An apparatus and system for a marine propeller assembly are provided. An aft retention member that may be used with the marine propeller assembly includes a base, an opposing nose and a conic body extending therebetween along a centerline normal to the base. The aft retention member also includes at least one protuberance extending radially away from a surface of the conic body. The protuberance extends axially along a surface of the aft retention member from the base arcuately convergent to a predetermined point between the base and a tip of the nose.

A marine vessel has a hull with a bottom, a bow, a stern, and a propulsion arrangement including at least three propulsion units arranged at the stern of the marine vessel. The marine vessel has a base line and a centerline. The at least three propulsion units include a fixed centerline shaft propulsion unit with a shaft line and a propeller, and two turnable propulsion units with respective propellers and arranged at opposite sides of the fixed centerline shaft propulsion unit for steering of the marine vessel. For improving thrust efficiency, while maintaining optimal steering capability, the propeller of the fixed centerline shaft propulsion unit is arranged at a given distance aft of the stern of the marine vessel.

A marine vessel has a hull with a bottom, a bow, a stern, and a propulsion arrangement including at least three propulsion units arranged at the stern of the marine vessel. The marine vessel has a base line and a centerline. The at least three propulsion units include a fixed centerline shaft propulsion unit with a shaft line and a propeller, and two turnable propulsion units with respective propellers and arranged at opposite sides of the fixed centerline shaft propulsion unit for steering of the marine vessel. For improving thrust efficiency, while maintaining optimal steering capability, the propeller of the fixed centerline shaft propulsion unit is arranged at a given distance aft of the stern of the marine vessel.

A structure adapted to traverse a fluid environment includes an elongate body having a root, a wingtip, a leading edge and a trailing edge; and a plurality of rigid projections each extending from a respective position along the leading edge and/or the trailing edge generally along the same plane as a front surface of the body.

A structure adapted to traverse a fluid environment includes an elongate body having a root, a wingtip, a leading edge and a trailing edge; and a plurality of rigid projections each extending from a respective position along the leading edge and/or the trailing edge generally along the same plane as a front surface of the body.

A fluid-redirecting structure includes a rigid body having an upstream end, a downstream end, and an axis of rotation, the rigid body incorporating a plurality of troughs each spiralled from a tip at the upstream end to the downstream end about the axis of rotation, the troughs being splayed with respect to the axis of rotation thereby to, proximate the downstream end, direct incident fluid along the troughs away from the axis of rotation.

A fluid-redirecting structure includes a rigid body having an upstream end, a downstream end, and an axis of rotation, the rigid body incorporating a plurality of troughs each spiralled from a tip at the upstream end to the downstream end about the axis of rotation, the troughs being splayed with respect to the axis of rotation thereby to, proximate the downstream end, direct incident fluid along the troughs away from the axis of rotation.

A method and device is provided for increasing the efficiency of jet drives by recuperating effective power from the propulsion flow. A ducted propeller in the propeller housing, driven by a driving engine via a drive shaft, conveys the fluid for the jet drive out of the interior V.sub.i of a radial turbine . The fluid is accelerated axially and ejected backwards against the direction of travel. This creates thrust. Because the pressure in the interior of the turbine decreases, new fluid from the environment flows directly via the blades of the rotating radial turbine from the outside to the inside, thereby driving them. A guide apparatus is missing. The power of the radial turbine is transmitted via a transmission to the drive shaft of the propeller, which relieves the driving engine and increases the efficiency of the jet drive. The invention is particularly suitable for electric drives.

A propeller assembly is provided. The propeller assembly includes a central hub including a forward end, an aft end, and a hub body extending therebetween along an axis of rotation of the central hub. The propeller assembly further includes a first retention member including a first radial interference member, the first retention member coupled to the forward end of the central hub and a second retention member including a second radial interference member, the second retention member coupled to the aft end of the central hub. The propeller assembly also includes a fairing platform extending between the first retention member and the second retention member, wherein the fairing platform is retained by the first radial interference member and by the second radial interference member.

A propeller assembly is provided. The propeller assembly includes a central hub including a forward end, an aft end, and a hub body extending therebetween along an axis of rotation of the central hub. The propeller assembly further includes a first retention member including a first radial interference member, the first retention member coupled to the forward end of the central hub and a second retention member including a second radial interference member, the second retention member coupled to the aft end of the central hub. The propeller assembly also includes a fairing platform extending between the first retention member and the second retention member, wherein the fairing platform is retained by the first radial interference member and by the second radial interference member.