Cumberland 44 Refit - The opportunity to be consuming less than a liter per mile...

Jean-François Desmars is a true sailor, first a hardened racer aboard 470s and then J/80s. He next tried his hand at a Lagoon 43 PC, followed by a Lagoon 440. Neither of these two catamarans really matched his program. At the time (nearly 20 years ago), he was still seeking sporty rides, so a fairly radical Petter 50 satisfied his taste for “fast blue water sailing”. For some fifteen seasons, Jean-François sailed single-handed or with a crew to the UK or Norway - the great North Atlantic being his cruising playground every summer. But it came time to reduce sail: “Having spent many nights at the helm and maneuvering a rather advanced catamaran, fatigue and age set me thinking about more reasonable sailing,” says Jean-François.

The objective: less than a liter per mile

The choice between monohull and multihull was quickly settled. “All the comparisons converged in favor of the latter: more space and more conviviality, less weight and lower fuel consumption,” notes the sailor. As for the choice between sail and motor, it was logically the appeal of ease of use that favored a boat without a rig... so, go for a powercat! A venerable 18-year-old Cumberland 44 became Casa Marissss (the 4th of her name). This model is an owner’s version equipped with two 285 HP Volvo KAMD300s.
Let’s talk about fuel consumption: “A 45-foot production powercat equipped with twin 300 HP engines already consumes 80 liters (21 US gallons)/hour at 17 knots, and for a less roomy monohull, it’s even more. Getting a 15-ton boat up on the plane is excessively energy-consuming. By being more reasonable, we can appreciate that, if we want to go to sea responsibly, the first step is to significantly moderate our cruising speed.”
To validate this step, the lessons we can learn from sailing are invaluable: “A very good recreational sailboat (mono or multi) rarely goes along at average speeds of more than 8 knots, 10 for exceptional units, and sometimes tacking, which lengthens the distance to the goal. Transposing these figures to our second-hand power catamaran, we opted for a target speed of 8 knots, a value very close to the Cumberland’s hull speed.”

The new life of a powercat

Jean-François launched a vast program to optimize and improve his powercat, with the aim of significantly reducing fuel consumption. For the time being (see below), the biggest parts of the project, such as sugarscoop extensions and bulbous bows, have not yet been completed. “I decided to start with the most accessible elements: weight and propulsion,” he explained.

A weight-saving cure - by almost two and a half tons!

We started with the anchor chain, which was made lighter (10 mm instead of 12) in a reinforced specification (Force 7). A drastic tidy-up removed all superfluous weight (unnecessary tools, spare parts, etc.), - in total, some 500 kg/1,100 lbs removed. The second crucial point was liquid mass: “I installed a 110 l (29 US gal)/h watermaker and sailed with 100 l (26 US gal) reserve ...