"An object submerged in a fluid experiences an upward buoyant force equal to the weight of the fluid it displaces."

This physical law is the foundation of all floatation devices, from ships and submarines to lifebuoys and plastic marine buoys.

The basic formula for calculating buoyancy is:

Fb=ρ⋅V⋅gF_b = ho cdot V cdot gFb​=ρ⋅V⋅g

Where:

• FbF_bFb​ is the buoyant force (in newtons, N)
   

• ρ hoρ is the density of the fluid (in kilograms per cubic meter, kg/m³)
   

• VVV is the volume of the fluid displaced by the submerged part of the object (in cubic meters, m³)
   

• ggg is the gravitational acceleration (approximately 9.81 m/s²)
   

Example Calculation:
If a buoy displaces 0.02 m³ of freshwater (with a density of 1000 kg/m³), the buoyant force acting on it would be:

Fb=1000⋅0.02⋅9.81=196.2 NF_b = 1000 cdot 0.02 cdot 9.81 = 196.2 , NFb​=1000⋅0.02⋅9.81=196.2N

This means the buoy can support roughly 20 kg before it begins to sink.

In the design of floating buoys, engineers must calculate the required buoyancy to ensure that the buoy can support its own weight and any additional load it may carry, such as equipment or netting. Safety margins are usually added to compensate for factors such as wave motion, water absorption, marine growth, and weathering.

Design Factors:

1. Shape: Spherical buoys offer excellent structural integrity and minimal stress concentration. Cylindrical or conical shapes may be used for specific hydrodynamic properties.
 

2. Wall Thickness: A thicker wall increases strength and pressure resistance, particularly important in deep-sea or high-load applications.
 

3. Material Selection: Common materials include polyethylene (PE), polypropylene (PP), EVA foam, and other engineered plastics, chosen for their lightweight, buoyant, UV-resistant, and corrosion-proof characteristics.
 

4. Internal Structure: Some buoys are solid (made of closed-cell foam), while others are hollow with sealed compartments or filled with air or foam for added safety.
 

Modern buoys may also incorporate ballast systems or stabilizing features to improve their behavior in rough waters. For industrial or oceanographic buoys, calculations extend to dynamic load resistance and long-term flotation under varying salinity and temperature conditions.

As environmental considerations grow in importance, buoy designers are also looking at sustainable materials and manufacturing techniques. This includes using recycled plastics and biodegradable components while still ensuring structural integrity and performance.

In conclusion, while the buoyancy formula is relatively simple, its practical application in buoy design involves a wide range of engineering and environmental considerations. Precise buoyancy calculation ensures the safety, stability, and longevity of floating buoys in all types of water environments.