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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #1  
Old 06-20-2005
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rigging

i have a 1972 seafarer 34 with a standard rig. while sitting at the dock the rig seams to pulsate or vibrate with the wind. I have tuned the rig and have tensioned the shrouds to what is recommended by the tension gauge manufacutrer for the size of the wire. Is this normal or am i looking at a precurser for a disaster?

Dan Kelley
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Old 06-20-2005
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rigging

Normal vibrations: induced harmonics energized by the motion of the wind ''exciting'' the exact (natural) frequency. This is how a violing works.

If the mast is noticably vibrating, you can change its natural frequency by changing tension, etc. Dont know the rigging configuration on a Seafarer 34 but if you have lower stays, increase the tension of the forward and slightly slack the aft lowers - to induce a slight forward bend/bow of the mast. The preloaded bow will significantly change the frequency. If these vibrations are quite noticable (as in ''pumping'' mast) simply put a loop of rope/line around the mast and draw up tension with a winch on the deck, etc. - this for ''storage'' when you''re not on the boat - this will significantly change the natural frequency.

Do all these vibrations matter....? Ultimately, yes as all metals have a certain ''limit'' of applied cyclical stress that will fatigue the metal (typically a loads of 30% of the breaking strength and greater). Slight vibrations - usually not a problem; but, vibrations that are noticiably ''moving'' can indeed shorten the ''life span'' of the components.
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Old 06-20-2005
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rigging

I have been rigging boats for years and have lived aboard my own sailboats for about 20 years. Every once in a while, I get some noise and after all this time, I''m fairly used to what''s ''normal'' and what isn''t.

There is an old New England sailor saying that refers to ''the blow of the eye''. It doesn''t count among monkeys and fools because they don''t know what they are looking at anyway, but among regular sailors it means that if it looks right to an experienced eye, it probably is. And if it looks wrong to you, you are probably right in thinking so.

I have several times gotten manufacturers tension specs from them at the behest of a customer (20 years in yacht service) and tightened, or, ''tried'' to tighten the rig in accordance with the factory specs. Mant times, this is just WAY too tight and results in excessive rug hum and even howling in 20 or 30 knot winds.

It''s too tight. Back it off. Center your rig properly and ease the tension until your rig is snug, but not twangy as a bass guitar. When sailing, observe the lee shroud and see if it is ''floppy''. If it is, center up sails and take up one turn on each side, always keeping the rig balanced.

Once you get your rig adjusted so that your shrouds do not go limp even in YOUR most aggressive reaches, then it is right for you, and the boat, and it will not howl at the dock. Much. Maybe a little. Sell the tension guage or give it to a competitor at Christmas and tune your rig by your own ''blow of the eye''. You''ll get to know it fast. Have confidence.

By the way, once you''re adjusted, ring-lock or cotter all turnbuckles and cover any exposed cotter pins with tape. Yeah, yeah, I know you knew that.
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