Who is inventor of loose leech?

The use of the 'Cunningham hole' is interesting because the explanation says increasing downhaul tension moves the draft forward in the sail. In my experience, this is opposite to what it does in a windsurfing sail, at least in cambered race sails.

Wikipedia quote: By either hauling or easing the line, the tension in the luff can be changed, thereby shifting the point of maximum draft of the sail forward or aft respectively, optimizing sail shape and thus performance.

Sailquik, pulling more DH on windsurf sail effectively does the same thing as pulling more cunningham? More DH loosens leech so depowers the sail.
Cunningham also depowers the upper sail by moving the draft forward. Therefore depowering the leech. Just does it a slightly different way, due to much stiffer mast??

A bit off topic, but an interesting read for those who missed it.

www.clubmarine.com.au/exploreboating/articles/24-3-50-knot-out

yes, all true. But the draft definitely moves back. That does not mean the sail becomes unstable. When sailing the draft is still locked.

Draft moving slightly back with finer entry is great for upwind, and also for reaching in lighter winds (high apparent wind compared with true wind speed). Maybe not so good for deep downwind speed sailing in strong winds. Sometimes it's better that have less DH and more OH for upwind. Keeps the leech tighter. But during speed sailing sessions, I never change the DH to sail upwind. Too time consuming and hard to do on the water. I DO adjust the outhaul for upwind though. That is easy and makes a big difference..

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sailquik said..
The use of the 'Cunningham hole' is interesting because the explanation says increasing downhaul tension moves the draft forward in the sail. In my experience, this is opposite to what it does in a windsurfing sail, at least in cambered race sails.

Wikipedia quote: By either hauling or easing the line, the tension in the luff can be changed, thereby shifting the point of maximum draft of the sail forward or aft respectively, optimizing sail shape and thus performance.

Well I think they are simply different controls. But let's give a bit more detail on how they work.

A Cunningham hole is or was traditionally used in conjunction with a stretchy luff panel and this is meant to flatten the luff entry rather than to bend the mast as we windsurfers do. In the days of cotton* and then dacron sails, the luff panel cloth was positioned so the cloth bias would be under tension - that being stretchier than if you line up load with warp or weft.
The tension is applied to the boat mainsail for upwind work so that the boat will point higher - or to allow the jib to be sheeted in tighter, also for upwind work.
Another aspect of the luff panel tension is that it can stabilise the sail entry shape, compared to a rig with no luff panel tension - so in that sense it can hold the sail draft forwards. Laser dinghies are obvious examples of this, although their adjustable luff tensioner can't strictly be called a Cunningham hole. The Laser sailor bends his (unstayed) mast by sheeting in hard which in turn adds pressure to the mast via the boom, or by cranking on the kicking strap for upwind work. Those are two control options we windsurfers don't have.

(*The original Cunningham hole was invented to deal with the sag you got with cotton sails when they got wet!)

Our windsurf rigs are different from this concept, so downhaul and Cunningham hole tension are not the same.
Our windsurf racing sails are cut with non-stretch luff panels so that downhaul tension bends the mast. And so increasing downhaul tension flattens the sail at the luff - which might be good for upwind work or because it also releases the leech when we are overpowered. Where the leach is released with extra mast bend, the sail drive should stay where it was, even though the luff is flattened. But when we add downhaul on the beach we usually add outhaul too.

The RS:X boys will let their adjustable downhaul off for heading downwind, because the reduced mast bend gives them more belly in the sail to go broad. Obviously they slacken the outhaul too, and that's good for twist which you want more of when heading downwind.

Speedsailing has also been mentioned on this page, and let's not forget that twist is very important for them - they need their sails to depower and to exhaust well, but they also need a lot of twist when heading so broad off the wind.

Those early windsurf rigs were simply different beasts.
They started as simple triangles of dacron cloth, sleeved over a crude mast and held in a triangular shape by a sloppy floppy wishbone boom.
Any twist in the sail leach was only held back by the weight of the boom, or by the sailor hanging off the boom.
But the sails would still twist open at the head as the mast bent sideways under load. The lack of battens and lack of sailcloth panel tension meant the shape of the sail could easily distort - and flattening off with downhaul and tightening the downhaul knot and perhaps adding a tack strap tensioner was all you could do to keep control in windy weather. The bendy boom meant outhaul would slacken under load.

The sails then developed of course and boom attachment got better (slowly) and battens were added at the head first to flatten off the foil shape there. Eventually we had a pulley and cleat arrangement at the mast foot which could be used to add tension to the luff panel. But these were the windsurfing equivalent of Topper dinghy rigs. A bit basic.
What year did we stop rolling our sails around the mast?

It might be interesting to document the changes in our rigs with photographs from each year, if someone can be bothered to do the research.
On topic, loose or open leaches always existed, as did sail twist, but the concept of the 'loose leech' came to mean something more special for a while in windsurfing, once the concept of using downhaul to control mast bend came into play.

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Basher said..
Those early windsurf rigs were simply different beasts.
They started as simple triangles of dacron cloth, sleeved over a crude mast and held in a triangular shape by a sloppy floppy wishbone boom.
Any twist in the sail leach was only held back by the weight of the boom, or by the sailor hanging off the boom.
But the sails would still twist open at the head as the mast bent sideways under load. The lack of battens and lack of sailcloth panel tension meant the shape of the sail could easily distort - and flattening off with downhaul and tightening the downhaul knot and perhaps adding a tack strap tensioner was all you could do to keep control in windy weather. The bendy boom meant outhaul would slacken under load.

The sails then developed of course and boom attachment got better (slowly) and battens were added at the head first to flatten off the foil shape there. Eventually we had a pulley and cleat arrangement at the mast foot which could be used to add tension to the luff panel. But these were the windsurfing equivalent of Topper dinghy rigs. A bit basic.
What year did we stop rolling our sails around the mast?

It might be interesting to document the changes in our rigs with photographs from each year, if someone can be bothered to do the research.
On topic, loose or open leaches always existed, as did sail twist, but the concept of the 'loose leech' came to mean something more special for a while in windsurfing, once the concept of using downhaul to control mast bend came into play.

They also had a leech tightening line from memory