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Title: Props 101 Post by: MANBEARBEAVER on July 02, 2009, 07:21:07 AM (http://gnartown.com/images/prop.PNG)
1 ) Trailing Edge 2 ) Face 3 ) Fillet Area 4 ) Hub or Boss 5 ) Hub or Boss Cap 6 ) Leading Edge 7 ) Back 8 ) Propeller Shaft 9 ) Stern Tube Bearing 10 ) Stern Tube Materials Aluminum - The most common prop material. Reasonable durability which will suit most applications. Stainless Steel - Stronger than most other prop materials. These props offer a higher efficiency due to the added stiffness of the blades. Pitch The pitch of a propeller relates to the theoretical distance that propeller would travel forward in one revolution. For instance, a 14 pitch prop theoretically would travel 14 inches in one revolution while a 20 pitch prop would travel 20 inches. This is theoretical because it doesn't factor in slip, which in the real world reduces the actual distance traveled. Cup Many of today's propellers incorporate a cup at the trailing edge of the propeller blade. This curved lip on the propeller allows it to get a better bite on the water. This results in reduced ventilation, slipping, and allows for a better hole shot in many cases. A cupped propeller also works very well where the motor can be trimmed so that the propeller is near the surface of the water. The cup will typically result in higher top end speed on one of these applications. Switching from an un-cupped to a cupped propeller will reduce your RPM. The actual amount of RPM decrease is dependent on where, how much, and the quality of the cupping. Typically, a cupped propeller of the same pitch and diameter will reduce your RPM by approximately 200. Rake Rake is the angle of the blade away from a line perpendicular to the drive shaft. |