By: Bill Jennings
You have probably heard the boating term “deadrise." You will be glad to know its meaning is not as ominous as it sounds. It refers to the amount of angle that forms between the boat bottom and a horizontal plane on either side of the center keel, measured at the transom. This angle usually runs between 16 and 24 degrees and comprises what we refer to as a V-bottom hull design. The trademark of such designs is that the contours of the hull travel in a straight line to the keel. It’s easiest to picture if you imagine looking at the craft from behind. This is the story of how and why the V-bottom became the norm for today’s pleasure boats.
For centuries, boats were constructed using a ‘displacement hull’ design by which their bottoms were either flat or melon shaped. These displacement designs cruised through the water by displacing water around the hull. Many types of boats today, such as ocean tankers, trawlers, river barges and standard sailboats, have displacement hulls. Interestingly, a displacement hull moving through the water creates a bow wave that acts to place a specific limit on the maximum speed that a displacement hull can achieve. This speed limitation affects smaller vessels more significantly than larger vessels.
Back in the late 50’s, a naval architect by the name of Raymond Hunt came up with a hull design he called a ‘Deep Vee," in which the bottom was pointed downward to the keel forming a pointy bottom. Tests showed that if a bottom could be made in a ‘V’ shape, the size of the bow wave would be reduced and in addition, the ride would be much smoother. Think of striking a water surface with an axe vs a frying pan. Unfortunately, the early experiments with pointed bottoms resulted in boats that would list, or tip to one side.
By the early 60’s, available marine engine horsepower was on the rise- triple digits in outboard horsepower and even more for marine inboards. As greater marine horsepower grew, smaller boats were able to power onto a plane, which lifted the boat partially out of the water, causing it to virtually skim across the surface.
Then along came Don Aronow. This tall good-looking developer from New York relocated to Miami and became obsessed with fast boats. Don and his associates built an offshore boat with a 24-degree deadrise and campaigned it to win almost every race he entered. High horsepower allowed his deep V boat to push up onto plane and skim across the water, reducing the amount of wetted surface and drag. The pointed entry also dramatically reduced wave impact on both boat and driver. With his fast-growing reputation, Aronow began building boats and called his company ‘Formula,' because he claimed to have found the formula for fast boats. Thunderbird Yachts recognized the potential and purchased Formula to add a performance line to their quality yachts. Despite a non-competition clause, Aronow simply opened a new factory, right next door. He named this company, ‘Cigarette.'
The preferred method of smuggling drugs into the U.S. at the time was to fly to an island near Florida and use offshore boats to make the final run to the mainland. Aronow’s boats proved ideal for this job and drug runners filled his order books as well as provided practical feedback on design suggestions. The American Power Boat Association (APBA) offshore circuit provided an opportunity for runners to practice high speed handling in a competitive environment. During this period, I raced with these interesting individuals.The rules were simple: what was discussed at race locations, stayed at race locations.
Meanwhile, Don Aronow began a profitable pattern of selling boat companies and opening another next door, under a different name. With his mafia connections, Don had plenty of muscle to discourage the lawsuits that would follow. Aronow’s nameplates included Cigarette, Magnum Marine, Donzi, Squadron Xll, USA Racing, and Blue Thunder. Boat builders everywhere began to incorporate deep V designs into their boat moulds. Don Aronow cannot claim total responsibility for the development and promotion of the V-bottom, but I can assure you he was referred to as ‘The King’ for good reason. So, what happened to Don Aronow? Well, he got shot. But that’s a whole different story which I’ll save for another article.
Original deep V hulls had a deadrise that ran for the entire length of the boat. This worked in very rough conditions but lacked stability, so designers came up with a“modified-V hull." This compromise gave the front of the hull a wedge shape to slice through the water but tapered the wedge to a flatter angle as it moved towards the stern of the boat. Further design improvements introduced “Chines," or add-ons to the hull, where the bottom of the boat meets the sides. Shaped like an upside-down V, chines serve to deflect spray, improve turning response and offer greater stability at rest.
Then “Pads” were added to the V. This hull design element is a flattened section of the V bottom, usually located at the stern of the boat. When you trim up a boat to increase speed a pad will provide better control than the same boat without a pad.
While “Steps” in boat hulls date back to WWl, they have made a recent comeback. These “Steps," or notches, across the V bottom are molded into the hull to introduce air under the boat. The water that runs aft of a step contains small bubbles. Because aerated water produces less drag than solid water, stepped hulls with equal horsepower usually produce a speed gain. Some boaters argue that steps reduce cornering stability, but I have not noticed this to be a significant factor in any of the recent stepped hulls that I have tested.
Today, boat builders everywhere have benefited by incorporating the features of a deep-V design into some if not all their boats. Displacement hull fans will tell you that their boats are more efficient. What they don’t mention is that their displacement hull has a speed limit and therefore there is no need to install an engine any more powerful than is necessary to reach their particular boat’s ‘hull speed’. Ever wonder why so many 30’ sailboats use a 9.9 hp outboard motor? A larger motor would be a waste, because it could not push their boat beyond its built-in speed limit, which using the formula for this example is 7.34 knots. The so-called efficiency comes in the form of a smaller, less expensive engine. Therefore, if you have no need for speed, a displacement hull will work for you.
When buying a deep V boat, it’s essential to consider all factors, including the engine’s horsepower, where you boat, usage and weight distribution. If you already have a deep-V boat, its degree of deadrise will be listed under its specifications.