skirt finger

A skirt finger is a narrow, flexible tube or flap made from reinforced rubber or fabric material, attached vertically to the perimeter of a hovercraft's main inflatable skirt. Each finger hangs down from the skirt edge and makes contact with the ground or water surface, creating a dynamic seal that confines the pressurized air cushion beneath the vehicle. Without these fingers, the air would escape sideways and the hovercraft would lose lift.

Hovercraft maintain their cushion of pressurized air through a balance between continuous high-volume air supply and controlled leakage. The skirt system uses either a continuous bag skirt or a segmented finger skirt. Finger designs use separate lengths of tube, typically 150 to 300 mm long, spaced around the hull perimeter. Each finger is independent, so damage to one segment does not compromise the entire seal; worn or torn fingers can be replaced without removing the main skirt structure.

Wear and performance in service

Skirt fingers experience constant flexing and abrasion from contact with decks, water, rocky terrain, and vegetation. They fray, split, and lose elasticity over time. Pressure losses increase as fingers degrade, forcing the lift fans to work harder and consume more fuel. Operators monitor skirt condition regularly; fingers are typically replaced after 500 to 2000 operating hours depending on duty cycle and landing surface. Ruptured or heavily thinned fingers must be addressed promptly, as a localized loss of seal creates a jet-like air escape that can destabilize the vehicle.

The name 'finger' reflects the resemblance to a row of flexible digits hanging down to touch the surface. Alternative designs exist, including segmented bag skirts and fully continuous bag systems, but finger skirts remain common in military and commercial hovercraft because they balance simplicity, maintainability, and cost. The fingers are usually secured to a stiff ring or weld plate at the top and left free to hang and flex at the bottom.

Material selection is critical. Early hovercraft used natural rubber, which degraded quickly and hardened in sun and salt spray. Modern fingers are typically rubberized nylon, nitrile rubber, or specialized elastomeric compounds that resist ozone, UV light, abrasion, and fuel residues. The fabric reinforcement prevents the finger from thinning excessively under pressure and repetitive contact, extending service life and maintaining pressure seal integrity across a wider range of landing conditions.