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Old 29-04-2010, 10:02   #31
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Originally Posted by Dockhead View Post
Most roller furling foils have two luff tape slots. I don't think there is any necessity to sew them together if you have that kind of foil. I am planning to implement this kind of rig by simply buying a new yankee, jib, identical to the old one. I will use the new jib for ordinary sailing, and just hoist the old one in the second slot for a twizzle. The roller furler will roll up both jibs at the same time. I am looking forward to trying this out.
If you want to be able to roller-furl, when setting the twin-jib rig you will need to drop the first jib, attach the heads of *both* jibs to the halyard swivel, then hoist them together. I've run the second jib up the spare headfoil track after the first jib was set, using a spare halyard. This works well but I cannot roll up the sails -- the second halyard (not on the swivel) will wrap around the headstay. I need to drop the second jib first if I want to reduce sail.

This is the advantage of the twin-sail, single lufftape arrangement.
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Old 29-04-2010, 11:09   #32
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If you want to be able to roller-furl, when setting the twin-jib rig you will need to drop the first jib, attach the heads of *both* jibs to the halyard swivel, then hoist them together. I've run the second jib up the spare headfoil track after the first jib was set, using a spare halyard. This works well but I cannot roll up the sails -- the second halyard (not on the swivel) will wrap around the headstay. I need to drop the second jib first if I want to reduce sail.

This is the advantage of the twin-sail, single lufftape arrangement.
That's interesting. What if you drop the first sail and hoist them together on one halyard, but in different tracks? Wouldn't that work?

The problem with sewing them together is that you will need two old jibs; you can't use your regular working jib as part of the rig.

Plus the two sewed-together jibs would be twice as heavy and difficult to handle. I can't imagine handling a sail twice the size of my 800 square foot yankee jib; you'd need four people to budge it.
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Old 29-04-2010, 14:45   #33
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Smacksman - I am still trying to visualize this setup. At the universal joint, do the poles cross each other, one sitting above the other, or do the two ends meet? Do you have any issues of chafe on the inboard ends of the poles? Also, for 18' poles, what would be a reasonable diameter of the pole?
Here is a pic of the final Mk.2 universal in a rope crucifix form -

The loops of the crucifix are a little long so the overlap is a bit too much but it still worked beautifully allowing the poles to rotate laterally and axially. The pole ends were being chewed by the expensive stainless Mk1 universal so I leathered the ends in Cape Town (excellent shop in town sells hides and leather off-cuts, palm, needles and waxed twine).
Letting the pole ends overlap takes the stress out of the universal after the first Mk1 design was trying to force the pole ends to a point which soon distorted the pole end fittings.

Alma's poles were about 16ft. long and 'reverse engineered' starting with the pole end fittings that were available in Lanzarotti, a short length of ally tube with i/d that would fit and then the body of the pole was tube that would fit the o/d of the end poles. It ended up about 2"/50mm diameter thick walled (about 3mm) ally tube for the middle section like ally scaffold pole with the sections pop riveted together. Very cheap and cheerful. The poles also did a good job spreading the awning in harbour.

The compressive loads on the poles are not anywhere near those of a spinnaker pole on a close reach. Here is a clip of me pulling the ends of the poles apart in 20 knots or so of Trades. I would never be able to do that with a bag up in that strength of wind!

@Dockhead - That is exactly what I would do for bigger sails of heavier working cloth and if I had only one furling gear then I would set it up in harbour and set off with it rolled and ready for action. If circumstances and weather changed and you had to beat with it then sailing close hauled with one of the twins nestling inside the other works well for a few hours. I wouldn't like to do it much longer than that for fear of chafe on the stitching. Anyway, engines are for windward work

Also a good argument for twin roller reefing forestays. Excellent flexibility for choice of sailplan and good insurance.

Slightly off-topic but with reference to furling gear. If the sections of the foil are secured with grub screws and not pop rivets, make sure that the grub screws are glued in with Loktite or similar. From new furling gear fitted in Knysna, South Africa to the time we arrived in Brazil, a quarter of the grub screws were lost forever and many of the remainder had unscrewed so that the top swiveler would not slide down the foil and therefore sail could not be dropped. This is a potentially dangerous situation. End of lecture.
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Old 22-06-2010, 02:39   #34
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Size of jibs? Well if they are on a furling gear then the bigger the better. Often, the length of pole you can easily stow on board is the deciding factor due to the width and curvature of your side decks.
If you are heading for the Trades then they blow on average 15 knots so maybe try your boat out locally in that sort of breeze with a jib poled out and another set flying and sheeted to the end of your main boom with the main stowed. It will give you an idea before spending a lot of money.
I think I read somwhere you had two 120% genoas sewn together, that's quite a large sail area and would be more than the main and genoa for us. At what sort of wind speed did you start to reef them in?

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Old 22-06-2010, 05:24   #35
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Hi Pete,
No - they were a pair of No.1 jibs with quite a high cut foot, less than J - maybe 90%J. Sorry to be vague but it was a case of working backwards from what we had and then finding a second hand sail that matched to make the pair for the twizzle rig. The mention of 120% is the ideal length of the twizzle poles - a fifth longer than the mitre length of each twizzle jib.

We would have liked to use two genoas as many times we could have done with the extra canvas but the poles would have been too long to safely stow on board. As it is so easy to reef, the bigger the sail area the better.

We reefed when we began to feel uncomfortable. We took a few rolls in earlier at night when the wind picked up or when it shifted away from dead aft or when the sea state got lumpier. But about 20 knots would be a good average. The most when I was on watch was 35 knots gusting 45 knots and we reefed till there was about 25% of the jibs out and we were quite comfortable. That happened when we were out of the Trades and into the ITCZ where it was quite wet and squally. The SE Trades were just blissful sailing across the South Atlantic.
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