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What Is A Boat Hydrofoil?

A hydrofoil is a wing-like attachment mounted to the outboard motor cavitation plate -- providing lift at the stern of the boat and preventing bow-rise.

Boat hydrofoil

How does a boat hydrofoil work?

The foil is shaped in such a way that it generates lift as water flows over and under it. This lift counteracts the weight of the vessel, reducing the amount of hull surface area in contact with the water. As a result, hydrofoils decrease hydrodynamic rag, allowing the vessel to glide more efficiently through the water.  

What are the benefits of using a boat hydrofoil? 

Lower bow-rise allows better visibility and safety.  The hydrofoil improves boat performance and enhances stability.  Hydrofoils bring the boat on plane faster, allow consistent planing at lower RPMs, and create steadier turns and higher top end speeds.  A hydrofoil also reduces fuel consumption.  A hydrofoil prevents “porpoising”, which is the unstable bouncing of the bow against the water, common with small motorboats. 

How should I choose a hydrofoil? 

Consider the type and size of your boat. Different hydrofoils are designed for specific boat types, such as powerboats, sailboats, or pontoon boats.

Doel-Fin Hydrofoil Wings

For example, Davis Instruments' Doel-Fin features a two-piece design that allows it to work with any size engine or cavitation plate, making it ideal for all sizes of boats that have outboard motors or outdrive units (including inflatable dinghies). Davis Instruments' Whale Tail  on the other hand, is designed specifically for ski boats. Additionally, the size and weight of your boat will impact the hydrofoil's effectiveness, so choose a model suitable for your boat's specifications. Look for hydrofoils that have been specifically engineered for efficiency and performance, and consider factors such as the shape and size of the foil, the material used for construction (typically aluminum or composite), and any additional features that may enhance stability or control. For example, Doel-Fin's unique wing-shape was designed by an aeronautical engineer to provide maximum boat lift and fuel efficiency while reducing drag. The two-piece design allows each foil to flex independently and absorb shock, increasing stabilization and control. 

Definition of Marine Terms - Full List