Explaining wings and fins from pike to tuna, vulture to swift

Challenge

Why do pike have broad tail fins, but tuna have narrow? Why do vultures and pheasants have broad wings with ‘fingered’ wingtips, but swifts have narrow, simple wings?

Solution

These questions above cannot be answered by thinking about aeroplane wings. However, they can by using simplified propeller theory, with results evident from fan and propeller design: efficient thrust production at low speeds – obvious for the pike, but also vital for loaded or rapid take-off in vultures and pheasants – requires broad, high-lift foils like a desk fan. At high speeds, narrower foils produce thrust efficiently, accounting for tuna, swift and Spitfire propeller design.

Publications