[C320-list] A High Pitched Whine Noise

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Thanks Larry. I especially appreciate the white paper reference.  Very interesting.

It sounds like we have the same issue. Perhaps application of the antifouling coating causes the edges of the prop to be more "rounded" since I would expect the coating's dry film thickness would likely build up and stay adhered to the blade surface than the edge.  

Perhaps the super slippery GFO packing doesn't apply the same amount of damping to the propellor shaft as the more traditional flax packing, thus allowing the high frequency harmonics to occur.  Just a thought.

I'm glad I now have a term for my issue "prop singing".  

Very interesting and thanks for your info.

Dave  

Dave Swanson
S/V Emily Ann
2007 C320 MK II, No. 1107
Mukilteo, WA



On Sep 10, 2010, at 1:20 PM, Melissa&Larry Leibman <theleibmans at verizon.net> wrote:

> Dave,
> 
> I have had a similar noise on Easy Going for the last two seasons. The winter 
> after we purchased her I applied antifouling to the prop using my usual Interlux 
> application schedule and that season upon launching noticed the whining noise in 
> a similar rpm range to yours. Coincidentally we had also changed the flax 
> packing to GFO so I assumed it was related to that. However, after sticking my 
> head down in the engine compartment I convinced myself the sound was coming  
> from further aft than the stern tube and was likely from the propeller itself. 
> 
> 
> The noise seems to be mostly an annoyance at this point and I generally just 
> avoid that fairly narrow rpm range. A potential way to mitigate propeller 
> singing is to chamfer the trailing edge. Although I did not do this on Easy 
> Going, I did do a very modest flattening of the trailing edge this past 
> off-season. I'm somewhat loathe to remove much material from the prop to avoid 
> imbalance issues. After launch this season the noise was still there. It may be 
> less, I'm not sure.
> 
> Here is a reference to a white paper with some information on the phenomenon if 
> you are interested.
> 
> http://www.hydrocompinc.com/knowledge/whitepapers/HC138-SingingPropellers.pdf
> 
> Larry
> Easy Going, #609