Mast Vibration

[chas]

I have noticed that my mast vibrates in the fore and aft plane in certain wind conditions on my mooring. Normally the wind is fairly light - 10 - 15 kts. The only control I seem to have is the babystay - cap shrouds and forestay/backstay go to the top of the mast and the inner shrouds are in the wrong plane. I have tried adjusting this but with no effect. I have not experienced this sort of vibration before but this is the first time that I have set up the rigging myself on this boat. Is it unusual? Will it cause damage? Is there anything I can do? Would be grateful for any advice

 

[Guest]

Chas I've had this to and it can drive me nuts trying to get rid of it especially at night. Its the resonance in the rigging. I have had some success by adjusting the topping lift/main sheet/ kicking strap and BTW it wont cause any damage

 

[vyv_cox]

Sadler 34 is prone to this, I suspect because the babystay to mast angle is very acute and it is difficult to get sufficient tension on it to be effective. Babystay should not be tightened too much anyway, maximum mast displacement about half its fore and aft thickness. There's probably not a lot that can be done but I have toyed with the idea of hoisting a slide up the mainsail track and attaching a runner to it, tensioned off aft. This might help although I have never got around to trying it.

 

[oldsaltoz]

G’day Chas.
Before you go making any major adjustments to your rig; have you tried letting your mainsheet out a little. The wind over the topping lift line can cause the condition you describe. Let us all know what you find.

Andavagoodweekend Old Salt Oz……

 

[chas]

Thanks for the help. I will try to get out one evening this week and have a play.

 

[dickh]

Try tying a length of cord to the offending stay and then to another stay or the mast, I have tried this on a boat I had and it worked, but you will need to experiment.

 

[VMALLOWS]

Do let us know if you solve it......the mast 'panting' on my Sadler29 drives me crazy some nights (usually light winds, significant chop). I've tensioned the babystay as much as seems reasonable (about 2" forwards mast bend).

 

[pvb]

Vortices...

I experienced a nasty case of mast pumping on a 36ft Westerly in the mid-80s. No amount of rig tuning would cure it. In the end, the mast makers (Kemp, I think) admitted it was a known problem, caused by wind vortices around the mast. They provided an anti-vortex strip, which is a length of flexible plastic, about 5" wide, which is hoisted in the mast groove. The strip helps to break up or shed the vortices. It worked, but was a pain to use.

 

[chas]

I tried playing around with the topping lift and the mainsheet. I find that If I have the former hardened a little more than normal and leave the latter slack, it eases the problem, although it is still detctable. I will try a little more experimentation.
Thanks for the help.