low frequency vibration

[ChuckF]

While out off Cape Cod yesterday in beautiful weather yesterday, we noticed a strange vibration that seemed to be coming from the hull itself. We were going at about 3-4 knots at the time. I looked at the standing rigging to see if anything was visibly moving, but didn't see anything.It would last a few seconds and then disappear. It happened two or three times yesterday. I have noticed it before, but for some reason it seemed stronger yesterday.Any ideas?ChuckWatery Tart

 

[John Radcliff]

From my Laser days

If I recall correctly, this is the trailing edge of the centerboard or rudder having some flutter. This can be caused by a warping of the trailing edge. If you get a chance, closely examine the trailing edge of both CB and rudder. You may need a large, flat guide to determine where the warping or oddity is. Just a guess. For repair ideas, try searing the web for 'Laser centerboard hum' or something like that.

 

[gball]

Centerboard hum/ 170

Chuck,I've felt/heard the same thing in my 170, albeit in heavier breezes only. I wonder if the two strips installed on the bottom of the hull (along either side of the CB trunk) don't occassionally cause some racket via vibration/water flow? That's been my theory, although hull harmonics can ocassionally cause this-- at a precise speed, the hull begins to shudder slightly. CB trailing edge is another culprit.I too have had this problem while sailing my dad's Laser--- while screaming downwind on a run. I think John is on to something.Full sails,Mike G.s/v Lil Sport -h170 Alachua, FL

 

[ChuckF]

the centerboard seems like a good bet.

Thanks for the ideas. I will try the "laying of the hands" on the centerboard the next time I hear it to see if that is the source.ChuckWatery Tart