# Topping Lift Vibration



## cktalons (Jun 2, 2011)

When the wind is at just the right speed, it hums through the mast and is much louder than I'd like to tolerate. I figured out that the line that's causing the vibration hum is the topping lift, so I'm not sure how to make it stop (can't exactly remove tension from that one). But I'm still green to sailboats. Is there anyone out there who can help me get rid of the Humming Mast?

For reference, I have an Islander 30, and don't have anything to rest the boom on to relieve tension from the topping lift's line.

*UPDATE: Tried manipulating and taking weight off the TL, but the mast is still humming, so that's not the issue after all. Any ideas what else could be making the humming, besides lines running through it? I've played with different tensions with the other lines and nothing is working. I'm going crazy here!*


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## gpittman (Nov 19, 2011)

Hi. I assume you are talking about this happening while sailing with the main up. True? Not sure about the Islander but most boats don't need the topping lift rigged with the main up. Removing the topping lift and securing it to the mast may help and eliminate the noise and vibration.


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## priscilla (Mar 20, 2000)

Courtney, My main topping lift has the same problem, if its tight it hums a tune...I can ease it off a bit as I have a 2nd lift from the mizzen holding the main boom. Perhaps try easing the main sheet BILL


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## deniseO30 (Nov 27, 2006)

topping lift should be loose when sailing. The sail won't have the right shape and may even be like a big pocket to the wind with the TL holding the boom up.. Hum could be the boat telling you more speed! LOL


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## Faster (Sep 13, 2005)

Experiment with tension of the lift (via topping lift itself or mainsheet tension as mentioned) to see if you can tone it down.... Change the wire/line whatever to a different size perhaps..... Fashion a temporary crutch, or a short strop to the backstay to support the boom and get the tension off the normal topping lift.

I'm assuming this is while not sailing, as otherwise the TL should be slack, as mentioned above...


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## cktalons (Jun 2, 2011)

The mast hums when at anchor, yes. It doesn't make a sound when sailing, as my boat doesn't have a vang, therefore the TL is loose. The only sound I hear then is the whooshing sound in the wind and the splashing against the hull, in other words, absolute heaven.

Chris12345, I'm going to play with it and see what I can do, but if I can't get it to stop humming, do you have any musical requests?


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## ottos (Aug 12, 2008)

I've got to think that since it's not the TL, you've got to see if your rig is properly tensioned. But I'm no expert....

Cute sheltie - I raised two of them


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## CarbonSink62 (Sep 29, 2011)

If no one else has taken it, I guess I will:

How do I stop my mast from humming?

*Teach it the words!* :laugher :laugher


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## Aac (May 24, 2008)

Tie a line around the topping lift about 2 feet above the boom and then to a winch on the coach roof. Put a little tension on the line and the harmoinics should stop - works for me.


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## RichH (Jul 10, 2000)

In all probability, the MAST is vibrating due to an induced harmonic vibration that is 'exciting' the 'natural frequency' of the mast. This is what causes adjacent strings on a musical instrument to vibrate ... or what causes a violins strings to vibrate when rubbed with its bow.

To stop the vibrating at this 'node' of natural frequency you will have to change the natural frequency of the mast ... either by changing rig tension, adding MASS to the mast, or (most commonly) by 'bowing' the mast.

Artificially bowing the mast (called 'prebend') will increase stiffness and most importantly changes the 'natural frequency' of the mast. 99% of all mast manufacturers specify that proper mast set-up include this 'pre-bend'.

Standard and 'proper' prebend is: 3/4" forward bowing (prebend) on a single spreader mast OR 1/2" prebend for EACH spreader set on a multiple spreader rig.

•This is 'easy' to do on masts with lower forward and aft stays ... simply increase the tension on the forward lower shrouds and decrease the tension on the aft lower shrouds while sighting up the front of mast until you get the 'correct' PREBEND. 
•If the boat has running backstays, simply apply tension to the runners.
• If the boat doesnt have lower foreward/aft stays, then you will have to radically change the backstay tension or install running backstays (or hang a weight on the mast, etc.). alternatively as a temp. 'remedy' when moored or docked, simply loop a jib sheet around the cap shroud and put a little bit of winch tension onto the jibsheet --- temporary solution.

A mast that constantly 'sings' / hums due to an induced excited 'natural frequency' will soon cause the rigging terminal connections to FAIL by fatigue failure. If the oscilations become very extreme (mast *pumping*) the mast vibrations can cause the rigging terminals and wire to fail by tensile/ductile failure (impact).


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## priscilla (Mar 20, 2000)

Aac is right, take the tension off the topping lift...its that simple!


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## FSMike (Jan 15, 2010)

cktalons -
Used to have the same problem on an infrequent basis. Sometimes we could cure it by increasing the tension, otherwise we gave up and ran the main halyard to the end of the boom and used it for a topping lift. That made me think that a larger diameter topping lift would fix the problem, but we never got around to it before the boat was sold.


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## MarkSF (Feb 21, 2011)

I have a bungee cord that secures the boom when at rest, goes around the backstay. A second one out to the shrouds stops the main halyard from banging against the mast.


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## chris_gee (May 31, 2006)

The topping lift vibrating and making a noise is fairly common when the wind speed is such to set up a harmonic with the length and tension. You can vary the length slightly by raising or lowering the boom and can vary the tension by tightening or loosening the mainsheet, to break the harmonic.


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