Symmetric v Assymmeric Spinnakers

Originally posted by transient "assys in small slow boats are the wrong tool for the job"

But I submit that at some stage in the equation a spinnaker at all is an expensive and complex piece of kit of marginal benefit. If you are genuinely running square it can make little difference to performance because every half knot of speed is a half knot less apparent wind. At what point is it more sensible to take the N12/Icon route and just have a dangly pole, which provides nearly as much interest for the crew and costs a shed load less money?

Originally posted by iGRF 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?

Yep, your missing something....I don't think anyone has developed an assy that sails efficiently dead down wind.

A decent symm will run well and reaches reasonably well  (not as tight as an assy granted)

A wing wang assy runs badly and reaches well.

Anyway, my argument in the hornet thread was qualified with the statement "assys in small slow boats are the wrong tool for the job" which narrows my it down IMO.

There's a place for both kites it's just that in recent years sailors have let fashion and ease of use dictate instead of reason..........Oh, and partisan attitudes have played their part of course.

Edited by transient - 13 Aug 13 at 11:32am

Originally posted by Peaky If the ratio is less than 0.53, he claims that in sub-planing winds the boat will run square quicker

I have always felt that FB was being over simplistic about that, and I wish I had his level of dedication and committment to do the research... Manfred Currys and Frank Bethwaites are very rare beasts though, and I hope I'm at least smart enough to know I'm not that smart or committed.

But even if FB's polars are right in steady wind speed and direction, he of all people demonstrated that there is no such thing, and all it takes is getting the right side of some shifts, and exploiting the direction changes in the gust fronts, and the skilled crew with the kite is way ahead (and the unskilled one a mile behind!).

Its a lesson I learned the hard way at a light airs open meeting at Llangorse in 1989 or 90... There will be occasions where people who just sit in the middle of the boat with the jib poled out come out ahead of those who have the kite up and hunt the shifts and the gusts, but they don't seem to be that many, and in any case who's having more fun?

As far as I understand it, single luff kites (at least on the 18s) evolved from double luff ones, orginally being set on the same poles?

I think it would be kind of cool, Jim...

Bethwaite identified the ratio of total sail area : total weight as being critical to downwind performance. If the ratio is less than 0.53, he claims that in sub-planing winds the boat will run square quicker than it will tack downwind (i.e. use a canting pole or symmetric kite). For a given all up weight this effectively puts a minimum limit on the area of a ‘proper’ asymmetric kite. All Bethwaite's asymmetric boats are designed to exceed this limit.

IMHO there is also a maximum sensible kite size for RTC racing, which can be estimated by using a Sail Carrying Power : Total Sail Area ratio. If the ratio is less than 0.90 it is difficult to hold the kite on a reach.

The only boats I have identified that meet both requirements (a boat that sails downwind like a true skiff but can also reach) are the 800 (just) and 29er.