Hi Richard (and others),
Tuned in late, but writing to say this is exactly the method Anke and I have settled on for our new rig (Split Junk Rig approach using flat parallelogram panels lashed to a 'round-only' curve, similar to Roger Taylor's 'hinged rig').
Roger's hinges allow 50% gaps along battens (and total gap in the fwd stretch) , but he reports good results. Lashing will remove the other 50% - likely at some cost - but we're still hoping for a solid gain while retaining the ease of construction from flat panels, and experimental flexibility.
Set-wise, this should be the equivalent of the round-only method, giving up only area along the battens. Roger's experience seems to indicate that loss to turbulence or other gap effects is moderate to nil.
One trick we've come up with:
We'll separately loft rounds (relative to straight-edge baseline) for 2, 4, 6, 8, and 10% camber, marked off at one foot intervals (which is our grommet spacing along top and bottom panel edges). For each camber, we'll mark off the round height at each station along a 'ruler' (likely a paint stir-stick), and then use these to set the lashing length at each grommet for the desired camber for any given panel. This should allow us to set camber with 'quality control'.
The best lashing we've come up with is several round turns of heavy nylon twine, seized near panel edge with a slipped constrictor knot.
Our principal interest is obtaining reasonable drive and pointing improvements in our ketch, SJ main, and to see how little camber, if any, we can get away with in the mizzen. We assume that a totally flat mizzen would have trouble setting downstream of an SJ main.
Chances are, once the dust settles, we'd then sew up a 'final' rig using round-only (barrel) method and closing the gaps.
Dave Z