I don't know why my post keep getting cut off in mid sentence - but this time I was ready for it!. Here is the part that was cut off:

So if 2" shafts are undersized, or even marginally sized, for these rudders, then it seems like one of the 254 shafts would have experienced damage over the past 18 years. In that lost post, I postulated that there were around 30,000 catamarans (35-60') sailing currently (I think this number is low, but a reasonable assumption). I also postulated that 50 of them had damaged their shafts (I know of 2, including this Alpha, and think that 50 is high, but a reasonable assumption). None of these boats have rudder shafts larger than 2". Maybe a couple do, but none larger than 2.5". The vast majority of them have rudder posts less than 2".

So this gives a failure rate of 50/60,000 - 0.08%. Let's assume my estimates are way off and there are only 10,000 catamarans and 200 of them have damaged rudder shafts. This is 200/20,000 - 1.0%.

So somehow the real life experience is not obeying the engineering numbers and skiing similes. If 1% of catamarans were damaging their rudder shafts, we would be hearing about that, don't you think? I mean, I have been in single boatyards with 100 catamarans in them and have not seen a damaged shaft yet. Lagoon made 700 38' catamarans last year alone - and that is only one single model of the 8 models they produce. They use 1.5" rudder stock, and if they are breaking 14 shafts each year, they are somehow managing to keep that very quiet. Likewise, Leopard and Fontaine-Pajot produce large numbers of boats each year. They are delivered on their bottoms from South Africa and France (across the Bay of Biscay). These also have 1.5" rudder shafts and I haven't heard of one being damaged yet.

BTW, the waterski analogy is equally as absurd as the snow ski one for the exact same reasons. Your legs are not in anyway analogous to catamaran hulls - either in construction or connection (go ahead, pick up one foot - see?). Water skis, exactly like snow skis are moving through different media and phase states and each are exposed in different media at once and at different altitudes and attitude.

I realize you have put in a lot of brain time thinking about the dynamic forces acting on skis and are excited to transfer these thoughts to catamaran rudders, but you simply have to give this up. It is non-sensical. Unless you want to talk AC72 rudders - then you may have some luck (but not much even there).

Mark