Rudder hums when powering upwind

[Babylon]

Is this normal? Have a transom-hung rudder. There is also a fair amount of play in the pintles - should these be checked and replaced?

 

[rotrax]

What's it humming?

 

[irl2605]

Beneteau 260,s used to do this at 5 to 6 knots .. They had twin rudders and you could play with the angles with various degrees (pardon pun) of no success. Solution seems to be a very dubious pair of flexible rubber joints on the new 25.7s ... So its prob a vibration somewhere ..

 

[Babylon]

What's it humming?

http://www.firstworldwar.com/audio/itsalongwaytotipperary.htm

Chorus

It's a long way to Tipperary,
It's a long, long way to go.
It's a long way to Tipperary
To the sweetest girl I know.
Goodbye Piccadilly,
Farewell Leicester Square,
It's a long long way to Tipperary,
But my heart lies there.

Up to mighty London came
An Irish lad one day,
All the streets were paved with gold,
So everyone was gay!
Singing songs of Piccadilly,
Strand, and Leicester Square,
'Til Paddy got excited and
He shouted to them there:

Chorus

Paddy wrote a letter
To his Irish Molly O',
Saying, "Should you not receive it,
Write and let me know!
If I make mistakes in spelling,
Molly dear", said he,
"Remember it's the pen, that's bad,
Don't lay the blame on me".

Chorus

Molly wrote a neat reply
To Irish Paddy O',
Saying, "Mike Maloney wants
To marry me, and so
Leave the Strand and Piccadilly,
Or you'll be to blame,
For love has fairly drove me silly,
Hoping you're the same!"

Chorus

 

[irl2605]

So the boat hums it and you sing along .. Nice ..

 

[Babylon]

So the boat hums it and you sing along .. Nice ..

Extra wartime verse:

That's the wrong way to tickle Mary,
That's the wrong way to kiss!
Don't you know that over here, lad,
They like it best like this!
Hooray pour le Francais!
Farewell, Angleterre!
We didn't know the way to tickle Mary,
But we learned how, over there!

 

[monkfish24]

Humming can be caused by misalignment between the rudder and keel.

Most likely the play in your pintles is causing this so it may be worth changing the pintles or adding some bushes as said.

 

[Babylon]

Humming can be caused by misalignment between the rudder and keel.

Most likely the play in your pintles is causing this so it may be worth changing the pintles or adding some bushes as said.

Thanks Monkie - will get the pintles sorted

 

[Tranona]

Thanks Monkie - will get the pintles sorted

You might just leave it if the hum is tuneful and it indicates the boat is going well!

 

[Lakesailor]

When I changed the rudder on my Seahawk from a funny shovel-shaped thing to one based on a blade from a Prelude it introduced a hum when hard on the wind. There was absolutely no play in the pintles/gudgeons. Although I did bevel the forward edge and after edge I think the vibration came from the water flow detaching from the rudder blade surface. However it was 100% better than the original with more bite, less weather helm and no stalling. I quite liked it.

Before and after

 

[Twister_Ken]

My Fireball used to hum just before planing. Regarded it a warning to get ready to shift trim

 

[William_H]

Rudder

I find that play in the pintles is particularly annoying and I would fix that first. However the hum while I have heard it on boats is a fickle thing. I suggest perhaps perfecting the foil shape of the rudder front to back and smoothing it off if at rough might just stop the hum. good luck olewill

 

[penfold]

Hunter Sonatas and Impalas often do this at hull speed; the pintles don't really have any part in the matter, in fact I found having good pintles can make it worse as the vibration is transferred from the rudder to the hull better. I have read that it can be reduced/cured by cutting a square edge on the trailing edge of the rudder, this detaches the attached flow cleanly and theoretically prevents the harmonic vibration or at least moves the excitation frequency away from whatever the harmonic of the rudderblade/pintle assembly is. New Sonata and Impala rudder blades are supplied with the square trailing edge as standard these days.

 

[testmonkey]

Humming is caused by vibration coming from unclean flow on trailing edges of blades. First thing to look at is trailing edge of the keel. You may feel the vibration on the rudder but more probably the source is the keel. As an example read Beneteau 25 tuning guide:

"...trailing edges on keel and rudder, what you have to do bringing the 90° angle to approximately 30°, but only by one side. This will make the keel blade asymmetrical, but will eliminate low speed vibrations. When the boat surfs, anyway, you will anyway feel the boat vibrating." source: http://srs-ccs.ch/cms/upload/docu/B25/B25_North_Sail_Tuning_guide.pdf

 

[vyv_cox]

Hobie cats are renowned for producing a howling noise from the rudders. As others have said it is caused by a flow effect from the trailing edge. The cure that always works on Hobies is to file a flat about 3 mm wide down the trailing edge(s)

There have been many posts on this forum about singing propellers. Nobody reported any of the lyrics, but filing flats down the trailing edges soon shut them up.

 

[AngusMcDoon]

"...trailing edges on keel and rudder, what you have to do bringing the 90° angle to approximately 30°, but only by one side. This will make the keel blade asymmetrical, but will eliminate low speed vibrations. When the boat surfs, anyway, you will anyway feel the boat vibrating."

The trailing edges on my foils are asymmetric. I have often wondered why. Now I know.

 

[Twister_Ken]

The trailing edges on my foils are asymmetric. I have often wondered why. Now I know.

To match your spinnaker?

 

[AngusMcDoon]

To match your spinnaker?

They have asymmetry on opposite sides though.