Jib Shudder

[Jeff D]

I was out yesterday for a great sail - 15 - 20 in almost flat seas. On the way back in I was close hauled and the jib started a rhythmic shuddering. Based on the telltales both the jib and main were trimmed correctly. I tightened the leech drawstring which helped but did not eliminate the phenomena/problem. The boat is a Ty daysailer with a working jib. Any thoughts or suggestions?

[Steve Laume]

After applying some tension to the leach line, you could try moving the jib cars a bit. I am not a great authority on sail trim but I would think moving them forward a bit could help tension the leach. I may be all wrong and in fact moving them aft might help so my approach would be to play with them until things looked better. Was your halyard nice and tight? These are pretty windy conditions where I am lead to believe you want a fairly flat sail.

The best way to deal with this problem might be to buy a brand new jib. Nice and flat with good air flow, where you would be sure the shape or condition of the sail was not to blame.

I would be playing with the controls and if I couldn't control the flutter would caulk it up to an older sail and live with it, Steve.

[tjr818]

I too get this occasionally on my CD27. I have roller furling, and sometimes the oscillations seem pretty sever. The other day I was out in 15-20kts with a reefed main. I rolled the working jib about 1/3 in and the oscillation stopped. I am thinking that it is a question of forestay/backstay tension. Anybody have some ideas?

[Jeff D]

I have CD roller furling so the luff tension is hard to adjust. This is a 5 month old working jib with no adjustment to the jib cars (I have fixed bullseyes on the cabin top

[Jim Evans]

I fly a yankee on my CD33, and my traveller does not extend far enough forward along the toerail. My 130 genny is fine, with no shudder at all, but my yankee is a problem when going to windward. I needed to find a way to tighten the leech of my yankee, because I was having exactly the same problem as you with jib shudder when going to windward.

Anyway, I decided to try rigging a snatch block to my aft shroud turnbuckle, as you can see in the first photo. It solved the jib shudder problem. Granted, it's sort of a jury-rig affair, but short of extending my traveller further forward, it's an easy and relatively inexpensive solution. So, now I rig a snatch block on both sides when I fly the yankee. I would not use this rig in any winds over 15 knots or so, as I don't like the idea of creating a load on the turnbuckle that is not in line with the shroud. I use a lightweight webbing to attach the snatch block as a weak link in the rig. It's hard to see in the photo (I've not yet figured out how to upload good quality photos despite Cathy's detailed instructions!) but the webbing is attached to the turnbuckle near the pad-eye. The 2nd photo shows the original sheet angle on my yankee.

Although the 130 is a better performing sail for boat speed, I like using the yankee for better visibility, and it's just easier to handle.

<IMG width="600" src="http://i855.photobucket.com/albums/ab11 ... G_1399.jpg">

<IMG width="600" src="http://i855.photobucket.com/albums/ab11 ... 0195_1.jpg">

[SurryMark]

As an experiment, you might try pulling the clew down, just by tying a line near it and running it through anything down by the deck. (Loop on the stanchion fitting?) Or have somebody hold it down. I believe this is called a barber haul. If it works for you, you can figure out how to rig it. A snatch block is handy, but expensive.

((You were out in 15-20 knots of wind with a nearly flat sea?))

[Joe Myerson]

((You were out in 15-20 knots of wind with a nearly flat sea?))

Mark,

He's on the Chesapeake, remember.

--Joe

[SurryMark]

((You were out in 15-20 knots of wind with a nearly flat sea?))

Mark,

He's on the Chesapeake, remember. :)

--Joe

Ah, the winter wonderland I dream of, instead of hauling Tula just because the water gets hard.
(sorry for the thread hijack)

[Duncan]

You appear to be trying to use your genoa track, instead of the inboard track for your working jib (this jib track is empty in the first photo you posted).

It looks as if you need track cars and blocks for your jib tracks. These are available from Garhauer at reasonable cost.

I fly a yankee on my CD33, and my traveller does not extend far enough forward along the toerail. My 130 genny is fine, with no shudder at all, but my yankee is a problem when going to windward. I needed to find a way to tighten the leech of my yankee, because I was having exactly the same problem as you with jib shudder when going to windward.

Anyway, I decided to try rigging a snatch block to my aft shroud turnbuckle, as you can see in the first photo. It solved the jib shudder problem. Granted, it's sort of a jury-rig affair, but short of extending my traveller further forward, it's an easy and relatively inexpensive solution. So, now I rig a snatch block on both sides when I fly the yankee. I would not use this rig in any winds over 15 knots or so, as I don't like the idea of creating a load on the turnbuckle that is not in line with the shroud. I use a lightweight webbing to attach the snatch block as a weak link in the rig. It's hard to see in the photo (I've not yet figured out how to upload good quality photos despite Cathy's detailed instructions!) but the webbing is attached to the turnbuckle near the pad-eye. The 2nd photo shows the original sheet angle on my yankee.

Although the 130 is a better performing sail for boat speed, I like using the yankee for better visibility, and it's just easier to handle.

<IMG width="600" src="http://i855.photobucket.com/albums/ab11 ... G_1399.jpg">

<IMG width="600" src="http://i855.photobucket.com/albums/ab11 ... 0195_1.jpg">

[Jim Evans]

Thanks, Duncan, for your suggestion of using my inboard jib tracks to control jib shudder. I should have addressed that, as that was the first thing I tried. Granted, the inboard tracks get the block about 18 inches further forward, it was not enough to control my jib shudder.

I never liked using my inboard tracks either, for several reasons. Sure, they help me point a little closer, but off the wind, the jib sheets would chafe on the shrouds. And when I went forward, my feet would never fail to find those blocks on the inner tracks. So, I've removed the blocks from the inner tracks, and left them stowed below.

Since my first post on the jib shudder issue, I've installed a 2nd snatch block so I have one on each side now, and I'm satisfied with using that method to control my jib shudder on the yankee.

[Carl Thunberg]

Jeff,

With fixed jib leads, you don't have a lot of control over the shape of the jib. I also have fixed jib leads on my boat. Not to point out the obvious, but bearing off a bit would probably help a lot. Does it happen when you're pinching?

I'd also suspect the cut of the new sail, but it takes a sailmaker's trained eye to figure out what might be causing it. I'm thinking the culprit might be a slight roach to the leech of the sail, but that's just a hunch. Usually only mainsails are cut with a roach. Andy Denmark is, or was, a regular contributor to this Board and this is his area of expertise. Hopefully he'll read this and speak up.