In addition to bills comments I would like to add that apparently there is another phenomenon at work and nobody has figured yet what it exactly is.

some describe it as "tripping", A long daggerboard (long is closely related to high aspect of course) tends to introduce nervous behaviour of the boat in trapezing conditions or gusty conditions. triggered be various thing of whcih increase in windforce is just one in my opinion the boat quickly raise its windward hull necessitating the skipper to dump the main or head up violantly. This behaviour can be so nervous and unpredictabel that a boat skipper combination is all over the place. Raising the daggerboards a little calms the boat down very quickly.

There is another report that indicated that in lights winds the smaller daggerboard isn't at a disadvantage to a longer one. This came from a design that was identical in every respect except the daggerboard size and aspect ratio. Boyer A-cats also don't seem to loose as much or even anything in both ends of the spectrum (big wind- light wind). In medium winds the difference was noticable with the bigger boards being a little faster.

Someone needs to take out some time and try to discover why these thing are happening. I have a few thoughts but no time or resources to test them. But one thing is for sure the theory suggest significant differences all over the wind spectrum but in reality this is not always reflected.

A few things that I thought of ;

-1- in light winds the boat moves relatively faster (as ratio of windspeed) than at higher speeds. This is mostly because wave making drag and other forms are far less significant at the speeds. So less sailforce and relatively more speed. This would allow the boards to be smaller than the ideal size at medium wind ranges. The difference could be something like a factor of 1.25 to 1.75

-2- At high winds control of the boat and smooth sailing is far more important than power. It must be compared to a racers that full breaks and than fully accellerates at each corner instead of a driver maximizing is cornerspeed by carefull steering and achieving the biggest corner radius. The latter will be faster around the corner. Same with boats I think.

-3- Overly high aspected board may have a to small (or narrow) band of optimal performance. Especially in gusty conditions the onslaughts of sailforces and waves may shake the board off it optimal working point often enough. It is well understood in wing design that short stubby wings give improved control and more dependable lift in violent manouvres. Besides nothing is more draggy than a ventilating or cavitating foil. The whole flow is disrupted for a realtively long time. A short board or wing quickly establishes attached flow again in addition to having a higher threshold for disruption to occur. I refer to the Inter rudders at this point. Many sailors have experienced that it is easy to stall them (or have them ventilate) especially with rudders you wnat sharp and large lift forces without "complaints".

-4- Shorter low aspect boards are in general very much stiffer than the longer ones. Also high aspected boards are more sensitive to disturbances and also to imperfections on the boards surface. I think that a low aspect baord can be made critically smaller with a more ellipical leading edge (milder entry). For example the inter boards are so narrow that there is a relatively short leading edge section that has to build up to full width in probably 1/2 or 1.3 of say the boyer Taipan/ Mossie boards.

I'm not saying that these are explanations but in aspect like these the answers to why should be found.

It is very possible that a combination of they above or a selection of them with several other explanations conspire to loose much of the theoretical and laboratorium established gains. Even to such an extend that there is hardly any difference between the two schools of thought. It wouldn't be the first time something like this happened.

One of the great examples are the America cups keels. One keel was absolutely superior in theory, computer models and lab test (under carefully regulated conditions) In real life sailing is was a monster to sail. Bad behaviour all alround as the it would fall off its intended and advantagious optimal working point all the time and transition into a draggy dirupted flow mode. The keel was not forgiving enough of the constant changing heel of the boat and the associated angular rotation of it. Do not forget that these rotations introduce all kinds of 3 dimensional turbulance and currents not to mention continiously changing flows ALONG the keel or blade.

Theory was established on lab test. Designing more than often includes adapting the theory to real life conditions which are more than not continiously changing.

So the jury is still out on this one

Regards,

Wouter