Tiller vibration or cavitation

[mikehennessy]

Hi Folks.

I took my new boat out for the third time today in 6-8 MPH breeze.  When the wind was at the top of the range, I had vibration in the tiller.  I tried raising and lowering the centerboard with no effect on the vibrations.  When the wind fell below the upper range, no vibration.  The boat was either on a beam reach or close reach points of sail

Any idea on the cause or a possible cure?

Regards,
Mike

[Vipersdad]

Was your rudder all the way down?

[mikehennessy]

I put the set pin in, tightened the bolt and then removed the pin in case of bottom contact (kick-up option).  Appeared to hold and be down fully when I inspected the rig.

[bruce]

Hey Mike, you have a new Sunday Cat as I recall, so wear in the gudgeon/pintles isn't it. I'd leave the pin in next time, just to verify the rudder's down. A buzz or vibration for me is usually the CB, as you checked, so don't abandon that possibility yet. Interestingly, since I replaced my CB pendant with a thicker, fuzzier line, Yale PhD Racer line, for handling, I rarely get a buzz (lol), and when I do it's very faint.

Also, 6-8 mph breeze is pretty moderate for the CB buzz, mine usually is more in the 8-12 range. Different boats.

I don't recall a buzz when I was using Com-Pac's uphaul line on the rudder, but I suppose that could buzz too. Try slacking that.

While I've got you here, we've talked about cringle earings before, to make reefing the tack easier. I made up a loop with a diamond knot out of 3/16" Dyneema that works well. Bulky, but easy to grab and stays in the cringle on its own, or can be pulled out if you've got a purist on the foredeck. They won't like my dirty sail either.

[Roland of Macatawa]

Hi, Mike:

Do you perhaps have slight play between the rudder blade head and the rudder housing?

On my 2012 SunDayCat, with the factory flat plate rudder, there is some small gap.
My rudder blade head is 5/16" thick but the rudder housing has a 3/8" wide slot.
So even if you crank down on the tightening bolt, you end up with point contact between rudder and housing not surface contact.
I've read elsewhere on this forum of others putting a thin shim between the rudder blade and the rudder housing.

I however don't have a significant problem with this, so am only speculating.
But perhaps worth checking.

Best Wishes, Roland