Mast humming?

Jackdaw · Dec 11, 2014

Not humming, but banging?

The LONG roller inside the mast can bang and clang when the stick is up and the sail is off. We have a Jeanneau next to us in the spring with this problem, and I want to go fill his mast with expanding foam.

justsomeguy · Dec 11, 2014

You're getting a resonating frequency as air passes around the mast, I think.

The malady has a name, but it escapes me at the moment.

Maybe wrap a line around it? Like an automobile's antenna, that should interrupt the resonance.

joker460 · Dec 11, 2014

Is the boom still up and the topping lift tight? Mine hums at C# when the wind is right and it sounds like it's coming from the mast.

I would agree with Jackdaw, the sound from an inmast swivel with no sail is a banging,rattling sound. I raise the swivel to half way up the mast and then stuff rags against the foil to prevent the rattling.

John T1594 · Dec 11, 2014

Topping lift

My rig hums as well but mostly when the boat sits in the water. On my boat (2000 H340) with a B&R rig and no backstay it is my topping lift that resonates. Sometime from the wind and sometimes from the propeller vibrations of passing boats. I can easy the topping lift or slacken the main sheet to let the boom come up some and usually lessens the noise.

centerline · Dec 11, 2014

when does the sound occur? does it just sit there and hum all day, rain or shine, wind or calm?????...
ive heard metal objects hum when there is a high voltage loss nearby, such as parking under high tension power lines, but im sure this is not the case at the boat yard.

the humming could be a very low note being played by the wind thru a hole somewhere in the mast, or it could be harmonic vibrations being set up against one another on the rigging...
in a perfect condition, when the wires are tensioned perfectly to fit the condition, a vibration can be set up in one that will cause another to vibrate also, and it can cause a very audible resonating hum...
according to the experts, this is easily accomplished in a lab, but is rarely found outside the lab. but I have experienced it a couple of times during my years in the crane business when both load lines were under load and the wind was blowing just a little... and you cant really feel it because the energy waves are spent thru the production of sound...

but it may be something much simpler to explain than all that....

Kermit · Dec 11, 2014

Masts hum for the same reason hummingbirds hum. They don't know the words.

Stu Jackson · Dec 11, 2014

http://www.c34.org/faq-pages/faq-mast-pumping.html

In mast furling with the sail removed requires that the skipper stuff the furling gear as joker suggests.

RichH · Dec 11, 2014

justsomeguy said:
You're getting a resonating frequency as air passes around the mast, I think.

The malady has a name, but it escapes me at the moment.

Maybe wrap a line around it? Like an automobile's antenna, that should interrupt the resonance.

Its what makes musical instruments sound their notes .... just a harmonc frequency response from (in your case with an in-mast furler system):
1. the mast is vibrating at the same frequency of the air (vortexes) blowing past, etc. the mast.
2. that BIG open slot at the back of the mast is acting like a 'FLUTE' when air at a precise speed blowing across it at a certain angle.

For case #1 - The remedy for casy of vibration of the mast .... BUT you dont have a backstay ... so one possibility is to tie a 'rope' between the two cap shrouds and tighten down on them ... OR raise a 'heavy weight' aloft thats in firm contact with mast.
OR as others have noted, wrap a halyard around the mast from top to bottom in close 'spiral' to break up the "voretices" (swirling globs of wind) that are shedding from the mast. One or more of these will usually relieve the 'problem'.

However and for case #2, if the 'note' that your mast is producing is because that BIG open 'slot' is acting like a gigantic FLUTE .... youve got to somehow close down that slot opening.
The best way, I envision, to do this 'slot closure' is to get two (cheap) 3/8" or 1/2" dia. 'ropes' tied together side by side ....and with sails slug tied in between the ropes and so tied as to keep the ropes as close to that slot as possible and with the slugs spaced apart about every 36" ... and then raise 'the contraption' like you would when raising a 'standard' mainsail. Without the slugs, any halyard that goes straight up along the slot will whip and slap and can rub the anodizing off the mast. The contraption would go on the outside of the mast.
That you dont notice such vibrations when your mainsail is inside, would tend to indicate that your mast has become a FLUTE so perhaps you should attempt the "hindu rope trick with sail slugs', etc. as a first attempt.

All U Get · Dec 11, 2014

Kermit said:
Masts hum for the same reason hummingbirds hum. They don't know the words.

I thought there was a piece of material you could raise in the slot to the masthead, filling it in, to help keep the resonance down.

All U Get

centerline · Dec 11, 2014

Stu Jackson said:
http://www.c34.org/faq-pages/faq-mast-pumping.html

In mast furling with the sail removed requires that the skipper stuff the furling gear as joker suggests.

thats an interesting read... I have understood it thru a more scientific and confusing explanation (from a different industry), but in the concept that it is explained in the link, using a sailboat mast and rigging, it cuts thru all the confusing terms and makes it reasonably simple to understand

.....

Dunlookin · Dec 11, 2014

On the positive side...

I had a grilfriend once who made the same noise and everything worked out in my favor....

Just sayin'

justsomeguy · Dec 11, 2014

Dunlookin said:
I had a grilfriend once who made the same noise and everything worked out in my favor....

Just sayin'

DougMc · Dec 11, 2014

Is your halyard in the slot and tight? I take the out haul wrap it around main halyard and pull it 5 or 6 feet out from mast and then tighten both outhaul and halyard. This is quieter than with sail in mast, do not know what noise GF would make.

Jeff Jellick · Dec 11, 2014

Rick486 said:
Hi all:
I am getting some trouble from my boatyard saying my mast is humming (44DS - roller furling main). The main is out and stored at home. I have never heard my mast humming in 7 years of ownership. I think it is the halyards. How about you guys? Do your masts hum?
Thanks

Are you sure it is the mast? From time to time I have the same thing (sound) on my 2006 Hunter 45 CC, and on my boat it is caused by the tension in the topping lift line being a little too tight. The humming sound appears to be from the mast, but in reality is coming from the topping lift. Try reducing the tension in the line, and see if the sound goes away.
Jeff

RHUMB RUNNER · Dec 12, 2014

If you let the boom rest on the boom vang and not rely on on the topping lift it should stop. I had the same problem until I let the vang take the load.