Mysterious Sound Coming from Boom

[hogfighter]

I have always been impressed with the knowledge base on CF. Hopefully someone much smarter than myself (not very hard to accomplish) can assist me with my issue.....

I have a furling main on my Hunter 430, which furls into the mast. Whenever the wind is above around 8-10 knots, a mysterious sound comes from the boom....sounds like someone turned on an electric motor. You know, kind of a hum, as if there's a vibration going on. It does not appear to matter from which direction the wind is coming from, but it is caused by the wind vibrating something in the boom.

The only two lines that physically lead into the boom are the main outhaul and the mainsheet. I have slackened both considerably, thinking that it might be either of those.....it did not stop the noise or change it in any way.

Please help me, as the sound is driving me to drink. Which at least gives me a reason to do so.....Thank you!!

[atoll]

when you have finished drinking from that bottle,blow across the top of it.......

the noise you will hear is the same resononance as you will get when wind blows across booms and masts that have larger gaps in them,like in mast furlers.......

cure ,havent worked that one out yet.......

[pillum]

If it's wind speed related rather than boat speed related it sounds like some kind of resonance, probably induced by wind above a certain speed flowing across someting on the boom, possibly the mainsail slot. Try putting masking tape over the open part of the slot and see if it goes away. These things are a process of elimination, shrouds/stays inducing vibrations etc. This is purely theoretical, hopefully someone can chip in with some empirical experience of a similar thing. Other than that just buy more drink!

[MarkJ]

Sounds like harmonic resonance.

You could try tuning your rig a bit - adjust the shrouds a few milimeters. See if that fixes it.

ooops, first thing to do... change the main halyard tension

[hogfighter]

Okay....thanks. I'll start with masking tape, then check out the tension on the halyard / rigging. Much appreciated!

[minaret]

Originally Posted by atoll

when you have finished drinking from that bottle,blow across the top of it.......

the noise you will hear is the same resononance as you will get when wind blows across booms and masts that have larger gaps in them,like in mast furlers.......

cure ,havent worked that one out yet.......

I have an in mast furler on my boat. The factory documentation goes into this problem at some length. The phenomenon is apparently called "fluting", and my boat came from the factory with an "anti-fluting device". The factory pamphlet says that the mast will begin fluting with the wind anywhere aft of abeam and no sail deployed. Therefore, it says, you MUST install the anti-fluting device when at the dock or at anchor. Factory stats say when fluting in 25 knts. of wind the sound can be heard from 2 miles. Definitely enough to annoy the neighbors!
The anti-fluting device is simply a doubled strip of stiff plastic material which slides into the slot and is hoisted to the masthead, filling the slot. It's a pretty hefty chunk of gear for my 76' mast slot, but it still only takes a couple of minutes to hoist. I always do it, goodwill in the marina is priceless, and after living aboard for 15 yrs. halyard slappers etc. drive me crazy...
Don't know if this has anything to do with your boom vibrating, but I suppose it could. Maybe if you tried some sort of anti-fluting device...

[atoll]

Originally Posted by minaret

I have an in mast furler on my boat. The factory documentation goes into this problem at some length. The phenomenon is apparently called "fluting", and my boat came from the factory with an "anti-fluting device". The factory pamphlet says that the mast will begin fluting with the wind anywhere aft of abeam and no sail deployed. Therefore, it says, you MUST install the anti-fluting device when at the dock or at anchor. Factory stats say when fluting in 25 knts. of wind the sound can be heard from 2 miles. Definitely enough to annoy the neighbors!
The anti-fluting device is simply a doubled strip of stiff plastic material which slides into the slot and is hoisted to the masthead, filling the slot. It's a pretty hefty chunk of gear for my 76' mast slot, but it still only takes a couple of minutes to hoist. I always do it, goodwill in the marina is priceless, and after living aboard for 15 yrs. halyard slappers etc. drive me crazy...
Don't know if this has anything to do with your boom vibrating, but I suppose it could. Maybe if you tried some sort of anti-fluting device...

ha ha!! was on a moody 67 a few years back,up and down the red sea and around the agean and ionian,the hum drove us to drink!!!!,fortunately the owner was paying.........

[hogfighter]

Mystery solved.....after taping up all holes on the boom (to no avail), I was holding onto the Topping Lift for support. I could feel the sound reverberating through the line! I slackened the line, no more sound. Thank you all for the help!