Boats come in all sorts of shapes and sizes. One thing is universal when it comes to boats: They all have hulls. Boat hulls also vary in shapes and sizes, but can be broadly categorized to fit a few specific boating needs. We’ve summarized various types of boat hulls, and the strengths and weaknesses of each hull type. To get started, it’s important to know the two purposes of boat hulls, and why hulls are designed to meet those two key purposes.
A. Hulls That Plane
Boat’s that are meant to travel at fast speeds are designed with a hull that planes while moving quickly through the water. When a boat is at rest in water, the buoyant force pushing up on the boat matches the boat’s weight pushing down. As the boat travels faster, the boat acts as a hydrofoil, and lift helps to push the boat upwards. At a speed specific to the boat, the boat will begin planing, where it will glide across the water, and lift is the primary force keeping the boat afloat. When a boat is planing, less energy is required to keep the boat at a high speed than a flat bottom hull design. Generally speaking, the faster the boat travels through the water, the more challenging it is to handle the boat – particularly in rougher waters.
B. Hulls That Displace
Displacement hulls are designed to displace as much water as possible while remaining fairly stable and efficiently using energy to travel through water. They can range in a wide variety of sizes, from small sailboats to huge cargo liners and cruise ships. These hulls are not designed to move at fast speeds, and are designed to be well balanced and be economical.
All boats have hulls that are designed to be able to displace enough water to support their own weight without sinking, but not all boats have hulls designed to be able to plane. Many boats are referred to as semi-displacement, or semi-planning boats, such as sailboats. They may be primarily designed to travel through water at non-planning speeds, but develop some dynamic lift when moving at faster speeds or can easily plane when reaching a certain speed.
Flat Bottom Hulls
Boats that have a very flat hull are known as flat bottom hull boats. The biggest advantage of flat bottom hull boats is their stability, as they have a fairly wide center of gravity, which make them excellent for fishing. Examples of flat bottom hull boats would include row boats and dingy boats. Flat bottom hull boats are not designed to travel at high speeds or travel through rough water, so they are typically found in small sizes on small bodies of water.
Round Bottom Hulls
A great example of a round bottom hull boat is a canoe or kayak. The hull is rounded to allow the boat to travel through water easily at slower speeds to limit the amount of drag on the boat. Round bottom hulls are almost always displacement hulls, and can range wildly in their overall stability. Smaller boats like sailboats and canoes that have a rounded hull can be very unstable, however many ocean faring boats like cargo ships and cruise ships designed to withstand rough weather have a round bottom hull.
Like the name suggests, the shape of the bow takes a V shape when viewing it from the bow. The V Hull shape is very common in power boats and is the most common shape for fiberglass motorboats, as it allows the boat to quickly accelerate to a planning speed, achieve a speed higher than other hulls of its size can offer, and using as little fuel as possible. V-hull boats also give the driver better control at higher speeds, as the V Hull shape allows the driver to bank into turns.
The V-Toon technology of Manitou mimics the physics of a V-Hull fiberglass boat, allowing our pontoons to bank while turning. The extra space in our V-Toon hulls also allows the driver to cruise through rougher waters better than a fiberglass boat can.
A multi-hull boat can describe any boat with more than one hull to use for displacement and/or planing. Multi-hull boats typically are more stable boats than mono-hull boats for their size and weight. Mono-hull boats will often need a stabilizing weight or force in the center of the hull to keep the boat stabilized, which is not necessary for most multi-hull boats. Common example of a multi-hull boat would include catamarans and pontoon boats, which commonly use two hulls for added stability and for easier traveling through water. Many pontoon boats, like ours, have a three hull design to give them some positive characteristics of a V Hull boat.
Boat hull forms can come in a variety of shapes and sizes based on the purpose of the boat. A hull may take a a sharper angle towards the center of the hull, known as a hard chine, or have a smoother angle that doesn’t go as far into the water, known as a soft chine. Because of the various hull forms, many hull shapes like a round bottom hull can take on characteristics of other hull shapes, like the stability of a flat bottom hull. Hulls can also be made out of a variety of different materials, as summarized in our article here. Boater Exam put together a short and sweet video on various hull types for boats.
This post was put together by Mike Hall, a boating enthusiast.