ZF Marine today introduced the “Project Disruption” concept at the Fort Lauderdale International Boat Show. The new propulsion package is the first contra-rotating system for inboards with traditional shaft-drive systems.
The concept lets inboard-boat builders take advantage of contra-rotating propellers; the most obvious advantage is improved efficiency. The concept takes a standard ZF Marine transmission and utilizes a strut-housed underwater gearbox to transmit power to the twin propellers. Initially, the concept was designed for water-sports towboats and ZF said it can be scaled to larger boats.
The “Project Disruption” concept (above and below) lets inboard-boat builders take advantage of contra-rotating propellers.
“For many years, there has been little innovation in inboard shaftline technology,” Keith Stanley, pleasure craft product line manager for ZF Marine, said in a statement. “ZF saw the opportunity to bring all the benefits of contra-rotating propellers to this most traditional of propulsion systems. We started with tow sports because it presented a unique opportunity to investigate the concept at full scale while subjecting it to a wide variation of loading conditions.”
In addition to increasing efficiency and acceleration, ZF said the concept will give boatbuilders the chance to consider a wider range of transmission ratios than what is possible with single-prop applications. It should give naval architects the ability to optimize the propeller-to-gear ratio.
Lastly, the contra-rotating propellers will address one of the biggest shortcomings of single-prop inboards — poor performance when backing up. They will eliminate the propeller torque, which basically only lets a boat back up in one direction.