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@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@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@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@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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