As you remember I complained about the noise my prop made....not a nice singy songy sound but something
reminiscent of a seized bearing...and loud too. The trick was to co-ordinate everything with the annual haulout.
So I teed it up with Glen at Porters that I would drop the prop in and he would do it on the spot (he did). Then I
had to get the shipwright to take it off as soon as the boat came out of the water so I could pick it up and run.
I wanted the prop off, fixed and back on so no extra time on the slip was needed.
It all went very smoothly.
Apparently the noise is made by the trailing edge of the prop and Glen machined a flat area 5or6mm wide
along the length of each blade to upset the flow off the edge. 'No guarantees' said Glen. Anyway with the haulout
complete and back in the water, it was time to try it. Success. Well worth the effort and extra cost for a much
quieter travel. The job was done at Bay View Marina and much thanks from me for the co-operation shown.

And thanks for getting back to us.

That's great news Sam,
Can't help but think that it is largely Sam and the effort in research and planning that had a lot to do with your successful outcome, congrats!

This sparked a memory cell or two, I remember a thread years ago when we were discussing the similarities of a rudder trailing edge and a prop trailing edge.
From memory they both had the same issue of tip vortex shedding, and the solution at the time was making the trailing edge actually asymmetrical. This meant the water molecules exiting off the trailing edge where biased to one side or the other, reducing turbulence around the trailing edge from buffeting.
The experts were saying if you get hum and the trailing edge is round, square off an edge. If the trailing edge is squared, round it! Either way would reduce the noise level
My rudders are asymmetrical on the trailing edges for the same reason.

shaggybaxter said..
That's great news Sam,
Can't help but think that it is largely Sam and the effort in research and planning that had a lot to do with your successful outcome, congrats!

This sparked a memory cell or two, I remember a thread years ago when we were discussing the similarities of a rudder trailing edge and a prop trailing edge.
From memory they both had the same issue of tip vortex shedding, and the solution at the time was making the trailing edge actually asymmetrical. This meant the water molecules exiting off the trailing edge where biased to one side or the other, reducing turbulence around the trailing edge from buffeting.
The experts were saying if you get hum and the trailing edge is round, square off an edge. If the trailing edge is squared, round it! Either way would reduce the noise level
My rudders are asymmetrical on the trailing edges for the same reason.

Yeah common problem in dinghies and sportsboats.
Trick is usually a 45deg on the trailing edge, angled from port to stb to give slightly more lift on stb for race starts :)

To finish the thread off here is a picture of the prop. The light coloured strip on the side edge of the top blade is where it has been machined and you can pick it up on the other two blades.

Yes....it matches the wooden pistons in the motor.