I'm not saying a uni-rig is without advantages; Hell in 60 minutes I'll be landyachting across the beach using a single mainsail.
The whole point of the exercise is to put some reality into the myth-making that happened around the uni-rig properties.
In relation of sailarea/weight the A cat is having the most sailarea compared to it's weight of most of the boats discussed.
Actually it doesn't, not even by a long stretch. You are forgetting the spinnakers that many boats nowadays have. I mean, EVERYTHING is counted as sailarea or nothing is. On larger boats you have the code 0's and screachers that can be set even on beam reaches and low upwind courses.
When looking at spi-less setups there are also very simply counterexample in the beach cat field,
18 sq. 75+75/18.0 = 8.33
F16 sloop 1-up 107+75/18.7 = 9.73
A cat 75+75/13.94 = 10,8
F16 uni 1-up 107+75/15 = 12.1
C-class 200+150/27.87 = 12.6
Interenting to note the C-class specs !
Actually even the old (underpowered) geezers, when sailed singlehandedly, are not that far off the A-cat/C-class specs.
Hobie 16 150+75/19.5 = 11.5
Hobie 17 sport 150+75/18.86 = 11.9
Prindle 16 135+75/17.34 = 12.12
nacra 5.0 147+75/17.82 = 12.5
Now how many of us have singlehanded sailed or raced boats like the P16, H16 and nacra 5.0 and others in the past, over a wide range of conditions ? I think we can all attest to the fact that they were easily enough controlled. Basically all Hobie 16 that are singlehanded just HAVE to fly the jib as on that design the jib luff is also the forestay.
Now I have singlehanded the F16 singlehanded as a sloop as few times and it is pretty calm and easily controlled that way. Lots of power low in the rig giving a stable consistant drive.
And I would actually argue that boatweight is not very important when analysing heeling and righting forces. A better comparison would be to look at sailpower relative to the product of the width of the boat and the weight of the crew. Why, because even on a singlehander the boatweight is only contributing about 25% of righting moment.
When looking at the A-cats and F16's the difference in boat weight is 43% but the difference in righting moment is only 19%.
So actually when looking at the real heeling moment estimate (boat weights included) then some of the other boats mentioned so far have higher sail area to righting moment ratios then the A-cat has. And that makes the A-cat relatively underpowered in my book; note that the F16 is the only MODERN boat in the following listing next to the A.
F16 396/18.7 = 21.2
Hobie 16 435/19.5 = 22.3
Hobie 17 sport 446/18.86 = 23.6
A-cat 334 /13.94 = 24.0
Prindle 16 423/17.34 = 24.4
nacra 5.0 446/17.82 = 25.0
F16 396/15 = 26.4
Downwind a spi is more efficient than a jib, so if we discuss outside class restriction, with any boat you would go for a spi.
If there is no restriction on the total amount of sail area that can be had then we see sailboats (not landyachts) with a sloop rig and a spinnaker.
Indeed, the spinnaker makes the jib almost negligiable on the downwind legs but it doesn't affect the jib added performance one bit on reaching legs and on upwind legs. Basically, adding a jib costs you nothing on the downwind legs but still increases performance on all other (non-spi) legs.
Wouter
