| Propeller Glossary | | Print | |
In your search for the perfect propeller, you’ll come across a lot of terms. Here are the basics: Blades: Blades are the “business ends” of all propellers. High-performance marine propellers range from three- to six-blade models. Blade shapes range from rounded, where the blades are configured in shapes resembling dog ears and teardrops, to cleaver, where the trailing edge of the blades are completely straight.Cavitation: You don’t think of water as “boiling” when it isn’t hot, but it can under certain circumstances, in this case propellers creating low pressure at their leading edges. As the water boils, bubbles form and attach to those edges. When they burst, they cause pitting and other damage to the propeller blades. However, cavitation generally occurs when a prop blade is already nicked, bent or otherwise damaged. Cupping: Cupping or cup is the “concavity” in a propeller blade that is created when its edges are curled. Diameter: When a propeller spins, it makes a circle. Diameter is the distance across the circle. Pitch: The theoretical distance—generally expressed in inches—a propeller will move a boat forward with each rotation. Rake: The angle from the center of the hub to the tip of each propeller blade. Rotation: The direction in which a propeller turns. In outboard rotation, each propeller rotates toward the outside of the boat. In inboard rotation, each propeller rotates toward the center of the boat. Slip: Expressed as a percentage, slip is the difference between theoretical and actual pitch. |
