Prop Parameters


There are numerous propeller variables in displacement yacht design. Given the restrictions of draft, and the massive drag to be overcome with most ocean crossing yachts, props are forced into a predictable pattern.

However, the efficiency of the FPB, and the low cruise power needs, allow a variety of options.


In our case we are using a three bladed wheel with relatively small blade area. This allows high aspect ratio blades which are very efficient. However, with fewer blades you have a tendency toward vibration and prop noise. This is not a problem for the FPB (she is proving to be almost silent and there is no vibration) because of the following factors:

  • Extra propeller tip clearance from the hull.
  • 2.5″/62mm prop shaft (way oversized).
  • Extra heavy hull plating (12mm.15/32″)
  • Careful engineering of bearings and alignment.
  • Low power requirements at cruise.

Posted by Steve Dashew  (March 19, 2010)

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