Paul wrote:
Considering a better aspect ratio (higher mast) is not a realistic way to go (though it would be the most effective), what else can be improved? There is one major issue in which the sewn-in, cambered junk rig (and the split rig, too) defers from the bm rig: the batten pockets and separate panels, which reduce the amount of "good" profile shape to about 60-70% of total sail area. Hmmm! Hinged battens with flat sail don't suffer from this, as well as David T.'s wingsail. Taking the wingsail aside, due to its other aerodynamic benefits: would a hinged batten sail work significantly better upwind than a sewn-in camber sail?
Paul,
I had my Albin Viggen Malena’s sail, with both flat JR (tan), the same sail with hinges (NL #24), and finally a new (blue) sail of the same size and with cambered panels (NL #30). I don’t dare to draw too firm (or objective) conclusions - there were so many factors flying about - but here are my subjective impressions, as I remember them 30-35 years later.
Btw. when I rigged Malena with her first JR in 1990, I had already sailed her a lot for the last nine years, so I knew her well.
- · 1990: Her first flat sail was a huge disappointment when it came to sailing in light winds and upwind. There were a few missed tacks - unheard of with the original rig.
Malena was simply a lame duck in light winds. Had I not found a way to improve the rig, I would have scrapped the sail and refitted the Bermuda rig.
- · 1991: When I modified the battens with hinges to produce a symmetric 10% camber in the same sail, the boat was like transformed. Suddenly she became powerful and close-winded. In light winds I even overtook another sister boat by being more close-winded.
Now, suddenly Malena felt over-rigged - the 80kg mast on a 1400kg boat, simply became too much. The remedy was to chop a metre off the mast and plane off 1-2cm of its diameter.
- · 1994: The first sail with 8% cambered panels, planned from the start, was built. The mast was still the shortened one, so one of the panels of the new sail was rolled up tightly on the boom, pending the arrival of a new mast.
So how did these two sails compare?
For brute force, the hinged batten sail may have been the strongest. However, the hinged sail had 10% camber versus 8% in the barrel-cut sail. On the other hand, the cambered panel sail had had the max-camber point positioned further forward (35% versus 50%), so the added weather helm experienced with the hinged sail, was gone. Overall, I felt that the cambered-panel sail was as fast or a little faster to windward than the hinged sail.
Many words have been produced about the possible reduced efficiency in this sail, near the battens. However, if we look at the first and last meter of these panels (near luff and leech), one will see that the groove is almost none-existing; the air entering the sail and leaving it will meet an almost homogenous sail (consistent angle of attack and departure).
I know, I know, these are armchair speculations from my side, so I leave it to you to look more closely into it. Until you find any hard evidence, I conclude that the cambered-panel sail is about as efficient as the hinged sail, and with much more freedom to vary the sail’s mast balance. This last point is important when planning a real JR for a real boat to sail on real water.
Conclusion: hinged sail - been there, done that; thanks but no thanks...
Cheers,
Arne