mike612 said...

Maybe you could explain why your mainsheet is run through a block that provides tension on a downhaul when there is load on mainsheet.

mike612 you posed this question in another thread and got a flippant response, hopefully this explanation is a little better for you.

(taken from www.seabreeze.com.au/forums/Land-Yacht-Sailing/Construction/need-help-with-first-build/?page=3 )

the mast is the key thing to put the draft (or curve) in the sail and take it out to get better speed, the down haul also assists the flattening but it also moves where the draft forms in the curve of the sail, down haul brings it forward which give forward motion rather than tipping force.
There are several versions of down haul systems, the one I have used over the years is....



Its also worth noting in that thread how informative the threads were back then without all the garbage and crass comments being made where people actually discussed the theme of the subject and were interested in learning rather than quote upon quote, the innuendo and social comment.