Graham

Now I have had a good look at photos of your rig.

(click to enlarge)

From the photo above it looks as there is a strong vertical stretch along the luff and leech, in particular at the leech of the top panel. I wonder; what you call heavy tabling around the sail  -   is that the extra layers of Odyssey, or is there also a special webbing? The thing is that whatever it is made of, it appears to have stretched so that the sailcloth inside the edges has to take big loads. That is when cambered sails suffer; when the boltrope is too weak or elastic.

I noticed this early on the blue sail of my Johanna: The webbing used for boltrope was too elastic so the load moved to the sailcloth. Hand-stitching on an extra boltrope (old halyard), mostly cured the problem. See the write-up “Wrinkles”, page 3.

If you are to make a new cambered junksail (I hope so), I suggest you give the leech a double (sandwich) layer of 50mm seatbeltwebbing for boltrope at the leech. A single layer should do along the luff, head and foot. It is imperative that the boltrope takes up all the tension from the sheets along the leech. The sailcloth in each panel is only meant to collect the wind and deliver the wind-force to the spars and boltropes surrounding them.

Anyway, good luck,
Arne

PS: When I, in an earlier posting, suggested adding a tabling along the luff and leech, it was not to make it work as a boltrope, but rather to make the edges stiffer and  more resistant against fluttering, when reefed away.

PPS: Could it be an idea to divide the new sail (similar AR) into 8 panels to ease the load in each panel?

I should have added another item to my previous list:

Prevent relative horizontal movement (due to pitching and rolling) between battens and mast, and pairs of battens when reefed. Short batten parrels and standing luff parrels will help. Right now, I'm drawing on my wingsail experience, and making UHMWPE components from 10mm sheet, with a semicircular cutout to engage on the mast, that will be fastened the lower battens. These will entirely prevent such movement. It doesn't seem reasonable to fit them to the upper battens, because of the mast bend and the mast taper. A YHP and short batten parrels on the upper battens will still be needed, to permit some adjustment.

Quite right, Arne. Horses for courses. What will suit a weekender won't be good enough for a serious coastal cruiser, let alone a rig for an attempt to sail around the world non-stop.

I'll try to sum up what I've learned about making rigs with longevity in mind.

1. The cloth breaks down near the leech, mostly in the lowest three panels, due to flapping when the sail is reefed. A doubler up the length of the leech, with a width of up to10% of the sail width, will go a long way towards mitigating this.
2. The topping lifts will chafe the lower panels, due to trapping loose cloth between a rope and a hard spar. Putting a soft plastic hose onto the topping lift spans will help, but my preferred solution is to make a triangular sail-catcher of cloth, with heavily reinforced edges, sew it to the foot of the sail, and tie the topping lift directly to it. 
3. The mast lift will chafe the luff of the sail, for the same reason, and a triangle of cloth here will spread the load.
4. The bottom three panels near the luff are subsceptible to chafe when reefed, again due to being trapped between mast and batten or batten parrel, and a doubler that covers the entire mast area in the lower half of the sail is a good investment.
5. The topping lifts will chafe the seams of a vertically seamed sail, so our modern practice of making an entire panel from one piece of cloth is preferable.
6. The battens will chafe vertical seams also, so a patch should be fitted under a batten pocket.
7. On a high peaked sail, the peak and throat should have three or four patches of increasing size, to spread the loads into the sail, as for bermudan sails. On a low angled yard, there should be a doubler along the head, and putting the yard into a pocket of heavier material is an elegant way of achieving this.
8. Battens should be smooth. Anodised aluminium and gloss-painted wood are satisfactory.
9. The mast should be smooth, hard and round. Anodised aluminium is good, as is gloss-painted, glass-coated wood. A rough, faceted surface is bad.
10. The cloth and stitching should have some UV protection. I use black thread. Acrylic cloth is very good. Mustang and Top Gun seem to be OK, but I would only use a normal polyester sail cloth that had had an anti-UV treatment.
11. The only way to check whether you've done enough is to go out and make a passage of at least 10% of the length of the longest passage anticipated. The OSTAR organisers are right to specify a qualifying passage of 500 miles. For an attempt to sail around the world non-stop, starting from NZ, a 4000 mile proving passage would be indicated, and Hawai'i would be an obvious destination, with facilities enough to make the inevitable repairs and modifications. I'll readily admit that I don't know how to make a sail that I could guarantee for 40,000 miles without attention being needed.

Arne: Aubrey's sails were made of inexpensive polyester and had lived for about 10 years in the Med before he sailed down to S Africa.  He had never covered them.  I think it's fair to say they fell to bits simply because the cloth had degraded so badly.  They'd have died a lot sooner on any other rig!

This is getting interesting.

Firstly, we must understand that we have different needs and live under different (sun) conditions. While Australians and Kiwis clearly must protect (themselves and) their sails from the burning sun, Ketil Greve and I, who live under «sub-arctic rain» at 59°N, need not worry that much about that.

Secondly, we use our sails differently. Ketil does racing. Performance has priority over longevity, so his present sail is of spinnaker cloth (details, please, Ketil)! I just potter about, so any cloth, which comes in wide panels, and which my sewing machine likes, can be used.

The fact that I now am quite fond of the Odyssey, for my use, doesn’t mean I think it is the only usable sail material for making cambered panels. As early as in 2006, Sebastian Hentschel entered the scene with his 80sqm cambered panel sloop JR (see newsletter 48). That sail was made from ordinary (cheapish, stiff, doped) Dacron sailcloth.  However, Sebastian is now on the third sail on his Peregrine in less than 10 years. He is a sailmaker, so is probably trying new ways and materials. I can clearly understand why David Tyler, with his extreme long-distance sailing in mind, searches for some tough UV-proof and chafe-resistant sail material, so again, I am not trying to push Odyssey on him, or anyone else  -  it is just good enough for me.

I notice that the matter of form stability of the cloth is sometimes up here. I would not be too worried about that. The load in a junk sail is only a fraction of that in a western sail of the same size (gaff, lug, etc), so the cambered panels will not blow out of shape, as far as I have seen. A ripstop-woven cloth like Odyssey would never be accepted for ordinary sails, as its diagonal stability is very poor, but for my use it is still perfectly good.

A digression  -  about designing sails: Whatever the sail planform you are to make, do not think that you save anything by reducing the number of battens. By saving one or two battens, you increase the load on the remaining ones, and the load on the cloth in the taller panels will also be increased.

Finally, after all this focusing on (lack of) longevity of some junksails, let us not forget what the long-distance cruising people under western sail have to endure. From the books I have read, it appears that they are doing sail repairs in every other harbour.

Cheers, Arne

PS: Annie, sail cloth problems are not restricted to the cambered sails  -  re-read Abrey Hinchcliffe's report in NL29, p.25. And yes, about sailing with pointy rigs. It happens that I sail for an afternoon in friend's boats, and then I silently congratulate myself for having converted my boat to JR.