The Evolution
of an idea

Sea Rider is a motorboat drive that can be defined as a stern group with surface propeller. Sea Rider currently covers a 50 to 4,000 bhp power range. The project includes a particular propelier design with a concave area in the back of the blade.

Main features
of "Sea Rider""
drives

lnstallation astern is fast and without any waste of time in aligning the shaft, which usually requires instead careful positioning and bolting of three or four separate hull appendages.
Sea Rider can be mounted without affecting transom geometry and without modifying either its structure
or shape.

The engine connected to Sea Rider can be mounted in any position: amidships or right astern, without the complication of installing a costly buiit-in "V-drive" or expensive silencers or mufflers.

The Sea Rider unit has been kept as compact and short as possible to reduce protrusion astern to a minimum, while maintaining efficiency. Simplicity was the objective throughout the development of this unit in order to ensure reliability and durability.

The draught of the entire Sea Rider body was reduced as much as possible: this was also helped by the propeller position which projects out of the hull by half of its diameter only. In "Deep-V" hulls propeller draught may be even less than keel draught.

Engine wear and a high mechanical noise were among the main drawbacks of surface propellers, since the engine ran at high rpm even at cruising speed.
Sea Rider has solved this problem: its surface propeller has similar power absorption as submerged propellers, since it works with maximum efficiency even at lower (cruising) speeds.
This also results in more immediate response to controls in manoeuvring.

Tunnel rudders were employed to overcome some of the disadvantages of conventional rudders or directional propellers.
The semi-circular "shield" around the propeller's upper half ensures greater protection and safety.
lt also enhances handling and thrust by channelling the jet in the direction required.
The two vertical rudder blades, which form the continuation of the shield, act as "side walls".
They run below hull level thus ensuring, if needed, effective direction control by working in turbulence-free waters. These side walls reach as far as the propeller diameter's outer edge, so as to reduce the likelihood of damage when navigating in shallow waters.

In addítion to the advantages of a conventional drive, it provides increased surface propeller efficency without its penalizing limitations. Last but not least, as the latest result of extensive investigatìon on wide speed range planing hull drives, Sea Rider is currently employed both on pleasure and work vessels (navy and passenger), thus becoming a landmark in the field of transmission. The undewater exhaust system employed in the Sea Rider drive provides several considerable advantages: reduction of noise and suppression of exhaust gases, which may give serious problems in today's highiy powerful diesel engines. The ventilation of the propeller's upper section provides smooth thrust progression when passing from underwater to surface operating mode.

This gives the engine greater acceleration, ensures good exhaust gas emptying (thanks to low pressure in front of the blades), reduces the likelihood of exhaust pipe back pressure and does not require any silencer.

The "V" geometry of the Sea Rider body ensures that when the propeller's thrust is reversed the resulting flow from the disk's upper half is channelled under the hull without obstruction.
No efforts were spared in combining all of these features in order to produce a high quality, cleanly stylish product.

Propeller: this type of propeller is a further advancement in the field of surface propeller design. A consequence of the Sea Rider project, it has the ability to eliminate one of the main drawbacks of this type of propeliers: difficult handling when going astern.

Section: the back of the-blade features a concave surface towards the outer edge, whose action delivers the necessary thrust when propeller rotation is reversed.
Efficiency: it was proved through numerous tests ín the Genoa University cavitation tunnel.