Glossary > #BEAM

BEAM – Ship’s width

In the maritime world, the term “BEAM” refers to the width of a ship or boat at its widest point. This fundamental measurement is crucial for the design, stability, and performance of a vessel. Understanding the concept of beam is essential for anyone involved in ship design, construction, or navigation, as it directly impacts the functionality and safety of the vessel. This glossary entry explores various aspects, including its definitions, measurements, and impacts on stability and performance.

What is BEAM?

Definition

At its core, the width of a ship is the distance between the two widest points of the vessel’s hull. It is usually measured at the waterline, although other specifications, such as maximum beam or beam at deck level, may also be used. As sources like Discover Boating emphasize, the beam is a critical dimension in naval architecture, influencing the stability, maneuverability, and overall performance of the ship.

  • Maximum width (BMAX): The maximum width is the widest point of the ship’s hull, often located at the midpoint of the vessel. According to Wikipedia, it is the lateral distance between the two farthest points of the hull.
  • Width at waterline (BWL): This is the width of the ship at the point where the hull intersects the water’s surface. It is crucial for determining the ship’s stability and load capacity, as noted by Marine Insight.

Significance in Design

The beam is a fundamental parameter in ship design and construction. It influences several key aspects of the vessel:

  • Stability: A wider beam generally provides greater initial stability, reducing the likelihood of tilting or capsizing in calm waters. However, as Discover Boating explains, it may compromise secondary stability, making it harder to right the vessel if it capsizes.
  • Maneuverability: While a narrower beam can improve speed and maneuverability by reducing hydrodynamic resistance, it may also result in decreased stability.
  • Capacity: The beam affects the internal volume and deck space of the vessel, impacting cargo capacity and passenger accommodation.

Measuring Beam

Calculating Beam

The beam is often calculated using standardized formulas, especially for monohull vessels. One common rule, as stated by Discover Boating, is to relate the beam to the overall length (LOA) of the vessel. The formula ( \text{Beam} = \text{LOA}^{\frac{2}{3}} + 1 ) provides an estimate for the beam in feet, assuming a typical monohull design.

Variations in Beam Measurement

Different types of vessels and design philosophies may require various beam measurements:

  • Moulded Beam: This excludes the thickness of the hull planking and measures the internal width of the hull.
  • Extreme Beam: This includes the thickness of the hull planking and provides the total external width of the vessel.

Width on Centerline (BOC)

For multihull vessels, such as catamarans and trimarans, the width on the centerline (BOC) is used. It measures the distance between the centerlines of the hulls and is key for assessing the stability and performance of multihull designs.

Width and Vessel Stability

Initial and Secondary Stability

The beam plays a key role in vessel stability:

  • Initial Stability: A wider beam increases initial stability, making the vessel more resistant to tilting in calm conditions.
  • Secondary Stability: In rough waters, a narrower beam can be advantageous as it requires less energy to right the vessel after tilting or capsizing.

Impact on Performance

The width affects various performance characteristics:

  • Speed: A narrower beam reduces drag, allowing for higher speeds, while wider beams increase hydrodynamic resistance.
  • Handling: A vessel with a narrow beam can execute sharper turns and respond more quickly to steering inputs, which is advantageous for racing vessels.

Implications for Design and Operation

Types of Vessels and Considerations

Different types of vessels have varying width requirements based on their intended use:

  • Racing Yachts: These often have narrow beams to maximize speed and agility.
  • Cargo Ships: Wider beams are preferred to enhance cargo capacity and stability.
  • Multihull Vessels: These typically have greater width to provide additional stability and comfort for passengers.

Navigation and Operational Considerations

The width also affects navigation and operational aspects:

  • Anchoring and Docking: Wider beams require larger berths and can pose challenges in narrow waterways.
  • Cargo Capacity and Distribution: Wider beams allow for more even weight distribution, increasing cargo capacity and stability.

In summary, the width of a vessel is a critical dimension that affects every aspect of its design, stability, and performance. From influencing the speed and maneuverability of the ship to determining its stability and capacity, understanding the beam is essential for anyone involved in maritime operations. By balancing the width with other design parameters, naval architects can optimize the vessel for its intended purpose, ensuring safety, efficiency, and comfort on the water.