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Strange lee/weather helm effect |
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Marine Boy 
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Joined: 01 Sep 05 Location: United Kingdom Online Status: Offline Posts: 42 |
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 Topic: Strange lee/weather helm effectPosted: 29 Jun 06 at 10:40am |
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My Xenon (two-hander asymetric) has had a neutral helm since I first set it up (so much so that you can steer with two fingers in an F3, but I decided to play with the shroud settings (big mistake). I moved the shrouds down about an inch and now on one tack I have weather helm and the other I have lee helm (both quite pronounced). I can understand the weather helm as the CE has moved aft, but lee helm?
Checked for twist in the foils and visually the mast is vertical (side to side).
I didn't have time to put the shrouds back but as this is the only change I made I am presuming returning them will put everything right, but why?
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Bruce Starbuck
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Joined: 14 Sep 04 Location: United Kingdom Online Status: Offline Posts: 124 |
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Posted: 29 Jun 06 at 10:49am |
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You're talking about upwind, right? It sounds very strange. There's no logical explaination for that, but these things are so hard to describe with words. I bet it's something dead obvious though, which is probably something else other than mast rake. Raking the mast back would affect the feel of the boat a bit, but obviously by the same amount on both tacks assuming you dropped both shrouds back the same amount. So, dunno.
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Chris Noble
Really should get out more 
Joined: 26 Nov 04 Location: Scotland Online Status: Offline Posts: 710 |
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Posted: 29 Jun 06 at 2:38pm |
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This is going by purely what you have said above but if befor ehand you had very light and neutral steering it sounds as if you had the right settings initially, usually you would drop the shroud points for slightly heavier weather and at the same tyime what we ofund in the 200 was that you had heavier steering until you raised the centre board a bit which helps tremendously infact its the same in the 300 by lifting the board up a bit in the white stuff it eases the steering ive found. So give that a try. Could also be a problem with your sail shape perhaps the slot asweell or maybe your spreader lengths and angles are not the same which could possibly give this problem but you would probably see characteristics of this in the mast which you say is straight but it could be worth checking all the same. Did you move the mast heel position also or just drop the pins a bit. An inch sounds like quite a big difference i know that the difference between our light and heavy settings in the 200 are not as much as that but we also move the mast heel position which makes a difference. |
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FOR SALE: I14 2 Masts 2 poles 3 Booms, Foils Kites/Mains/Jibs too many to list. |
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49erGBR735HSC
Really should get out more
Joined: 30 Mar 05 Location: United Kingdom Online Status: Offline Posts: 1991 |
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Posted: 29 Jun 06 at 3:13pm |
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The actual construction of the Xenon hull may be causing this effect. We noticed that on the Omega, when the rig loaded up the hull over an extended period of time that indentations in the hull became present within the points near the shrouds. What may have happened is by moving the shroud down one pin, you have increased the loading on the hull to the extent that one of the shrouds is causing the hull to flex on one side when the boat is powered up while the other side is still rigid when loaded up. The Laser Vagos made from the same hull material don't use high rig tensions probably for the reason that the hulls are not rigid enough to support high loads without flexing. |
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MainlySwimming
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Joined: 28 Nov 05 Online Status: Offline Posts: 65 |
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Posted: 29 Jun 06 at 3:44pm |
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I asked the Topper rep at the Boat Show in January what the main differences were between the Xenon and the Omega...he pointed out the alloy bar running across the Xenon and said something like "that's to stop it folding up like the Omega does when you put lots of rig tension on"....
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Martin W
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Joined: 27 Sep 05 Location: United Kingdom Online Status: Offline Posts: 3 |
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Posted: 29 Jun 06 at 3:51pm |
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Could you have the lower shroud tension much more on one side than the other . They are only done up with bits of string and it is quite easy to do. If one was very tight, and the other loose this might make it different one side to the other. If you tension them before putting on jib tension, it may even make the mast lean to one side regardless of the shroud tension, by twisting the whole rig. The mast would bend one way on one tack and the other on the other.
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Martin
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m_liddell
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Joined: 27 May 05 Location: United Kingdom Online Status: Offline Posts: 583 |
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Posted: 29 Jun 06 at 8:28pm |
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Check the spreaders.
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Chris Noble
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Joined: 26 Nov 04 Location: Scotland Online Status: Offline Posts: 710 |
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Posted: 29 Jun 06 at 8:36pm |
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really stupid suggestion, is your tiller bent?
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FOR SALE: I14 2 Masts 2 poles 3 Booms, Foils Kites/Mains/Jibs too many to list. |
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Marine Boy
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Joined: 01 Sep 05 Location: United Kingdom Online Status: Offline Posts: 42 |
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Posted: 29 Jun 06 at 8:53pm |
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Thanks for the replies all...
No, tiller is fine.
If you let go of the tiller on one tack it comes toward you and goes away on the opposite tack (equally about 4 seconds from central to fully across, beating in an F2).
My theory (fwiw) is that the shrouds are of unequal length (and always have been) but that when I originally set it up, because the CE was so close to the CLR that any sideways deviation of the mast wouldn't be that obvious. Now that I have moved the CE, the bias is now exagerated.
I have a suspicion that when it was 'balanced' (before I played silly bu**ers) that it pointed higher on one tack than the another but that I couldn't detect it.
I will do some serious measuring before I return to the original shroud settings and report back.
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Calum_Reid
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Joined: 09 Apr 04 Location: United Kingdom Online Status: Offline Posts: 59 |
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Posted: 29 Jun 06 at 9:52pm |
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Shrouds are rarely the same length. It is sensible to measure them. You will be very lucky to have a set of exactly identicle shrouds!
OH and btw this talk of boats not being able to take rig tensions etc and using low ones to prtect the boat seems odd because when your sailing alon up the beat your leward shoud often goes slack meaning that there must be more tension in the windward shroud that the ammount of tension you have pulled on. Now you can stop the leward shroud going slack but it takes ALOT of tension. For example in the 400 (admitidly in a big breeze) we would sail with over 500lbs and still have a slack leward shroud. |
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