Propeller Anatomy

  1. Hub: the hub or boss of a propeller is the solid center disc, bored for the propeller shaft, to which the propeller blades are attached.
  2. Keyway: most propeller shafts transmit the torque from the shaft to propeller though a key. The key is a long, slender rectangle of metal along the shaft that fits into a slot or keyway milled (cut away) into the interior at the hub.
  3. Blades: the propeller blades are the twisted fins or foils that project out from the hub. It is the action of the blades that drives a boat through the water.
  4. Blade Face and Blade Back: the blade face is the high-pressure side, or pressure face, of the blade. It is the side facing aft, the side that pushes the water when the boat is moving forward. The blade back is the low-pressure side or suction face of the blade, the side facing ahead.
  5. Blade Root and Blade Tip: the blade roots is the point at which the blade attaches to the hub. The blade tip is the extreme outermost edge of the blade, as far from the propeller shaft center as possible.
  6. Leading and Trailing Edge: the leading edge of a blade is the edge of the blade that cleaves the water. The trailing edge is the edge from which the water streams away.
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