What does the kicker do?

Lot's of oversimplification in the diagrams.  Because much of the force is applied to the mast through the sail, pulling 'downwards' (down the leech) on the upper mast.

Originally posted by Medway Maniac Indeed, a completely different situation on an unstayed rig. So far as I can see, on the RS300, if the boom is to rise then the mast has to bend below the gnav attachment point, but the leech tension should be maintained as the mast tip also moves forward. Likewise the EPS. Using a conventional kicker on the EPS would have little effect on leech tension (might be a little softer even), but it would result in less rig movement, since the boom end wouldn't lift as much. Would be interesting to try it. Would also be interesting to know designer Yves Loday’s rationale in adopting a gnav; maybe just to avoid fouling the raised daggerboard?

I imagine it was fashion rather than function in the case of the EPS, particularly since the 'lowers' act well below the upper impact point of the GNAV strut. It seemed to be the de rigeur device of choice about the time I came on the scene, almost every boat I've owned has one and it was only when they rigged the V2 with a proper kicker I got to see the difference, which was not the best option on the spaghetti RS700 mast we used.

Why however do you feel a conventional kicker wouldn't tighten the leech? I did flirt with rear sheeting for a while which occasionally I'd like to revisit, I'm sure my windward work was better, but without an elastic band the downwind clew first stuff doesn't happen so easily in light air having all that warp off the boom end, you could almost do with some sort of variable system that could be changed on the fly.

The V3000 has the boom joined to the mast using a hole and pin arrangement (as do the Vago and RS500 tom name but two)