Shakin' in the Wind?

[capngeo]

Sitting here on the boat in the slip; the wind's picked up to the mid 20's. The entire boat starts this weird vibration... the entire rig begins to quiver. The hull picks up the harmonic and the entire boat feels like a 1970's "Magic Fingers" bed.

I've had this boat since 1986... been in hurricane force winds and she never did this! I messed with the backstay tensioner (I normally leave it very loose in the slip), but tight or loose she is still shaking. WTF is going on?

[Rakuflames]

Originally Posted by capngeo

Sitting here on the boat in the slip; the wind's picked up to the mid 20's. The entire boat starts this weird vibration... the entire rig begins to quiver. The hull picks up the harmonic and the entire boat feels like a 1970's "Magic Fingers" bed.

I've had this boat since 1986... been in hurricane force winds and she never did this! I messed with the backstay tensioner (I normally leave it very loose in the slip), but tight or loose she is still shaking. WTF is going on?

Haven't you noticed that the hull acts like a bell and magnifies sound? The wires are just like wires on a violin -- make them vibrate and they'll give out a pitch.

Shortly after I got my boat she was on the hard for about a week in a boat yard. I stayed on the boat. Christmas night the wind whipped up to about 35 mph from the north (I had two wreaths hanging on the bow, and the north edge of both were completely stripped down to the wire by the time the wind dropped) -- and I kept hearing a thumping. It sounded like the boat was really thumping around on the stands. I found it unnerving. I really didn't think the boat was going to fall over, but I couldn't sleep either, and I went to a motel for the night. Before I left I looked and i couldn't even see the very slight movement in the stands, but the hull magnified the sound so that I knew I wouldn't be able to sleep.

I think it's why you can hear little shrimp eating the algae off your hull. Here in the slightly brackish water of the river I can hear crabs do it. They're tiny little things but they sound like two-pounders!

[model 10]

wind direction?

[rebel heart]

I get it all the time in La Paz here at anchor because the wind direction has nothing to do with how the boat lies; too much current. I'm actually looking out the window right now at a turnbuckle that's got a bit of hum in it.

A lot of the time it's a halyard or even flag pennant that is vibrating, and it in turn is vibrating the whole rig.

[capngeo]

But damnit I've had this boat 27 years! The wind is coming just abaft the starboard beam. Went topsides and felt each stay, turnbuckle and halyard... nothing is loose, but its all dancin'

[rebel heart]

Originally Posted by capngeo

But damnit I've had this boat 27 years! The wind is coming just abaft the starboard beam. Went topsides and felt each stay, turnbuckle and halyard... nothing is loose, but its all dancin'

7 years for me; it happens man.

[bobconnie]

Ahh, Sometimes a bungee cord wrapped in the RIGHT Place ( ya gotta try to find out where!) Will cure the problem, we never had the problem on our Clovin cus of the wrapped and filled and parceled rigging we had, but have had it on other boats we have owned and sailed ! Sounds like a goofie idea but it will reduce or remove the sounds you are getting. Just a thought

[Rakuflames]

Originally Posted by capngeo

But damnit I've had this boat 27 years! The wind is coming just abaft the starboard beam. Went topsides and felt each stay, turnbuckle and halyard... nothing is loose, but its all dancin'

BUT you just TUNED (get it? tuned?) your rig and changed how it all vibrates.

You may never hear it again. you may re-adjust your backstay, or the wind will not be from JUST that angle, or whatever, but this is the whole principle behind stringed instruments: you make the string (which is often wire) vibrate, and then everything else is designed to magnify the sound.

[daddle]

To rid the rig of oscillations it is usually best to loosen the standing rigging. But who knows?

Maybe the aft lowers, if any, are too loose. Maybe you could induce a little mast bend somehow. Put a little running back on, or inner forestay, or babystay .... What do you have available?

Failing that, a series of tequila shots at Bandito's, applied with abandon, will allow you to sleep right thru the shaking.

[delmarrey]

An old Indian trick is to wrap the halyards around the mast. This disturbs the foil of the mast which brakes up the harmonics.

Where my boat sits, if I get a westerly, my mast starts to pump so I just loosen up the hyd. backstay and it quits.

[daddle]

Originally Posted by delmarrey

An old Indian trick is to wrap the halyards around the mast.

The other old trick must be how this is accomplished without a bosun's chair. ???

[roverhi]

I changed the topping lift for the boom from wire to synthetic. Boat started to sing to me in over 10k winds. Drove me nuts for a couple of days till I figured it out, now it just drives me crazy.

[Andrew Troup]

I was going to say topping lift, too...

On one occasion a friend hunted high and low for what seemed like hours (at least when he told the story, it took hours!). Finally, dejected, they put their hands on the boom and rested their head on their hands. The pitch went up!

I didn't remember the story a few years later, one Xmas.
We were anchored in a deserted bay surrounded by high hills, in 10/10 dark cloud cover, intermittent showers and gusty, miserable conditions ... and a light plane was circling above, looking for a gap to land. We were hoping the fuel wouldn't run out. Half wondering if Santa had joined the C20th and chartered a Cessna ....

Long after any small tank would have been empty, even the fumes would long since have dissipated, we checked the rig, and it turned out to be vortices shedding from our topping lift causing the backstay to resonate sympathetically ...

[capngeo]

Argh... Tension gauge says everything is normal.

Rigid vang, so no topping lift rigged... Boom tent and Bimini up.

The only thing that I see different is the marina moved a floating home to the slip next to me... Must have something to do with the air flow. Regardless, got no sleep last night!

[Hudson Force]

'Whole lot of shakin' going on! Most have had this at times. I'm surprised you went so long without experiencing this resonance. I have sometimes reduced this by cinching a line from my mast to an upper shroud abou six feet above the deck, but I rarely dampen the whole shake.