hydrodynamics

70 Sunreef Power Cat Hull Mods Double Efficiency

Laurent Bourgnon family on Sunreef Yachts 70 Power JAMBO - Photo Courtesy of Sunreef Yachts

Laurent Bourgnon family on Sunreef Yachts 70 Power JAMBO - Photo Courtesy of Sunreef Yachts

Sunreef Yachts said last week that modifications it has made to the 70 Sunreef Power catamaran JAMBO have nearly doubled the yacht’s fuel efficiency.  The fuel consumption on JAMBO dropped from 13 liters/hour/engine at 10 knots at 2,300 rpm, to 7.5 liters/hour/engine at 10 knots at only 1,500 rpm.

The mods are a demonstration of one of the fundamental principles of the hydrodynamic laws that affect boat hulls.  Basically, Sunreef lengthened the hulls’ overall length, in part by added bulbous bows to each hull.  Swim platform extensions also added waterline length. Stated simplistically, the principle is that longer (waterline length) hulls can go faster than shorter hulls. 

View of bulbous bow on 70 Sunreef Power Cat JAMBO - Photo Courtesy of Sunreef Yachts

View of bulbous bow on 70 Sunreef Power Cat JAMBO - Photo Courtesy of Sunreef Yachts

In the case of JAMBO, additional efficiency is derived from the bulbous bow design, which “cancels” part of the normal bow wave by creating another bow wave exactly opposite in phase to that normal bow wave.  Bulbous bows have been used on commercial vessels, warships and many larger yachts for many years, but the decision to use them on mid-size yachts is complicated by such factors as expense and more complicated hull fabrication.

In any event, the improvements demonstrated on the Sunreef power cat are significant and obviously worth the effort for JAMBO’s owners.  You can read more about the Sunreef pwer catamarans in our earlier coverage here.

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Posted by Tom in Boats, Cruising Under Power, Powerboats