While we might not intend to go out in seas rough, and taller than your VHF antenna, we never know when we might end up in those conditions if we venture far enough offshore.
There are three basic hull forms, and we need to look into the capabilities and limitations of these three main hull types to discern which of these three is actually the best to have if you end up offshore in rough waters.
If we were to assume that the three different hull forms, if they were the absolute best of their type, then we get a perfect picture of which of these hull types is truly the best for the situation.
Seaworthiness is a serious issue when we are considering going out into the open waters. While you might feel confident and sure of yourself on the waters, the ocean is unpredictable and being prepared for anything that might happen is where your own seaworthiness comes in.
Let’s first discuss how each hull handles in rough waters, and then discuss the best hull type to have and why. We will also have a little look into which hull type to avoid.
What Type Of Boat Best Handles Rough Waters?
While there are displacement, semi-displacement and planing hulls, that are the three main categories of hull, there are other categories as well. These include flat-bottom hulls which mean the boat will glide over the water, and are best made for lakes.
There are also V-shaped hulls which are the best type to have, they are also planing hulls, and they are common among powerboats as they allow the boat to reach high speeds and plane on the water while remaining steady in choppy conditions. The deeper the V, the better it can handle.
However, there is more here to discuss, as hulls are not so easy to break down, and while a V-shaped hull might be the best for choppy waters, it is also about the type of boat. Can you imagine a huge tanker ship with a V-shaped hull?
So, let’s have a look at what the types of hull are and how they affect the ship on the water.
The Types Of Hull
There are three types of hull we will look at.; displacement, planing, and semi displacement. However, do remember that V-shaped hulls are also fantastic, however they are most commonly used on powerboats.
When it comes to bigger water faring vessels, and others, not every vessel is made for a V-shaped hull and so, there must be something else that can stay stable through those choppy, crazy waves out on the open ocean.
Displacement hulls are very common, and their biggest limitation is their speed, which is restrained to that of an open ocean wave of the same length as the hull at the waterline. Such lower capability will reduce the skippers’ options when they try to avoid bad weather at a macro level.
It can reduce agility locally, so these boats cannot zig and zag around breaking waves.
A displacement hull often draws in more water than planing hull counterparts, which limits their ability to take a shortcut through the shallows.
However, when we are talking about pure ocean-crossing ability, displacement hulls are epic, they are frequently ballasted to increase their range of stability to 90 degrees or more, they use little fuel when run below their full-displacement speed too.
Their hulls round bilges, upset buttocks and emerging transoms create little wave-making drag at low speeds like such. All the molecules of water being displaced by the hull separate and then gather again gently, so the resistance to wave-making is low.
They also have a low center of gravity, which makes the boat less susceptible to wind as well, and if the hull is well-designed then it is easier to keep pointed to the wind at low speed than if you had a planing hull. Since displacement hulls can only travel at low speed, this is perfect.
A displacement hull is basically a vessel that plods along, using little fuel, with gentle motion in every direction. With a large rudder behind a large, slow-turning prop providing good lift to both sides.
Displacement hulls are a perfect hull for breaking seas, it is better able to survive a lot of water on deck, and with its displacement and stouter construction, it has a larger area of positive stability.
While planing hulls can be suitable for offshore ventures, most of the ones made today are not well suited for choppy water, offshore adventures. Their hulls are usually too wide for their length, and are too flat, full forward and too flat aft.
Much like displacement trawlers with ballooning deck houses, there is a gap between the amount of hull beneath the water, and the boat above the waterline. This can create top heavy boats that are hard to handle in rough waters and winds, and are more likely to blow over.
However, we cannot say this for all planing hulls, as if you were to have a well-designed, deep-V planing hull with a proportioned structure and a responsive steer, with predictable handling and powerful propulsion, you could feel safe and confident in any weather offshore.
Planing boats tend to be agile and speedy and so a well-designed deep-V can work well, however, the same cannot be said for every planing hull.
Semi-displacement hulls are not well understood, they operate in a speed/length region, supported by buoyancy like a displacement hull, and also by dynamics like a planing hull.
They have nearly flat buttocks aft, with the transom immersed below the water line, which if there is enough power, will allow the stern to create lift, so the boat can plane.
Semi-displacement bulls have a center of gravity more forward than planing hulls, so they plane easier and at lower speeds. They are also heavier than planing boats, with deeper and finer hull sections forward to give a comfier ride.
In terms of speed and agility, these hulls are halfway between displacement and planing hulls. If properly designed, they might make for fantastic rough water hulls.
Which Hull Is Best?
So, which hull is best? Well, to be short and sweet about it, the answer is a displacement hull. This design has been superior for ages now, almost every sailboat, cruiser, trawler, and cargo ships use displacement hulls, and they do this for a good reason.
Any ship or boat that needs to cruise for a long period of time and cross oceans will have a displacement hull.
However, as we said earlier on, it also depends on the boat. A speedboat couldn’t have a displacement hull, just like a cargo ship couldn’t have a deep-V. Yet both of these designs are great and sit well in rough waters.
A deep-V hull is best for speedy vessels, providing that wave-braking ability like a knife, but displacement hulls are better for slow and steady vessels to plod along through treacherous waters unscathed.
If you have a powerboat, you want a deep-V to face rough waters, for a sailboat, a trawler or a bigger ship, you want a displacement hull.
Why Are Displacement Hulls The Best?
So, let’s just break down what is so great about displacement hulls, and we will try to keep it a little less scientific. They have a low center of gravity, therefore they can use their buoyancy to support their weight.
They lie low in the water, and the deeper the draft is, the better the boat will handle. Since the hull is less affected by waves below the waterline.
Understanding why a displacement hull works so well in rough waters is all about gravity and weight. These hulls mean there is more hull than boat and since they’re not top-heavy, they’re more stable.
What Hulls Should You Avoid In Rough Waters?
Theoretically a planing deep-V hull, a displacement hull, and even a semi-displacement hull all have the potential to handle rough waters well, but we know you want to know which hulls should you avoid like the plague.
Well, there are two types of boat hulls that are god-awful, even just facing a single wave. These are flat-bottomed hulls and pontoon hulls.
Flat-bottomed hulls handle terribly with waves. If you want to experience the wettest, choppiest ride of your life, making you feel like you are on the world’s most unpleasant rollercoaster, feel free to take your flat bottom onto the shoreline.
Really, it is best to keep these boats on lakes and calmer waters. Flat-bottomed hulls are not made for the sea.
Then there are pontoon hulls, these used floaters to lay on top of the water. They are very stable, but when waves come along, they handle about as well as a car with flat tires.
Much like with a flat-bottomed hull, they have nothing to help them cut through the water, and their center of gravity is far from that of a displacement hull. Keep these in calm waters.