7 November 2001 Greg Customer Service I have four questions re my h356 hull 271: 1. How much should the forestay sag to leeward? 2. What is the correct angle between the boom and mast? 3. Why does the leech shake when close hauled. (In mast furling) 4. What could cause the arch, pedestal and cockpit deck to vibrate when close hauled. All these questions are related to the same problem. When sailing in 17-20 kts winds with gust to 25-27 last Saturday, the arch, pedestal and cockpit deck began to vibrate and shake violently. The arch was moving 3/4 of an inch at a little greater than 60 cycles a minute. The pedestal was moving close to two inches at about 40 cycles/minute. The cycles were counted once and could be off. The deck was vibrating enough to cause my legs to shake. The vibration did not seem to be coming from the rudder because the wheel was moving less than the pedestal. Only the deck section behind the pedestal was vibrating. My daughter, who was sitting just forward of the wheel did not feel any vibration in the seat and only a little in that part of the cockpit deck. If the mast and shrouds were shaking, we did not notice it. The main was reefed between three and four feet. The jib was furled about 30 inches. Heel was about 15 degrees increasing to 25 degrees in the gusts. Pinching or falling off with a slackened main sheet stopped the vibration. But each time we headed up the vibrations started again. This was not a little shaking. This was violet, and in my opinion, bad enough to cause structural damage. As an architect I have just enough knowledge of stresses and strength of materials to know I don’t know enough about boat design, but enough knowledge to know this is a serious issue. When sailing closed hauled the last 6 to 8 inches of the leech flutters, even with the leech line pulled tight enough to cup the leech to windward. A bit more info: On delivery the forestay sagged at least two feet to leeward. Tied at the dock you could swing the forestay at least 18 inches in both directions with very little pressure. The dealer adjusted the rig so that the forestay movse about 6 inches when pushed and sags about the same in 15 kts. The reason I mention this is that sailing in similar conditions before the rig was adjusted did not cause the vibration - although the leech still shook. The rod kicker has been located (probably so the main saloon hatch can open) so that the main sheet cannot be 2-blocked. Really cranking down on the sheet leaves about 6 inches between the two blocks. The boom cannot be pulled down enough to straighten the leech. I believe this is causing the leech flutter? Could the leech cause a harmonic vibration? Is the rig too tight? We have had a nice 12-knot day with flat water to check the rig tension. However, my stay tension gauge went right off the scale. This is my first B & R rig so I have nothing to compare it too and feel a little lost here. Your advice and help is greatly appreciated. Will Dennehy
- Status
Experienced same leech flutter
Will, On my maiden trip with "Java", we were expericencing the same leech flutter you have described. Mike, a well travel sailor, on the boat felt the main sail was not cut properly since we could not pull down on the vang or main sheet any more and unable to flatten the main. We felt the vibrations but not as severe as you described. My furling also has quite a bit of sag but will be taken care of when the dealer comes to finish up all the little things. We were in 25 - 30 kt winds, pinching like crazy. Jim S/V Java
Will, On my maiden trip with "Java", we were expericencing the same leech flutter you have described. Mike, a well travel sailor, on the boat felt the main sail was not cut properly since we could not pull down on the vang or main sheet any more and unable to flatten the main. We felt the vibrations but not as severe as you described. My furling also has quite a bit of sag but will be taken care of when the dealer comes to finish up all the little things. We were in 25 - 30 kt winds, pinching like crazy. Jim S/V Java
Jim & Will
We experiance the same on our 260. We pull on a heap of vang and haul in as tight as we can with the mainsheet but still this incredible vibration. As Will said enough to shake her to bits or break something. My view is that we have too much bend in the mast. As the mast becomes straighter the sail takes its natural shape and so the leech becomes tighter. We have quite a bit of pre-bend in the mast (to depower the sail a bit) and so the leech is a bit floppy!! Any thoughts on this theory would be appreciated.
We experiance the same on our 260. We pull on a heap of vang and haul in as tight as we can with the mainsheet but still this incredible vibration. As Will said enough to shake her to bits or break something. My view is that we have too much bend in the mast. As the mast becomes straighter the sail takes its natural shape and so the leech becomes tighter. We have quite a bit of pre-bend in the mast (to depower the sail a bit) and so the leech is a bit floppy!! Any thoughts on this theory would be appreciated.
"Vibrations"
I dont own a 356 but a 355 which has a different rig. My last boat was a 34 with the B&R rig. Tuning the rig is not brain surgery, but it MUST be done correctly. There was a discusion somewhere else on this site about tuning the B&R so I wont get into it here, but I can tell you for sure that forestay tension is far TOO loose if you have 2ft of deflection. However, if your main sheet,outhaul, and vang are on full and you still can't flatten the main then it for sure is cut wrong! Bending the mast with your backstay adjuster also flattens the main. I suggest that you get someone from your local sail loft to go for a test sail and get his/her opinion. The vibration that you are talking about does come from leech flutter, but with an improperly tuned rig and/or poor sail shape you are not going to be able to elimanate it without addressing these two issues.
I dont own a 356 but a 355 which has a different rig. My last boat was a 34 with the B&R rig. Tuning the rig is not brain surgery, but it MUST be done correctly. There was a discusion somewhere else on this site about tuning the B&R so I wont get into it here, but I can tell you for sure that forestay tension is far TOO loose if you have 2ft of deflection. However, if your main sheet,outhaul, and vang are on full and you still can't flatten the main then it for sure is cut wrong! Bending the mast with your backstay adjuster also flattens the main. I suggest that you get someone from your local sail loft to go for a test sail and get his/her opinion. The vibration that you are talking about does come from leech flutter, but with an improperly tuned rig and/or poor sail shape you are not going to be able to elimanate it without addressing these two issues.
Leech Vibration
I only had a few weeks to sail "Some Kinda Wonderful" before haul out. BUt i did notice that trimming the main on this loose footed sail(furling version) took some getting used to. I found the vibration in the leech, although not as violent as you are describing, was due to having the outhaul too tight. The sail needed some breathing room, and sailed remarkably well on a close reach with what looked to me to be too "loose" a sail. I haven't discussed this with Hunter, but maybe we need to re-train ourselves away from conventional sail trim. Since I made this adjustment, I had no problems with the leech.
I only had a few weeks to sail "Some Kinda Wonderful" before haul out. BUt i did notice that trimming the main on this loose footed sail(furling version) took some getting used to. I found the vibration in the leech, although not as violent as you are describing, was due to having the outhaul too tight. The sail needed some breathing room, and sailed remarkably well on a close reach with what looked to me to be too "loose" a sail. I haven't discussed this with Hunter, but maybe we need to re-train ourselves away from conventional sail trim. Since I made this adjustment, I had no problems with the leech.
footloose!
Good point mark! my dealer told me to keep the foot really tight, but coming from loose footed dinghys I let the foot out until the sail shape looks good, depending on the wind and my sailing angle-better performance and no vibration! you can use the vang to flatten the upper sail without overtightening the foot.maybe we'll meet next summer, since we'll be sailing north! Chuck Wayne H356 www.escape
Good point mark! my dealer told me to keep the foot really tight, but coming from loose footed dinghys I let the foot out until the sail shape looks good, depending on the wind and my sailing angle-better performance and no vibration! you can use the vang to flatten the upper sail without overtightening the foot.maybe we'll meet next summer, since we'll be sailing north! Chuck Wayne H356 www.escape
- Status