Bilge Keel

A bilge keel is a pair of long fin-like projections fitted along the turn of a ship's hull, below the waterline on either side, to reduce the vessel's tendency to roll in waves. British naval engineer William Froude, known for his pioneering research into ship hull resistance and stability, studied and helped develop the bilge keel for the Royal Navy during the 1870s as a way to steady ships without the drag penalty of a deeper keel. Bilge keels remain a common, relatively simple and inexpensive way to improve a ship's stability and are fitted to many merchant and naval vessels today.