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Propellor cavitation

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Alan Dixon View Drop Down
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Joined: 07 Sep 2009
Location: Sunderland
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Post Options Post Options   Quote Alan Dixon Quote  Post ReplyReply Direct Link To This Post Topic: Propellor cavitation
    Posted: 16 Oct 2016 at 5:46pm
I have just stripped the propeller and shaft from Charlotte I had suspected electrolysis on the prop, but on close examination can find little evidence of this, there are no pink patches but the leading edges are of the prop are badly damaged I could use them as a file or saw! 
I believe the damage is being caused by cavitation I have tip to hull clearance top of aperture of 22mm and at the bottom only 17mm. The max aperture is 410 mm I have a 14" prop.
I suspect the unequal clearances are causing a pressure point and cavitation as well as the transmission noise I have had.
Considering sculpting the aperture to give equal clearances? Any comments welcome

Alan Dixon "Charlotte"
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Brigitte View Drop Down
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Post Options Post Options   Quote Brigitte Quote  Post ReplyReply Direct Link To This Post Posted: 17 Oct 2016 at 12:19pm
Wouldn't it be easier just to fit a smaller prop?

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Post Options Post Options   Quote admin Quote  Post ReplyReply Direct Link To This Post Posted: 18 Oct 2016 at 9:27pm
Not uncommon for the shaft to be slightly high or low of the central point, I have a 13" prop for that reason.  14" would be a bit tight.  

You could, I imagine, expand the prop aperture slightly but would this cause other issues?
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Alan Dixon View Drop Down
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Post Options Post Options   Quote Alan Dixon Quote  Post ReplyReply Direct Link To This Post Posted: 20 Oct 2016 at 10:46am
I do not want to change the prop if I can avoid it, I have good thrust and performance with my engine propeller combination.
I have spoken to the production manager from Jeremy Rogers, who confirms that the skeg is solid and I can re shape the aperture bottom and forward to relieve the pressure points and hopefully reduce the cavitation and the transmission noise I have always had. 
So I will be making a lot of dust with grinder, sander and filler next week If this fails then the prop has lasted 11 years and 2,250 engine hours by the time I wear out this new prop the engine will probably need replacement.
Alan Dixon "Charlotte"
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