Boat Propellers: Terminology
Sante Marine Propeller has everything you need regarding boat propellers! We don’t just sell propellers, we repair & re-pitch them as well as providing skeg & cavitation plate repair and shaft straightening. We are here to make sure you spend less time out of the water and more time on it having fun!
For your reference, here are some of the general terms and also a few technical ones in the propeller business.
Propeller Term
What it means...
Diameter
The diameter of the imaginary circle scribed by the blade tips as the propeller rotates.
Radius
The distance from the axis of rotation to the blade tip. The radius multiplied by two is equal to the diameter.
Blade Face
Pressure Side, Pitch Side. Aft side of the blade surface facing the stern.
Blade Back
Suction Side. Forward side of the blade surface facing the bow.
Leading Edge
The edge of the propeller blade adjacent to the forward end of the hub. When viewing the propeller from astern, this edge is furthest away. The leading edge leads into the flow when providing forward thrust
Trailing Edge
The edge of the propeller adjacent to the aft end of the hub. When viewing the propeller from astern, this edge is closest The trailing edge retreats from the flow when providing forward thrust.
Blade Number
Equal to the number of blades on the propeller.
Blade Tip
Maximum reach of the blade from the center of the hub. Separates the leading and trailing edges.
Hub
Solid cylinder located at the center of the propeller. Bored to accommodate the engine shaft. Hub shapes include cylindrical, conical, radius & barreled.
Blade Root
Fillet area. The region of transition from the blade surfaces and edges to the hub periphery. The area where the blade attaches to the hub.
Rotation
When viewed from the stern (facing forward): Right-hand propellers rotate clock wise to provide forward thrust. Left-hand propellers rotate counter-clockwise to provide forward thrust.
Pitch
The linear distance that a propeller would move in one revolution with no slippage.
Cylindrical Section
A cross section of a blade cut by a circular cylinder whose centerline is the propeller
Pitch Line
Reference line used to establish the geometric pitch ang1e for the section. This line may pass through the leading and trailing edges of the section and may be equivalent to the chord line.
Geometric Pitch Angle, a
The angle between the pitch reference line and a line perpendicular to the propeller axis of rotation.
Controllable Pitch Propeller
The propeller blades mount separately on the hub, each on an axis of rotation, allowing a change of pitch in the blades and thus the propeller.
Fixed Pitch Propeller
The propeller blades are permanently mounted and do not allow a change in the propeller pitch.
Constant Pitch Propeller
The propeller blades have the same value of pitch from root to tip and from leading edge to trailing edge.
Variable Pitch Propeller
The propeller blades have sections designed with varying values of local face pitch on the pitch side or blade face.
Rake
The fore or aft slant of a blade with respect to a line perpendicular to the propeller axis of rotation.
Aft Rake
Positive rake. Blade slant towards aft end of hub.
Forward Rake
Negative rake. Blade slant towards forward end of hub.
Track
The absolute difference of the actual individual blade rake distributions to the other blade rake distributions. Always a positive value and represents the spread between individual blade rake distributions.
Skew
The transverse sweeping of a blade such that viewing the blades from fore or aft shows an asymmetrical shape.
Aft Skew
Positive Skew. Blade sweep in direction opposite of rotation.
Forward Skew
Negative Skew. Blade sweep in same direction as rotation.
Cup
Small radius of curvature located on the trailing edge of blade.
D.A.R.
Developed Area Ratio is blade area expressed as the percentage of a circle shaded by the propeller.
We repair most propeller makes & styles up to 36 inches.
