The wires inside my mast are encased in a PVC tube. I would think the banging you hear is the tube against the mast.

I could see the pvc thing. That leaves me with 2 questions: How did it come loose sailing in 5 knots of wind, and how do I fix it? Really not wild on the idea of pulling the mast right now! Guess I may have to deal with it.

I installed a gently-used radar unit last summer and became a little more familiar with the internal layout of the mast, so here's my 2-cents.

Inside the mast is the PVC chase containing the bulk of the wiring running up the mast. Your tube should be on the front of the mast, port side, slightly offset from midline. You can tell by a small pop-rivet about every 6-8 ft of height. My guess is that either one of those broke loose, or the rivet didn't catch the chase pipe when originally installed.

I would take a small diameter drill, and carefully drill out the rivet closest to the noise (with a depth-stop, to make sure you don't foul any electronic wires). You can then either put in another rivet to hold the pvc chase in place.

I tried to get into the chase for my readar wires, but it's pretty hard to get into with the mast up (drill wants to push the pvc away). Hope that helps!

I dropped the other option on my "either" comment, but didn't delete the word... (was going with tap hole and put in a screw, but I don't think the pvc would hold too well!)

Tom something else that has been done. Is that your right about the pipe pulling out of the pop rivet. Have seen it done where the old one is drilled out then taking coat hanger and bending it 90 degrees and inserting it into the old hole which has the rivet drilled out and pulling the pvc tube back to the mast. Then drilling a new rivet hole close by the old one and inserting a new rivet. Then filling the old hole with a rivet. Probably the pvc pulled out as it was banging around and made the hole for the rivet bigger

Good point Randy- Probably would ensure it didn't just come out again from the enlarged hole, and pulling it in tight would better guarantee no slack in the tube (and potential for continued noise).
Tom

From your description that the vibration shakes the whole boat, it is clear to me that the problem is NOT something loose inside the mast. (Although you could have that too.) You are experiencing common "mast pumping." This is caused by wind on the mast, setting up a vibration. While I can help you with the diagnosis, I'm not helpful with the solution. It has to do with the way the rig is tuned. I tune my boat for performance, have mast pumping, and just live with it. Although my mast doesn't pump unless the wind is up around 12 - 15 knots.
Fred Jackson
Amante #2209

Our boat is a mk11 and does the same thumping occassionally. The wind has to be fairly strong and from certain directions to start the ocsilations. Next time you are aboard your boat and it starts the thumping, stand beside the mast and grab it and apply side pressure on the mast and see what happens. I can't help thinking it is just what Fred suggests. We had a c30 that did that all the time, and one jsut ignored it.

Togaygo,
I've heard that by disrupting the air flow around the mast that you can stop the pumping. One way I heard of doing that is to take a spare halyard (spinnaker?) and wrap it around the mast a few times. You obviously can't do that above the spreaders, but by starting just below the spreaders, and putting a few (2-3?) wraps around the mast, it should stop the pumping....or so I've heard! ;)

I too have suffered from this, it is disturbing when sleeping aboard. It could be the boat shaking barnicles I thought at first when looking out on deck that it may be due to the fact that I keep my jib sheets tight and I noticed them bouncing when this occures. Im am not sure if it is the mast pumping or it could be the headsail wrapped around the foil pumping or occilating. Has anyone experienced this with the head sail removed?

Steve,

I have also been disturbed, many times, by the wind pulsing the furled jib, that pulsing sets up a harmonic shaking of the mast, that causes something in the mast, halyard, antenna wire, mast head light wire, or all of them to bang against the mast and clang-clang-clang all night long.

(My comments are all related to being tied up at my marine slip.)

I have spent a lot of time trying to come up with a good solution to this problem, I have tried tightening the internal halyards and I have tried slacking the internal halyards. I have tried to tighten all of the standing rigging to "tune" out the bounce but so far nothing has worked all of the time.

This past season I tried to tension the jib sheets (with the jib furled) and this has helped the most. By controlling the ability of the jib to vibrate in the wind, you can reduce the mast bouncing but not eliminate it entirely.

When the mast pulses, the whole boat shakes and this shaking is as annoying as the clanging. The tight jib sheets helps reduce this shaking quite a bit.

I have considered several solutions and I have an advantage over many in this group in that I remove my mast every season when the boat is placed indoors for the winter.

My current plan is to use some kind of rubber, inflatable, softball sized, item that can be shoved up the mast 15 or 20 feet and with a hose that leads to the base of the mast, hand pump the rubber bladder so that it provides interference with the banging items.

I seem to remember that just like a guitar string, if you could shorten the length of the wire or halyard that is banging inside the mast, you change it's harmonic frequency. This change might make it impossible for the pulsing mast to get the wire moving enough to make any noise.

The right rubber bag for this job might be a drug store ice bag.

Another idea I just had is to use a blood pressure cuff with an extension on the squeeze bulb.

I'll have to keep my eye open for one at a garage sale.

It will stay on my project list for this winter (again!)

William, what hull number are you? You don't post this in your signature, so I don't know whether you have a Mk II similar to mine.

My mk II has a similar resonance issue, but it seems minor compared to what you're describing. Rather than tightening up everything to minimize it, though, I have gone the opposite direction...slacking everything. Still, even though minor (we can't hear it in the V-berth, for example), I still would like to find the source. As you remove your mast annually, I wonder if you could photograph the interior of your mast and post an on-end view for us to have a look at. I would like to better undertand the conduit business, where the wires run, and where the halyards run.

Larry,
I can do that for you right now. A couple of years ago I wanted to put together a collection called "Nooks and Crannies". Unfortunately only one or two members sent me stuff, so it got shelved. Below is one that was sent to me, showing the base of the mast, the wiring conduit, and the wires coming out of it. You won't see any halyards because they exit above the deck, which is at least 12' above the base.

Larry,
My boat is a 1993 Mark 11/2 tall rig.

I went looking on my computer for my picture of the inside of the mast but it's too dark to be useful.

Tom's photograph is much better but it is not representative of my mast. My mast has the TV antenna wire and the radio antenna wire outside of the conduit. I am sure these are the source of my mast clanging.

Tom, thanks. Now I understand the situation. If I had a borescope I could have a look in there to confirm that all the wiring is indeed running within the conduit. I'll have to talk to my surgeon about borrowing his proctoscope.

Bill, you are probably right. If I have a subdued issue because I only have halyards outside of the conduit, probably the case, then you would have a serious noise issue with the combination of halyards and wiring slapping around in that large mast tube. If you pulled the stick you could reroute the wiring fairly easily, as well as verify that the conduit is properly attached along its full length. Not a bad idea if livability is an important issue, as it seems to be in your boat's case.

If you're the kind of person who likes puzzles, it would be an interesting exercise to reroute the two errant wires with the stick in place.

Of course, this only addresses the symptom, not the underlying cause: the resonance in the rig with certain wind directions and velocities. I am going to take the sails off the boat this week, so over the winter I'll try to visit during various wind events to determine the presence (or not) of the resonance with bare rigging.

Just took the jib off, and I noticed that if I shook the bare furler, the forestay was rattling loudly inside the furler...so there's another potential source of the problem.

Just paid the boat a visit today. I tensioned and slacked every halyard I could think of, pulled down my YC burgee in hopes that it may have been the flag creating the resonance, did an Indonesian sabooki dance on deck, kicked some stuff, got frustrated and left. Mast still pumping. I do think I was able to rule out the pvc wire lead though as it sounded like a halyard knocking around in there rather than the harder rapport of plastic.

Was at the boat on a gusty day recently and can confirm that the resonance I have commented on is still present even though the sails are off the boat. Sounds like a sort-of-metallic vibration that eases in, stays for a short while, then fades out, total duration 5 to 10 seconds. While it is noticeable in the salon, we cannot hear it in the V-berth.

My guess is that it's the forestay rattling inside the headstay furler.

Any comments? Has anyone come up with a silencer for this?

You're right, there are two separate issues.

Mast Pumping: see [url]http://www.c34.org/faq-pages/faq-mast-pumping.html[/url]

Wire slaps in mast: We had the same problem when we bought our boat 10+ years ago and it was 12 years old at the time. The PO, for some reason, had been able to live with wire slaps for those ten years. Perhaps he never slept on the boat! Turned out to be the anchor light wire which the factory had cleverly installed OUTSIDE the conduit. Go figure... Once correctly slid into the conduit the slapping went away.

Testing the tension of lines on deck makes a lot of sense. Different winds do different things to our jib sheets at anchor so we adjust accordingly. Also, many folks like their burgees hanging, but we find they make more noise than they're worth at night.

I believe it's mast pumping. My 1988 Cat 36 MKI does this in as low as 5kts at rest at like 45 degree wind angles. As the boat spins around at anchor you can feel and hear when the pumping starts and stops and watch the wind angle. I can confirm that wrapping a halyard around the mast resolves about 90% of the issue. Thank goodness because that pumping down below is scary as hell frankly. It just feels too painful on the boat to me. We always wrap the mast now whether at dock or anchor. It's just a couple times around from below, no need to climb at all. I describe my issue and show the wrap in one of our stupid videos ;-) This issue seriously bothered me, even had a rigger out to completely tune the rig. No change. He said some masts just pump and it is what it is. https://www.youtube.com/watch?v=c8AV8XRvDZs&t=5s   my description of the pumping is right at the beginning and the images of my wrapping halyards fix is at 10:15. Hope it at least helps to know these boats just do this and it's "normal". I still don't like it.