I've added some photos to the Sunplucker album showing a couple of propeller first drive units I've tested.
The nozzle shown is fiberglass over cordage. It would have been much easier to make it by turning from nylon or pvc on a lathe. Or gluing together washers cut by a laser.
I was trying to form a nozzle having a cross section described as a NACA 0021 profile inclined so that the nozzle exit is near cylindrical. That had more drag than I liked.
The propeller was a 6" pitch prop from a small outboard cut down to fit the nozzle. I don't think the pitch was high enough. (Stock pitch on a trolling motor is about 4 inches).
The downshaft fairing shown was cut from composite decking material on a band saw to a 1 1/4 inch width. A one-inch hole was bored at the 1/3 mark, and then then the sidewall was split with a box cutter and the fairing sections were matched, glued and stacked onto the downshaft.
The props in my setup are protected by the keels on the catamaran. I have been able to run it up on the bank without causing prop damage so far.
John Casperson
Posted by: john_casperson@yahoo.com
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