Graham,

Ok, flat sail, then. However, if you have the sailmaker run a webbing type boltrope around the sail, you can any time you wish, add a little camber in the sail. You simply fit one or two small tucks at the luff of each lower panel, and at the leech of the top panels, and possibly also at the leech of the lower panels. That was what I did to force a bit camber into Malena’s flat Hasler-McLeod sail (below), back in 1993. It certainly was an improvement. Even 3 - 4% camber will make sailing to windward easier than with a sail, which is completely flat.

Anyway, good luck!

Arne

David Tyler wrote: That's bad. Really bad. In the second panel up, it can't be fatiguing of the cloth by repeated pulling on the diagonal, or straightforward overloading. It must be UV damage.

Well, I'm not sure that I like the word 'must'.  It certainly seems that way, but without actually having sailed with Graham's sail, I couldn't swear to the loading put on the different panels.  We all set up different luff parrels all of which, separately and in combination have slightly different effects on our very different sails.  I wouldn't have expected the second panel to get much sun on it, because it is well protected by the other cloth at anchor, and reefed early. 

I've been in touch with my friend Patrick Selman, a sailmaker in Cornwall discussing sailcloth.  Here are some of his comments:

'Clipper is still made.  It's polyester, and coated  with a UV coating,  it lasted  well but the sun will slowly destroy all plastics.  But if you like green I DO HAVE SOME.  If you send your address I will send you samples.

Not, I realise, deeply informative at this stage, but I just thought I'd mention it so that those following this thread will be aware that I'm trying to chase up an alternative to Odyssey and 'conventional' polyester.  I asked Patrick what the green material was, but he hasn't yet replied; however he is very aware of the fact that I want something that can live without a cover.

If you make your own cambered sails, you can shrug your shoulders and accept that every few years you have to set aside a week to make a new sail.  Not that big a deal in the scheme of things (and quite enjoyable for some of us).  Bearing in mind it will have a limited life expectancy, you can go back to scouting around for bargain fabric.  However, if you have to go to a sailmaker, this is a very different issue and those of us (like me) who stand up on our hind legs and pontificate, have a joint duty to do our best to source an appropriate material for sails for our fellow junkies.  My personal feeling is that Sunbrella type acrylic is the way to go.  Has anyone used this for cambered sails that have done much work?  (I know Ivory Gull had acrylic sails.)  Let's hope we find something.

One of the reasons junk rig suits me is that I am something of a ramshackle character and I am not the least bit concerned about a few wrinkles etc.  Arne's sails look beautiful to my eye and my black cambered sail owed much to his inspiration.  I loved the look of it and the performance was outstanding.  I am going to miss it.  There has to be a reason why my sail failed so spectacularly after such a short period but I don't know what it is.  Either poor construction or UV damage or probably a bit of both.  I note that both Alan on Zebedee and David on Tystie have sailed many offshore miles with cambered sails, so it is not just that the sails are only suitable for inshore work.

I do know that the Dacron sails on my previous rig withstood 15 years of hard sailing, sometimes with the portholes in the water in the days when I cruised without an engine and had to hang onto my sail when entering crowded anchorages in gusty conditions.  The sails were always covered when not in use, but I must have been underway for at least 100 days each year, probably more.  After about 12 years I began to get a bit of splitting on the leach of both main and jib but kept them going for another couple of seasons by regular applications of stickyback Dacron.  By that time they were ready for the rubbish tip but I was happy with their service.  It was then, faced with new sails and a rebuild of the standing rigging, that I decided the time had come to fulfill a long-held desire to convert to junk. 

I originally intended to build a flat-cut Dacron sail, noting that Ron Glas is still sailing with Jock's original flat-cut Dacron sails after all these years, although they do look a bit tired, admittedly.  That's 40 years!  However I was seduced by the promise of a UV stable sail and the performance of camber.  I don't regret it, I had fun and learned a lot, but now I need a new sail and, faced with not knowing why my cambered sail failed, I have decided to leave experimenting to other brave souls and stick with tradition.  To me that means moderate weight Dacron, vertically cut, triple stitched and flat-cut.  I do believe that a sail like this will have less stress on it, but I'm not saying there aren't other ways to go, just that I know this way will not fail me, and when I am offshore, especially since I am becoming increasingly frail, that is the major criterion.  If I was sailing inshore on a performance cruiser, I'd probably make different choices.

I have always admired those who build their own junk sails on "the kitchen table" and was attracted to the idea that you could cross oceans with large holes in your sails! (You'd better have vertical seams though if you try that!)  Eric the Red had sails made out of bed linen, originally, and Donald's second set were cut from an old cotton sail given to him in the West Indies, though he spent a lot of time repairing them.  My cambered sail didn't just have a few holes.  The entire top panel came apart in my hands and a small hole in the second panel above the boom also allowed me to split the sail from luff to leach with one finger.  I did not "destruction test" the other panels but see no reason to trust them further.  Today I took the sail ashore and put it in the rubbish bin. 

Possibly, Mark

However, if those smiling wrinkles along Johanna's battens (not to be confused with large, diagonal, camber-robbing creases) are so untidy in your eyes, I think that Slieve's and David's method with adding broadseams or false broadseams to the barrel cut panels, is a faster and simpler method to remove those wrinkles. Both methods, barrel only, with no tension along the battens, and barrel plus broadseam, will offload the corners, as long as there is a strong boltrope at luff and leech.

Graham

What you say, below, indicates that you think the load will be lighter on a flat sail than on a cambered one. I am not so sure if that is the fact, or need to be:

Take a close look at Johanna’ s sail. It is made with about 8% camber (much less in the top panels), using the simple barrel cut method with no broad-seaming. To let the sail bulge to maximum camber, I, after a while, slackened the sail as much as 10cm (1.7%) along each batten. As a result, I got a bit extra camber, but I also, without thinking of it then, relieved the sail from quite some tension in each panel’s corners. The ’smiling’ wrinkles you spot along each batten is not stress wrinkles, but ‘slack wrinkles’. To me this seems to have been very kind to the sail. If one is put off by those untidy wrinkles, one can use Slieve McGalliard’s or David Tyler’s refined barrel cut method, adding 3(?)  broadseams along each batten.

See how the two Davids did it here to make Footprint’s sail (under Documents and David Tyler's files):

http://www.junkrigassociation.org/members_files

Two factors should indicate that flat sails see less stress:

·         The flat shape produces less force for the same area.

·         The flat sail will not flip-flop back and forth as the boat is rolling in calm winds.

However, a baggy panel can take the wind force with less tension, simply because it is baggy. Just imagine a slack line (to balance on) and a similar taut one. If a tension-meter were fitted to both, the slack line would show a lot lower tension.

I do repeat, and I do stress: On cambered panel sails the fitting of boltropes must be taken seriously. They must not stretch, and they must stand up to sun, rain or whatever.

Sooo...
this is what I recommend to do to make a cambered sail last:

·         Find a sail material with the best sun- and chafe-resistance that you can afford. Form stability is of less importance  -  the panels will not blow out of shape.

·         Build camber into the sail, using the barrel method. If you fear you get eye-sore of looking at the wrinkles along the battens, add broadseams to take away about 1.5 – 2% along each batten before assembling the sail along the battens..

·         If the simple barrel-only method is used, rig the sail with some slack (1.5-2%) along the battens.

·         Pad the batten pockets at the mast well.

·         Do not use metal eyelets anywhere, much better with webbing hoops which spreads the loads.

·         Add tablings (1 – 3 layers) along luff and leech if you are to do serious offshore sailing. They are not meant to act as boltrope. Their mission is to make the luff and leech stiffer and heavier and thus reduce wear, caused by fluttering (of reefed panels).

·         Fit a good boltrope around the whole sail. If in doubt, double it along the leech.

·         Make an easy-to-use sail cover, which quickly can be dropped over the sail, in harbour. If that still is too awkward to use, just make a “sail bundle-end bag” so at least the luff and leech areas are protected.

Cheers, and good luck,
Arne.

PS: Even if one is to make a flat sail, I recommend adding a boltrope and some tabling, to reduce the likelihood of fluttering and tearing the luff/leech.