Springer is a medium water plane twin hull vessel measuring 4.2 m long and 2.3 m wide, with a displacement of 0.6 tonnes. The catamaran-type configuration provides sufficient geometric stability to be able ignore roll and pitch effects under most conditions, hence for all practical purposes the vehicle can be treated as possessing three degrees of freedom. The vehicle is propelled by two 24 V, 74 lbs electric Minn Kota Riptide® transom mount saltwater trolling motors, powered by eight Sonnenschein SL135 12 V 135 Ah batteries, four placed within each hull as two pairs of parallel connected batteries wired in series to produce 24 V. The batteries are connected to a RoboteQ AX2850 digital motor controller in the starboard-side hull, and the battery terminals are accessible via cables that can be reached through portholes in the side of the hull for charging. The motor housings contain leak detectors and optical speed encoders, and are connected to the motor controller via custom made circuitry in a separate box next to the controller. The RoboteQ can accept either R/C radio commands or serial data (RS 232) from a PC, and this box also houses circuitry for commuting between radio control and serial control of the motors. Schematics of these circuits can be found in the Springer manual available through the web site.