I'm glad you asked that question, I've been wondering the same thing.

(sits back and awaits enlightenment from the numerous studied and informed windsurfers on this forum)

I think if you downhaul the sail properly, neutral should be either a) the exact boom length given in the specs (but in your case, it's a range of lengths, not so simple) or perhaps just adjusting the boom so the clew isn't pulled out at all. Or maybe 2cm.

OK I give up. Greenleader, what's the answer?

I use neutral or negative for more power in downwind runs. If the spec says boom length + 1-4, I would use the boom length. For my cammed sails I would use no outhaul tension. Set the boom to where the sail naturally sits with the correct DH. For negative, it's below the natural set of the sail. No cam sails may need a little outhaul just to get to minimal rec setting.

You would need to move your harness lines back to take advantage of the the extra power / backhand pressure.

Windxtasy said...

How do you know if you've downhauled the sail correctly?

Manufacturers specs are a good starting point. I use pryde sails and they're reasonably accurate once the sail is stretched in. The other indicator is the shape of the sail. I have marked a couple of my sails with a sticker where the ripple in the top part of the sail stops for the preferred setting.

There's a good rigging tips video on the Pryde site, tha approach applies to any sail