Banging sound in mast on anchor

[Elcano]

Hi,

the banging starts with a light swell already and is quite disturbing during the night. 
I tightened all the lines/halyards that are running through the mast, but no effect. 
All I can think of is the newly installed radar and the data cable. Is that possible and do you have ideas how to stop it?

Thank you.
Thomas

[Charlie-Bravo]

I presume this is a recent development given your deduction that it could be due to the recent additions, and you haven’t also got in mast furling with a new racing sail installed.

Is it a tap, bang, clatter, rattle, slap or ping? (other noises can happen)

Lets hope it’s not the new radar it’s self coming loose, or falling apart internally, but as your avatar shows you like a trip up the mast it may be worth popping half way up to give it a shake, little rattles always seem louder with a mast attached to the offender, especially when you are trying to sleep.
Whilst you are up there, if you are not sailing alone, get a person to hop from one side of the boat to the other to induce swell like movements and the associated noise, it may help with the deduction process.

If the new radar is firmly attached and no noises coming from within, you can assume it to be innocent and move on to the next suspect, the cable. Where the cable exits the mast pull the slack out of it whilst the crew are still moving from one side of the deck to the other, …. any change in frequency? or perhaps blissfully quiet . Alternatively push some of the excess cable into the mast to make the cable rest on the internal mast surface.

Have you tried slackening the lines and halyards as well?

Looking forward to your solution found post.

CB

[Elcano]

Thanks for your thoughts CB. Love your idea with the radar itself! Will double check as soon the swelly anchorage is history.
Yes, I slackened the halyards which increased the banging 🙃. The sound is very close to a the typical banging halyard in the marinas, so that‘s why I suspect the cable.

Will report the progress

[Elcano]

OK, the night sleep is secured!
I checked the radar data cable, removing the ceiling panel around the mast foot. I could feel no vibration on the cable so the cable could be ruled out. Since I have our 409 I fixed the spinnacker halyard on a life line and the main halyard on one of the hooks of the lazy bag. as I found out now, these two points are not enough, because of not enough tension to the halyards. So the halyards are fixed to two fix points on the side deck and…..banging is over!

Where do you fix your halyards when on anchor?

Cheers

[Don Reaves]

I have a Sun Odyssey 35 with traditional mainsail. After lowering the main, I move the halyard to the end of the boom where the topping lift is attached. (I don't have a stiff vang, so I need the topping lift.) The halyard becomes a backup for the topping lift.

I don't have a spinnaker halyard, but I have a topping lift for my whisker pole. I lead it forward to the bow pulpit when I'm not sailing. I don't clip it directly to the pulpit because the metal-on-metal joint can create chattering noises when it gets windy. So I use a clove hitch with the snap shackle attached to the standing part instead.

[MartyB]

Generally with halyards, do not not let them rest against and tie at the bottom of the mast. This causes a LOT of the banging you hear. I tie my 2 jib and spin halyards on the bow pulpit. Main at the back of the boom as mentioned with the boom lift.
The spin/whisker pole lift, it comes down the front of the mast, but does not bang or rattle, as it is contained by the mainsail cover. It only comes out of the mast 3-4' above the cover, and ties at the bottom, or if I pull the pole eye up, the bottom is inside the cover.
Another option that works, is to wrap the halyard out and around the shrouds. Main halyard go forward, head sail behind the shrouds to an attachment point at the base of the mast. Or out to the side of the boat too.

Marty

[Charlie-Bravo]

Having furling sails most halyards hide inside my mast, only the spin halyard requires anti bang stowage, mine is attached to the pulpit via a soft shackle . 
My neighbour in the marina popped out for a sail the other day and his fore stay broke, rig only 5 years old, he dashed to the mast and slackened the spin halyard, detached it from the shroud base where it lives when not in use, and used it as an emergency fore stay to save the mast and rig. He has now developed a soft shackle on the pulpit so it’s already more or less in position for next time.

CB

[rene460]

Hi Thomas,

I have generally found that rigging noises from the mast result from one of two factors, both wind driven.

The most obvious, the flapping of halliards against the mast, which is a forced vibration resulting from vortex shedding when the wind passes the mast with the halliards on the down wind side when the halliards are tied against the mast.  As has already been noted, adjusting the tension of the halliard does not silence them, though it often does change the wind speed at which it occurs a little.   As others have found, tying the bottom of the halliard to the rails, or around the shrouds and back to the mast, so as to keep the halliard away from the mast.

The other mechanism, I found much more puzzling.  A loud hum, a bit like a tinny on the plane, buzzing past in the night.  I have got up to have a look, only to find nothing to be seen, also nothing to be heard!  Back to bed, and there it goes again.  One night while looking for that annoying tinny, I rested my hand on the main halliard which I had tied to the end of the boom (to get it away from the mast.  The halliard was vibrating distinctly, like the string of a double bass. Too low to hear, but transmitted down the mast and audible inside the cabin, especially close to the compression post.

This is a resonant vibration resulting from the wind passing the halliard and making it vibrate at its natural frequency.  Not easy to make any useful change in frequency by changing tension.  If you have a rigid vang, you can take the halliard tension and leave it just loose, though not so loose as to whip around too much.  Better, if you also have a topping lift, is to have the two at different tension, and also wrap the loose one around the other one or two turns.   Try and wrap the turns so they contact about a quarter of the distance to the head of the mast.  This tends to create a more complex natural frequency situation, where the halliard damps the topping lift vibration and vice versa, and raises any common natural frequencies well above where they are a problem.  Again, problem solved.  You can test it by resting your finger lightly against the lines.

I have not experienced any issues with vibration coming from inside the mast, (the original question), though there are several mentions of this in the forum archives from masts with in-mast furling, and I think some from wiring.  I suspect my boats have always been on the smaller end of the range, and perhaps don’t have enough free space for things to move around.

rene460

[Elcano]

Very cool ideas guys 👍🏻. Took me a year to find out that my toping lift ist the humming culprit.
Learn a lot, thanks!

[Don Reaves]

I had the same issue that rene460 described with my boom lift, which I had replaced with a 7/64 inch dyneema line. When under tension, it hums like a banshee. Definitely within normal hearing range. That is in part why I use my main halyard as a boom lift. With the halyard doing most of the work, the dyneema is slack. It really only gets used while I am under way with the mainsail down.

There is another reason for slapping sounds, and that's when the boat rocks. That's when you can hear things inside the mast if they're allowed to move. Luckily, mine are all well constrained, so it's not a problem. However, when I added a whisker pole, the problem showed up. After checking all the lines used to control the pole, I discovered that the problem was the control line inside the pole. I recently discovered that I can take the tension off this line by raising the lower end of the telescoping pole an inch or so, which I do using the tail of the topping lift. Problem solved.

[Charlie-Bravo]

1/64” sounds a little slim Don,  even if in dyneema.

CB

[Don Reaves]

Jul 28, 2023 12:04:33 GMT Charlie-Bravo said:

1/64” sounds a little slim Don,  even if in dyneema.

CB

Quite right. It was 7/64. I've since replaced it with a slightly larger line. I've corrected the previous post.