Sail Area and Displacement Ratio

The Sail Area to Displacement Ratio calculator computes the ratio of the sail area of the boat to its displacement in the water. the Bruce Number, also known as the Bruce Roberts Formula, is a metric used in yacht design to assess the relative seaworthiness and stability of a sailboat. It's named after Bruce Roberts, a prominent naval architect who popularized the formula.

INSTRUCTIONS:  Choose units and enter the following:

• (SA) Total Area of Sails
• (D) Boat Displacement

Sail Area-Displacement Ratio (SA/D): The calculator returns the ratio as a real numbers.

SA/D Level Indications

• 16 to 18: Offshore Heavy Seas Cruisers
• 18 to 22: Mid-range Cruiser
• 22 to 26: Inshore sailing and racing boats
• 26 and up: Specialty Racing boats

The Math / Science

The formula used for the Sail Area-Displacement in this calculator is:

SA/D = `(SA) / D^(2/3)`

where:

• SA/D = Sail Area - Displacement Number
• SA = Total Sail Area
• D = Displacement of Boat

Displacement

Displacement, in the context of a boat or a ship, refers to the weight of the volume of water that the vessel displaces when it is floating in the water. It is essentially the weight of the water that is "moved aside" by the hull of the boat when it is floating or submerged in water.  Displacement is typically measured in tons (or tonnes) or in pounds (or kilograms) depending on the size and type of vessel.

Types of Displacement:

• Light Displacement: The weight of the boat without any cargo, fuel, crew, or provisions.
• Normal Displacement: The weight of the boat fully loaded with crew, fuel, cargo, and provisions.
• Loaded Displacement: Similar to normal displacement, but also including the weight of additional equipment, stores, and water.

Displacement is important because it affects the boat's buoyancy (ability to float), stability, and overall performance in the water. It is a crucial factor in determining a vessel's design, capabilities, and seaworthiness.

Displacement can be calculated using various methods, including direct measurement (placing the boat in water and measuring the volume of water displaced) or through more complex calculations involving the boat's dimensions and hull shape.

Displacement in boating refers to the weight of the water displaced by the boat's hull when it is floating or submerged, and it plays a significant role in determining many aspects of a vessel's design and operation.

Sailing and Navigation Calculators:

• Bruce Number: Computes the ratio of the square root of sail area to the cube root of displacement of a sail boat
• Sail Area / Displacement Ratio: Compute SA/D ratio for sail boats.
• Displacement-Length Ratio: Computes a metric to describe how heavy a boat is in relation to its waterline.
• Capsize Screening Formula: Computes a metric to describe a boat's stability in rough seas.
• Vessel Displacement Volume: Computes the cubic feet displacement associated with the weight displacement.
• Weight of Seawater: Computes the weight and mass of a volume of seawater.
• Time to Sink: Compute the time it takes for a breach (water in) to surpass the displacement of the boat.
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