Hi All, I'm not sure what is meant by class 2 and 3 levers (and I have a masters degree in engineering!), but this looked like an interesting problem and I have been helping out a student doing these types of problems, so I thought I'd have a go.

So, I drew a couple of very simplified free body diagrams of a 2.2m beam cat with wing and a 2.5m beam without.

The diagram is drawn at the point that the windward hull just leaves the water and the crew(s) is not trapezing. It is simplified by assuming the heel angle will still be zero and it ignores the difference between the side and centreline of the hull. None of this should matter for comparison purposes. It also assumes that the force generated by the sail, height to centre of effort and crew weight remain constant.

So on the diagram F(crew) is the downward force of the weight of the crew, F(sail) is the sideways force generated by the sail, centred at a height of D(sail) from the waterline.

OK, so taking moments around point (0,0), we see that in both configurations a clockwise torque of F(sail)xD(sail) is generated. i.e. it doesn't matter to the mast what the beam is, the capsize force is the same.

Still taking moments about (0,0) in case 1, the righting moment produced by crew weight is 2.5xF(crew) and in case 2, it is also 2.5xF(crew).

So in other words, a 2.5m platform produces the same righting moment as a 2.2m platform with 0.3m wings.

There will however, be an advantage to the 2.5m platform in that is also gains more righting lever from the windward hull itself, since its self-weight will act further from the pivot.

Presumably the 2.5m platform will have less windage as well, and no wing dragging in the water to leeward. The 2.2m hull will probably lift a hull earlier, so maybe a lightwind advantage if the extra weight and air drag doesn't cancel it out.

So, conclusions? Designing a new F16 - 2.5m beam everytime.

Got a narrow grandfathered design, add wings to get the leverage but check this is actually faster once you've done it!