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Discussion Starter · #1 ·
Hi All,

I have a noob question here. The wife and I are weekending on the boat like normal. Currently we are in the slip, experiencing 16 knots winds on the port beam, with gusts into the low 20s. During the gusts the boat "shakes." It appears to be coming from the mast and standing rigging shaking in the gusts. Is this normal? We're weekend sailors and we've only experienced this a few other times.

I have the shrouds tuned properly according to the instructions and recommendations from the Seldon tuning guide that others from Sailnet have suggested, so I don't think it's from too-loose of a rig. But I thought I'd ask the experts. :)
 

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One of None
Hunter 34
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Masst pumping? Pumping Mast - SparTalk

Size, make of boat would help those wanting to help. Certain speeds of wind will cause "oscillation" of just about anything from boats to bridges. Usually its' the cables but the mast could also.
 

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It is probably some part of the standing or running rigging. When it is happening one of you can go upstairs and put your hands on a piece of rigging and see which one makes it stop.

Even a tiny little rope (like my 7/64" topping lift) can make a huge amount of noise through the mast if the wind speed vibrates it at a resonant frequency.

Reducing windage above will make the boat more comfortable below.

Using a bungie or spare line to tie halyards off of the mast and pulling on a shroud might be enough to get it to quiet down. I keep my topping lift quiet by using the main halyard to lift the boom while in the dock and leaving the topping lift slack.
 

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One of None
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I'd be hard pressed to sleep at night if in a slip with nothing but tall rigs all around me!
 

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Over Hill Sailing Club
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It's likely the furled headsail/forestay. Try to roll it tight to catch as little wind as possible. Maybe check to make sure there is enough tension on the headstay. If it's too loose it may cause the pulsating and need adjusting anyway to improve performance. Sight along the furled sail to see if there is a noticeable amount of sag.
 
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Discussion Starter · #7 ·
Thanks for the idea smurphy, I did as you suggested and the furled jib is pretty tight already and the forestay is rather devoid of sag. Perhaps it's just the perfect combination of wind speed and direction relative the the position of my boat creating a easy vehicle for vibration?
 

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Over Hill Sailing Club
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I think that's right. Mine does just what you describe occasionally but not for any detectable reason. It just seems to be some combination of conditions that gets the thing cycling. It is annoying.
 

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I had a Pearson 26 where the mast would "pump" in certain wind conditions. It had single lower shrouds which do not prevent fore and aft movement like double lowers do. I've since had boats with double lowers and haven't had that problem.
 

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Aft-swept spreaders considerably change the geometry of the rigging from a mast with unswept spreaders and a single set of lowers (like Jim's Pearson 26). The aft-sweep allows you to prebend the mast and control the amount of bend by adjusting the relative tension on the uppers and lowers. Your mast should have enough pre-bend that pumping is not an issue.

On my Pearson with aft-swept spreaders there is about 1" of pre-bend with the backstay adjuster off, and 2" of pre-bend with it on.

If one of your shrouds is vibrating as a resonant frequency there are a lot of potential easy fixes. The first thing is to figure out what part of your rigging is vibrating, and that just means going around feeling the rig when the noise is happening.
 

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Over Hill Sailing Club
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I have double lowers and have never had the mast oscillate. Am sure it is the furled sail on the forestay that does it on occasion. I can definitely see how a single lower shroud set up would allow the mast to move.
 

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Corsair 24
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my mast will vibrate when hit on the beam while not sailing...when sailing its tuneable and not present...but has double lowers, and intermediates and an adjusteable backstay.

single lowers as mentioned are more prone to it as are those masts that use different rig tunes than at the dock

if you have one of those types of boats there was a very good thread a few months back on how to stop mast pumping while sailing and at the dock...
 

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I have one of those clip-on SSB antennae on my backstay and it has a flat profile (three "tubes" side by side). The wind catches that at the wrong speed and the backstay wobbles. Tried everything, can't fix it.

Also I woke up one night with what sounded like a dingy with an outboard going round and round the boat. After a while I went up on deck - total silence. I discovered a halyard that I make off on the grab handles on the coach roof that was ever so slightly too tight and it was resonating like a double bass. But you could stand right next to it and not hear a sound - only once down below.
 
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omatako I wonder if the normal ssb "isolaters" do the same...my backstay has the normal round black cylinder thingies
 

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If your boat has a backstay adjuster, you might try applying a little tension with the backstay adjuster when in the slip and the wind is gusting. A slight change in tension might be enough to change the harmonics of the rig and quiet it down.

Some people fully ease the backstay adjuster when in the slip. I think that leaves a masthead rig too loose, and prone to pumping in gusts, even when the rig is otherwise tuned perfectly. Try leaving just a little tension on it.
 

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Discussion Starter · #19 ·
Thanks all. Unfortunately I do not have a backstay adjuster. while I confirmed my lowers (and the rest of the rig) is tuned appropriately, I'll try putting another half turn or so on the lowers to see if that improves things. :)
 

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all other adjustments aside I was specifically wondering if the isolaters could cause that even when adjusting backstay and all other rig?
 
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