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Mainsail luff shrinkage---acceptable?

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Stefan Lloyd View Drop Down
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Post Options Post Options   Quote Stefan Lloyd Quote  Post ReplyReply Direct Link To This Post Posted: 08 Mar 07 at 1:11pm
Originally posted by brys

QED if anyone sails with anything other than a brand new sail at any major competitions they are at a distinct handicap!

 

Yes. Did someone tell you sailing was a cheap sport?

 

I don't think this is just about the bolt-rope. Mylar headsails also shrink. 

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PeterV View Drop Down
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Post Options Post Options   Quote PeterV Quote  Post ReplyReply Direct Link To This Post Posted: 08 Mar 07 at 6:59pm

I have a Finn as well but I haven't tried applying any rig tension yet, I leave that to the boats I sail with stays.

I don't think it's just the sail creasing, on older sails the bolt ropes can be very short and no amount of tension will pull them back into shape.

 

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Post Options Post Options   Quote Guest Quote  Post ReplyReply Direct Link To This Post Posted: 08 Mar 07 at 7:59pm
Originally posted by Stefan Lloyd

Originally posted by brys

QED if anyone sails with anything other than a brand new sail at any major competitions they are at a distinct handicap!

 

Yes. Did someone tell you sailing was a cheap sport?

 

I don't think this is just about the bolt-rope. Mylar headsails also shrink. 

I have already said the bolt rope shrinkage is a red herring ... the film sails lose size in all dimension due to creasing ...

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Medway Maniac View Drop Down
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Post Options Post Options   Quote Medway Maniac Quote  Post ReplyReply Direct Link To This Post Posted: 08 Mar 07 at 10:12pm

Originally posted by Guest#260

I have already said the bolt rope shrinkage is a red herring ... the film sails lose size in all dimension due to creasing ...

So, Im trying to work out why it helps to unpick the stitching and slide the sail down the bolt rope as others have suggested? Surely that means the bolt rope has shrunk, whatever has happened with the cloth creasing?

To those who have unpicked the stitches: when you've freed it, does the sail luff elongate relative to the bolt rope, or vice versa?

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Post Options Post Options   Quote Charlie Quote  Post ReplyReply Direct Link To This Post Posted: 08 Mar 07 at 10:25pm
Originally posted by PeterV

I have a Finn as well but I haven't tried applying any rig tension yet, I leave that to the boats I sail with stays.

Ok i should of said luff tension, i knew what i meant at least.

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Post Options Post Options   Quote brys Quote  Post ReplyReply Direct Link To This Post Posted: 08 Mar 07 at 10:47pm

I spoke today with a sailmaker of many years experince and wisdom. He suggested that bolt ropes will indeed shrink. Especially iIf a sailmaker (who is in business to make money) uses inferior quality rope for his bolt ropes. dodgy cheap ropes are quite hard to detect as such until they have indeed shrunk! 

The cost of similar diameter ropes can vary by up to a hundred times......if you could get away with using a material that was  costing say 5p a meter rather than spending 5 a meter would not you?  (ethics don't come into this, as by the time the rope has shrunk chances are other factors will have worn out the sail in any case.) 

I certainly do not buy into the creasing theory.....film sails are usually carefully rolled by most crews and any how 10 inches is a hell of a lot of creases in a 30ft luff. That is nearly 3%!   In IRC racing let alone one design 3% on a finishing time can mean quite a few places lost!

As usual it is a case of buyer beware!

If you have any control over what materials go into your sails make sure you ask about what type of rope your sail maker uses for bolt ropes......Pre-shrunk, pre stretched dimensionally stable ropes must be clearly specified....even if the cost is marginally more, at least you will reduce the onset of shrinking luff lengths!

If you are stuck with a MOD supplied sail and locked in by class rules (written by the manufactuer/integrator in most cases) they hard luck.....unless you get a class association committee with some big gonads to sort out this sort of issue with the manufacturer....

 

 

 

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Post Options Post Options   Quote Ian29937 Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 07 at 9:32am

I believe both theories - I think film sails do shrink slightly from creasing, but only slightly and I'm sure the bolt ropes do shrink, why else do some sailmakers add an extra length to allow for re-stitching.

HOWEVER I've never worried about this.

Surely the effect of the shrunken bolt rope is simply to put on some negative cunningham tension.  The actual sail fabric isn't affected by this.  Therefore you can easily redress the effect by applying some positive tension to pull the bolt rope back to it's original length, returning the sail to it's designed shape.

Or am I missing something?

Ian

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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 07 at 9:57am
Originally posted by Ian29937

Or am I missing something?

The extra tension on the luff affects the mast bend to an extent. How much depends on the rig, but on modern rigs which use the downhaul to control topmast bend it could be quite significant.
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Post Options Post Options   Quote Guest Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 07 at 10:14am
Originally posted by Medway Maniac

Originally posted by Guest#260

I have already said the bolt rope shrinkage is a red herring ... the film sails lose size in all dimension due to creasing ...

So, Im trying to work out why it helps to unpick the stitching and slide the sail down the bolt rope as others have suggested? Surely that means the bolt rope has shrunk, whatever has happened with the cloth creasing?

To those who have unpicked the stitches: when you've freed it, does the sail luff elongate relative to the bolt rope, or vice versa?

The rope does shrink but the effect from creasing is in all dimensions of the sail ... UV also plays it's part.

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Post Options Post Options   Quote jeffers Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 07 at 2:32pm
Originally posted by brys

If you are stuck with a MOD supplied sail and locked in by class rules (written by the manufactuer/integrator in most cases) they hard luck.....unless you get a class association committee with some big gonads to sort out this sort of issue with the manufacturer....



Who needs a CA with big gonads to agrue with the builder? We have found in the Blaze class that have a good relationship between the CA and the builder usually gets most issues resolved to the benefit of all.

One the question of sails the Blaze X has had a Sobstad main since the start of the X series. Sobstad then decided to start hiking the price. The new Blaze X's now have a North sail  (and very nice it looks too) designed by the same guy to an almost identical cut (has to be slightly different to avoid patent/copyright disputes). This change was pushed for at the AGM by the class members, here we are with a resolution....

Just my 2p....your CA is what you make it, if you are not in it don't complain!
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