Counter-Rotating Boat Props: Powering The Seas Efficiently

Counter-rotating propellers, also known as coaxial contra-rotating, are a technique used in some marine transmission systems. Two propellers are arranged one behind the other, and power is transferred from the engine via planetary gear transmission. This technique is used to minimise the effect of torque, which can cause the boat to roll slightly to one side under heavy prop torque.

Counter-rotating propellers are used on torpedoes

Counter-rotating propellers are also used in some marine transmission systems, in particular for large speed boats with planing hulls. Two propellers are arranged one behind the other, and power is transferred from the engine via planetary gear transmission.

On smaller boats, the stern of the boat can move sideways due to the higher pressure of the lower prop blade compared to the upper prop blade. This is known as 'prop walk'.

Counter-rotating engines cancel out torque steer, which allows the engines to be set up straight without having to have less efficient toe-in on one or both engines. On a deep vee boat, counter-rotating props also negate the tendency of the boat to roll slightly to one side under heavy prop torque.

They are also used in some motor boats

Counter-rotating propellers, also known as coaxial contra-rotating, are a technique whereby parts of a mechanism rotate in opposite directions about a common axis, usually to minimise the effect of torque. They are also used in some motor boats, in particular large speed boats with planing hulls. Two propellers are arranged one behind the other, and power is transferred from the engine via planetary gear transmission.

The propeller-induced heeling moment is compensated, which is negligible for larger ships. More power can be transmitted for a given propeller radius. The propeller efficiency is increased by recovering energy from the tangential (rotational) flow from the leading propeller. Tangential flow does not contribute to thrust, conversion of tangential to axial flow increases both thrust and overall system efficiency.

On smaller boats, the higher pressure of the lower prop blade compared to the upper prop blade causes the stern of the boat to move sideways, which is known as Prop Walk.

The mechanical installation of coaxial contra-rotating shafts is complicated and expensive and requires more maintenance.

They cancel out torque steer

Counter-rotating boat propellers, also known as coaxial contra-rotating propellers, are a technique whereby parts of a mechanism rotate in opposite directions about a common axis. This technique is used to minimise the effect of torque.

Counter-rotating boat propellers cancel out torque steer, which allows the engines to be set up straight without having to have less efficient toe-in on one or both engines. This means that the boat will not roll slightly to one side under heavy prop torque.

On smaller boats, the stern of the boat can move sideways due to the higher pressure of the lower prop blade compared to the upper prop blade. This is known as 'prop walk'.

The mechanical installation of coaxial contra-rotating shafts is complicated and expensive and requires more maintenance.

They can be used to set engines up straight

Counter-rotating propellers are used on some boats to set the engines up straight. This technique, also known as coaxial contra-rotating, involves parts of a mechanism rotating in opposite directions about a common axis, which minimises the effect of torque. This cancels out torque steer, allowing the engines to be set up straight without having to have less efficient toe-in on one or both engines.

On a deep vee boat, counter-rotating propellers also negate the tendency of the boat to roll slightly to one side under heavy prop torque. This is also known as 'prop walk', where the stern of the boat moves sideways due to the higher pressure of the lower prop blade compared to the upper prop blade.

They can also be used to stop a boat from rolling to one side

Counter-rotating propellers, also known as coaxial contra-rotating, are a technique whereby parts of a mechanism rotate in opposite directions about a common axis, usually to minimise the effect of torque. This technique is used in some marine transmission systems, particularly for large speed boats with planing hulls.

Two propellers are arranged one behind the other, and power is transferred from the engine via planetary gear transmission. This technique cancels out torque steer, allowing the engines to be set up straight without having to have less efficient toe-in on one or both engines.

On a deep vee boat, counter-rotating props negate the tendency of the boat to roll slightly to one side under heavy prop torque. This is achieved by compensating for the propeller-induced heeling moment.

In smaller boats, the higher pressure of the lower prop blade compared to the upper prop blade causes the stern of the boat to move sideways, which is known as Prop Walk.

Frequently asked questions