Ah, I had made some projects around the idea of an "electric motorization"... But the "reasonable" people got the better of my enthusiasm. I ended up siding with the "classics", the serious ones, the ones who are "sure". Now, I devour with greed, and a touch of jealousy, all the information concerning the exciting "Energy Observer" project.
In search of autonomy
Our Lady has been equipped with two Cummins diesel engines developing 150 horsepower each. These should, in principle, give her a maximum speed of 17 knots, with a modest range of only a few hundred miles... Nothing to do with our aspirations.
To cross an ocean, it seems reasonable to me to count on an autonomy of 3000, even 3500 miles. Even if we were to adopt a speed much lower than the theoretical capacities of the machines, it is not possible to obtain a sufficient autonomy with such powerful engines. Knowing that one can absolutely not make the whole crossing with the engines running "at idle" under penalty of damaging them (6.5 knots, idling...still!). At low rpm, the carburation is incomplete and the unburned particles accumulate in the exhaust system until they clog it.
We keep the original diesels
Fortunately, by acting on the different parameters concerned, many things become possible that will allow us to keep these wonderful Cummins engines built to last more than 30,000 hours (I have examples). In all likelihood, and barring a major accident or bad luck, they should logically outlive me, which makes me very happy.
Consumption is related to length and weight
But before we start messing with the mechanics, two general considerations: The fuel consumption of a motorboat is inversely proportional to its waterline length and directly proportional to its weight.
Looking for those extra pounds
To consume less, let's start with a good weight loss program. This is not the most expensive thing to do and the effectiveness is real and immediate.
Everything that is not useful on board must be removed... The limit being the approval or disapproval of the co-owner. For the Lady, it was more than 2 tons of various "trinkets" which were thus dismissed.
Some significant examples:
Toilet facilities: No less than 5 toilet bowls, including four electric ones. When you live with two people, that's a lot of spare parts. It would have been necessary to establish a schedule of use of the various "vases" in order to be sure that they are all used at regular intervals, otherwise, it is the breakdown assured for the one which did not receive enough visits. That's the last straw! Constipation has been elevated to the rank of major plague on board! Obliged to invite incontinent people to compensate! Classy. In short, after consultation, we fired two of them (I was leaning towards three, out of pure selfishness, because I'm the one who's helping out...).
The second floor bazaar: The space was very nicely appointed, and many boat show vendors were making sales thanks to this incongruous appendage, and especially its lounging facilities. The problem was that this joke weighed close to a ton! A ton whose center of gravity was located at more than four meters high. In short, all this stuff represented almost half of the overweight, and a good proportion of the dunnage.
Another thing: as she was not equipped with a watermaker, she had four tanks in her bosom that allowed her to carry 1.2 tons of water! (Yes, I know, a 1.2 ton breast! Hello poetry). Thanks to the installation of an osmosis unit capable of supplying sixty liters per hour, the storage capacity was reduced to 400 liters.
The list is long of the unloaded elements, that Malou has sold everything at low prices.
Extend the waterline length
As for the waterline length, we have added 60 centimeters to the back of the hulls, in the form of two nice skirts which, moreover, make welcoming docking platforms for the dinghy.
In the next episode, the author explains how he adapted the propellers and rudders, going slowly to consume less .
