Abstract: Rapid shaft stop devices and transmissions are described that utilize permanent magnets for coupling and/or braking and are useful for electronic propeller guards and other equipment. In an embodiment, one or more capacitive discharge pulses are used to rapidly stop a shaft. A magnetic transmission is provided having axially oriented magnets on each side of an air space junction that transmit torque across the junction with a torque/speed profile that particularly suits boat propellers. The junction may include a bearing and allows slippage when the propeller resistance exceeds a given value. This slippage acts as a variable gear reduction. One or more electromagnets may be energized and thereby add to or subtract from one or more magnetic fields and provide electronic control of torque and of gear reduction ratio for devices such as watercraft drive systems.

Abstract: Electronic methods, devices and kits electronically protect swimmers, animals and other objects in water from propeller strikes, and alleviate propeller damage. Desirable embodiments include continuous ultrasonic sensing and detection by separate sensors to minimize reaction time for stopping internal combustion engine and electric motor driven propellers. Electric boats having direct drive to propellers are particularly amenable for electronic propeller protection. A variety of sensors may be used, including tactile, ultrasonic, galvanometric and infrared sensors. Optionally, the devices and systems can improve performance, safety and economy of boat rental operations by discouraging, limiting and even reporting propeller strikes to a boat custodian, who may be at a different location when the boat is used.

Abstract: Electronic control systems, devices and algorithms are described for improving boat efficiency, safety and convenience, particularly for electric motor powered boats. The overall efficiency of electric boat propulsion is improved by matching the needs of the propeller with the magnetic field requirements of the motor. Efficiency also is improved by limiting slip at different boat speeds. Rapid and fully electronic propeller shut off systems also are described for enhancing public acceptance of electric boats and more convenient cruise control systems are described for improving public acceptance of the boating experience.

Abstract: High speed electric watercraft of various configurations are provided that utilize at least one submerged enclosed hull containing an electric motor and at least one other parallel float positioned higher that the enclosed hull to provide buoyancy for a platform that can carry one or more individuals above a water surface. The watercraft optionally include features of (1) a rounded front end on the platform, (2) a platform length that is shorter than the float for stability against tipping, (3) entryways that do not require stepping over a vessel hull, (4) dimensions fore and aft that minimize spray onto the rear of the platform, (5) shock absorbers to provide a smoother ride, and (6) adjustable struts that connect floats with the platform to allow control of the platform height above the water surface. These and other features are made possible by a fast electric design that avoids certain problems of vessel type watercraft.

Abstract: New electric boat designs are provided that exploit the weight of a battery to stabilize the boat and in some cases to overcome the hull speed limitation problem. The battery mass is enclosed in one or two torpedo-like structures that are mostly or completely submerged. A platform is spaced above the torpedo(s) via one or more struts that may allow wave energy to pass through the watercraft rather than collide with large vertical surfaces. The design minimizes wake formation, wave sensitivity and is useful for new kinds of electric boats that can dive with an air bubble to allow submarine use, higher speed pleasure craft, and sailing craft that can remain stable in shallow draft waters. The stabilized watercraft optionally have computer monitoring of wave activity and control for greater resistance to adverse weather conditions.