Originally, they were intended to help the deep-V hull reach planing speed, since each strake has enough horizontal area to act like a tiny flat-bottom for lift. What are Strakes and Chines on a Boat Hull Sometimes called running strakes or lifting strakes, these molded strips run lengthwise along the hull bottom and are virtually universal on modern planing boats. Many people also feel catamarans look unusual. The main drawback to a catamaran is less usable inside volume than a monohull, so the cabin and cockpit layout are often compromised. Catamarans also generally have a shallower draft and require smaller engines than similarly sized monohulls. Using two hulls bridged by a deck, the catamaran design provides additional beam, increased stability and, at the same time, increased speed (the slim twin hulls have little drag). Catamarans As one of the oldest hull shapes (imagine two logs tied together), catamarans occupy a small niche in America and larger niches in some other areas of the world. Like most compromises, a modified-V is not the best in any condition, but it does provide a good solution to most family boating needs, since you never know whether you'll be skimming across a smooth lake or fishing offshore on a choppy sea. The wedge-shaped forward hull cushions the ride like a deep-V, and also pushes the spray aside. The flatter sections toward the stern add stability as well as increase the speed, just like a flat-bottom. Modified-V Sometimes called a warped plane, this is the most common hull for small boats, because it combines some of the best characteristics of the other shapes. In addition, because the deep-V has more drag than a flat-bottom, the deep-V hull requires more power to reach the same speed. The better riding qualities are offset by added draft (making deep-V hulls less suitable for shallow water use) and reduced stability (deep-V hulls tend to roll in choppy conditions when at low speed or at rest). This provides the smoothest ride in rough water, since the hull knifes cleanly through waves rather than pounding, which is why this design is so popular for offshore sportfishing boats. Deep-V Hulls The opposite of a flat-bottom is a deep-V, which is wedge-shaped from bow to stern. For that reason, most modern powerboats will be either deep-V, modified-V or hybrids, such as catamarans. The downside to a flat-bottomed boat is that it can pound your fillings loose in even a mild chop. And small skiffs are often flat-bottomed because a flat hull offers maximum stability. You'll also find that many tournament waterski boats are nearly flat-bottomed, because the shape creates a smooth wake for skiing. Flat-bottomed designs are popular for the high performance boats that literally skim across the smooth water of lakes and rivers to achieve maximum speed. Flat-Bottom Hulls Unless you're buying a simple rowboat, few boats are actually flat-bottomed, but this term also refers to a hull that has almost no deadrise, or just a few degrees at most. The Carolina Skiff 2480 is a flat-bottom fishing boat. You'll see how deadrise works in a moment. Deadrise is usually measured in degrees at the transom as a method of comparison between boats, but you can measure deadrise at any point on the hull. The most important term to understand when considering hull shape is "deadrise," which is the angle that each side the bottom of the boat makes with an imaginary horizontal line-learn more by reading Motorboat Terms: Different Powerboat Types, Uses and Definitions. Let's take a look at the strengths and weaknesses of different hull shapes. In the end, each boat buyer has to make choices based on a particular set of needs. Weight may be a prime factor for trailer boaters, while strength may be more important to skippers who venture far offshore.
In some cases, you may want to sacrifice stability for speed or vice versa. There is one truism here: no boat design does everything well. You wouldn't choose a Rolls-Royce to drive on a rugged off-road trail and so, when planning a boat purchase, you should give as much consideration to the shape of the hull as you do to the price and the color. When you think about it for a moment, however, you realize that some cars are better at freeway cruising while others are designed for more rugged conditions. This may come as a surprise to many boat buyers who are used to owning cars of every shape and size, without having the exterior actually affect their driving pleasure.
How your boat's hull is shaped will have a huge impact on how happy you are with the way it performs.