bad vibes

[gstej]

Hello,

We have a Pacific Seacraft 37 that is new to us. At the dock we are able to feel subtle vibrations below that we assume is harmonics (vortex shedding)? We are wondering how to confirm. I cannot feel or hear any vibration in the mast, although the halyards when tight do vibrate in a breeze. It is felt off and on, day and night. Not clear if it is related to windspeed.

I should mention that we experimented with a large fender up the mast as well as wrapping the mast with halyards in a spiral, neither of which seemed to help. There have been two occasions where even in near calms I have felt the vibrations below, and even standing on the dock next to our slip. We have done many, many experiments to attempt to find the cause (shock cords on shrouds, different docklines, moving halyards, playing with the topping lift and mainsheet tension, etc.)

When we first got the boat we ordered new rigging that matched the original with the exception of the lower terminals that are Sta-loks. After our mast was stepped we had a local rigger come out to assist us with tuning. It is a masthead rig with an inner forestay and running backs. Everything is 1x19 stainless and correctly dock-tuned (prebend, in column, slight rake) except the jibstay which has the furler. I am not confident that the jibstay tension is correct but in an effort to deal with the assumed harmonics I began tensioning it. I put the loos pt-3 on our backstay (already tensioned to ~12%), and monitored it with each turn on the forestay, stopping when I saw a turn in the forestay start to tension the back. I worry that I have overtuned the jibstay but have no method to confirm its tension short of removing the furler entirely. (Our jibstay has a profurl "classic" furler).

Our current settings per loos pt-3

capshrouds (9/32") both 17 (11%)
forward lowers (1/4") both 11 (12%)
aft lowers (1/4") both 7 (8%)
babystay (1/4") 2 (our running backs are slack)
backstay (9/32") 19 (12%)
jibstay (5/16") unknown

Is harmonics the only likely cause of the vibrations below?

Thanks very much in advance.
g