As part of a continuing process to reduce weather helm, I recently shortened the forestay on my H30 to reduce mast rake. I re-tensioned all other rigging to slightly more than 25% of breaking strength suing a Loos Tension Guage. Everything looked good. The following weekend, I sailed the boat to check the results. Still too much weahter helm, but otherwise the boat was fine. Upon returning to the marina, I made a cursory inspection of the riging and chainplates. To my dismay, I noticed some deformation in the hull directly below the chainplates. There is now a dinner plate sized depression in the hull below both the forward and rear shrouds on both sides of the hull. More so on the rear shrouds than the front. I immediately reduced tension in those shrouds. The next day, I sailed the boat again in 15-18 knot winds. There seemed to be no further deformation and other than the weather helm issue, the boat handled fine. Regarding fixing the problem, my idea is to slack the shrouds and then use a hydralic jack and a jig from inside the boat to push the opposing dimples out. Once I have them eliminated, I would then glass in some plywood pressure blocks to strengthen and stabilize the area below and around the chainplates. Any comments or other possible solutions would be welcomed. David Popken SV Orion
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Steve O.
over-tensioned
25% is too much. Max tension should be 20% and that's on the largest daimeter wire.
25% is too much. Max tension should be 20% and that's on the largest daimeter wire.
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Ed
Too much tension
The upper rigging wires can be up to 20% of their breaking strength, but 15% to 18% is considered normal. The lower rigging wires should be tensioned at 10% to 12% of their breaking strength. You'll shorten the life of the rigging and of the chainplates if you tension them too high. ~ Happy sails to you ~ _/) ~
The upper rigging wires can be up to 20% of their breaking strength, but 15% to 18% is considered normal. The lower rigging wires should be tensioned at 10% to 12% of their breaking strength. You'll shorten the life of the rigging and of the chainplates if you tension them too high. ~ Happy sails to you ~ _/) ~
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Justin - O'day Owners' Web
Stop and get some advice
David - One of the best parts of boat ownership is the continual learning process, but there is a limit. I would not do anything without some local advice. You need to make sure that the hull isn't damaged by broken fibers at the area of the dimples. You may well be able to push them out but you may need to do more than just block them from behind. I'd get a surveyor or fiberglass guy you trust around. As far as your rig goes - moving the rig forward is a good plan to reduce weather helm but tightening the rig won't do much to affect it. I'd be looking at your mainsail. Sounds like you need to reduce the draft. Justin - O'day Owners' Web
David - One of the best parts of boat ownership is the continual learning process, but there is a limit. I would not do anything without some local advice. You need to make sure that the hull isn't damaged by broken fibers at the area of the dimples. You may well be able to push them out but you may need to do more than just block them from behind. I'd get a surveyor or fiberglass guy you trust around. As far as your rig goes - moving the rig forward is a good plan to reduce weather helm but tightening the rig won't do much to affect it. I'd be looking at your mainsail. Sounds like you need to reduce the draft. Justin - O'day Owners' Web
Reducing rake is not worth the hassle
I hate to say it but you went to a lot of trouble modifying your standing rig for nothing. I played with the rake on my H23 for years without success until I realized that the biggest contributors to weather helm are insufficient mainsail twist and excessive heel. Both are easily solved with sail trim. I've described how I solved the problem in the Smaller Boats Forum. Try the Forum Archives under "weather helm" or "H23 weather helm" and see what pops up. Good luck. Peter H23 "Raven"
I hate to say it but you went to a lot of trouble modifying your standing rig for nothing. I played with the rake on my H23 for years without success until I realized that the biggest contributors to weather helm are insufficient mainsail twist and excessive heel. Both are easily solved with sail trim. I've described how I solved the problem in the Smaller Boats Forum. Try the Forum Archives under "weather helm" or "H23 weather helm" and see what pops up. Good luck. Peter H23 "Raven"
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Dave
breaking strength or yield strength
If you perform a tesile test the breaking strength is known as the "ultimate strength" but the material starts to fail at the "yield point" this is the point beyond which the material has permanent plastic deformation. I suggest you start with this value in your calculation. Of course you must know the material the wire is made from to get the yield strength. What did you use for your calculation and why? Dave
If you perform a tesile test the breaking strength is known as the "ultimate strength" but the material starts to fail at the "yield point" this is the point beyond which the material has permanent plastic deformation. I suggest you start with this value in your calculation. Of course you must know the material the wire is made from to get the yield strength. What did you use for your calculation and why? Dave
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David Popken
Yield Strength
I used the tables that came with the Loos tension guage. I had to make some assumtions. i do not have th tables with me, so I cannot comment on them very accurately. I also used the "25% of breaking strength" statement from Nigel Calder's book on cruising. In any case, it is clear that I overtensioned the rigging. My more pressing issue is the hull.
I used the tables that came with the Loos tension guage. I had to make some assumtions. i do not have th tables with me, so I cannot comment on them very accurately. I also used the "25% of breaking strength" statement from Nigel Calder's book on cruising. In any case, it is clear that I overtensioned the rigging. My more pressing issue is the hull.
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David Popken
I Disagree
If you have ever used a windsurfer, you know that to "steer" the board, you pull back on the mast to head up and push the mast forward to fall off. I must assume that it will work on a sail boat as well. There is a very clear discussion of a boat's balance and the CE or center of effort in John Rousmaniere's book. I beleive it's called "The Annapolis Book of Seamanship".
If you have ever used a windsurfer, you know that to "steer" the board, you pull back on the mast to head up and push the mast forward to fall off. I must assume that it will work on a sail boat as well. There is a very clear discussion of a boat's balance and the CE or center of effort in John Rousmaniere's book. I beleive it's called "The Annapolis Book of Seamanship".
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David Popken
You're Right, 25% Is Too Much
Clearly, I know that 25% is too much tension now. The real issue now is the fix for the hull.
Clearly, I know that 25% is too much tension now. The real issue now is the fix for the hull.
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MArk
Sail shape critical
David, Here's an article where they suggest 10-15% tension and why: http://www.trailersailor.com/content/tips/read.cgi?2 Regarding your weather helm problem, I have to agree with Peter. If your sail is too full, the lift moves back on the sail causing more heel (and twist). More heel moves the sail driving force out over the lee rail. It's like flying a twin engine plane with one engine out, it wants to spin. Much of the sail force goes to turning the bow into the wind instead of driving forward. You'll do better by flattening your sail (outhaul, cunningham, vang/kicker) and don't forget to the adjust the jib blocks. Reef early and don't sail with over 20 degrees heel. Read link below. Happy (fusion powered) sails *_/), MArk
David, Here's an article where they suggest 10-15% tension and why: http://www.trailersailor.com/content/tips/read.cgi?2 Regarding your weather helm problem, I have to agree with Peter. If your sail is too full, the lift moves back on the sail causing more heel (and twist). More heel moves the sail driving force out over the lee rail. It's like flying a twin engine plane with one engine out, it wants to spin. Much of the sail force goes to turning the bow into the wind instead of driving forward. You'll do better by flattening your sail (outhaul, cunningham, vang/kicker) and don't forget to the adjust the jib blocks. Reef early and don't sail with over 20 degrees heel. Read link below. Happy (fusion powered) sails *_/), MArk
Windsurfers, heel and modern boat design
I agree that windsurfers are steered by moving the mast forward and aft to change the location of the CE relative to the CLR. However, a significant amount of mast movement is needed, and it has to be done constantly, which is why a windsurfer mast is designed with no stays and a pivot at the base. The same arrangement won't work on a sailboat. In addition, a windsurfer is a planing hull that is sailed with almost no heel. Moving the mast is ineffective if heel is not controlled first. I used to think that moving the CE forward relative to the CLR was a cure for weather helm until I had a Catalina 30 round up repeatedly because of severe weather helm in heavy air. I was sailing under headsail alone (CE far ahead of the CLR) so I expected lee helm, but the boat was heeling so much in the gusts that the driving force in the sail was being moved outboard of the centerline on the leeward side. It was the resulting turning moment that kept rounding the boat up to windward. Reducing sail area reduced the heel and the problem went away. Most sailing manuals cite an aymmetric hull shape underwater as the cause of heel-induced weather helm, but I don't think I've ever seen a reference to the turning moment caused by the eccentric CE when heeled excessively. Maybe it's because most sailing texts are written for full-keeled boats or planing hulls. The large amount of lateral area underwater makes a full-keeled boats hard to rotate (yaw) about the CLR. Planing hulls have very little keel area in the water, but they are designed to sail with very little heel (crew hikes out or rides the trapeze) and are so responsive that any remaining tendency to yaw can be controlled by small movements of the rudder. By comparison, a modern fin-keeled production sailboat has a similar underwater shape to a planing hull, so it's almost as easy to yaw. However, there is usually no "movable ballast" available to keep the boat flat, so the only other way to control yaw is with the rudder. As heel increases, the rudder becomes less effective at controlling the yaw. The solution is to use sail area and sail trim to control the heeling force. As MArk pointed out, most modern fin-keeled production boats shouldn't be sailed with a lot of heel. Unfortunately, many people still have this desire to sail with the lee rail buried (obtained from pictures of classic boats under full sail). That's fine if you're on a narrow, full-keeled boat with low freeboard, but a light, beamy, fin-keeled production boat with high freeboard should be sailed at lower angles of heel. Just my two cents. Peter H23 "Raven"
I agree that windsurfers are steered by moving the mast forward and aft to change the location of the CE relative to the CLR. However, a significant amount of mast movement is needed, and it has to be done constantly, which is why a windsurfer mast is designed with no stays and a pivot at the base. The same arrangement won't work on a sailboat. In addition, a windsurfer is a planing hull that is sailed with almost no heel. Moving the mast is ineffective if heel is not controlled first. I used to think that moving the CE forward relative to the CLR was a cure for weather helm until I had a Catalina 30 round up repeatedly because of severe weather helm in heavy air. I was sailing under headsail alone (CE far ahead of the CLR) so I expected lee helm, but the boat was heeling so much in the gusts that the driving force in the sail was being moved outboard of the centerline on the leeward side. It was the resulting turning moment that kept rounding the boat up to windward. Reducing sail area reduced the heel and the problem went away. Most sailing manuals cite an aymmetric hull shape underwater as the cause of heel-induced weather helm, but I don't think I've ever seen a reference to the turning moment caused by the eccentric CE when heeled excessively. Maybe it's because most sailing texts are written for full-keeled boats or planing hulls. The large amount of lateral area underwater makes a full-keeled boats hard to rotate (yaw) about the CLR. Planing hulls have very little keel area in the water, but they are designed to sail with very little heel (crew hikes out or rides the trapeze) and are so responsive that any remaining tendency to yaw can be controlled by small movements of the rudder. By comparison, a modern fin-keeled production sailboat has a similar underwater shape to a planing hull, so it's almost as easy to yaw. However, there is usually no "movable ballast" available to keep the boat flat, so the only other way to control yaw is with the rudder. As heel increases, the rudder becomes less effective at controlling the yaw. The solution is to use sail area and sail trim to control the heeling force. As MArk pointed out, most modern fin-keeled production boats shouldn't be sailed with a lot of heel. Unfortunately, many people still have this desire to sail with the lee rail buried (obtained from pictures of classic boats under full sail). That's fine if you're on a narrow, full-keeled boat with low freeboard, but a light, beamy, fin-keeled production boat with high freeboard should be sailed at lower angles of heel. Just my two cents. Peter H23 "Raven"
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Allen Schweitzer
More Sail Trim
David, Forgive me if this sounds obvious, but it seems that de-powering the main will sove your problems. Perhaps easing off on the traveler in addition to the vang/cunningham/outhaul suggestions that were already made. I've got a Catalina 30 & it solves this problem every time. Or, if you really want to move the center of effort forward, maybe you could look into a bow sprit to mount your forestay farther forward. Just a thought. Allen Schweitzer s/v Falstaff C-30 Hull# 632
David, Forgive me if this sounds obvious, but it seems that de-powering the main will sove your problems. Perhaps easing off on the traveler in addition to the vang/cunningham/outhaul suggestions that were already made. I've got a Catalina 30 & it solves this problem every time. Or, if you really want to move the center of effort forward, maybe you could look into a bow sprit to mount your forestay farther forward. Just a thought. Allen Schweitzer s/v Falstaff C-30 Hull# 632
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David Popken
All trim options
have been tried with no noticable change in weather helm. Over heeling is also not an issue as the boat never goes beyond 15%, even in 20+ knots of wind.
have been tried with no noticable change in weather helm. Over heeling is also not an issue as the boat never goes beyond 15%, even in 20+ knots of wind.
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David Popken
Thanks Peter
Well summarized. You obviously have done your research too. The only problem with your conclusion at least in my xase is that I have never buried the rail. I have excessive weather helm when the boat is heeled less than 15%, so that cannot be the issue. I have read Wallace Ross and others on sail trim and weather helm and feel confident that my trim techniques are sound, so for my boat, the only solution I can see is to reposition the CE by moving the mast forward. And actually, as a result of the first round of repositioning, the problem has been reduced to a great degree, but not enough.
Well summarized. You obviously have done your research too. The only problem with your conclusion at least in my xase is that I have never buried the rail. I have excessive weather helm when the boat is heeled less than 15%, so that cannot be the issue. I have read Wallace Ross and others on sail trim and weather helm and feel confident that my trim techniques are sound, so for my boat, the only solution I can see is to reposition the CE by moving the mast forward. And actually, as a result of the first round of repositioning, the problem has been reduced to a great degree, but not enough.
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David Popken
New main
I purchased a new main because the opinion on the forums here was that my old main was too baggy and could not be flattened, therefore the cause of my weather helm problem. I own and understand the use of vang, cunningham, outhaul and main sheet tension in flattening the sail. Believe me, the sail is flat. And as I have said previously, the boat has excessive weather helm with less that 15% of heel. One thought regarding sails, the boat has a 150% genoa with a very large overlap. Could reducing the area of the foresail be a possible solution?
I purchased a new main because the opinion on the forums here was that my old main was too baggy and could not be flattened, therefore the cause of my weather helm problem. I own and understand the use of vang, cunningham, outhaul and main sheet tension in flattening the sail. Believe me, the sail is flat. And as I have said previously, the boat has excessive weather helm with less that 15% of heel. One thought regarding sails, the boat has a 150% genoa with a very large overlap. Could reducing the area of the foresail be a possible solution?
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Garry @ S/V TASHTEGO
For Peter Suah
There is actually an excellent discussion of the effects of roll on yaw in John Letcher's "Self Steering for Sailing Craft" including how to make your wind vane compensate.
There is actually an excellent discussion of the effects of roll on yaw in John Letcher's "Self Steering for Sailing Craft" including how to make your wind vane compensate.
About your sail trim, David
You mentioned using the vang, outhaul, cunningham and mainsheet tension to flatten the sail. The sail may be nice and flat but if it doesn't have enough twist you'll still have weather helm. Tight vang and tight mainsheet usually mean a tight, closed leech...and some weather helm. Here's an easy check the next time you notice the weather helm. Look at the top batten of the mainsail. Is it pointed to windward? If so, you don't have enough twist (the leech is closed). Normally, the top batten should be parallel to the boom. In heavy air, open the leech some more, either by increasing backstay tension (bend the mast) or easing the mainsheet until the top batten is pointing off to leeward a bit. I also noticed that you didn't mention the traveler. Did you try pulling it up to weather as you eased the mainsheet while keeping the boom at the proper angle to the wind? This will ease leech tension and open the sail some more. I know you're committed to moving the mast but I see that as a drastic move. All else being equal, you'll probably have more lee helm in light air than you did before. Just my two cents, but I'd try to exhaust every other option first, especially since sail trim is so easy and any changes are quickly undone if they don't work. Happy sailing. Peter H23 "Raven"
You mentioned using the vang, outhaul, cunningham and mainsheet tension to flatten the sail. The sail may be nice and flat but if it doesn't have enough twist you'll still have weather helm. Tight vang and tight mainsheet usually mean a tight, closed leech...and some weather helm. Here's an easy check the next time you notice the weather helm. Look at the top batten of the mainsail. Is it pointed to windward? If so, you don't have enough twist (the leech is closed). Normally, the top batten should be parallel to the boom. In heavy air, open the leech some more, either by increasing backstay tension (bend the mast) or easing the mainsheet until the top batten is pointing off to leeward a bit. I also noticed that you didn't mention the traveler. Did you try pulling it up to weather as you eased the mainsheet while keeping the boom at the proper angle to the wind? This will ease leech tension and open the sail some more. I know you're committed to moving the mast but I see that as a drastic move. All else being equal, you'll probably have more lee helm in light air than you did before. Just my two cents, but I'd try to exhaust every other option first, especially since sail trim is so easy and any changes are quickly undone if they don't work. Happy sailing. Peter H23 "Raven"
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