The new Rybo hulls were designed by Donald Blount, a member of YachtForums. They are fast and ride very level, with minimal bow rise. I have the pleasure of watching a wide variety of large sportfish boats running on-plane everyday, as I live near a major inlet that has no speed restrictions. Without question, Rybo’s appear to be running faster than most. It’s possible the owners are pushing their boats harder than the rest, but these boats are running noticeably more level, along with some Merritt’s.
Each of today’s builders try to strike a combination of a good wave-penetrating ride and stability at rest. There are so many factors that figure into this equation, including weight, CG, shaft angle, horsepower, deadrise, entry, hull flair, chines, strakes, etc.
For sportfish boats, I think one of the more important additions include tunnel-pocketed props. They reduce shaft angle, allow a shallower draft and help to recess protruding appendages. Tunnels can also help induce ventilation, which can increase RPM’s. As a side benefit, tunnels can actually help a sportfish back-down better, as they provide a nominal amount of lift when the props are reversed. The forward section of the tunnel helps divert reversed water downward, which should add some lift when backing down. As a by-product, the exit point of the tunnels reduces the overall surface area of the transom, which can also offer less resistance when backing down.
For the express boat you’re building, you need to consider where you will be operating the boat and what your expected cruise speed will be. If your native waters are rough and you will be running at higher speeds, then the simple answer is go with a deeper deadrise, sharper entry and reduced beam. If your waters are calmer, or if achieving higher top speeds and stability are a greater priority, then the opposite may apply. But… deadrise, entry and beam are simple parts of the equation. Your designer will need to consider all of the parameters mentioned above and more. Weight, CG, hp and operational speed must also be factored in.
If it all possible, try to minimize tabs. If a good hull form is achieved and the CG is right, you will need very little tab. Yes, they are helpful for getting on plane, but they should not be relied on to set the proper ride angle of the hull. Speaking of... I really like the underwater exhaust systems that use exhaust pressure under the hull (near the transom) to add lift when coming on-plane and help ventilate some of the running surface too. There’s at least one company (can’t remember the name) that is marketing re-fit kits for this, as well as OEM components to incorporate the system into new builds.
Among other considerations is how the hull works above the waterline too, such as spray and wave deflection. A narrower beam boat tends to be a little wetter, especially in choppy, quartering seas with windy conditions. Builders such as Buddy Davis address this with pronounced (Carolina) bow flairs and tumblehome transoms.
I’ve only touched on a couple of areas and Lars has already provided some good advice. The plethora of design considerations is the reason most people opt to purchase boats from existing builders with a refined and proven history. But… that doesn’t mean they can’t improve on their existing designs… or you and your designer can’t build something better.