by having the pivot point offset. as you tighten the forestay the leech get tightened. which is not a bad thing, but you need to be able to counteract the tightness of the leech by adding topping lift. if you had no offset, you would have zero leach tension. which is bad.
but yes as you add topping lift(lift up on the club) the forstay will tension. also which will also bring the backstay into the mix, which may then add bend to the mast with will change the shape of the main.
change one thing, and 5 things react… too much bend in the mast, and the main looses it shape… so its really is a balancing act of adjusting and tweaking and finding the right mix. but you really want to have some tension in the forestay otherwise the leading edge of the sail will want to flutter which is not good. Imagane a blade with the leading edge of it wing all loosey goosey… nor real efficient…
in heavy air you will need more tension…and lighter airs less tension…
