Propellor size?

[Oliver]

Our existing 20" x 15" right handed prop fitted to a 60ft trad Jonathan Wilson nb with a Beta 43 engine has started singing between 1100 & 1400 revs - but only when going forward.

 

We've had the boat dry docked and there was a slight nick in one blade which was ground out. The stern gland packing has been replaced but the noise has got even louder.

 

Problems with the gearbox and the prop shaft have been ruled out as the source of the noise.

 

When we had the boat built originally, there was a lot of discussion between the surveyor, shell builder, Beta etc as to the size of prop to fit and we ended up with the 20" by 15". The gearbox has a 3:1 ratio. We like the way the boat handles with this size prop and how responsive it is but can't put up any longer with the noise it makes.

 

We've been told that changing the prop for a different size should stop the singing.

 

If you've got a Beta 43 in a 60ft NB with a gearbox ratio of 3:1, what size prop have you got and are you happy with it?

[Neil TNC]

Our existing 20" x 15" right handed prop fitted to a 60ft trad Jonathan Wilson nb with a Beta 43 engine has started singing between 1100 & 1400 revs - but only when going forward.

 

We've had the boat dry docked and there was a slight nick in one blade which was ground out. The stern gland packing has been replaced but the noise has got even louder.

 

Problems with the gearbox and the prop shaft have been ruled out as the source of the noise.

 

When we had the boat built originally, there was a lot of discussion between the surveyor, shell builder, Beta etc as to the size of prop to fit and we ended up with the 20" by 15". The gearbox has a 3:1 ratio. We like the way the boat handles with this size prop and how responsive it is but can't put up any longer with the noise it makes.

 

We've been told that changing the prop for a different size should stop the singing.

 

If you've got a Beta 43 in a 60ft NB with a gearbox ratio of 3:1, what size prop have you got and are you happy with it?

 

I can't help with the prop size, but don't think that is the problem....Earnest's prop was prone to singing after blade damage (we did get quite a bit of that!) I have always sucessfully cured this by dressing up the blade edges with a dolly and club hammer and then bevelling the leading edges approx 45 degrees, with angle grinder. I usually do this to the tip of the blades. I have been doing this sucsessfully for 10 years.