Pretty obvious to me. Roughly I see the following. Not valid 100% in absolute terms, but true if one considers the kit actually used and its development.
Bigger sails are deeper, so develope greater side pull that needs more fin lift to be compensated, so need a bigger fin. To carry a bigger fin with more lift, you need a wider tail in order to have enough leverage to keep the board flat. This is the main thing.
Of course, along with wider tail, other design features come along. Larger volume will keep you afloat with your heavier rig; thicker rails will not bury so easily when pumping a big sail... and so on.
As for rockerline, I see that Carbon Art reveals their rocker pattern (and more rocker patterns are measured i. e. by the Planche Mag test team) and I see it's the same (exactly for some ranges, roughly for others; slalom range is actually divided in two, with small differences) throughout the ranges; so I guess it's not that important relatively to max sail size (in other words: CA SL 52, suggested sails 4.5 to 6.5, and CA SL 62, suggested sails 6.0 to 8.0, share the same rockerline). I guess that intended use range is more important and I guess i. e. different iSonic models have different rockerlines depending on focous on speed sailing, high wind slalom, light wind slalom or early planing.
Last edited by geo; 12th September 2007 at 12:57 AM.