OK imagine a wing on a modern plane and the small triangles they strap on the end of the wing (winglets). they act to stop the circulation of flow around the end of the wind making it more efficient.
Why could you not do something similar on a national and have a winglet on the top?
Jon
P.s. if someone steals the idea I want commission!!!
You could, but there are lots of reasons why it wouldn't work well.
Modern aircraft wings are stunningly efficient anyway but the winglet adds a tiny bit more efficiency, not just by acting as an endplate, but by 'unwinding' the tip vortex. (The gain is small but the fuel saved in flying a large aircraft halfway round the world is significant.) To do this the winglets have a twist which assumes that the high pressure side of the wing will always be on the same side. (hopefully the bottom!)
The dinghy sail alternates the high/low pressure side every time you tack so a fixed twisted winglet would have the wrong twist half the time.
You could try a flat endplate but dinghy sails have a very low aspect ratio and are stunningly inefficient (in aircraft terms). The flow over them is a lot more turbulent than over a wing and I suspect that all you would do is to add drag and weight to the top of your mast.
I look forwards to being proved completely wrong! Go try it.
Somewhere down the discussion group there should be an entire thread on this subject. Got to admit I thought it was an interesting idea but if it worked then suspect that the ACC boats would already use it rather than having square top mains...
Would winglets then become unmeasured sail area if they work?
There was one ACC boat that tried it as a boom, 'Enterprise' winner of the 14th cup. (amazing what google knows!) you could actually walk along it and it would double as a sunshade!!
But boom restrictions have stopped it.
I think I might go back to the drawing board!!
You would be better basing your considerations upon sailplane design, of which the prevention of drag is taken to be of prime importance. It is also worth considering that drag has the same effect in water as it does in air.
maybe but I don't fly!