Rudder vibrates while sailing.

[rhythmsurfer]

My 1981 Hunter 36 just received a new rudder from Foss Foam. We bought the boat without sailing it and sent it to the yard to get a new bottom, new rudder, and bunch of other stuff. I searched the forums and all I can find is when the boat is in gear with the motor running. My rudder only vibrates when I am sailing. Any ideas?

Tony

 

[Ed Schenck]

Was the rudder bearing checked before you launched? A rudder will go into an oscillation if the bearing or sleeve that post rides in is worn. Hard to check in the water. But I am afraid you already know.

 

[rhythmsurfer]

Not sure.

I will ask the mechanic on Monday. I don't think he replaced the bearing. Thanks for the knowledge.

 

[Hermit Scott]

Lock your wheel or lash the tiller to keep it from wearing while sitting at the dock.

 

[Stu Jackson]

Take the guy who did the work OUT on your boat and show him. All the descriptions in the world won't be as good as that real world experience.

I keep saying the internet is not too good for helping out with sounds, smells and electrical issues without wiring diagrams. This is another example: vibration. Thanks for adding to the list.

 

[rhythmsurfer]

Glad I could help Stu. I don't have a brake on my pedestal but we don't get much movement in our marina. Still lash the wheel to the cleat?

 

[kappykaplan]

Yes, lash the wheel. My pedestal brake doesn't work, and I lash the wheel after every sail.

 

[RAD]

Also check the adjustment on the steering cables cause they had to loosen them to remove the rudder and maybe there too loose giving more play to the rudder

 

[rardiH36]

Just for reference, my 1980 Hunter 36's rudder does not vibrate at any speed range, wind range, or heel angle. So vibration is not a design feature!

 

[RichH]

Are there any 'sharp' or 'pointy' shapes to the leading edge of this rudder? Parabolic-like leading edge shapes are the only shapes that will permit a rudder to NOT 'vibrate'. So if you have untrimmed molding 'flashes' - thin 'lines' of excess FRG where the mold came together, then simply sand down to a smooth surface.
Any such 'sharp protuberance' , even teeny errant shapes, on the leading edge on a rudder or keel will/can promote .... 'induced harmonic vibrations' when the foil is at 'vibration critical' (nodal) speeds.

 

[Morgan30]

Is it a high speed short vibration or is the rudder wiggling? Like moving back and forth 1/4 to 1/2 inch a move? Sort of like feeling prop thrust on the rudder? But, you are under sail.

 

[rhythmsurfer]

Well I found out what caused the rudder to vibrate. The 35lb danforth and it's rode were rubbing up against the steering cable. Glad that was an easy fix. Thanks for everyone's input.