The Angle of Attack is the angle of the hydrofoil as it flys through the water.  In technical terms, it’s the angle between the chord line of a hydrofoil and the relative flow direction of the water (imagine a straight line connecting the leading and trailing edges of the hydrofoil). It determines how the hydrofoil interacts with the water flowing past it, affecting how much lift and drag it generates.

How Angle of Attack Relates to Hydrofoils:

Lift Generation:

As water flows over the curved upper surface of a hydrofoil wing, it travels faster than the water moving along the flatter underside. This faster-moving water creates lower pressure above the hydrofoil, while the slower-moving water beneath creates higher pressure. This pressure difference generates an upward force known as LIFT. Additionally, the hydrofoils deflects water downward when at a positive angle, and this further contributes to the lift.

Drag Trade-off:

As the Angle of Attack increases, not only does lift increase, but drag (resistance) also increases. If the AOA is too high, the hydrofoil can cavitate and cause a sudden drop due to air pockets introduced into the hydrofoil. 

Optimizing Performance:

With hydrofoils, the design (or shape) and angle of attack is very important. If you have too much angle the boat could porpoise or drop when the hydrofoils get too close to the water’s surface. Not enough angle, and the hydrofoils won’t lift the boat enough to eliminate drag.  

In essence, the angle of attack is a balance point that determines the efficiency and performance of the hydrofoil, influencing both speed and stability.

How much lift is created by the Hydrofin Super Fly Hydrofoils?  

In partnership with Morrelli and Melvin, Hydrofin spent over 6 months designing, engineering, and testing the optimal foil shape, installation method, and angle of attack. Unlike other hydrofoil vessels, Hydrofin’s were intentionally made not to lift the boat completely out of the water. Instead, they were engineered to achieve maximum performance and efficiency while keeping the boat safely in the water.