Stus-List Howling rigging

Don Wagner don.wagner at verizon.net
Sat Aug 1 09:40:50 EDT 2015


The vibrations and the singing noises that you have observed are classical  examples of vortex shedding. They were originally described by a German fluid dynamics engineer, Theodore von Karmann.
If you are interested, do a search on “vortex shedding”. Wikipeda has a good description of the phenomena with some pix.  You might also search “ von Karmann vortex street”

I’ve experienced it in my rigging, and occasionally from my centerboard at certain wind speeds or boat speeds

Don Wagner
C&C 41 CB 
Der Baron

From: Joel Aronson via CnC-List 
Sent: Saturday, August 01, 2015 2:39 AM
To: cnc-list at cnc-list.com 
Cc: Joel Aronson 
Subject: Re: Stus-List Howling rigging

Had a similar hum while coming back from Newport.  The engineer on board put a clothes pin on the shroud to change the harmonics. Worked for several hours.  

Joel

On Saturday, August 1, 2015, Russ & Melody via CnC-List <cnc-list at cnc-list.com> wrote:


  Don't listen to him, Jim.  I can tell he's just making things up. The name was Peat and we don't have pints of rum... maybe a litre or two. 

  And to settle the ghost, try hoisting a fender alongside the mast about half way up. You will be amazed how it can settle the rig if you have oscillation. I had to do just that at the Boho Bash, 4 weeks ago.

  Go ogle vortex breaker. 

          Cheers, Russ
          Sweet 35 mk-1

  At 09:56 PM 31/07/2015, you wrote:

    Dennis, where the hell did you come up with that?

    Jim Watts
    Paradigm Shift
    C&C 35 Mk III
    Victoria, BC

    On 31 July 2015 at 21:04, Dennis C. via CnC-List <javascript:_e(%7B%7D,'cvml','cnc-list at cnc-list.com');> wrote:

      It's the ghost of Penelakut Pete.  He drowned in Clam Bay when he fell overboard after consuming a few pints of rum.  Legend says he only comes out on breezy nights.


      Dennis C.

      Touche' 35-1 #83

      Mandeville, LA


      On Fri, Jul 31, 2015 at 9:26 PM, Jim Watts via CnC-List <javascript:_e(%7B%7D,'cvml','cnc-list at cnc-list.com');> wrote:

        On our latest trip north, we anchored in Clam Bay and had a strange problem. At a certain wind speed, the shrouds would start to hum, sometimes making the boat shake with vibration. The major vibration was felt in the small rod running to the underside of the upper spreaders and in the mast and backstay.  I backed each shroud one off half a turn and it really didn't do much except make those shrouds look loose to me, but I'm sure I can't tell the difference of 1/128th of an inch. It eventually faded as the wind dropped. 

        For the next ten days, in all sorts of conditions, we didn't hear it, but when we anchored in the same bay 10 days later, we got it again. 

        Any explanation except witchcraft?

        Â 

        Jim Watts

        Paradigm Shift

        C&C 35 Mk III

        Victoria, BC


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-- 
Joel 
301 541 8551



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