Rhythmic jib

[Ilanortho]

Hi;

Request advice on Hunter 34 self furling 110 genoa.

In a good breeze (>16 knots) the whole forestay and genoa rhythmically pulsate/ shiver. Is incredibly annoying and seems it would be damaging after a while. I have adjusted the jib car, tried tightening and loosening the halyard, jib sheets and the shackle and nothing seems to work. Occurs even when the telltales look good. Is like a harmonic vibration from hell.

Any suggestions?

Thanks. Ilan

 

[kloudie1]

Leech line tightened? This is the little line in the leech of the sail that can be tightened and cleated in place. Pull it in (tighten) until the leech just stops shaking and cleat it there. Letting it shake the rig will induce a fatigue failure in the future..

 

[Jackdaw]

I would check your rig tension. In particular your forestay. It's probably too loose, and in particular for that amount of breeze. When the forestay is too loose in big breeze, the trimmer will often over-trim the sail in an attempt to flatten it, as the sail has way too much depth in it due to the loose forestay (sag). This flattens the sail but also pulls the forestay back, where often the leading edge will quiver in the pressure.

Forestay tension.

 

[Ilanortho]

Sounds exactly like what may be happening; the whole thing shakes. Thanks. Ilan

I would check your rig tension. In particular your forestay. It's probably too loose, and in particular for that amount of breeze. When the forestay is too loose in big breeze, the trimmer will often over-trim the sail in an attempt to flatten it, as the sail has way too much depth in it due to the loose forestay (sag). This flattens the sail but also pulls the forestay back, where often the leading edge will quiver in the pressure.

Forestay tension.

 

[Ilanortho]

Will check; don't recall a line that can be cleated. Thanks. Ilan

Leech line tightened? This is the little line in the leech of the sail that can be tightened and cleated in place. Pull it in (tighten) until the leech just stops shaking and cleat it there. Letting it shake the rig will induce a fatigue failure in the future..

 

[kloudie1]

On a darker note, Jackdaw is right.. and ya need to check the infamous compression post/ beam notes on the site here to check yours to make sure the mast support hasn't gotten spongy and allowing the forestay to get slack when under load. Almost all 34's are going to encounter this problem sooner or later unless extraordinary care has gone into sealing the mast base after the mast has been removed.

 

[Jackdaw]

Sounds exactly like what may be happening; the whole thing shakes. Thanks. Ilan

I forget what kind of rig a H34 has (masthead B&R?), but usually adding backstay will help tension the forestay and reduce sag. But I'd also look at your overall base tension.

 

[kloudie1]

It is the "belts and suspenders" B&R.. A B&R with a backstay.. I had forgotten that when my mast base went soft, I thought I had great tuning at the dock, but under load, stuff would loosen up a good bit.. and the jib did as you say, Jackdaw.

 

[Ilanortho]

Now I'm starting to feel some chest pain!

I read those posts before I bought this scow and had the surveyor address this issue during the survey, but he could not find evidence of this and was reluctant to start taking the trim completely off to check it.

On a darker note, Jackdaw is right.. and ya need to check the infamous compression post/ beam notes on the site here to check yours to make sure the mast support hasn't gotten spongy and allowing the forestay to get slack when under load. Almost all 34's are going to encounter this problem sooner or later unless extraordinary care has gone into sealing the mast base after the mast has been removed.

 

[Ilanortho]

Sorry but what is B&R?

It is the "belts and suspenders" B&R.. A B&R with a backstay.. I had forgotten that when my mast base went soft, I thought I had great tuning at the dock, but under load, stuff would loosen up a good bit.. and the jib did as you say, Jackdaw.

 

[kloudie1]

The guys who designed the standing rigging on the H-34 (and a bunch of other Hunters). Here is a snippet to read:
http://www.boats.com/reviews/boats/the-bampr-rig/

 

[Ilanortho]

Very fascinating. Thanks

The guys who designed the standing rigging on the H-34 (and a bunch of other Hunters). Here is a snippet to read:
http://www.boats.com/reviews/boats/the-bampr-rig/

 

[jeff356]

Very fascinating. Thanks

I have a 2003 356 with no backstay and recently have had the same pulsating issue with the jib to the point that it shakes the mast when sailing in 17+ knots. Only seems to occur on certain points of sail, not sure if more so when jib is partialy furled and leading edge is not smaller.

Tried tightening the halyard, sheets, adjust cars etc. to no avail. Seems the forestay might be a little loose. Is that easily checked / adjusted? Guessing you need to bring down the sail.

Any thoughts on what to look for or is a rigger to be called?

Jeff
s/v LegaSea
2003 Hunter 356

 

[Dan_Y]

The mast would pump and jibe shake on our '91 30T conventional fractional when going up wind. Adding a bit more prebend to the mast by tensioning the cap shrouds fixed that problem but requires the rig to be retuned. Don't know enough about rigs though to know if that's your problem. Just a thought...

 

[ALNims]

Jackdaw is most likely right. I had the same problem. I recommend that you get a LOOS tension gage to help you tension the rig. Selden has a good book on rig tensioning. I have attached an electronic copy. There is a section on B&R rigs too.

 

[jeff356]

Thanks for all the weigh in to the issue, hope I did not hijack this original post.
I think you are correct in the that the forestay is a little loose contributing to the issue, just from an informal walk around the marina and talking to other sailers and Hunter owners. Did some research on how to raise the ProFurl furler to get access to the forestay adjustment.
By way of background this is my second year of sailing along with this boat and this year I wanted to sail more and motor / motor sail less. In an attempt to accomplish this I have been working more with sail controls, which included car movement to sailing conditions. This year seems to be pretty good on wind conditions and this last outing was no different. Expecting 12 - 17 knots I moved the cars BACK and went out, but as the wind built and I furled the jib but did NOT move the cars forward to keep the same angle of the sails against the sheets. I think this only further added to the issue and possible why this was not an issue prior as the cars were always in the middle and never adjusted. Always need to be aware and put the pieces of the puzzle together.
Enjoy time on the water but also the challenge to keep learning and applying what has occurred prior.

Jeff
s/v LegaSea
2003 Hunter 356