Hi Wouter,
I am going to respond to some of your comments one last time. I have a request for you. Do not ever use my name again on any of your posts. I do not think your intent is honorable and I do not want to be a part of it.
You know that my training is that of an engineer. Engineers know more than most other professions that there are many solutions to the same physical problem. Some are better than others but there are always many solutions to a given problem. That is part of the fun and pleasure of engineering. Your comment about me and "only one solution" is your invention. I have never said that.
>About pitchpole and H14s and 16s: I did my design work on the SC product line in the mid 1970s. At that time the H14 and H16 were the largest and fastest growing classes in the US. They were the chinning bar at that time and their sailing characteristics were the ones to improve on.
Inter 20 vs Tornado: Why do you think the position you bring forward exists? Let's look at shapes of bodies and drag coefficients. The last piece of the puzzle in the physics of pitchpole is a rapid rise in drag coefficient as the bow of the boat is pushed underwater and the water begins to impinge on the deck. If we look in an aerodynamics text book and find a table of drag coefficients of bodies of various shapes, we see that a flat plate has a very high drag coefficient, flow perpendicular to the surface of the plate. If we take that same flat plate and round/roll the edges with significant radius like the I20 shear line along the foredeck, there is a significant drop in the drag coeficient. This would reduce the I20's tendenct to pitchpole relative to a Tornado. When the deck becomes the bow of the boat, the shape that is parting the water, how draggy the deck is becomes important relative to pitchpole.
Elliptical hulls: When the best and finest F40 one design boat was designed it looked like a scaled up SC20. On the big cats and tris the elliptical hull shapes are the industry standard. In the beach cat business a newer boat cannot look like an older design for fear of being called a copy cat. No one would buy a new boat that looked like an older design even if the older design was superior in some aspects.
>Shared Lift: I first used the shared lift idea on the SC17. Half the lift to counter the side force from the sail was carried by the forward sections of the hull, deep Vee shape, and the other half carried by an oversize rudder. The aft end of the hull was round in cross section and can slide across the water sideways easily and this lets the boat tack much easier than other boardless beach cats. This 17ft boat developed a PN of 73 relative to the 16.5ft long H16 with a PN of 76. This performance improvement shows that the shared lift concept works. The SC17 also tacks much easier and faster than the H16 and is much much more pitchpole resistant.
>Shared lift and spinnakers: The European beach cats are slow to come to S Florida so I haven't sailed any of them. But looking at pictures of them sailing with spinnakers, I see a big difference from the spinnakers I sail with. I look at pictures of these European cats sailing double trap and I notice the leech of these spinnaker sails is just in front of the mast. These are very high aspect ratio spinnakers. The spinnakers I am use to are fairlead to the rear beam or transom. When sailing hot, the leech is only a couple of feet in front of the rear beam fairlead point. Now let's go back to the text book and aerodynamic theory. I see that the short footed, high aspect ratio spinnaker has a much higher lift to drag ratio than the long footed, full size, low aspect ratio spinnaker. This means that the resultant force from the high aspect ratio spinnaker will cross the platform, the boat, at a point, very near the CB trunks, that has little to no effect on helm. The full size spinnaker with its lower lift to drag ratio will generate a resultant force that crosses the boat in front of the CB trunks and this causes lee helm. The high aspect ratio smaller spinnaker will sail higher and faster than the low aspect ratio when sailing high in general. The larger low aspect ratio spinnaker will sail faster and deeper than the smaller high aspect ratio spinnaker when sailing low in general.
So, there you have it, Wouter. If you sail with these short footed, high aspect ratio spinnakers, you can live with the helm with the CB located in the classical position. If you go with a full size spinnaker, the boat requires the CB trunk to be located further forward to balance the helm.
Take a look at Alinghi. This boat has a second daggerboard half way between the main beam and the bow to trim the boat out when large headsails are used.
I'm tired of writing. Goodby Wouter,
Bill