See full version: Deep V, Shallow V, or Variable Deadrise Hull Performance
Bay boats often have a moderate deadrise angle, sometimes with chines. The chines serve the same purpose on these hulls as on deep V hulls, but aren't needed as much because the form of the hull makes it more stable, shallower draft, etc. Action Craft, Sport Craft, Mako, and Aquasport are examples of manufacturers that employ a medium deadrise angle on many smaller to mid-size boats. here
Some of the older Formula boats made impressive use of chines to give a great ride in rough water, but still possessing reasonable handling characteristics and ordinary draft. Our friends had a Formula 24 express cruiser with twin 165 hp Mercruisers, and we had an Aquasport 240 with a 230 hp OMC sterndrive. I had plenty of opportunity to observe the difference in how the boats rode in various conditions. The shallower hull of the Aquasport made it fast, stable, and efficient, but we would really take a pounding in larger waves, while the Formula seemed to glide in and out of waves without the earth-shattering crash of a boat doing a belly flop. The Aquasport, despite the relatively flat entry, was a wet boat until we added some mahogany spray rails up forward. Those did a great job of deflecting spray, but were far enough forward so as not to affect hull entry.
Each chine decreases the overall deadrise angle of the hull. In the picture, a dotted line shows how effective deadrise angle is lower because of the chine. Chines provide some flat surface area in the water, which means more lift compared to an angled surface. The boat will draw less water and will have greater roll stability, and chines can deflect spray which would be thrown up. They can also cause pounding in heavy waves, because if they are large enough to really be effective, they are also large enough to prevent the boat from slicing cleanly into a wave.
Flats boats have flat bottoms or very shallow deadrise angles. This is great for use in shallow water, getting on plane quickly, etc. but will pound the heck out of you in chop. These hulls sometimes have a very steep deadrise angle up very far forward, feathering out into a much shallower deadrise angle pretty quickly as the hull widens out. If the nose of the boat is kept down, such a design can slice through small chop pretty well, but once the waves get to a certain size, you will be hitting them with the entire forward section of the boat all at once, and the relatively flat sections are going to pound. here
The fastest offshore race boats are catamarans, but when conditions get really rough, the superior ride of a deep V hull can win the day. Those boats have one purpose, and have very deep deadrise angle hulls that don't work so well for the average boater. Some of the disadvantages of a very deep V hull include:
Currently, all Rec-Lite watercraft (Sea-Doo Spark and Yamaha EX) lack the weight and deep-V hull to track, handle or cushion a rider over aggressive seas. The added weight and subtle deadrise of the GTI, VX and even STX-15F provide improved rough water tracking and handling, but will still communicate turbulence concurrent to their particular weights and designs. Sea-Doo’s new ST3 hull (RXT, GTX, Wake Pro, Fish Pro) offer extraordinary stability while stationary and at cruising speeds, and excellent comfort at all times, but at the cost of predictable tracking and handling in tumultuous seas.
In chop, the hull design of Yamaha’s GP1800 gives it a ability to track and handle that is unmatched, but as noted, is intentionally light on insulation. The new 2019 FX platform shares much of its design and rough water talents with the GP, but manages to distribute and deflect vibrations far better, providing a smoother, more insulated feel. Finally, Kawasaki’s Ultra retains the industry’s most aggressive deadrise and the heftiest weight, giving the craft both incredible rough water comfort (ie. insulation) as well as instinctual handling and proven tracking. This all comes at a cost, and the 310-horsepower Kawasaki’s fuel consumption while getting the craft to plane is substantial.
Most naval architects (boat designers and builders) will agree on four major types of hulls design: flat-bottomed hulls, round-bottom hulls, V-shaped hulls, and multi-hulls (ie. pontoons or catamarans). Because nobody has properly executed a multi-hulled PWC, we’re going to leave that one out and focus on the prior three hull design types. more
Finally, the balance of vehicle weight and horsepower (power-to-weight ratio) plays a final component. Obviously, overall vehicle weight plays a central part in the watercraft’s displacement, as a heavier craft or one with a prominent deadrise will have a great (or deeper) draw. “Draw” is how much of the hull is physically in the water while at plane, and for many watercraft, this alone can delineate what makes a craft smooth and predictable in the rough, or jarring and unpredictable. A heavy, deeply-keeled hull will ride smoother and more comfortably, but will require more power to reach plane. A lighter-weight hull with less deadrise will reach plane far easier, but typically telegraphs more vibrations to the rider.
Finally, in discussing the “rough water hull” behavior, I break down characteristics in to three categories: Tracking, Handling and Comfort. It’s important to understand the specificity of these three as they are uniquely different and, while a particular hull design can excel at one, that same hull design can fail at another. So let’s discuss each of these individually. First, here are some basic definitions of the terms that will be used in this essay:
A recent conversation with a reader was particularly revelatory, he complained, “The [Yamaha] GP1800 handled terribly in the chop. It beat me up. I couldn’t take it anymore. So I bought a [2018 Sea-Doo] RXT-X 300.” Curious, I asked what he meant. I queried, “Did the GP1800 behave erratically?” “No,” he replied. “Did you ever feel like it was unpredictable?” He said he didn’t understand. I asked, “Did the ski feel like it was darting or hunting in one direction or the other?” “No,” he replied again. Then I stopped and asked, “Did it feel like you were being rattled and shaken apart?” Wasting not one second, he replied, “Exactly.” here
Whether you’re just getting started with learning power trim adjustments, or wondering how to use trim tabs in rough water, we’ve gathered some valuable tips for using your boat’s trim. We’re sure these will come in handy as you begin searching for your boat’s perfect trim — regardless whether you’re boating in a lake or on the ocean. It’s important to remember each boat’s trim is different, so for every boat, factors such as the balance of trim, weight of the boat, sea conditions, speed, etc., are a little different. While these are general tips, it’s important to always operate your boat with caution as you begin discovering your boat’s ideal trim. [links]
To maximize the control of your trim and address both of these issues — avoiding prop slip and making lateral adjustments — adding trim tabs to the transom is ideal. more
Mastering your boat’s trim so you can use it to your advantage isn’t easy — it takes the right set of tools, knowledge and patience.
To give boaters the ability to adjust and maintain the proper angle, outboard and sterndrives feature a power trim adjustment that gives you the ability to tilt the drives’ angle out or in. However, this means the propeller handles the power trim, which was designed to force the boat in a forward motion. When the prop is used for trim, the prop is pushing the boat forward in addition to raising and lowering the stern — this increases the prop slip, killing your boat’s performance. The power trim adjustment is also ineffective at slower speeds and unable to correct listing.
Boats handle best when they run parallel with their at-rest waterline — you’ll notice a more comfortable ride, increased speed and more efficient gas mileage. The bow of your boat meets the water at a specific angle — and that angle has a direct correlation to how efficiently you operate your vessel.
Size: A bigger wake means more energy. This means more explosive pop wakeboarding and more push wakesurfing.
At WakeMAKERS, we think about a quality wake requires two things: size and shape. Each is equally important.
Shape: Just as important as the size, the shape of the wake is often a second thought or completely ignored.