Seaplane with Hydrofoil

Classical seaplanes have a lot of drag while speeding up on the sea. Additionally, the floats have a lot of drag and weight once the plane is on the air.  Adding hydrofoil at the bottom of the plane solves all these problems. This is not a new idea and was utilized in the early days of aviation (Piaggio P.7, 1929). However, the idea remained on paper in the upcoming decades.

David B. Thurston on his book ‘Design for Flying’ proposes hydrofoil for seaplanes. Water is about 800 times the density of air, so a hydrofoil of very small size could lift an amphibious hull out of the water early in the takeoff run and significantly reduce overall drag. It also helps in handling higher waves, as the hydrofoil was on strut some distance under the hull, and the strut and foil could slice through waves with less impact than a hull. A retracting hydrofoil that is faired in flight should have less drag.

I also propose the hydrofoil to double as vertical and horizontal stabilizer for the plane once it’s on the air. This would reduce the air drag and weight induced by the main stabilizer at the tail.

This design in a way is tested on hobbyist level RC planes. However, it would make more sense to see it on autonomous seaplanes at a bigger scale. Sea allows almost infinite runway and requires minimal infrastructure compared to a runway on land. Deploying more planes on the sea would be strategically beneficial for the implementing country while the country can launch planes almost anywhere from the sea compared to stationary airfields.