Hi Boss,
I see that several sailors interested in boat design have repeated what they read in various yacht design books, classical yacht design and ship design. I would point that there is one area in the CLR calculation where beach cat design differs from classical yacht and ship design.
Ship design and sailing yacht design, displacement mode, take into account in the CLR calculation the vertical projected area of the side of the hull. This is because the side of these ships is a very large underwater area, like 100ft long and 20ft deep for example. This large steel wall underwater can certainly generate much side force. It takes large tug boats at full thrust to spin these ships/yachts around or push them sideways becuase of these large underwater walls along the sides of these vessles.
A beach cat hull differs from this concept of a ship's CLR.
Our beach cat hulls sail, much more so than a ship, on top of the water and have a very round hull cross section shape from water line to water line. Our hulls, those designed for centerboards, slip sideways very fast with boards up because they are poor shapes at generating side force. Just try sailing to windward or on a close reach with boards up. The hulls slip sideways rapidly in an effort to find a speed where the lift from the hulls equals the side force from the sails. This point of sail can be found and the boat will also move forward but slowly because there is also so much drag in this condition. The important point here is that for these round bottom hulls to work at generating side force, they must be moving across the water sideways at a significant sideways speed. Now, put the daggerboard down and this sideways hull speed becomes very very small. Therefore the sideways lift from the hull is very close to zero. So, take this term out of your equation when sizing daggerboards for round bottomed lightweight boats, guys.
In the case of a boardless beach cat hull design like the H16 or P16 you have the significant vertical wall and a sharp corner along its bottom edge. This underwater hull shape is designed to not slip sideways and it is the total underwater lifting body of this sailing system so certainly take it into account in this case.
Good boat designing, guys,
Bill