Symmetric v Assymmeric Spinnakers

I watched a very slick video from yesterday of a 505 being gybed with those two poles, and there is a discussion in the Hornet thread, which maybe prompted this thought, and mention about fireballs havign a problem getting going on the new tack after a gybe in lighter air which has prompted this post.

Now, I'm assuming all Assym kites are designed rightly with a leading and trailing edge as per most sails, i.e. with an entry and an exit by means of a leech with some degree of twist.

So my question how can it be efficient, that a symmetric spinnaker has to reverse the flow at every gybe and the trailing edge becomes the leading edge. I've never used them, wouldn't, they seem a)dated and b)inefficient at anything other than dead running, plus to difficult to bother with anyway with all that pole switching, bagging and nonsense.

So why why why persist with them?

Somebody tell me, why keep these anachronisms going rather than work a bit harder on developing Assyms to sail dead downwind if need be, a la Alto?

There has to be something else I'm missing, care to share it with me?

Edited by iGRF - 13 Aug 13 at 9:28am

What like cranking an old car with the handle and it starts first time?

Originally posted by iGRF So my question how can it be efficient, that a symmetric spinnaker has to reverse the flow at every gybe and the trailing edge becomes the leading edge.

You're right of course, it can't be efficient. However I suspect its not *quite* as bad as if might be, because the pole tends to pull the luff down and the leech flies free, so there may be a degree of bringing the fullness a bit more forward with that.

Originally posted by iGRF rather than work a bit harder on developing Assyms to sail dead downwind if need be, a la Alto?

Going dead downwind is never fast, but I suspect people do it a lot less than they think. Its been bemusing me on my canoe that I can be on a deep reach on one gybe, with the windex looking to be apparently along the centreline of the boat, then I gybe 45 degrees onto the other gybe to make the mark, and the windex seems to be still on the centreline. Don't know if its optical illusion or what. The only time dead downwind is fast is if you lose less time running than two gybes are going to take...

On the other hand, and its a big on the other hand, its very easy to lose a whole bunch of time by setting off on the wrong gybe or at the wrong angle, even both. So whilst sailing the right angles is faster for a good crew, sailing the wrong angles can be a lot slower for a less expert one. So I suspect a lot of the prejudice about sailing angles is developed through lack of the specific skills... Not that I'm saying I've got that level of skill, just that I can recognise the need for it! And its no trivial level of skill when you consider that the optimum angle changes every time the wind strength changes.

I guess, thinking about it, I'm not sure where the need for Alto type systems, even if they really work, exists, given dinghies with a single downwind sail. In class racing under rules that permit both people will use whichever is faster, which to date has been universally the sprit kite. In handicap racing sooner or later the handicapper will sort it out, and to be quite honest its never going to make much difference, because as soon as you are nearly square and the apparent wind is well behind the beam the law of diminishing returns set in because every increment in speed is a decrement in apparent wind: you can't go much faster than about 2/3 or 3/4 wind speed no matter how big or efficient the rags are.

I don't know that you really need complicated two boat testing to establish pros and cons. Must be possible by now to get some sort of dinghy sized windspeed and direction measurement at the mast head, and that, used together with GPS to develop real polar diagrams, is most of what you need to stablish what works. It would be a sad day though if we were all sitting with speed and direction readouts and polar diagrams in our dinghies...

More like cooking a meal with fresh ingredients than putting a ready made in the oven. When you get it right the taste is so much better.

I remember doing a Merlin Salcombe Week back in the early nineties with one of the Merlins converted with an asymmetric, don't think it did any better or worse, however, I do believe it was a trial boat for what would become the RS400!