Join Date: Nov 2009
Thanked 79 Times in 78 Posts
Rep Power: 10
Re: Vortex shedding-certainly real
About 30 years ago we sailed our 18í catboat to Block Island for a rendezvous. The weatherman got it wrong, however, and that night the wind came out of the NW at 50 mph (Force 8). It was pandemonium in the Salt Pond, with lots of boats dragging anchor and fouling each other. As the wind arose, the standing rigging started buzzing and eventually the mast would periodically go into resonance, driven by vortex shedding. At that point the whole boat vibrated. Didnít get to sleep that night, but at least our 7 lb danforth held our 2500 lb boat and no one came down on us. Being in shallow water shielded us from the keel boats.
Vortex shedding is a well-known phenomena: just not appreciated in those circumstances.
BTW, weíve stored our 35í sloop with mast up for 22 years without incident. The mast vibration in higher winds is minimal, and nowhere near what we experienced 30 years ago on our catboat. I will say that I have never visited the boat during a noríeaster, however.