans-serif;">The highly profiled skegs allow for beaching and for integrating the propshafts, protecting the propellers and avoid the periodic replacement of shaft seals and saildrives oil changes. This centered positioning also has a positive effect on the boat's handling when maneuvering in port. <em>Sono 2</em> will be equipped with ten orientable solar panels and two wind generators. With this catamaran, our way of sailing is going to be different, favoring electrical regeneration. We'll take a breath of fresh air while working on decrypting the weather forecast and doing our routing. Is this all ecological and hedonistic? Well, yes, it is! Story to be continued, but you don't have to believe us…</span></p>
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<p><span style="font-family: tahoma, arial, helvetica, sans-serif;"><strong>In favor of one main internal combustion engine</strong></span></p>
<p><span style="font-family: tahoma, arial, helvetica, sans-serif;"><strong>By</strong><strong> Maxence Valdelièvre</strong></span></p>
<p><span style="font-family: tahoma, arial, helvetica, sans-serif;"><em>Maxence is the founder of Tenderlift. A naval architect, he was also in charge of prototypes at Catana before becoming one of the top specialists in on-board hydraulics and carbon rams. Still a pioneer, he is now testing innovative configurations (energy, maneuvering, motorization) on his Class 6 </em>One Cat<em> that we’ll soon be seeing applied to cruising catamarans</em><em>. </em></span></p>
<p><span style="font-family: tahoma, arial, helvetica, sans-serif;">Traditionally a catamaran has two motors, and the ever-optimized living space leaves the engines a small and difficult space to access for maintenance. They represent a budget of 5 to 10% of the total cost and their weight, 5 to 8% of the displacement. We’ve sought to reduce the impact of this, to end up with a lighter, more spacious and more economical catamaran. Size is a cost factor; weight is just as important. The objective is to make a catamaran that sails well, is simple and safe to use, capable of quickly getting out of capricious weather, lighter in weight and with a structure which suffers less strain: a virtuous circle!</span></p>
<p><span style="font-family: tahoma, arial, helvetica, sans-serif;">Many owners of cruising catamarans use just one engine to reduce wear and fuel consumption, and for comfort. The existence of a second engine could therefore be called into question. The propulsion system is calculated to deliver all its power at full speed, this is understandable for a fast motor boat that will often be going along the throttles pushed hard down, but on a cruising catamaran, a motor capable of turning at 3,000 or 3,400 rpm will rarely be used at this speed, mostly at 1,800-2,200 rpm (40% below its maximum power). It can be assumed that a 50 HP engine will only produce 30 HP at this speed. In fact, for hydrodynamic reasons, the propeller will only be producing 10 HP of real power. An energy nonsense, multiplied by two.</span></p>
<p><span style="font-family: tahoma, arial, helvetica, sans-serif;">Bi-electric motorization allows a strong optimization of these efficiencies. However, for a round-the-world project, this approach is considered irrelevant: cost and weight far exceed the traditional engine option. V Yachts, our support company, has therefore embarked on the construction of a tailor-made and innovative offshore catamaran. The O Yachts Class 6, the basis of this program, is a little large, but an empty hull doesn't cost much, except when alongside a dock. As soon as the composite phase was completed, the boat was delivered on one engine from Riga, in Latvia, to Canet en Roussillon, in France. Yes, only one good, low-revving, high-capacity engine coupled to a big propeller. Cruising speed: 9 knots at 1,800 rpm, peaking at 12 knots at 2,400 rpm. <em>One Cat</em> is empty so is ultra-light, but in reality, we won't add much more than the sails, some furniture and a 70 kg (150 lb) electric motor. The final weigh-in results give 15 tons lightship, and 17 tons laden, for a 62-footer. But what about second engine? A 10 kW Torqueedo power pack coupled to a 2 kW 48-volt Atomic lithium battery, 1 kW of solar panels and a 48-volt 2 kW alternator coupled to the main engine. The catamaran is able to move at 2 knots in calm and sunny weather without consuming any battery power. The electric motor also works as a hydrogenerator when under sail. Under way, this energy won’t be used for propulsion, the service bank can be switched on or certain bits of equipment can be coupled up to 48 volts. The final optimization we can perform: having a retractable electric motor in a well. No more drag, but above all, the machinery is out of the water when not in use. Conclusion: a reduction in the weight of the propulsion system by 30 to 40%, representing a saving of 250 kg (550 lbs) and €12,000 ex-tax, and as a bonus, it saves space. The disadvantages: the principle is based on the use of a single propulsion system - like a monohull - but there are still sails and a small electric motor. Having asymmetric power during port maneuvers will take a bit of time to get used to.</span></p>
