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What is the Hull of a Jet Ski? What’s it Made of? [Video]
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Simply put, the hull of a jet ski is its watertight shell on which the whole machine is built. The shell of each jet ski is covered with a top deck.
These two shells create a watertight body that accommodates the engine and many other important parts. Jet skis typically feature a V-shaped planing hull, which allows the machine to run on top of the water. These hulls are often made of SMC, Polytec, regular fiberglass, or even carbon-fiber.
If you want to find out more about jet ski hulls, this post is for you.
We at JetDrift have compiled all you need to know about their design and the most commonly used materials!
What is the Hull of a Jet Ski?
The hull of a jet ski is actually its body, which sits in the water. Basically, it looks like a huge bowl! This empty shell is considered the hull of the jet ski without any machinery, rigging, or other additions. Unlike many boats, a jet ski’s hull is always fully covered with a top deck. This top deck and the hull are attached and sealed to create the watertight body of the jet ski.
The line where the surface of the water and the jet ski’s hull meet is referred to as the “waterline.”
Here’s a great video on how a jet ski hull looks from the inside and outside:
What Kind of Hull Does a Jet Ski Have?
As a rule of thumb, jet skis feature a V-shaped planing hull, which is often used for powerboats as well. As the name suggests, this type of hull features a V-shaped bottom and a pointed front. The V-shape flattens out towards the rear side of the machine.
Thanks to this special “planing” design, jet skis can rise from the water and plane on top of it.
This results in much faster speeds, and a smoother riding experience in choppy water conditions.
One of the main advantages of this hull design is that the V-shaped bottom can cut through smaller waves.
The deeper the V-shape, the more effectively it cuts the chop. On the other hand, it sits deeper in the water and has a larger surface.
All of these result in more resistance and makes it more difficult for the ski to rise from the water.
That’s why jet skis with a deep-V hull are always slightly slower, require more powerful engines, and burn more gas as well.
Some of the most well-known jet skis with deep-V hulls are the Kawasaki Ultra 310 series.
When it comes to riding on rough waters, nothing can beat these large machines!
They are stable, predictable, and offer much smoother rides. On top of that, this hull design provides aggressive turns as well.
Shallow-V jet ski hulls come out from the water much easier, so they require less powerful engines.
On the other hand, they are more difficult to handle on choppy water and deliver much more vibration to you.
If you want to learn more about the different jet ski hull designs, don’t miss this great video from Kevin Shaw at WatercraftJournal:
What Type of Hull Does a Sea-Doo Have?
Sea-Doos currently have four different hull types, which are as follows:
- Spark hull: small dimensions, shallow-V shape, made of pure Polytec.
- GTI hull: medium-sized, moderate V-shape, made of Polytec and fiberglass.
- ST3 hull: the most stable hull in the industry, extra wide and offers a low center of gravity. Made of fiberglass.
- TR-3 hull: race-inspired design withdeep-V hull shape. Made of fiberglass.
What Does Planing a Jet Ski Mean?
When a jet ski is idling or going at low speeds, it sits completely in the water. But if you increase the speed, the hull starts to rise from the water. Once the jet ski reaches its “planing speed” the hull starts to ride on top of the water. So, the planing of a jet ski actually means its like a “plane” on the surface of the water.
Sure, the intake grate and the pump are still submerged into the water to propel the machine. But besides the rear side of the hull, it’s safe to say that the greatest part of it comes out of the water.
That’s why riding a jet ski is like flying above the water, especially if it’s as smooth as glass!
Parts of a Jet Ski Hull
The key parts of a jet ski hull are as follows:
- Keel: The spine (centerline) of the hull. The deeper the hull’s V-shape the lower the keel cuts into the water.
- Pad: A flatter area on the rear of the hull’s bottom. The keel of most jet skis turns into a flat area as it goes toward the rear of the hull. The main idea behind this flat bottom is to reduce water drag.
- Chine: The corner where the bottom and the side of the jet ski meet. A sharper (“harder”) chine results in more aggressive turns as it provides more traction at higher speeds. In contrast, a softer chine (softer corner) allows you to lean the jet ski more easily when you turn sharply.
- Strakes: Strakes or “lifting strakes” are little distinct ledges running horizontally on the bottom of the hull. They are designed to help lift the hull out of the water to get to plane quicker. They can reduce the wet surface of the hull, which leads to less water drag.
- Additions: Jet ski hulls are always equipped with several useful additions such as sponsons, bow eyes, reboarding steps, and splash deflectors. Furthermore, you also find the intake grate mounted onto the bottom of the hull. The jet ski’s HIN (Hull Identification Number) is also typically fixed onto its hull or top deck, most often on the rear platform.
What Are Jet Ski Hulls Made of?
In the past every jet ski hull was exclusively made of fiberglass. But over the years, more and more new materials have appeared on the market. Therefore, the newest jet ski hulls may be made of many different materials, which are as follows:
- SMC: Sheet Molding Compound
- Polytec: Fiberglass reinforced polypropylene (exclusively on Sea-Doo hulls)
- Regular fiberglass
- Carbon-fiber (mainly for racing jet skis)
- Aluminum (very rare, only used on AlumaSkis and some DIY projects)
What is a Sea-Doo Hull Made of?
The hulls of Sea-Doos are made of Polytec or with a fiberglass-based technology (CM TEC) depending on the model. The Polytec hulls debuted on the popular Spark series. Since then, more and more Sea-Doo hulls are made of this unique material. What’s more, some Sea-Doo hulls are made of a composite material, which also contains Polytec covered with a thinner fiberglass shell.
What is Polytec? It’s a fiberglass-reinforced polypropylene material, which was developed and patented by Sea-Doo.
This material is much lighter compared to regular fiberglass and SMC, which are still commonly used in the jet ski industry.
But do Polytec hulls work on full-sized jet skis? Find out from this video!
The hull of a jet ski is actually its shell, which keeps the entire machine afloat. It’s covered with the top deck, which is mounted on top of the hull. These two shells fit perfectly together and create a watertight body.
This body houses the engine, storage bins, battery, electronics, and many other important parts of the machine.
Regarding design, virtually every jet ski features a planing V-shape hull.
Jet ski hulls are typically made of SMC or Polytec, but some of them are still made of regular fiberglass. Racing jet skis often feature a carbon-fiber hull to reduce weight.
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