We did "graduated" camber on Auklet's mainsail – flat on the top two panels, a little camber in the middle two, and more on the bottom two. I have consistently wished for more camber in the middle two panels, wishing that we had made them the same as the bottom two. The difference in upwind ability with the full sail up is striking – to the point that I often sail with more sail area up than I might, going upwind, just to have that extra camber. It's not a lot, but it really makes a difference.

Shemaya

.. keep it simple...

Early in my days of cambered JR, I wondered if there could be a simple way of flattening the sail, as on Bermuda- and gaff-rigs. I didn’t find one, and since reefing and un-reefing is so quick and easy, in particular on small size sails below 25sqm, I dropped the idea. Nowadays I like to think that I tune the sail area instead of the sail camber  -  much easier. This worked exceptionally well on my small and quite tippy boats; the 5.5m Broremann and the 6.5m Frøken Sørensen.

My present boat, Ingeborg, very forgiving with her big, ballasted keel, has the same sail area as the originals with Genoa 1 set. On her, as on the others, I let all the four lower panels have the same 8% camber. On top of a Force 4, I will already have dropped two panels (= mainsail and working jib), and on top of F5, I will be down on 3-4 panels (= 15-20sqm). Only these three top panels have been cut progressively flatter than the lower section.

I have never, ever felt “ Oh dear, I wish I had cut panel 4 and 5 (from top) flatter”. Not for a single time. This makes life easier on the lofting floor, as I can produce four panels from the same pattern.

Arne

 
Broremann...


Ingeborg can be viewed here

Another point that's worth making is that whenever there's flexibility in a rig, and the boat is in a seaway, there's fretting, chafe and fatigue too - the rig is trying to destroy itself from the inside.

Anonymous wrote:

I think it is wonderful that people are keen to experiment with new ideas, and I keenly follow their progress.  For me, though, the answer to making a straight-battened cambered junk sail flatter as the wind increases is very simple. You have a lot of camber in the lower panels and incrementally decrease it as you go up the sail, something like 8%, 6%, 4%, and 2% in the fanned panels.  As the wind increases and you reef the sail, it flattens out nicely.  Chris Scanes built a shelf-foot sail this way some years ago for a friend of mine.

Bonsoir

I completly agree, both in my sailing practice and experimental practice !

Eric

Bonjour

I've experimented, and still do with flexible battens and what I call lambda sheeting; two sheeting points one , one third from the leech and the other at the leech.

The rational is that I don't like, on a rather phylosophical engenierring point of view to incorporate stiffness in a flexible world. It's like having a needle next to a balloon.

I used Mingming flat sail for the purpose. I used standard 8mm to 10mm glass polyester battens stiffen by doubling or trippling them in the forward part. It worked quite well, as such. The issues are that you need two sets of sheets (it doubles the spagethi dish in the cockpit) the forward one/third part of the sail must remain resaonnably stiff otherwise you experiement the "S bendind" of the area of the sail in front of the mast  it is both inneficient and destabilisation). As a consequence, the forward part of the sail is flat, the middle is bent and the rear is rather flat. In therms of aerodynomic it is far the optimal. It could work with additional camber in the forward part of the sail.

The reason I continue the experimentation of the lambda sheeting is because I would like to use it to devellop a flexible junk-wingsail with forward wishbone out of the same battens (and a round leading edge out of solded steinless tubes) and flexible tail behind. I've started to build the wishbones but I have no views yet.

Eric