Frequently Used Boat Prop Terms
Tuesday, April 14, 2009
By Todd Alan
For people with no previous association to boat propellers, the terms that are used when speaking about different types of propeller and propellers parts can seem quite confusing. This write up aims to increase your basic knowledge when it comes to dealing with boat props.
A boat propellers parts: Most commonly available boat props usually have three blades or four, and these blades are placed around the hub. The hub goes on to connect the propeller blades and the drive shaft. A boat moves forward due to the angle at which these blades are placed which gives them the ability to screw through water. The end of the prop blade that cuts through the water is referred to as the leading edge, and the other end is called the trailing edge.
A spline, while technically, is not a part of the propeller, refers to the drive shafts teeth. Hubs are designed in a way that allows them to fit shafts with given numbers of splines.
The features of a boat prop: Boat props are classified by their diameter and pitch, and this is often displayed as 2 numbers (in inches), such as 15.5 X 12. One can usually find this stamped on the props hub. The 1st number refers to the props diameter (which would be double the distance from the blades end to the hubs center). The 2nd number refers to the props pitch. The pitch refers to the distance that the propeller can theoretically travel through with every revolution. A prop with a 12 inch pitch could travel around 1 foot with a single revolution. Pitch is often looked upon as a theoretical figure because a prop pitch can experience slips in varied real world scenarios. A slip refers to the difference in ratio between the actual distance that is traveled and the props given pitch. This slip can be varied under similar conditions, an example being that an efficiently planned boat could experience only a 10 percent slip, where as a heavy work boat could experience as much as 80 percent slip.
The rotation can be either left or right hand. A majority of the boat props have right hand rotation. You can expect to find a left handed one on engines wherein double engines are needed to counter the motors torque which can lead to pulling the steering in one direction.
A cupped blade is used to describe blades that have undergone special treatment wherein the trailing edges are curved. This is known to elevate performance levels in specific scenarios.
The rake is used to refer to the angle created by the blade and the hub. A negative rake would indicate that the props blades point forward and this is normally done for adding strength.
In buying a new propeller, it is essential that you make a list of your engines specifications such as its make, brand, model, horse power, etc; and also the specifications of your existing prop including the material it is made of, its diameter, its pitch, the number of blades it has, etc. With these details taken care, you can well be on your way to get yourself a new boat prop.
A boat propellers parts: Most commonly available boat props usually have three blades or four, and these blades are placed around the hub. The hub goes on to connect the propeller blades and the drive shaft. A boat moves forward due to the angle at which these blades are placed which gives them the ability to screw through water. The end of the prop blade that cuts through the water is referred to as the leading edge, and the other end is called the trailing edge.
A spline, while technically, is not a part of the propeller, refers to the drive shafts teeth. Hubs are designed in a way that allows them to fit shafts with given numbers of splines.
The features of a boat prop: Boat props are classified by their diameter and pitch, and this is often displayed as 2 numbers (in inches), such as 15.5 X 12. One can usually find this stamped on the props hub. The 1st number refers to the props diameter (which would be double the distance from the blades end to the hubs center). The 2nd number refers to the props pitch. The pitch refers to the distance that the propeller can theoretically travel through with every revolution. A prop with a 12 inch pitch could travel around 1 foot with a single revolution. Pitch is often looked upon as a theoretical figure because a prop pitch can experience slips in varied real world scenarios. A slip refers to the difference in ratio between the actual distance that is traveled and the props given pitch. This slip can be varied under similar conditions, an example being that an efficiently planned boat could experience only a 10 percent slip, where as a heavy work boat could experience as much as 80 percent slip.
The rotation can be either left or right hand. A majority of the boat props have right hand rotation. You can expect to find a left handed one on engines wherein double engines are needed to counter the motors torque which can lead to pulling the steering in one direction.
A cupped blade is used to describe blades that have undergone special treatment wherein the trailing edges are curved. This is known to elevate performance levels in specific scenarios.
The rake is used to refer to the angle created by the blade and the hub. A negative rake would indicate that the props blades point forward and this is normally done for adding strength.
In buying a new propeller, it is essential that you make a list of your engines specifications such as its make, brand, model, horse power, etc; and also the specifications of your existing prop including the material it is made of, its diameter, its pitch, the number of blades it has, etc. With these details taken care, you can well be on your way to get yourself a new boat prop.
Posted byBertie at 5:33 AM
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