Oscillating mast

[michaelanthony]

Always a wealth of knowledge on this site!
Has anyone (especially Hunter 34 owners) had problems with a
oscillating mast. I'm sure my rigging is tuned correctly but with winds
around 20 knots I can feel a slight occillation with or without the
sails up.
Any suggestions?
Thanks,
Mike

 

[Benny]

Any oscillation or mast pumping I have experienced has been due to uneven tension on one or more shrouds.

 

[Allan12210]

I have felt a resonance that is due to the forestay being loose. It is increased when there is rolled up jib present. I reduced the resonant pumping by tightening backstay turnbuckles slightly. I've never really eliminated it.

 

[Alan]

Mast oscillating or pumping is due to your rig being too loose. You say you're sure the rig is tuned correctly. How do you know this???

 

[michaelanthony]

Thanks for the assistance.
Maybe my rig is not tight enough. To "tune" I'd take her out in 12 to 15 knot winds (just to where I feel the main needs a reef, make a note of the stays on the opposing side, if there is any slackness then on returning to the slip I make make two turns on aft and side turnbuckes. After doing this a few times I now have no slackness in any stay at any point of sail. But Alan, maybe this is still not enough. How can I tell or do I need a guage.
Thanks,
Miker

 

[Alan]

Mike,

For the sake of your rig and to make your life easier I would highly recommend using a tension gauge such as Loos. The investment in this gauge is well worth the results.
You can check things like mast rake a nd mast pre-bend without a gauge. But to get your setting correct and repeatable the gauge is very easy.
The Hunter 34 has a B&R rig which means the pre-bend is set while the mast is still down but you can make adjustments (though more difficult) after its up. Mast rake is simply set with the length of the headstay. Drop the main halyard with a weight to suspend just above the boom. The distance from this point on the boom to the mast is the amount of mast rake. But the cap and intermediate shrouds should be set with gauge to adjust headstay tension and masthead leeward bend.