The Physics & Calculations of the PowerSki JetBoard™of the G-Force Turn.
These calculations were made on a previous prototype using a 25 hp. engine. Since the Igniter 330™ production model has approximately 45 hp., the physics of a G-Force turn are much more extreme which translates to more power through your turns.
Thrust and Speed
In order to achieve high-speed performance, the water jet pump in the current Powerski Jetboard™ must deliver enough thrust to quickly accelerate the jetboard to maintain its speed, preferably from 15 mph to, in excess, of 40 mph. To overcome both the water's drag on the craft, and the air resistance of the combined rider and jetboard, both resistances, being proportional to the square of the speed, and the required thrust for achieving this range of speed, were calculated to be in the range of 130 to 330 lbs. In tests of the jetboard, a speed of 32-35 mph was measured on flat water at a measured pump thrust of 240-265 lbs.
Weight and Engine Power
The engine, as the primary power source, must have sufficient power to propel the weight, or mass of the craft and rider to the desired speed range of 15 mph to over 40 mph. The required engine-delivered power depends on the energy consumed per second to move the combined mass of the rider and craft through the water at the desired speed. This power is calculated from 1/2 the mass times the square of the speed, divided by the efficiency of the jet drive pump system. For the desired range of speeds, and applicable range of rider plus jetboard with a combined weight between 250 lbs. minimum to about 400 lbs. maximum, engine power of at least 14 hp. to more than 55 hp. are required. One attribute of the PowerSki Jetboard™, is that a jetboard and rider weighing a total of 350 pounds, can achieve a constant measured speed of 32-35 mph with an engine rated at 25 hp. output. This relatively high weight requires high-powered engines that are 30-50% of the total weight of the craft. That much engine weight requires precise placement within the hull in order to allow a rear-mounted rider to pivot the jetboard during turns without the use of a steering mechanism.
The PowerSki Jetboard™ is designed to support its own 100-150 lbs. plus a 250 lbs. rider, lying or standing behind the engine's location while the craft is moving at low speed before hydroplaning, and keep it from submerging the top of the engine compartment. This is achieved by a precisely calibrated craft volume, weight, and center of buoyancy relative to the longitudinal center of gravity. Once hydroplaning is achieved, this natural, stationary buoyancy becomes less important, because the vertical force component on the rear of the jetboard is controlled by its thrust and speed.
Placement of the Mechanical Components (Center of Gravity)
The PowerSki Jetboard™’s center of gravity (CG) is critical to its performance, stability and the capability of a rear-mounted rider to initiate and negotiate controlled, low and high speed turns without the use of a steering mechanism. Control and, most importantly, maneuverability by a rear-mounted rider is achieved by positioning the jetboard's mechanical center of gravity (CG) along the craft's vertical longitudinal center plane, located forward of the rider and at a horizontal distance in the range of 55%-85% of the bow.