What is the purpose of a stern on a boat?

Boating is appealing to many people because of its association with leisure. But there’s a lot to know about boat design, function, and terminology when you begin shopping for your vessel. Starting with, what is the stern of a boat, and why is it a crucial consideration when choosing a boat to purchase?

The rear of a boat is the stern, while the bow is the front. Many boats have their engines at the stern, while others use that location for seating or storage. But how did the term come about, and how can you describe the other areas of the boat?

Nautical Language Origins

While it might seem simpler to reference the back of the boat as the rear instead of giving it a special name, nautical vocabulary has a long and rich history. For centuries, sailors have used their own terminology to describe everything from the way the boat leans to alerting their shipmates of danger.

Plus, if boaters used the terms “left” and “right,” it would be confusing to explain where things were happening. After all, a boat changes direction all the time, so left and right would change just as quickly. Similarly, if words sounded too alike, given the noise and wind, miscommunication could mean a life and death situation.

While we’re discussing the stern, it makes sense to cover some other common boating terms. These terms cover the directions you’ll need to know on a boat.

Forward

If you go from the rear, or stern, of the boat to the front, you’re moving forward.

Aft

Aft is moving backward from the front, or bow of the boat.

Astern

Astern is a term referring to a boat’s moving backward (reversing).

Port

Port is the left side of the boat when you’re standing at the stern.

Starboard

Starboard is the right side of the boat while observing from the stern.

Back when boating required nothing but oars and able arms, the term “starboard” became popular because a “steering oar” controlled the vessel. Since most sailors were right handed, the steering oar was typically on the right-hand side of the boat. The evolution of the word then went from “steering side” to “starboard” as sailors combined old English words for “steer” and “the side of a boat.”

Port/Starboard Bow

Port bow is the front left of the boat (again, from a position at the stern). Starboard bow is the front right of the boat.

Port/Starboard Quarter

Port quarter indicates the left rear of the boat, while the starboard quarter is the right rear.

Amidships

If you’re amidships, you’re in the middle of the boat.

Topside

Topside refers to going above deck (on boats with multiple).

Transom

An area of the stern where the two sides of the hull meet.

The stern of the boat is where you’ll find the transom, but there’s more to it than a vertical area where engines attach. Here’s more on what is in the area and what your boat’s stern might look like.

A boat’s stern has many different looks, and a transom can vary in width, angle, and overall style. Four primary types are common: flat, canoe, reverse, and raked.

Flat Transom

A flat transom looks like a semicircle from the rear and has a broad vertical face.

Canoe Transom

Canoe transoms are rounded and more aerodynamic than other types. The design helps push water away from the rear of the boat.

Reverse Transom

Reverse transoms offer an angular shape and often steps or a platform for people to disembark. Handrails and swim steps are common additions to reverse transom designs.

Raked Transom

A raked style transom is more common in racing boats because it streamlines the boat’s movement through the water. A boat with a raked stern is more likely to have a longer bow. 

In short, the stern usually contains the boat’s engine. There are four primary types of propulsion for boats: inboard, outboard, stern drive, and jet drive motors. Not all of them perch on the transom, however.

Inboard Engines

Inboard engines are essentially automobile engines with some adaptations for marine applications. An inboard engine is inside the hull or forward of the transom. As the engine runs, it turns a drive shaft, which operates the propeller outside the boat. Most inboard engine boats use a rudder to control the steering of the vessel.

Outboard Engines

An outboard engine attaches to the stern of a boat in an area called the transom. While the stern is the back part of the boat, the transom is the vertical area where the two sides of the hull come together. Transom mount engines attach onto the boat transom with clamps.

An outboard motor is removable, portable, and often easy to attach. The unit includes the motor and propeller, and most are four-stroke engines. You steer an outboard engine via a tiller or sometimes a steering wheel. As you turn the tiller or wheel, the propeller swivels (along with the rest of the motor) and changes the boat’s direction.

Stern Drive Engines

Stern drive engines combine the features of both inboard and outboard engines. In a stern drive model, the engine attaches through the transom and connects to a drive unit. Essentially, the engine is inside the boat and attaches via a driveshaft to the propeller. The outdrive portion swivels to move the propeller.

Jet Drive Motors

Jet drive relies on water propulsion to get watercraft moving. Jet drives direct a jet of water to provide thrust, which is then visible behind the power boat as it moves. Jet drives exist in personal watercraft and larger boats, but they’re most common in shallow-water vessels.

What type of stern is ideal for your boat? What does the stern of the boat have to do with performance on the water? Stern style influences more than looks—here’s more on the different stern features and how to choose what will work for you.

Width (and Stability)

Though most boats employ engineering to avoid capsizing, it’s still a possibility for any sailor. That said, there are many features which help keep your boat on an even keel. Width is one of them. Wider sterns provide buoyancy and can help you tow dinghies or water sport equipment. Of course, the design of the boat influences its handling in the water, but a narrow stern may not encourage confidence.

Open Cockpits (or Not)

Because the transom enters the stern of the boat, it’s transitioning directly into the cockpit. For families who enjoy sailing together, an easy entryway is helpful. For swimming or water recreation, steps into the water are ideal. For competitive boating, however, or sport fishing, you may want another type of transom for better performance for those needs.

Additionally, if you boat on mostly flat water, an entirely open cockpit might be ideal. But if you need to navigate rough water, a more closed-off cockpit—and less inviting transom—is preferable. Boat insurance can be comprehensive, but that still doesn’t mean you want to end up using it.

Other Stern Features

Though design and appearance are essential parts of the stern’s features, it’s also an area that demands utility. On the stern of most boats, you’ll find cleats and chocks for securing sails, mooring, dock lines, and more. The hardware should be secure and immovable—and you need the right hardware for the configuration you want to have as you travel the water.

If you want to enjoy watersports, for example, you need the appropriate hardware to attach leads and equipment. Ultimately, you won’t want to purchase a boat—no matter how great its features or its price—if the stern won’t perform the functions you require. 

The front of the ship is called the forward or bow region, whereas the back end is called the aft. This is also interchangeably known as the stern, but it is more specific. The stern mainly relates to the section or the structural area aftmost in terms of the overall length of the ship. In simple terms, it is more of what you can see when you stand right behind a vessel and look ahead. 

The origin of the word stern is not clear. At the same time, some argue that it came from the distortion of the word ‘stiarne’, which was the allusion to the rudder as per the ancient Frisian and Saxon languages, many claims that it was based on the literal meaning of the word ‘stern’ which translates to serious and unrelenting! Well, if you look at the robust back of a large tanker, it does not look anything amusing or comical, does it?! 

However, some experts state that it derives from the era of Vikings in the 8th and 9th centuries when steering or manoeuvring was called ‘styra’ or ‘stjorn’ in the old pre-English languages. This later evolved as ‘styrne’ and, finally, stern in English. This also makes sense because the rudder, the principal device for steering or manoeuvring, is housed underneath the stern itself and attached to the stern frame.  

In a more technical sense, the term refers to the structural areas or section (s) associated with the rudder and propeller attachments. It is characteristic of the sternpost, the principal structural member of the stern. 

Functions and Importance 

Like any other structural member, the stern is intrinsic to the vessel’s hull structure. It provides closure to the hull volume in the aft part. 

Moreover, it also influences the propulsive and hydrodynamic behaviour of the vessel in its wake. Now, what is a wake? 

In simple terms, the overall effects in the water behind a vessel include the wave patterns, currents, eddies, and flow behaviour in that particular region. The trace of the ship behind its aft or these effects has a high degree of influence on the propulsive efficiency of the vessel as this influences the resistance. 

The higher the resistance, the less the hydrodynamic efficiency of the vessel, as we know. Hence, the shape and the disposition of the stern structure are very crucial for the hydrodynamic efficiency of a hull.

 Imagine having a flat box-shaped vessel like a barge with no defined stern form and the stern of a military frigate ship. Which of them shows better wake and speed characteristics necessary for propulsion? As obvious, it is the latter. Hence, depending on the vessel type and design, the stern is accordingly designed for dealing with the flow behaviour afterwards.

Also, the stern of the ship has a great deal of responsibility for bearing the loads and vibrational effects from the rudder, the propeller and associated shafting and attachments. 

Types of Sterns

Stern of a vessel can be of three principal types based on the topside form of the stern structure: Elliptical, Cruiser and Transom. 

Recapitulating, an elliptical stern was common during the 19th and early 20th centuries. When viewed from above, the deck line associated with this type of stern form appears to resemble a closed ellipse. When viewed sideways or in profile, an elliptical stern curves upward from the aft perpendicular.

 Earlier, when ships were made of wood, a series of timber panels extended from the bottom upward and bent towards the corners to form the profile of the elliptical stern. The curved edge of the elliptical stern raked above the bottom aftward. There was ample space for the rudder post. 

A cruiser stern is considered an improvement to an elliptical stern. However, unlike an elliptical rudder, the profile and design are such that the curved edge lies lower; thus, the rudder is entirely below the design waterline. Therefore, they have comparatively better resistance characteristics. They are also aesthetically pleasing and offer better wake characteristics in their wake. 

A transom is the most common stern choice for most cargo ships. They are simplest in construction and have a flat section from the deck to the waterline. They may be considered a cruiser stern cut off abruptly at some length from the aft to give rise to a flat section. Though they do not offer a curved profile like the above two, they provide tremendous flow separation and prevent forming strong waves aft and eddies. 

Some other forms of special sterns, which are advanced modifications of the above, include raked, scoop, bustle stern, or the constanzi stern, which is the special case of Queen Mary 2. 

Design and Construction

A ship can be a supported beam for all practical purposes. So, from the view of flexural or longitudinal bending forces, the maximum bending stresses tend to occur in the fore and aft regions. Moreover, the aft region is also prone to effects like pounding or slamming. 

Furthermore, this region also needs to withstand the loads from the rudder, propeller, and other appendages. So, the stern needs to be highly strengthened. Stiffeners of both transverse and vertical orientations are fitted throughout the plating. The plating of the aft regions, including the stern, need higher scantlings. Often higher grades of steel like high tensile steel are used. 

Furthermore, the type of stern also influences the arrangement. Cruiser sterns are characteristics of cant frames oriented all around the periphery of the shell plating and welded between the deck and the floor. The cant beams welded to the transverse deck beams further support the decks. 

However, cant beams are not provided in the case of transom sterns. Horizontal as well as vertical stiffeners stiffen the flat stern plating. All sterns are fitted with heavy solid floors along with a centreline girder. Horizontal stringers may be further provided to the plating. 

One very important feature of all sterns is the stern frame or the stern post. The stern frame is a lower feature that runs from the keel to some extent above. It is a structural frame that runs like a backbone, providing extra support and strength to absorb the loads from the tail shaft and the rudder connected to the frame. 

In older days, these frames were cast and externally fitted to the outer shell plating of the stern. However, in modern days, they come welded with the hull structure. The construction of the stern frame is based on the type of stern and rudder. Care is taken to ensure adequate clearance between the rudder and propeller and the stern frame. They are streamlined to avoid hydrodynamic issues like eddies or vortices.

Horizontal webs and stringers often support them for added stiffening. The scantlings of this frame once again depend on the vessel and the type of rudder. The rudder and propeller are connected upward and often maintain structural continuity with the plate floors of the stern.

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