wdp on back of patrol boat

Surface Drives: Props halfway out of the water? 1 Word: Efficiency

When most people hear the term surface drive, they think speed and high performance, but what these rather specialized propulsion units are really about is efficiency. Because the propeller blades break the water’s surface — they are called surface-piercing propellers — the engines powering them run under less load than with fully submerged props. Half of the propeller spins in the water. The other half rotates above the surface. This lets the boat make better use of the power of its engines and go faster than one with submerged props. (BoatingMag)

Check out this video of Surface Drives in action:

The engineering for this technology has been attributed to two independent inventors/innovators/enthusiasts: the late Renato ‘Sonny’ Levi and Howard M. Arneson. Sonny Levi had pioneered and developed his surface drive technologies in Malaysia, while Arneson followed for ultimate performance with a larger budget in California. You can find Arneson surface drives on the market today.

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The surface piercing or ventilated propeller is a propeller that is designed to intentionally cleave the water and entrain atmospheric air to fill the void, which means that the resulting gas layer surrounding the propeller blade consists of air instead of water vapour. Less energy is thus used, and the surface piercing propeller generally enjoys lower drag than the supercavitating propeller. The surface piercing propeller also has wedge shaped blades, and propellers may be designed that can operate in both supercavitating and surface piercing mode. (Wiki)

The Arneson Surface Drives are among the most efficient marine propulsion systems in the world. Their surface-piercing propeller design reduces underwater drag by 50% compared to conventional submerged propeller drive systems. The only surfaces to contact the water are propeller blades and a protective skeg. This results in higher overall speed, quicker acceleration, and a better payload to power ratio… AND… 50% less drag significantly improves fuel economy while lowering operating costs.

For work, pleasure, gas, diesel, or turbine power systems capable of torque outputs exceeding 30,000 ft. pounds, the Arneson Surface Drives come in ten model sizes and various configurations for each model. Available in, Aluminum or bronze castings, straight or drop-center models, 12 or 24 volt compatible systems, plus the new Arneson Dual-Fin surface drives available in the ASD8 and ASD10 models.

Comparisons-1(Photo credit: Arneson Industries)

Advantages of the surface drive by Arneson:

  • 15% to 30% speed increase over conventional systems.
  • 15% to 30% increase in fuel efficiency.
  • More efficient than I/O’s
  • Corrosion resistant
  • Size adaptability, from 100 hp to over 10,000 hp applications.
  • Low maintenance requirements.
  • Ability to adjust propeller submergence while underway.
  • Ability to adjust submergence to match horsepower output permits conversion of more thrust as appropriately needed.
  • Propellers ventilate to the surface rather than cavitate under the hull reducing noise and destructive hull and prop erosion.
  • Flexibility in engine installation location.
  • Less Vibration than Inboard or I/O applications
  • Shallow water operation (elimination of underwater appendages).
  • Accessible propeller servicing.
  • Steerage by the positive thrust of the propeller and not by the propeller thrust to the rudder. This is equivalent to sports car rack-and-pinion steering performance.
  • For all it’s sophisticated performance, it is a less mechanically complex and fragile design than other propulsion systems.
  • Most models are available in Magnesium Bronze or Aluminum.
  • No limitations to shaft angle, blade top clearance, draft to restrict selection of optimum diameter propeller.
  • Adaptable to a wide range of engine applications, whether gas, diesel, or turbine.

It might come as a surprise that a boat doesn’t necessarily need to be designed for surface drives. A V-bottom would need some rocker to generate bow lift because surface drives don’t create any, but a bottom designed for straight inboards or sterndrives can see performance and efficiency gains with surface drives. Among the first performance V-bottoms to break the 100 mph mark was a nonstepped Hustler 32 powered by 630 hp engines and Arneson drives.

The biggest downsides to surface drives are that they make docking more challenging because they lack the blade surface of a submerged prop and that they extend well aft of the hull, sticking out like appendages. But when you’re in search of speed and efficiency, looks aren’t everything. (BoatingMag)