Today while standing on four mile beach waiting for wind I had a good chat with fellow Sydney winter escapist Yuko who rode his own boards for a lot of years until he turned his hand to catamarans and parallel programming the matrix of processors found in graphics cards!!!
He stopped making his own boards when he came across the Nobile NHP which seemed to tick all his boxes. I had a good chance to take a close up look at the board and there are a couple of things that are great food for thought.
One of the biggies is the rocker line. It's curved through just a portion of the middle section and then dead straight right through to the tip. Overall there is a good amount of rocker but this is attributable to the curve in the middle section and not the tips. This is the opposite of convention 3-stage rockers which are flatter through the middle section and curved through the tips. His contention is that conventional 3 stage rocker is inefficient because the shape of the line that runs through the water when you're edging is kinked and curved along the part that sits deepest in the water which means it doesn't plane efficiently and creates too much drag. Whereas with a short curved section followed by a long straight line the section cutting through the water is dominated by the straight line and so planes early.
If you try to visualise the shape of the board section being pushed through the water, the NHP line is probably a bit more like an inverted aerofoil with the maximum chord toward the direction you are travelling. With this setup you maximize the flat planning area at the back of the board which naturally sits deeper in the water whereas the conventional 3 stage would have the maximum flat planning area in the middle, much of which will be out of the water when edging. I guess this adds up to earlier planning.
Just thinking about the trade offs, I suspect that the board may not carve as well as a continuous rocker because of the flat section you're dragging through the water. However, maybe having more flexible tips so that when you do edge really hard the board will flex and follow the curve you carve along. The tip flex many also overcome the need to have bigger fins or channels in the rails to make them grippy which is seems to be what is needed with very flat boards (my theory here is that with flat boards, when you edge hard the water has to pass under the board and so lifting the edge up leading to loosing your edge. With boards with lots of rocker, the water can more easily pass around it and so you keep your edge in the water and increase the drag to help load up.)
The latest version of Board-Off Design tool that I uploaded today has a version of the rocker profile sales as RockerTemplate #1. I think I'll give this one a try in board #3.