Vibrating jib!?

[kilkerr1]

Ello all

Had a great days' sailing this Saturday, Thames Estuary, Medway etc. Much fun was had bounding (for us - I use the term loosely) along to windward in Santa Teresa, and we got up to about 5 knots, which, for me, was most exciting. However, the closer to the wind we got the jib would start shaking, sort of vibrating, once so much that the entire boat (22ft) vibrated slightly too. We tried tightening the sheet more, easing off, all sorts, but the thing kept thrumming away in a very strange way. It was worse when on a starboard tack, strangely enough. So - I'm pretty sure it's not meant to do that. We're still quite new to all this and I'm sure there's a simple explanation, but it's eluding us at the moment! Any ideas?

Cheers.



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[Twister_Ken]

Look at the leech line. This is a line which runs down a 'hem' on the leech of the genoa. At some point near the bottom of the leech it emerges near a cleat (usually plastic). Heaving in an inch or two on this line and cleating it tightens the leech and should stop the sail 'motoring'.

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[qsiv]

Or, if you have any adjustment try moving the sheet lead forward a stop or so... in truth Kens sugestion is likely to be the one as in a fresher breeze you dont want the leach too tight, particularly if the sail has significant overlap.

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[kilkerr1]

Righto, thanks, sounds like it was a simple one after all! Next time we take her out (unfortunately not this weekend, hrrumph) we'll put your suggestion into action.



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[DeeGee]

Was your whole rig being 'vibrated' by the jib - at something like one or two cycles per sec (hz)? If so, this is panting, and is due to the whole rig, and in particular the fore/back stay being too slack. Whole lot goes whoom,whoom,whoom....not nice.

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[jzaat]

If you are not referring to just the leech fluttering ( which Twister Ken answered already) but more the whole jib:

I experienced this a couple of times on my previous boat, also significantly worse on one tack. It appeared that the presence of a spi-halyard being tied to the railing caused enough turbulence apparently to cause the whole jib to vibrate as a result.
A smaller flagline on the other tack seemed to cause the same effect to less extent.
This only appeared a certain windspeed, certain sail setting (to windward) and certain angle of heel it seemed. Tying the halyards out of the way along the mast solved the problem....


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[pugwash]

I had exactly the same problem a couple of weeks back and fixed it with the leech line but I'm stilling having trouble getting the lead of the jib sheets right, especially when I've got in a couple of rolls (or more). As I understand it, a projection of the sheet should bisect the luff. Great on paper but hard to detect by eye from the deck. I've been working on the basis of making sure all three tell-tales are parallel but those get rolled up. Obviously one could do it click by click on the track but is there a better way? The number of rolls is not always exact, so marking different positions on the track doesn't work. I'd sooner find a foolproof way of judging it by eye. Any good advice?

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[MainlySteam]

I am assuming from your post that you have a furling foresail and seek to be able to readily relate the genoa sheet car position to the various extents of furling. The easiest way I think to keep track of sheeting positions for various reefing extents is to have tack marks stencilled or sewn along the bottom of the foot of the sail. These are sometimes already on sails when delivered from the sailmaker, but usually they have to be added oneself. They are usually placed at the points where the area of the rolled foresail matches hanked sail sizes, so a 150% genoa would have marked along its foot the points when rolled to the sail overlap is 135%, 110% and 85%, but for casual purposes is not too important. When one finds the best sheeting position then the genoa sheet car position for each of these reefing points can be marked on the deck or track for future reference.

John

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[kilkerr1]

Thanks for all sugestions, though some refer to furling/rolling foresails - 'fraid we don't have roller reefing, just old fashioned up 'n' down type (and the term for that would be..?). Oh, but we do have twin forestays side by side...

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[Twister_Ken]

Term would be 'hanked-on headsails' if they attach by piston hanks (brass clips every 18" or so.)

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[Guest]

Move your track eye forward as far as it will go. Now pass a line through with a small block or eye in the end. Pass the sheet through it and bring the other end of the line back to a cleat.

Now set the job / genny and haul in the sheet to approx. what you want. The set of the sheet will be totally wrong and too far 'aft' ...... Now haul in the line that passes through the eye ..... the sheet will be brought downward until you stop at the proper sheet angle.

This method .... using a barber hauler is an old way to fix a problem - and it works a treat without having to replace / move / modify existing fittings.

I use it on my 1/4 ton cup boat and we won baltic sail reagtta some weeks ago - so nothing wrong there !!!!


<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !