Andrew Pace
Variable pitch propellers are used on boats that operate under a variety of conditions, trips and speeds. They are also known as controllable pitch propellers (CPPs) and are used when requirements exceed what a fixed pitch propeller can offer. CPPs have blades that can be rotated around their long axis to change the blade pitch. This means that the pitch can be varied to absorb the maximum engine power, making the CPP efficient for the full range of rotational speeds (RPM), operational conditions (load) and vessel speed.
| Characteristics | Values |
|---|---|
| Purpose | To adapt to various conditions, trips and speeds |
| How it works | The blades can be rotated around their long axis to change the blade pitch |
| Benefits | Reduced fuel consumption, reduced emissions, less noise, optimal drive from wind and engines, reduced drag when sailing, extended service life of engines |
| Use cases | Yachts, twin screw motor yachts, large ships |
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What You'll Learn
The pitch of the propeller can be changed to increase speed and decrease power
A controllable pitch propeller (CPP) has blades that can be rotated around their long axis to change the blade pitch. This allows the propeller to absorb the maximum engine power, making it efficient for the full range of rotational speeds (RPM), operational conditions (load) and vessel speed.
Yachts, when motorsailing, can coarsen the blade angle to attain the optimum drive from wind and engines and fully feather the blades to reduce drag when sailing. When a low in-transit speed is desired, twin screw motoryachts can adjust one propeller to feathering position while the other powers the vessel, extending the service life of the engines.
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CPPs are more efficient than FPPs
A controllable pitch propeller (CPP) is more efficient than a fixed pitch propeller (FPP) for several reasons. Firstly, CPPs have blades that can be rotated around their long axis to change the blade pitch, allowing them to absorb the maximum engine power. This results in reduced fuel consumption, emissions, and noise. CPPs are also more efficient in reverse as the blades' leading edges remain the same in reverse, optimising the hydrodynamic cross-sectional shape for forward propulsion and making it satisfactory for reverse operations.
CPPs are particularly useful when a boat is working under various conditions, trips, and speeds. For example, when motorsailing, yachts can coarsen the blade angle to attain the optimum drive from wind and engines, and fully feather the blades to reduce drag when sailing. When a low in-transit speed is desired, twin screw motor yachts can adjust one propeller to a feathering position while the other powers the vessel, extending the service life of the engines.
In contrast, an FPP-equipped vessel needs either a reversing gear or a reversible engine to reverse, which is not required for a CPP vessel. CPPs offer flexibility and precision performance, making them a popular choice for boats operating under diverse conditions.
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CPPs reduce fuel consumption, emissions and noise
A controllable pitch propeller (CPP) has blades that can be rotated around their long axis to change the blade pitch. This allows the propeller to absorb the maximum engine power, making it efficient for the full range of rotational speeds (RPM), operational conditions (load) and vessel speed.
The CPP's ability to vary its pitch means that it is more efficient in reverse than a fixed pitch propeller (FPP). This is because the blades' leading edges remain as such in reverse, so that the hydrodynamic cross-sectional shape is optimal for forward propulsion and satisfactory for reverse operations.
The CPP's efficiency in reverse means that a CPP-equipped vessel does not need a reversing gear or a reversible engine to reverse, unlike an FPP-equipped vessel. This results in reduced fuel consumption, reduced emissions and less noise. Yachts, when motorsailing, can coarsen the blade angle to attain the optimum drive from wind and engines and fully feather the blades to reduce drag when sailing. When a low in-transit speed is desired, twin screw motoryachts can adjust one propeller to a feathering position while the other powers the vessel, extending the service life of the engines.
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CPPs are used when requirements exceed what a fixed pitch propeller can offer
A controllable pitch propeller (CPP) is used when requirements exceed what a fixed pitch propeller can offer. CPPs have blades that can be rotated around their long axis to change the blade pitch. This allows the propeller to absorb the maximum engine power, making it efficient for the full range of rotational speeds (RPM), operational conditions (load) and vessel speed.
The pitch of the propeller can be adjusted to reduce resistance when sailing. For example, when a low in-transit speed is desired, twin screw motoryachts can adjust one propeller to a feathering position while the other powers the vessel, extending the service life of the engines. CPPs are also more efficient in reverse than fixed pitch propellers as the blades' leading edges remain as such in reverse, so that the hydrodynamic cross-sectional shape is optimal for forward propulsion and satisfactory for reverse operations.
Vessels with medium or high-speed diesel or gasoline engines use a reduction gear to reduce the engine output speed to an optimal propeller speed. A CPP vessel may not need a reversing gear or a reversible engine to reverse, unlike a fixed pitch propeller-equipped vessel.
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CPPs can be used to reduce drag when sailing
A controllable pitch propeller (CPP) has blades that can be rotated around their long axis to change the blade pitch. This allows the propeller to absorb the maximum engine power, making it efficient for the full range of rotational speeds (RPM), operational conditions (load) and vessel speed. CPPs are used when requirements exceed what a fixed pitch propeller can offer.
When sailing, yachts can coarsen the blade angle to attain the optimum drive from wind and engines and fully feather the blades to reduce drag. When low in-transit speed is desired, twin screw motoryachts can adjust one propeller to feathering position whilst the other powers the vessel, extending the service life of the engines.
The CPP is more efficient in reverse than a fixed pitch propeller (FPP) as the blades' leading edges remain as such in reverse also, so that the hydrodynamic cross-sectional shape is optimal for forward propulsion and satisfactory for reverse operations. This means that CPP-equipped vessels do not need a reversing gear or a reversible engine to reverse.
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Frequently asked questions
A variable pitch boat propeller is also known as a controllable pitch propeller (CPP).
CPPs are used when requirements exceed what a fixed pitch propeller can offer.
CPPs have blades that can be rotated around their long axis to change the blade pitch.
CPPs are efficient for the full range of rotational speeds (RPM), operational conditions (load) and vessel speed. They also result in reduced fuel consumption, reduced emissions and less noise.
Yes, CPPs require a hydraulic system to control the position of the blades.
