Paul Thompson wrote:
Graham Cox wrote: I remember David used acrylic on Tystie's big red sail. as he called it, the junk sail he had before going to a soft wingsail. I remember he had some chafe issues with it. I'd like to ask him about his experiences with that sail, his views on the best sail material to use (Odyssey 111?), and some other issues. I remember he had a vang on the boom to haul the sail across the mast when before the wind. How did that work in practice? Did it make a significant difference to the balance of the helm? My sail, at about 350 sq feet, won't be quite as large but it is still a big sail on a 24 foot boat. (You can see photos of my boat on Bruce Roberts Website on the Tom Thumb 24 page.) I also seem to remember, from photos I saw in PBO shortly after Tystie's launch, that he did not have fixed batten or yard parrels. I would have thought they are essential to control the sail when hoisting ot lowering. Perhaps I missed something. What were the significant factors in the decision to change the rig, and what other advice would you give to sailors contemplating relatively large, low aspect ratio single sails?
Graham, sorry for the delay in replying, I'm travelling around England with infrequent internet access.
Actually, Tystie had two "big red sails". the first was made by Chris Scanes (I was too busy boatbuilding) from acrylic, with barrel-shaped cambered panels in the lower part, and an essentially Hasler planform. This wasn't satisfactory, because 1. acrylic can't handle the chafe in such a big heavy sail, and 2. the Hasler planform is not really all that good. I came home from trips up to Lofoten and around Scotland (5000 miles), and made the second sail myself, to the planform that is shown in 'sailplans in current use' in the public pages, with shelf-foot cambered panels in the lower section. This was a great improvement, with better performance, and I sailed it for a further 10,000 miles. The running rigging ended up as:
3 part halyard; 3 part sheet with two 3 part spans (30:1 winches for both); a yard parrel that was fixed to the yard as far above the halyard attachment as possible; an upper luff parrel that started at the heel of the yard, went around the mast to the third batten down, around again to the fourth batten down, and to the deck; a middle luff parrel to the fifth and sixth battens down; and a lower luff parrel to the seventh and eighth battens ( the eighth being the "boom"). This lower luff parrel came aft through a clutch, and returned forward through a clutch to go up to a block in the middle of the eighth batten, around the mast and back to the becket of that block. This is not so much a kicking strap (if you pull too hard, the batten just bends), more a means of hauling the sail across the mast for running. This is very effective on a low aspect ratio sail, reducing weather helm greatly when running fast and overcanvassed.
All those luff parrels give good control over the tendency of the sail to crease diagonally, and Hong Kong parrels are not needed. They also give sufficient control over the sail when hoisting and lowering, so that fixed batten parrels become less necessary. I seem to remember having one fixed parrel on the yard, one in the middle somewhere, and one on the bottom batten. The effect was to reduce the drag of parrels around the mast, when hoisting and lowering.
Why did I change to the ketch rig? mostly for the usual reasons of having more options, more belt-and-braces, for ocean sailing. Why did I change to the wingsails? Because I'm an experimenter, and I don't like to do the same thing twice; and because the performance with two JR sails would not have been as good as with one JR sail. The extra performance of the wingsails made up for the loss in performance by going to a split rig.
Before I left to go voyaging, I made a sail to the fanned planform for Peter Manning's "Malliemac", the sistership to "Tystie". It will be interesting to sail her when she's launched next year, and compare how she goes to how Tystie goes now, under her improved wingsail rig. Who knows? It might be that I will wonder why I ever changed. A lot of "progress" turns out to be sideways, not forwards!
In conclusion, there's no doubt in my mind that the fanned sails that I made for Tystie and Malliemac are good sails. They are pushing the upper limit of sensible area, though they will be fine sails in a smaller size, say up to 400 sq ft. I have put a drawing, in a form that can be scaled to any desired size, into my own photo albums, in the 'Tystie' album.