Jerry

As in a lot of things in life its all about the balance, if you take a Formula 18 boat for example.

These weigh 180 kgs, if you reduce that weight to 120 kgs and leave everything the same you will have a faster boat, but one that is less stable, if you then take the lighter boat and make it wider it can become just as stable and forgiving, but still faster.

Also you can bring the mast height and sail area down untill the boat becomes just as stable and forgiving as it was before, and the speed will also be about the same as the original.

The analogy with the a cat and the hobie 18 is not a good one since, the a is not only lighter, but narrower, faster, and has a mast about the same height, also you have two people to hold the hobie down and only one on the A. There are too many other factors that are different which also effect the stability as well as the weight.

Most boats that perform to a similar degree and are of similar widths will have similar amounts of stabilty.

Take the F16 for example, it is lighter than the f18, but as it has much smaller sails it ends up at about the same speed, also because of those smaller sails it ends up being about as stable and forgiving.

Also bear in mind that the width of a boat has a direct bearing on its speed (upwind and reaching anyway).

So rather than worrying about weight, you need to look at the equation of righting moment/heeling moment. As a guide you can take healing moment as 1/2mast height * mainsail area + 1/3/jib height * jib area. Then righting moment is boat width * 1/2 hull weight + (boat width +3) * sailor weight. (sailor weight here is for every sailor on a trapeze, if they are not trapezing remove the 3, also I'm assuming that boat width is measured in feet.

Uffa Fox, a very well known and respected yacht designer once said 'weight is only any use in steamrollers' and he's right.