What is keel rake?

The keel rake or the skeg angle, is the angle at which the keel of a ship is inclined relative to the vertical. A vessel's fore and aft centerline (or keel line) is seldom perfectly straight, and as such the keel rake is the upward slope of the keel when looking sideways at the ship, similar to the rake of a ship's masts. The keel rake is positive if the keel is raking upwards toward the stern, and negative if it is raking upwards towards the bow.

The keel rake has an effect on the speed of a ship, and so is of particular interest in the design of racing sailboats. A large keel rake means the bow is low in the water and the stern high (when a sailing yacht is not heeled), which tends to reduce wave-making resistance at higher speeds. The same effect results in better windward ability in a sailing vessel, but makes it less stable and more likely to capsize than a vessel with less or no keel rake. Too little rake can adversely affect the vessel's sailing performance (particularly windward performance) by causing the bow to be too high and the stern to be too low in the water. To mitigate the effects of too much or too little rake, some sailboat designers use a skeg aft of the keel to add to the effective length of the keel.

Keel rake can have an effect on the trim and stability of a powerboat, as well as the propulsive efficiency of its propeller or jet drive.