Yacht hulls come in different types and sizes and, depending on yacht size, weight, and speed, the physics of moving through water varies. Yacht hull sounds like the least interesting boat piece, but its shape is crucial to boat performance. So, if you’re planning on checking out some luxe yachts, you need to be familiar with this.
To understand the importance of a hull shape, it is important to know why and how boats float on water.
Remember school days and Archimedes? This Greek scholar was the first person who defined floating. He noticed that the water level rose when he entered the bathtub and exclaimed the famous phrase ‘Eureka’.
He realized that the object in a fluid experiences an upward force equal to the weight of the displaced fluid – meaning that if a boat weighs 1000 pounds, it will displace the equal weight of water and sink into the water until 1000 pounds of water is displaced.
Boat density and the shape of its bottom control how much it will sink into the water. Each square inch of the boat submerged in water is being pushed upwards by the water pressure, making the boat float. It is not difficult to conclude that boats with a flatter surface will float more easily, as the weight is dispersed across the hull.
There several different types of hull, and they vary depending on whether it is a boat or yacht hull.
Boat hull types:
⦁ Planing hull – the boat glides on the water surface
⦁ Pontoon hull – pontoons create lift and flotation
⦁ Displacement hull – limited to lower speeds
Each of the hull types affects the boat movement and speed, and have specific advantages.
Yacht hull types:
⦁ Planing hull
⦁ Semi-displacement hull
⦁ Full-displacement hull
It is easy to explain the performance characteristics of each by imagining a knife and a box in the water. If you try to move a knife through water, it will easily cut the surface and manipulate the movement direction. However, since the knife is so narrow, it will not float on water.
The box has a big surface and will float, but it will be noticeably more difficult to move the box through the water. When the water is calm, it will move in a controlled way, however, in cases of turbulence, the box will rock and roll to the sides, move unpredictably and become uncontrollable.
Another big importance is that a knife cannot carry a lot of weight but is fast, while a box can carry weight, but moves slowly and steadily through calm water.
The Planing Hull
The planing hull has planes below the water. Water gives them a lift as the vessel moves through water, allowing fast speeds. Weight has a significant influence on agility, and this type of yacht cannot carry a lot of weight.
Friction also has a significant impact on performance, so if the vessel is left in water for a couple of seasons, the performance will decline. It uses a lot of fuel to move, which gets consumed fast. It is fit for low ranges.
The Displacement Hull
Displacement hulls have less initial but more dynamic stability, and the impact of weight is neglectable on performance. The yacht can carry more fuel and has a low fuel burn rate, as it doesn’t use much power to move through the water. The displacement hulls are good for long ranges.
The speed of vessels with displacement hulls is slower and can be increased by increasing the length. Stability can be increased by reducing the yacht’s weight. This type of hull provides most interior volume and comfort.
The Semi-Displacement Hull
Semi-displacement hull is a combination of advantages of each type of vessel with optimized performances. It represents the golden middle.
Since propellers have an impact on yacht speed, and there are many factors which affect the hull-prop relationship, Miami Yacht Services advises you to read about different propeller materials before choosing the best propeller for your vessel to optimize your yacht performance.