Buoyancy tanks are sealed, airtight compartments or foam-filled voids located within a sailboat’s hull, typically at the bow, stern, or sides, designed to provide flotation and prevent sinking in the event of capsizing or holing. They act as structural buoyancy, allowing the boat to remain afloat just below the surface for recovery.

Key Aspects of Buoyancy Tanks:
Purpose: The primary purpose is to displace enough water to offset the weight of the boat and equipment, providing emergency positive buoyancy.

Placement: Frequently found in the bow and stern of small boats and dinghies, which helps the boat remain manageable during capsizes.

Structure: They can be permanent sealed compartments (often made of wood or fiberglass) or filled with closed-cell polyurethane foam.

Advantages: They provide necessary stability for righting a boat after a capsize, keeping the vessel from sinking entirely.

Maintenance: It is critical for these tanks to remain completely airtight or watertight. UK Mirror Sailing points out that leaks can occur in the tanks or around the bulkheads.

Foam Usage: Many builders prefer two-part closed-cell foam for added rigidity and flotation.