Zee (or Sarah),
Wouter: the wind speed around here ranges from about a min of 4 knots to a high of 15 knots.
This sounds like pretty normal sailing conditions to me. It still dependents on what you get most of the time but if this is evenly spread out then I would certainly call it normal conditions. As such you are not really limited in the beach cat you choose as all are designed for this wind range.
The A-cat would excell in conditions ranging from 2 or 3 knots to about 6 knots. Wind with less then 2 knots speed are typically very shifty and patchy and as then all is related to sailor skill and not so much boat design. And of course a Hobie 16 floats about just as fast as an A-cat but due to handicap calculations gets more time allotted to do so. In effect in floating and "only just crawling" conditions the boats with slow handicaps get advantaged again.
An important point in winds conditions is the 5 knot threshold and it is indeed a 5 knot threshold. Pretty much the wind can only blow in two significantly different shapes. See the picture below :
![[Linked Image]](http://www.catsailor.com/bb_files/101415-Laminair_and_turbulent_wind.gif)
One wind pattern (in the vertical sense) is called laminair flow and the other is called a turbulant flow. The transition from one to another is sudden and tota, often this transition happens when the wind is measured to be 5 knots. However this transition speed may be higher or lower depending on chance local conditions. For example if the water temperature is very cool then the transition wind speed is pushed up to about 6 to 7 knots. The other way around when the water is relatively warm.
In effect winds ranging from 0-5 knots the windspeed increases proportionally when you move away further from the water surface. In all other conditions, 5 to whatever, the windspeed is zero at the water surface and then rapidly increases when moving to about 1 to 1.5 meters above the watersurface. Then it only marginally increases when moving further away from the water surface.
This is the fundament under the claim that 5 knots of wind is an important threshold when comparing different catamaran designs with one another. This is because different general designs respond differently to this transition.
The best catamaran design for laminair winds is a lightweight platform with a tall and narrow rig conprising only a single sail (= high aspect ratio). This mainsail must be cut or trimmed relatively flat with a open leech. The latter means that the leech needs to have alot of twist.
The best catamaran design for turbulant winds platform is much less easily defined as several different concepts seem to work well here. Because the wind as a whole contains ALOT more energy, even relatively close to the water surface, sail boats with jibs and spinnakers tend to perform much better then they did in laminair winds. In some instances they even start to perform better then the optimal designs for laminair winds as described above, that is right after the transition. With increasing winds the optimal laminair design tends to performance less and less with low aspect sloop rigged performing better and better. At strong winds the best platform to have is almost the direct opposite of the optimal laminair winds boat. In effect, a modestly weighted platform with a short low aspect rig with a jib (or spinnaker).
So as you see, how often a particular condition occurs at your venue does tend to impact significantly on the best design you can use, with the 5 knot threshold being an important component.
I think a second threshold can be found at 10 knots or so, but without a clear scientific basis as with the 5 knots limit. At 10 knots and higher you'll want to sail with a rig of modest height and not too much sailarea some weight in the platform will be nice to punch through the chop and waves and if you experience such conditions often then a boat like the Shadow will be excellent. Especially since it appears to have modestly sized and a very easy to use spinnaker setup. At these winds you don't really need alot of spinnaker area to get a good thrill.
I've thought about a spi and it sounds like a lot of fun but I havent really used one and no one here does so Im worried that Id be lost if I get it plus id be sailing alone and I dont want something too complicated.
I understand fully. Please don't get a spinnaker only because I'm vocal about favouring it. You must get the boat that you feel happy and comfortable with, not something that I or somebody else would prefer.
But I will say this. The fact that a particular design doesn't have many components doesn't mean that its sailing behaviour is uncomplicated as in easy and mild mannered. Modern high performance catamarans do require the user to know a thing or two about sail trim and how to depower the rig in conditions beyond 8 knots. The A-cat is most certainly no exception. If you don't have these skills then the boat either won't go or will feel moody and overpowered.
With respect to Dermots comment :
... and you won't have to lower the mast after every day's sailing, which you should do with a carbon mast to avoid delamination.
There are tricks to keep the mast on the boat and prevent mast damage when using carbon mast or even alu wingmast that tend to have the same issues with violant oscillations whne left unattended. But yes indeed, you will spend a few minutes engaging and disengaging these tricks (systems) when putting the boat into its parking.
I hope this helps,
Wouter
