# Dimensional Data and Design Characteristics of the BOREY Pump Jet Propulsor Derived from Open Source

By **Bruce Rule** - Jul 11, 2014

The BOREY pump-jet shroud is a conic section with a decrease in external diameter fore to aft from 19.6 feet (6.0m) to 14.2 feet (4.3m) over a distance of 16.3 feet (5.0m) measured along the axis of the hull, a decrease in the cross-sectional area of 48 percent.

The external form of the shroud suggests the BOREY pump-jet has an accelerating shroud, a design that produces positive thrust and increases the efficiency of a heavily-loaded propeller, defined as a propeller where the power being trasnmitted can be close to the maximum absorbable for the design of the propeller.

The forward end of the shroud is 14.9 feet (4.5m) aft of the point where the inner trailing edges of the stern planes attach to the hull.

The rotor turns within a circle with a diameter of 14.1 feet (4.3m). As viewed from astern, the mid-line of all nine rotor blades (projected) pass through the center of the shaft, i.e., there is no skew. The angular separation between the same point on the leading edges of adjacent rotor blades is 40 degrees (360/9). Each rotor blade has a length of 5.2 feet (1.6m). The end of each blade is a convex curve to match the inside diameter of the after end of the shroud. The blade to shroud clearance is less than three inches (0.1m). The apparent width of the blades – when viewed from a stern perspective - which does not allow for pitch – is about 3.5 feet (1.1m) at the blade root while the width at the end is about 2.0 feet (0.6m). The projected area ratio of the BOREY pump-jet rotor is about 88 percent.

The assessed accuracy of the dimensional values provided above is plus/minus three inches (0.1m)