Thanks to allof you who have responded to this issue.  What I have done so far is to tighten the sheets, (my sail hangs in its lazyjacks).  This puts tension on the topping lifts and seems to help.  I discovered that when the mast was vibrating the wind was 25 - 30 knots, gusting to 45 and it was during these bullets that the mast vibrated.  I have had 25 - 30 knots since without a problem but have yet to see stronger winds.  My steel hull of course is very good at transmitting noise and vibration. I have just moved Arion into a marina for a while since my health is a bit fragile so am feeling a bit more relaxed.  I'll try the wrapping idea if the problem reoccurs and report back.

On a Blind Date, a proa with a carbon ballestron rig there was a lot a vibration starting at

Ted Stone wrote:

That didn't come out quite right.  I meant "wrap the halyard or other ropes around the mast in a spiral in the hope that it will reduce the power of the cyclical vortex shedding or that it will change the resonant frequency of the mast.

Ted

My Freedom 39 Pilothouse Schooner now Junk - pictures soon - often shook as a Freedom rig in gusts, and she still does as a junk. She's 23 years old so the carbon fibre masts can take it. It's definitely them that shake ad transmit the sensation to the hull. Come to think of it our former boat, a Sunbird 32 schooner junk used to 'shiver' in gusts too. Ted's solution may well work - I'll give it a try and let you know.

Hi Graham,

The mast vibration is probably caused by cyclical vortex shedding.  One can get a similar effect by dipping a thin stick about 1' into a body of water and then moving it very quickly through the water.  The stick will vibrate.  At least it used to when I was a child playing in streams and ponds.  Vortex shedding creates similar vibration problems on tall thin factory chimneys and curing the problem is the reason for fitting the strakes one sees  spiralling up the outside of the chimneys .  If you Google vortex and helical there is a load of information on the web.

  If it happened to me, when the sails were furled I I would try wrapping the halyard or any rope around the mast in a spiral in the hope that it may act like a helical strake on a factory chimney dampen the natural frequency of the mast. 

If you do try this I would be interested to know if it works.

Regards,

Ted  

Well I may have sorted out the noise issue with my aluminium mast but it has been blowing 25 - 30 knots here for the last week and I have discovered that the top third of my mast still likes to vibrate in stronger gusts at anchor - I have not managed to sail the boat yet except twice in 10 knots of wind and smooth seas, when all seemed well.  At anchor, it is nice and quiet at 20 knots but then the wind gusts and off it goes.  I think vibrates may be an understatement.  Perhaps I should say it shakes, or occilates, and when it does it makes the whole hull shake.  It doesn't happen continuously, just in bursts.  I don't expect to suffer structural failure (at least I don't think so) but it is an extremely unpleasant feeling.  I tried tightening up the main halyard and even put the spare halyard out onto the bowsprit and cranked it up as a temporary forestay but putting the mast in tension made things worse.  The boat began bucking like a tethered bull.  Of course, there was no support athwartships, just fore and aft.  I find the least vibration occurs when I keep the halyard just tight enough to stop it flapping around but with no real tension on it.  I put a swifter around the halyard and topping lifts as high as possible to dampen movement also, as it looks like the wind pumps the halyards and lifts and this flexes the mast but I am not sure.  I don't know what the hell is going on.  I am beginning to wonder if my mast is made from an inferior grade of alloy.  I also wonder if my partners are properly engineered.  I could weld in a couple more knees to tie the deck beam into the hull and stiffen the cabin side more but I think any movement is likely to be in the fore and aft plane, and anyway I think the basic structure is strong enough.  Not that I plan to test it by lying ahull in a gale any time soon.  I am a bit rattled and plan to retreat into a marina and just daysail in fine weather until such times as I can sort it out or reassure myself I don't have a serious problem.  I remember David and others saying they got some vibration at anchor in certain windspeeds but I seems to me that mine is abnormal.  Hopefully I will get to sail the boat soon and see what happens under sail but I suspect that the mast will stand up to its sail fine.  Steel is notorious for transmitting vibration and I think that this is what is happening, rather than the basic structure being inadequate.  The question is, how much flexing / vibration is normal when anchored in strong winds?