As with all Nordhavn offshore passagemakers, the 40 is the embodiment of a full displacement hull design. The fundamental benefits of this type of vessel include long range, economical operation and extremely capable, seaworthy performance.
In addition to the fundamental advantages of a full displacement hull design, P.A.E. has developed a number of refinements that have contributed significantly to the Nordhavns 40's overall performance. The stern sections are very "full" to minimize pitching motion and maximize weight carrying capacity. This full stern provides large stowage areas for all the additional equipment and supplies generally required for long voyages. The unique shape of the stern sections also helps extend the upper end of the cruising speeds by reducing the drag caused by "squatting," common to full displacement hulls running at high speed-to-length ratios.
The Nordhavn 40's Modified Full Displacement (MFD®) hull also includes a slight tunnel area for the propeller, allowing a large diameter prop to be used without increasing draft. This large diameter prop increases efficiency and reduces cavitation, creating a quieter running boat.
P.A.E. did not rely solely on theory as it developed its MFD® hull for the Nordhavn 40. Instead it invested heavily in a complete tank testing program at B.C. Research in Vancouver, Canada. Among the breakthroughs achieved during this extensive R&D program were the addition of MAINTENANCE STRAKES™ to the bottom of the MFD® hull, which create gentle bulges in the hull form directly below the engine location. Not only do these revolutionary devices provide five feet of headroom in the engine room, they also allow the engine to sit lower for enhanced stability, minimum shaft angle and optimum thrust. The tank testing also revealed a surprising 2% increase in overall hull efficiency due to the positive effect the MAINTENANCE STRAKES™ have on the vessels' performance at higher cruising speeds.
A significant part of the tank testing program was devoted to experimenting with different bow shapes, including the addition of a bulbous bow similar to those used on commercial freighters. Typically, a bulbous bow will increase hull efficiency by reducing resistance. Theoretically, it will also dampen pitching motion in heavy head seas. After exhaustive tank testing into a wide range of computer-generated head seas, it was concluded that adding a bulbous bow to a hull in the forty-foot range actually created a mildly noisy, concussion action while running up swell. This action could become annoying while punching head on into heavy weather. More importantly, it was found that the full stern sections of the 40's hull already did an admirable job in reducing pitch. In conclusion, the more conventional bow was chosen to ensure a quiet ride up-swell. Further research on other Nordhavn hulls indicated that the advantages of the bulbous bow become more evident in the fifty foot and above range, and it is on these larger models that P.A.E. utilizes this design.
The performance chart indicates a practical, economical speed range of between 7 and 8.5 knots for the Nordhavn 40. At these speeds, she has a range of between 4,000 and 2,000 nautical miles, burning between l.5 and 4.5 gallons-per-hour. It is quite revealing that most long-range or rough weather cruising is done at speeds below l0 knots, even by boats capable of far higher speeds. Not only are many boats uncomfortable at higher speeds, but their owners soon discover that all the noise and rapidly moving scenery are not conducive to an enjoyable voyage. Additionally, if an owner has long-range cruising plans, the economics of running high horsepower, planing boats often preclude the desire to go faster than displacement speeds. Compare burning l.5 gallons per hour with 30 gallons per hour during a four-week cruise while running 4 to 5 hours per day, and one quickly appreciates the efficiency of a full displacement hull. Even if the faster boat's number of hours per day are reduced to compensate for higher speeds, there is a huge difference in fuel consumption and operating costs.
Most importantly, the crew of a Nordhavn MFD® design will arrive rested and relaxed, ready to enjoy their new surroundings. One Nordhavn owner, who sold his fast, planing boat said it best. "This was the fastest voyage I ever made on the slowest boat I've ever owned."