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What is a Boat Rudder? – Types & Important Facts to Know

Written by J. Harvey / Fact checked by S. Numbers

what is a boat rudder

Learning to operate a boat requires a lot of knowledge and practice, and it also helps to know what part of the boat is responsible for certain functions. For this article, let’s take a look at the rudder.

But what is a boat rudder, and what does a rudder do on a boat?

The rudder is found at the vessel’s stern and is part of the boat or ship’s steering mechanism. Keep reading to learn more.

Boat Rudder – Definition and History


The standard axial rudder definition refers to the steering apparatus on a vertical (or, in some cases, nearly vertical) axis. This boat part can be managed using a tiller, steering wheels, or buttons on a control console.

Boats are not the only vehicles to utilize rudder steering. Airplanes, for example, also depend on this apparatus to rotate on a vertical axis. Similar to boats, the rudder in aircraft is located at the rear – the stabilizer’s outer edge, to be specific.

The exact original date of invention of rudders is unknown. However, there is enough historical evidence to get a rough estimate of when rudders were invented, which points to the Ancient Egyptians during the BC era with their steering oars.

That said, many would argue that the Egyptian steering oar is not a true rudder. In this case, the design that most resembles the modern rudder on a sailboat is believed to have originated in China during the Warring States Period (475 to 221 BC).

However, the modern rudder used on the motor boat was conceptualized in 1843 with the advent of the balanced ships rudder.

Aside from the balanced rudder, many different kinds of rudder work on a ship or boat. Here, we will cover a few of the more common types and what sets them apart.

Types of Rudder and Their Purpose/Function


1. Balanced

This type is attached to the boat and supported by a pintle on the bottom and stock on the top, effectively holding the rudder in place. It is characterized by being partially positioned in front of the connecting post, which balances the rudder.

Balanced rudders produce less resistance and allow for smooth and efficient sailing. You can find this rudder on a ship used for commercial purposes or a vessel with medium size.

2. Unbalanced

An unbalanced sailing boat rudder is designed with a rudder stock that runs from the top to the bottom of its span’s forward-most point. The longer stock allows the rudder to make sharper turns without becoming undone.

Unbalanced rudders are often used on smaller watercraft. However, they’re not very popular today as they don’t perform as well as their semi-balanced counterpart.

4. Semi-balanced

The most common type you can find nowadays, especially on twin-screw ships, these rudders are only balanced in their lower half. As a result, they have positive features from both balanced and unbalanced versions – providing stability while ensuring ease of operation.

5. Skeg-mounted

The rudder is connected to and supported by a skeg, which gives it additional protection from possible damage due to debris. However, the basic skeg-mounted design makes it more difficult to turn a vessel; but this can be addressed with a semi-balanced design.

The semi-balanced skeg, or horn rudder, only uses a half-length skeg to support the rudder. The lower half of the rudder is not connected to anything, just like a spade rudder.

Skeg-mounted rudders are most often used on yachts with fin keels. Both full- and semi-balanced skegs can ensure the yacht can withstand heavy impacts, making the vessel sturdier and more resilient.

6. Transom or Outboard

The rudder is connected to the stern above the water, meaning it’ll only be partially submerged and can be removed while the boat is still afloat. Rudders utilizing this design are usually controlled with a tiller.

How Does a Rudder Work?


Rudders function by controlling the flow of water using its contact surface. When the rudder is straight, it maintains the flow of water and helps to keep a vessel on its course. The vessel is able to remain steady even with the different forces acting on it, such as the movement of surface water and wind.

When the rudder is turned to one side, it manipulates the water pressure. The resulting difference between the two sides creates a force shift that allows the boat to turn in the same direction where the rudder is angled.

When a rudder is turned to an angle, a certain amount of counterforce pushes back on the rudder resulting in resistance. This makes it difficult to turn a boat as often depicted in various entertainment media, and this resistance is more evident when using a tiller instead of a wheel.

The boat’s ability to make sharper turns is affected by the rudder’s design, as explained above. However, having a wider range for turning also comes with problems, such as being more prone to mechanical problems.

The size of the rudder directly impacts its performance. If it is too small, there would not be enough force to influence the boat’s course, whereas a too-large rudder will result in a lee helm. Even its placement affects performance, as positioning anywhere else but the stern may render it useless.

Frequently Asked Questions


Is a rudder the same as a propeller?

No, they are two different components found on a boat, and each has its function.

As mentioned above, the rudder is responsible for steering and maintaining the vessel in a specific direction. The propeller is responsible for moving the boat forward by rotating its blades and creating a pushing force.

It is by making use of both the rudder and propeller that we can properly move and control the boat when traversing the water. Having just one of them for operating a vessel would be difficult.

What does a rudder on a boat look like?

The rudder on each boat may look a bit different, and the type of hull on the vessel also influences this appearance. In general, rudders look like flat plates or sheets, and they often resemble a fin or blade.

Do small boats have rudders?

Some very small boats like kayaks can have a rudder, but these may not be enough in some situations or may be more likely to experience a malfunction.

Kayakers make up for this with special techniques for steering the boat, such as the stern rudder, where the paddle is held in a certain way to mimic how a rudder works.


What is a boat rudder? Now you know the answer, but be sure to keep learning about the other important parts and mechanisms found on a watercraft. Knowing the tools you work with is always a good way to improve, which also applies to boating.

Did you find this useful or interesting? What other boat part do you think warrants this level of attention? Tell us your thoughts and suggestions in the comments section below.

Remember to boat safely.

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