Ginga, fighter version
Shame shape as the small Ginga. No battens,but there is some trailing edge flapping. Adding battens would make it silent and presumably a little bit faster.
Flat, just with a curve at the nose
The curve is pushed by the tension applied onto the spine and helped (and tuned) with a tensionner.
Fully framed with 3mm carbon fibre spars. The central spar is thinned down to 2mm on a length of 20 cm to help it bending. The central spar is just sewn every 5cm to the sail.
Home made central cross: a piece of 4mm aluminium tube glued with epoxy cement and then shaped into some kind of clip.
Another type of central cross: a simple aluminium hook, epoxy glued on the spar and then bond with thread and cyano glue. That's much easier to make.
Tail tensionner, as in all Gingas, the sail is firmly tensionned to induce the central spar curve.
Nose reinforcement; make it strong ;-)