Hi Dave

Sounds like a lot of work to me! Remember that if you have too much sail up, or you need to reduce the power from your sails reef, reef, reef! With a junk rig reefing is dead easy so I would aim for a moderate amount of camber to suit your boat characteristics. On Footprints we have 6% on the lower panels and reducing in the upper panels. This is a good all round amount of camber for us because Footprints is a relatively light weight boat. Heavier boats like Paul's La Chica have more camber. Our 6% camber has proven to be effective in both light airs and stronger winds and both coastal sailing and ocean crossing. I found that when doing our 2 recent ocean crossings I very seldom had full sail up and often had either one or two panels down, and for a lot of time was down to only 4 out of 8 panels which was only about a third of our total sail area, and being the upper panels had less camber. 

Anke and I are planning our next boat and looking into cambered sails.

In reviewing all the great information developed by JRA members (and thank you so much!!) I had a brainstorm. Well... a braindrizzle, perhaps.

I observe that many folks would like as much as 10% camber, but settle for less -- sometimes much less -- in the effort to get the best match between performance over a range of conditions and other factors (aesthetics and handling chief among them).

In our case, we have a large, seasonal difference between summer cruising in mostly light air, vs. autumn/winter/spring cruising in potentially wild weather, punctuated by squalls and freight train gusts (williwaws).

It would be great to have a summer suit (deep camber) and a not-summer suit of sails (lower camber or none). Often, a weather pattern will settle in for weeks at a time, justifying considerable effort changing camber. If we could invest a mere hour or so to readjust in between, that would be most excellent! Quicker would be even better.

So, the proposal:

1. Shape panels for maximum desired camber (10%?).
   
   
2. Install lines of grommets along the straight-away traversing the fabric between batten ends at luff and leech (these are curved lines, relative to the battens, analogous to the curved edges of the 'lens' in the 'lens method' of construction... more sophisticated lines may be followed, if desired).
   
   
3. Lace up the grommets as one would a shoe, passing around the each respective batten. [Experiment may show half-lacing and/or simple brailing to be sufficient and quicker to adjust.]
   
   
4. Draw the two lines together until the desired camber is reached, adjusting tension as necessary, then make fast.

The bunt of sail between grommets would be controlled by the lacing, and held in-line along the battens. It would add turbulence, but (at least in fanned sails) Bunny Smith's experiments suggest this might be a bonus.

If this works, one could flatten out before setting out on a blustery day, or loosen up for a fast windward passage in lighter weather. Or racing/showing off? Or somewhere in-between for decent performance under dapper sails.

Note: Half-lacing/brailing would give very positive control, drawing against battens along the edges of panels.

Guidelines can be struck (marked between grommets) as the target for various percentages of camber, using whatever theory of curvature desired.

It seems likely to me that there would be a trade-off between low friction (for easy adjustment) and higher friction (for holding set edge shape). It's possible that friction could be induced in an otherwise low friction set-up.


*****


Any of you with experience under cambered sails, does this sound workable? How about advisable? Observations, suggestions, improvements or alternatives?

Dave Z