Mainsail luff rope - what's it for?

[Elbows]

This was a bit of a tangent on another thread, but I think it warrants a thread of it's own.

My mainsail luff rope has shrunk and I was planning on unpicking the bottom end and reattaching it a bit higher up to allow the sail to be tensioned properly. But that set me to wondering whether it was actually doing anything useful anyway as the sail is fitted with sliders.

I've been told that it's there to prevent over-tensioning of the the sail fabric, but that only works when the sail isn't reefed. When it's reefed the bottom end isn't anchored at the new tack so the full tension of the halyard is taken by the sail cloth anyway. If it doesn't matter when reefed, why would it matter when not reefed? Is there some other reason it's there that I haven't thought of?

 

[Greenheart]

Is it possible that originally, your sail wasn't fitted with sliders?

Then, the bolt-rope in the luff would have been what kept the sail attached to the mast. That's the only reason I can see for it.

I'm fitting sliders...can't wait to be free from threading the boltrope into the track.

 

[Daydream believer]

If you have sliders then the bolt rope would tend to spread the load along the front edge of the sail & give a neat edge. Of course one could have webbing up the front edge if not going into a grouve.
So if you wanted to totally remove the bolt rope & had a sewing machine it would be far easier to attach a good quality webbing. However it would be important to have one that is UV protected. I would also suggest pre stretching it first & applying some tension to it for a few days prior to sewing to the sail.
Hook it to the car & the greenhouse & give it some tension & park up, But tell the wife before she drives off:encouragement:.
Tension in the house could be quite high for some time to pass:ambivalence:

 

[Daydream believer]

I've been told that it's there to prevent over-tensioning of the the sail fabric, but that only works when the sail isn't reefed. When it's reefed the bottom end isn't anchored at the new tack so the full tension of the halyard is taken by the sail cloth anyway. ?

I would suggest that is not entirely true. The sail is reinforced at the reef cringle & sewn fairly tight to the luff so the bolt rope still takes the tension

 

[Elbows]

I would suggest that is not entirely true. The sail is reinforced at the reef cringle & sewn fairly tight to the luff so the bolt rope still takes the tension

It's very hit-and-miss though. Sometimes when reefed the bolt rope will slide up through it's sleeve and allow me to tension the sail correctly, other times it will get jammed up in the folds below the reef cringle and I can't pull out the horizontal creases.

I'm leaning towards removing it entirely as there doesn't seem to be any reason to keep it. I'm just a little concerned that it might be there for some vital reason I'm not aware of.

Does anybody have a sail without a luff rope?

 

[Spirit (of Glenans)]

Might be better to ask a sailmaker?
If you do something that causes damage to the sail it will cost money repair or replace anyway.

 

[wombat88]

I had an old Merlin dinghy sail where the luff rope had shrunk(?) and this added to general bagginess. The rope was in a pocket(?) so capable of movement. I cut the rope near the tack and re-enforced the outer material with tape.

When properly raised the rope then rode up into its pocket by approx 6-9" and this on a 17' sail. This implies that the rope was taking the tension.

It looked/felt better but I never expected it to last too long, lasted around 5years!

Older sails have the luff rope exposed and the material sewn to it. Not much one can do with them.

 

[Ruffles]

I replaced our old mainsail with a loose footed main some years ago. I think they are all loose fitted these days.

I had the same problem with the old sail. The bolt rope seemed to be causing the sail to bag. But I reckon this is simply the sail being stretched rather than the foot shrinking. I discovered this by accident when I hoisted the sail forgetting to attach the clew. The sail set much better! Obviously you can't sail like this but you can add a extending loop to the clew cringle.

Of course the real fix is to buy a new sail. You won't regret it!

 

[DJE]

I recently got our 1 year old mainsail back from the sailmaker after it's first season inspection. They said on their report:-

"NB: Untied bottom of luff bolt rope so it can shrink up inside luff tape as designed as luff stretched and rope shrinks, suggest this is NOT retied."

Still don't know what it's for though.

 

[rotrax]

Our NZ sailboat, a cheap steel Hartley 32 sailed like a brick with a mainsail-described by the Wellington Sailmaker-" as baggy as a Lascars hammock! "

In the sail store was a mainsail of similar dimensions that required a foot off the top to allow full hoist and was far newer. We were about to have this work done when the sailmaker suggested he take a look at the baggy one.

He found the luff rope and foot rope had both shrunk substantialy, causing most-but not all-of the baggyness.

He milked the ropes out, spliced in extentions, re-joined them and gave it back for us to try.

Not like a new mainsail, but so improved it became a new boat and sails much, much better.

The mainsail is reefed with a roller boom and has the foot fitted with sail slides in a track. I suspect the foot rope is important for this type of sail.

 

[Elbows]

I recently got our 1 year old mainsail back from the sailmaker after it's first season inspection. They said on their report:-

"NB: Untied bottom of luff bolt rope so it can shrink up inside luff tape as designed as luff stretched and rope shrinks, suggest this is NOT retied."

Still don't know what it's for though.

Interesting. I hadn't thought of just unpicking it and leaving the bottom end floating but it seems like a good halfway house option.

I've taken Spirit (of Glenans)'s advice and emailed North Sails about it. I'll report back when I get a reply.

 

[dunedin]

Personally I would not remove a luff rope to replace with tape. Likely could/would get thrumming noise from tape under tension

 

[Elbows]

Rob Dyer at North Sails was kind enough to reply very promptly...

Some sailmakers build sails with Luff slides without a Luff rope, but North sails always include a rope., so my advice would be to unpick the stitching at the Tack and let the rope ease up as your suggestion.

So it seems that a luff rope is not actually necessary, but North include one just because because. It's interesting that he didn't give a reason for it, I wonder whether it's just a traditional hangover from the days when that was the normal way of attaching the sail to the mast track.

Personally I would not remove a luff rope to replace with tape. Likely could/would get thrumming noise from tape under tension

It did cross my mind that the leading edge might flutter without the mass of the rope to damp it. My current plan is to unpick the bottom end and leave it floating as DJE's sailmaker recommends.