Anonymous wrote:

PS: I have never seen any warnings against cambered sails for offshore gaff rigs...

That might be because anybody who struggled with a large gaff main offshore in a hard blow either got swept overboard by the billowing sail or was knocked unconscious by the boom tackle block and didn't live long enough to give a warning. 

While I am not here to defend the gaff rig, my Gazelle ketch has a large gaff main. It's fairly manageable because you can "scandalize" it (depower it) by dropping the gaff halyard. Unlike easing the sheet on a pointy sail, this doesn't result in luffing and flogging. It just spills most of the wind. Still, I'd rather have a junk...

I hesitate to make any comment here given my recent conversion to junk and the limited miles that I have sailed under it but could I please inject into this conversation the hinged batten ! This gives the flat cut sail a pleasing curve and also appears to creat significant power from the rig.

Together with the considerable input from  Alan Boswell we installed a hinged batten junk rig onto my Irens designed 9m hull built out here in Turkey. The hinges were Delrin cones fitted into 50mm aluminium tube with the angle of the hinges being progressively flatter from bottom top to achieve a flatter reefed sail.

It seemed to perform pretty well but without a matched test boat it is essentially a subjective opinion.

I am however also with Alan now building another rig which inspired by David Tyler will be a soft wing but again with hinged battens. This will hopefully be the prototype for a sails I will have on the new 70’, 3 masted yacht that will be starting construction here in a couple of months.

There s no fool like and old fool !!

[moderator adds - see a YouTube video of Alastairs build and sailing his vessel https://youtu.be/FjKQ1QwqapY?feature=shared]

Anonymous wrote:

I guess I play in the cambered sail league, surprise, surprise, and for much of the same reasons that David Ty. and Paul Th. mention. As for how much camber is right, I don’t know. On my boats, I have settled on 8% camber in the lower horizontal panels. Those 8% camber is measured mid between the battens, so over much of the panel, this max camber is less than 8%. Anyway, I use telltales at the leech to monitor (and ensure) attached airflow along the leeside of the sail. Despite the obstacles along both sides, the airflow seems to stay attached quite well, until I over-sheet the sail.

The top panel of Ingeborg’s sail has only 44mm round along its yard and top batten (B = 4.90m). Even so, the airflow appears to stay attached, and there is no flogging or shivering along the luff or leech.

This summer I can celebrate 30-year anniversary for my first fully cambered panel sail, made for my Malena. Pure bliss.

Cheers, Arne

PS: I have never seen any warnings against cambered sails for offshore gaff rigs...

Malena in 1994

Arne, when this photo appeared in my PBO magazine 30 years ago, I decided that any junk sailing under my ownership would have sails with cambered panels. Since then, I have rigged two boats with cambered panels, one of which has crossed the Atlantic and successfully returned. I continue to bow before you, my sailmaking guru.

Kurt Jon Ulmer is coming close to seducing me away with his talk of flat sails, with a form of camber supplied by twist. I like his elegant sail designs in which there are no heavy loads on any part of the rig. Aboard my 32ft schooner, I sometimes peered through the alloy yard and could not see daylight at the other end - the concentrated forces at the peak and the throat were bending that spar, making me wonder what I would do if, like Sebastian Hentschel's 'Peregrine's, it would break.

I am also thinking about the Kingfisher 26 'Chopsticks', where a cambered sail was made to replace the flat one and the owner now discovered that she heeled much more than before under the flat sail and became almost unmanageable because of heavy weather helm.

Shirley Carter is now in the Indian Ocean, ⅔ of the way around the world in her ancient Vertue, 'Speedwell of Hong Kong'. Some time ago, she converted her Vincent Reddish style rig, giving it cambered panels in hopes of improved performance to windward. From reading Shirley's excellent blog, I discovered that she was dissatisfied with the new sail, perhaps largely for aesthetic reasons, and went back to her flat sail.

These thoughts are preoccupying me at the moment, since I have just bought another boat, 'Rosalina', a Rival 32. I think she might suit me in all respects except for her one great defect - she is rigged as a Bermudian sloop. I don't know if any other Rivals have been given junk rigs, but I have started chewing pencils and wondering how she would look as a junk, and wondering where I could get a mast for her.

Asmat

90% of all the junk sails I make are cambered sails with between 4% to 10% camber depending on the use case and the kind of hull the rig required to drive.  I'd not consider anything but a cambered rig for a heavy displacement hull. Light hulls like Kurt's can sail well with a flat sail but will always do better with a cambered sail.

Flat sails are slightly easier to handle but there is not much too it.

If you are making your own sail, a cambered sail made using Arne's methods is actually easier to make than a traditional flat sail. That said,  there is nothing stopping you from using Arne's methods to make a flat sail.... 

I think that this question has long been resolved in favour of adding camber. There are, of course, many flat sails that were made some time ago, and since JR sails last a long time, there can be little inclination for their owners to upgrade them. I would think that most, if not all, new sails have some camber built in. It's actually harder to make a sail by the old PJR method of making the whole of the lower rectangle in one flat piece and then adding pockets, than it is to make separate panels, adding one panel + one pocket at a time; that being so, one might as well make those panels with camber.

How much camber? Well, I've sailed something like 120,000 miles under JR, everything from short day sails in a dinghy up to ocean passages in a cruiser. I have long been saying that for a trade wind circumnavigation, one doesn't need so much camber as for coastal sailing. I would advocate a minimum of 4% camber for a long distance offshore cruiser, and a maximum of 10% for a cruiser that operates in challenging coastal waters. 

It's easy to add a small amount of rounding to the upper and lower edges of each panel and easy to get a sail made that way to set well. In fact, a little fullness in the panels tends to keep the luff and leech taut and free from flutter, which breaks down the cloth. It takes more work and skill to make deeply cambered panels and get a sail made that way to set well; but always, some camber is advantageous. Half a dozen times, I've needed, or at least been glad of, good windward performance to break free of the ITCZ, or 'doldrums', in light and fickle headwinds. Countless times, good windward performance has improved my comfort, wellbeing and safety when making coastal passages in tidal waters.

Flat sails have had their day.