I think it would be far more interesting getting SimonN's opinions of the potential use of wing sails in a class he sails such as the 18's (don't they still allow rig development?)
First off, Rob, I think this comment is very unfair. I haven't owned a Moth for about 6 months but if my back gets up to it again, I will buy another. I cannot actually imagine that I will never own a Moth again. I built my first Moth in 1973 - it was actually my second moth - and in the intervening years have owned (I think!) 9. And for the record, I stopped sailing 18's before I sold my last Moth!
However, I do currently sail a class, A Class cats, where wings have been tried and where I will possibly build a wing. However, there are some serious issues. The wing that Ben Hall built was, IMO, too heavy and not strong enough. It flexd too much which meant it wasn't quick upwind. That wing is now owned by Oracle Racing and the word is that they sorted this issue out. It was very fast downhill. But the really big issue with a wing on an A is weight and the centre of gravity. In any waves, an A pitches and with a heavy rig, it's not good. Ben Hall describved it as "the tail wagging the dog!"
Ben's wing weighed about as much as all the gear he took off his boat from the conventional rig, such as mast, sails, mainsheet system and track. The problem was that the weight was significantly higher. Another issue is that A Class rigs are tall - the mast is 9 metres long.
The A's also have pretty well developed rigs with wing masts and soft sails. The section length of the wing mast is about 335mm. There is a train of thought that such a rig is already fairly close to teh performance of a wing sail rig.
I do, however, believe that if we use unobtainium and build wing light enough, it can be a winner. Being a bit more serious, the way of reducing the weight of the rig is to reduce the complexity. Ben's wing had twist in the front and rear elements, but had no "middle" element to control the slot. The fear is that the way forward would be to build a wing with no twisting front element, which I think could be light enough. However, the lack of twist might really hurt the downwind performance.
I have been discussing this with Adam May non stop since he built his wing and we have the design but I am still not sure whether to build. I think there are still a few tricks to try with a conventional rig which will give us many of the downwind benefits of the wing but still give us the current rig for upwind and when the boat pitches.
Some have also commented on how difficult Ben's rig was to manage. Compared with the Moth, this wing was both very tall and far more area. The boat had to be rigged on it's side. The wing did break down into 4 pieces for transport. If I build a wing rig, I am not sure whether I would rig it like Ben or go for it C Class style. I would make the mast break down into 4 parts, which I know would fit into my existing trailer. I would simply make a carrying frame.
As for a wing rig on an 18' skiff, Dream on! The rig is far too tall and the sail area for too big. The weight would be a killer. Not only is the rig huge, but it needs to be able to handle a huge kite, 3 big guys hanging off it and the slamming of the Sydney Harbour chop. I just don't see it happening. I do know that somebody was talking about a cat style wing mast, which I think would work very well, but that's another story.
I hope that all helps. And just for the record, at this moment in time, based on what i have heard from Moth sailors I speak to, I am preparing myself for a wing ban. I hope that as it becomes more of a reality, people will consider the argumensts and make the right decision, as I stil haven't heard a single reason why people think it will be bad for the class. I was hoping this thread owuld have aserious debate about it, but unless I missed it, I haven't seen a well thought out rational for banning wings.