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Join Date: Sep 2005
Location: New Westminster, BC
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Even amongst the generic "types" there are differences.
Folders: include "geared" and non geared types. The gear types guarantee that both blades open (and fold) together. Non geared folders can (and do) occassionally open one side only, creating a lot of vibration and wobble that could, if allowed to, possibly damage shaft or struts. Drag wise they are comparable.
Feathering props include Max, Autoprop, Kiwi prop and others. They vary in price, with Max generally thought of as tops in both categories (price and quality) Figure $3-4K for a 3 blade for your boat. These are tops in performance under power and in reverse over folders and do not have the "1/2 open" problems of some folders. The nice thing about Max props is the blades rotate in reverse mode so that the blade itself is always acting in a forward direction, increasing efficiency quite a bit.
A midway alternative to either if these, with greatly reduced drag over a conventional Michigan wheel, is a Campbell Sailor prop. 2 or 3 blades available, we had good success with a 3 blade one on a 40 footer, replacing a worn out floppy folder. That prop cost $700, looking good against the prices of the others. If you google Campbell Sailor you'll get a link to a supplier.