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Asymspin Furling-bottom up


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Everyone puts the torque rope in the spin luff and sews it in.  What happens if you don't do that?  On a top-down system, the spin luff is separate from the torque line...seems a bottom up "ought" to work pretty much the same.   Advantage would be that the luff of the sail could then be light enough to project windward-especially if you loosen the halyard.  When you gybe, the torque rope "should" just rotate to windward again.  Anyone try using a torque rope outside the spin luff instead of sewing it inside the luff tape?

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Are you asking about a Code 0 sail or an Asymmetrical sail?

A Code 0 sail can be furled top down or bottom up depending on the design. The torsion cable could either be integrated into it or external again depending on the design. 

An Asymmetrical sail can be furled top down only with a torsion cable however some sail makers (all of them now) have a special sail for going deeper down wind which can be furled bottom up but there is no torsion cable in it however hte sail needs to be designed for it, such as the Helix by North Sails. 

Your last sentence "Anyone try using a torque rope outside the spin luff instead of sewing it inside the luff tape?" is essentially the only way it's done; with an external torsion cable for a top down asymmetrical furl. 

 

 

 

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Apparently I was unclear--the topic title is about bottom up furling.  I personally have used top down as well as bottom up furling (and have made my own sails for the past decade or so).  My asymspins (also in topic title) are nylon sails and when I make them for bottom up furling, I (and every sailmaker I know) sews the torque line into the asymspin luff.  I want to know if anyone has tried to furl an asymspin bottom up without the torque line sewn into the asymspin luff.  The torque line needs to have a platen so the spin fabric doesn't glom onto the line, but ya gotta do that with top down furling line as well.  I probably will experiment with it tomorrow when I go out, but thought I'd ask.

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I understood from OneSails that their FFR (Flat Furling Reacher) could be run with the cable either in the Luff Pocket or outside the Luff Pocket. It may have been a language misunderstanding, but I was always curious to try it. We decided to change over to a catamaran,  so sold the boat before I got the chance.

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Thanks, the one I am trying out works really well in the yard, but (as we all know) stuff in use with real wind cause issues.  The asymspin still has to be made for bottom up furling (straight luff, not so much camber...) but being able to separate the weight of the torsion rope from the asymspin luff should make the spin fly better (at least it does when using a top down furler).  

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There is no need to have a torsional cable in an A-Sail if furled bottom as it will have integrated strength built into it's panels to facilitate the furl such as the new Helix by North Sails and the OneSails.

In the end of the day, I think it's best you just talk to the sailmakers whom have designed the sails to furl like you are asking about. What you want to do can't be done the way you want it to (with a sew in torsion cable in a A-sym nylon sail). 

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No offense intended Rimike, but you are wrong.  North's helix just replaces a single torsion rope with some stiff fabric in the first several panels from the luff (and likely some tricky luff lines in the luff tape)--supposedly "self supporting sails".  I haven't disassembled one myself, but that's what their marketing seems to imply. If you look at their asymspin options, they offer anti torsion rope as an option for their asymspins.   Personally, I believe a helix asymspin would provide a horrible furl after a few seasons.  As we all know, a nylon sail will last and sail for dozens of seasons since nylon doesn't really lose shape (the miracle of nylon).  An asymspin without a torsion rope furling from bottom up will leave it loose at the top--the better the torsion rope, the better the furl.  However, the better the torsion rope, the heavier as well as the bigger diameter.  This does not promote good flying in a spinnaker-especially in light breeze.  In 1999 I began experimenting with furling asymspins and reverse engineered the roll-gen top down furler as well as created my own torsion line-which works better than most commercial ones--but the sail doesn't pack into a sack as easily, I do admit.   

"n the end of the day, I think it's best you just talk to the sailmakers whom have designed the sails to furl like you are asking about."  Seriously?  

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No offense taken, I learn from mistakes.

The only way to top down furl an A-sym is with a torsion cable. Only the head of the sail is lashed to the torsion cable's thimble (tack of the sail attached to a swivel on the furler and is independent of the rotation when furled).  As for bottom up furling an A-sym it is indeed very loose at the head, however these sails are closer to a Code 0 cut than a traditional A-sym.  

With a cable-less Code 0 which is furled bottom up, the luff is projected to windword and as the halyard is eased the sail allows for deeper angles. However its more of an A3 and heavy in material and not nylon. 

As for a proper engineered torsion cable for a 5T furled top down for say a 40' boat, say 18 meters it weights in at 10 lbs and is 15.6 mm in diameter. You mention light air so for light air, you would have a light air sail, so  the working load will be less, say 3 tons or something so the cable will me smaller in diameter and lighter in weight. 

What's confusing is you say you need a straight luff A-sym which is an oxymorn. The only "straight luff" sail would be a Code sail. 

Perhaps what you are after is an A-sym with smaller mid-girth sail and after you unfurl, ease the halyard to allow for deeper angles. When you want to furl tension the halyard and furl it from the bottom up? 

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This is real simple.  It is not a code zero.  It is an asymmetric spinnaker (actually should probably call it a gennaker) made with 3/4 oz nylon (Luff 30 ft, Leach 24 ft and foot 12 feet (or thereabout)).  It is mounted on a sprit on a furler.  It is cut flat 55% SMG since it is used on a very light boat which generates apparent wind so that even downwind the wind is from in front.  The next one I make will have a 75% smg since I use it more downwind than reaching).  To furl properly from the bottom up, you have to have a toque rope installed.  My question which apparently is confusing...has anyone who had their spins repaired or made their own left the torque rope UNINSTALLED, that is, OUTSIDE THE LUFF TAPE.  Now, I understand that most reading this have never made a sail so most of you don't know what is inside the luff tape of your sails (usually nothing unless you are flying a screacher or a bottom up furling asymspin), you just fly fly them.  That's OK, I'm trying to reach out to someone who has attempted to leave the torque rope outside the luff tape (like what is done with a top down furler) EXCEPT that it is furled bottom up.  It ought to work OK but if someone has actual experience and says don't do it, I'd like to know before I try it anyway.  The advantage would be that in lighter air, the weight of the torque rope won't drag the luff of the sail down and the spin will have a finer entry.   It will be easy enough to add a luff tape including the torque rope if it doesn't work like I think it will, but what the heck...nothing gets better without trying something new, right?

As an aside, this is exactly WHY the north sails helix was developed for larger boats - to allow the code zeros to project their luffs forward even in lighter breeze and not get dragged down by the weight in the luff.

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Multi Thom On our multihulls - F27 and then Dazcat 11.5  our screachers have had captive torsion ropes sewn in the luff and our kites have just had the torsion rope but not captive in the luff. One of the screachers had a home made torsion rope when we bought the boat. It worked but you had to sail deeper than with a proper torsion rope. I guess it could be the same thing with a kite but may not be as much of an issue if you go down to furl? 

When you rig the kites incorrectly for our top down furler and tie the head and tack to the torsion rope rather than just the head only and furl them then they do furl bottom up like a screacher.  They do not always furl nicely and you can nearly have a heart attack doing it. Got that T shirt in muppetry....

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2 hours ago, Bruce Sutherland said:

When you rig the kites incorrectly for our top down furler and tie the head and tack to the torsion rope rather than just the head only and furl them then they do furl bottom up like a screacher.  They do not always furl nicely and you can nearly have a heart attack doing it. Got that T shirt in muppetry....

I am interested in knowing how the torsion rope behaved in a gybe when you did this...did it stay aft of the luff on both gybes or did it lay on top of the luff after a gybe.  

Yah, a standard kite won't furl bottom up very nice at the top for a couple of reasons 1) the wind pressure above will cause the top to stay inflated while the bottom furls-so it'll be loose at the top (this is also why your screacher won't furl very nice unless you head down and furl) and 2) there's more fabric along the luff so even if you grunt down on the halyard, the luff and rope won't be parallel.  

 

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5 hours ago, RImike said:

Other than PHRF, does any other organization classify a sail with 75% and less mid girth a "code zero spinnaker"  and a sail 76% and larger mid girth a "spinnaker"? 

In past years the Racing Rules of Sailing called anything with an SMG of 75% or above to be classified as a spinnaker.  I don't know if it still does since I don't race anymore.  As a point of information, a "code zero" was a sail invented by cheaters.  Back in the day, some classes allowed carrying any number of spinnakers but limited folks in how many genoas they could carry.  Some folks decided to create a cheating spinnaker that was made with a midgirth of 75% as measured (so it was a spinnaker by definition), BUT, when flown, the sail had a straight hard luff and could be used as a genoa in light breeze to go upwind (not very high pointing, but better than the biggest genoa they were carrying).  Now, though, a code zero is pretty much anything that gets sails sold.

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I tried it out today and it worked like a charm.  The torque rope was always below the spin, the spin flew very well without the additional weight and thickness of the torque rope.  When it was time to furl, just tightened the halyard which brought the spin luff close to the torque rope again and furled quick and tight, bottom and top.  I expect I have to go deep to get a good furl, but that's what I'm used to doing anyway.  

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  • 1 year later...

I now have a couple years experience with furling bottom up with an external furling cable.  I have also started sailing with a traditional asymspin with a SMG of 82% so it works pretty well  even with a fat asymspin.  

Fat spins with a loose luff (needed for downwind VMG) will need an external furling cable since putting extra weight into the luff of a spin will keep it from flying well in the lighter winds or projecting windward.  I have been furling my new fat spin using my bottom up furler with an external furling cable.  It works very well.  I gave up furling top down because it takes a lot more effort to furl and occasionally you will get a back furl which causes you to do a couple gybes to completely unfurl from the furling cable.  Since I'm cheap I make my own furling cable.  With an external cable, the cable itself sees very little load.  Since I trailer sail I store my spin on furler off the boat...since the cable I make takes up more room since it is only moderately flexible.  To make a furling cable, you only need some 5/16" polyester solid braid line and some drip tubing from the hardware store (it is a little bigger than a half inch diameter).  Fish the solid braid through the tubing.  If you want to make it pretty, get some cable thimbles (3/8" work well (M10)) and crimps.  Otherwise you can finish with bowlines and sew the tube to the solid braid with your awl.  You want the furling cable to be almost the exact length of your spin luff.  When flying, the spin luff will separate especially if you allow some slack in the halyard; to furl, tighten first.  It is not a super tight furl and it is pretty bulky to keep up while trying to sail to weather, so best to lower back down soon after furling.  

Since the tubing is semi rigid storage is in big loops; can't just stuff it into a sack.  That's the biggest drawback, it actually works better than any store bought cable I've used or seen used (simply because it resists torque perfectly, top and bottom swivels operate together).  I can actually use a single line furler on my skinny spin with this external cable.   CDI flexible furlers is a similar concept although they don't actually offer a product for spinnaker furling.  

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I'm a bit surprised to hear this, and maybe it's because your sail is flatter than a typical cut.  Usually, for any reasonably sized A2 or A3 asym, you really must use top-down furling.

What I found was that with bottom up, what happens is that the top of the sail will not furl as fast as the bottom, and the still-inflated top of the sail will rotate back & forth around and twist on itself, creating an hourglass that is almost impossible to remove without taking the whole thing down on deck.

You can get away with bottom-up furling on code zero sail, because it's a flatter cut, with less material up high, so the bottom of the sail transmits the furling torque more effectively & quickly to the top of the sail. But even then, if you don't furl it fast enough, the same thing can happen. Top down furling will work better, even on a code sail.

To be honest, why not just use a spinnaker sock? Less expensive and pretty bullet-proof.

 

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On 9/3/2021 at 7:57 AM, Reference said:

I'm a bit surprised to hear this, and maybe it's because your sail is flatter than a typical cut.  Usually, for any reasonably sized A2 or A3 asym, you really must use top-down furling.

To be honest, why not just use a spinnaker sock? Less expensive and pretty bullet-proof.

 

It is actually pretty typical cut at 82% SMG asymspin.  The point, I think, is that the torque cable I make transmits torque perfectly along the 35 feet from sprit to mast swivel.  top swivel and bottom swivel are connected by semi-rigid tubing.  Sort of like the aluminum furling foils you see on older style jib furlers.  The issue with "store bought" torque cables is they do not transmit torque perfectly, there's always one or two twists at the bottom before the top starts to  twist.  

The reason I don't use a sock is that I sail single handed exclusively and need a reliable way to deploy and secure a spinnaker.  It doesn't help that my boat has a very skinny and crowned foredeck and no pulpit so going there and back is fraught with opportunities for Murphy to visit.  I have tried a snuffer (horizontal sock), but I'd have to modify the boat to accommodate it and it just isn't worth that since the furling system works fine for me.  

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Multi,

Nice work. Around that ~ 82% mid girth is a sweet spot for fast reaching/AP sail, in keelboat parlance 'A5'

For slower, rated keelboats, a full size A3 around 94 % mid girth is good also.

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