high pitched whine

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H4B

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Ive got one and it may be starting to annoy me. It definitly comes from somewhere near the p bracket /rudder/ prop , it only starts at speeds > 6 knots ( its actually a good sail trimming aid ). I am pretty sure its not air generated , hole in boom ,mast etc it just doesnt sound like that. Its not affected by holding the backstay or anything like that.

Any possible causes and remedies please
 
I'm sure I remember reading about this somewhere and the cure was to "rough up" the leading edge of the prop with a coarse file. I would strongly recommend more research rather than just trying my suggestion immediately !!!
 
Actually, if it's the prop then it's the trailing edge that is filed to a 60/30 degree angle.

Most unlikely to be the prop though. I'd bet on the rudder. Had several boats do it and quite enjoy it 'cos you're going fast. But, if you want to stop it, same as the prop, 60/30 angle across the TE will fool the vertical vortices shedding from the edge - but may well cause it to start at a different speed. (One cylindrical vortex rolls off one side of the blade, thus encouraging another to roll from the other side. This imparts a small alternating force into the blade, causing it to vibrate, and occasionally to resonate.)
 
Sounds technical enough to be the answer, as a test should i expect the pitch to change with movement of the rudder hence changing the TE angle to water flow. The 60/30 angle across TE , do you mean the same as the cutting edge of a chisel ?
 
Yes to the first question, although the tiller angle change would have to be quite large, because the flow will tend to stick with the blade for a few degees change.

No, to the second. Not the same as a chisel. 30/60 from a right angle to the longitudinal centreline, or, if the blade were a flat plate, an angle change of 60 on one side and 120 from the other.
 
Thanks boguing, sort of got the idea , having abit of trouble visualising it. I agree re ' cos you're going fast ' the noise always tells me 'we're in the grove' when racing, however on passage it can become abit like a torture for the off watch below. Next time i go to sea I'll experiment abit more re rudder angle and see what happens. Boat out of the water in Feb so chance then to tinker. (At first I thought it was the bearing in an old stow log impeller but last winter I removed it , hoping that I had solved the problem but was a bit miffed to still have it on relaunch .

Thanks all
 
Had same problem with new cutless bearing last season. Cured it by putting prop in gear.
After some 20 hours running the prop no longer whines, and neither of course does SWMBO
 
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