Ken Whiting of PaddleTV explains the purpose of rudders and skegs, and whether or not you need one on your kayak.
A rudder is a long fin-like blade that sits on the back deck of the kayak. When it is deployed by hull lines along the sides of the kayak, it drops down into the water. It is controlled by your foot pedals, which allow it to turn and help control the kayak.
A skeg is a fin-like blade that drops directly down from the hull of the kayak. For the most part, for hard shell kayaks the skeg is retractable, meaning it can go back into a housing inside the kayak itself. The skeg can be deployed at various depths. On some inflatable kayaks the skeg is permanently fixed to the boat or it is removable.
Rudder vs. Skeg
Both rudders and skegs are designed to help you control your kayak. The biggest difference between a rudder and a skeg is that a skeg does not turn like a rudder. A rudder is able to move side to side, which helps you steer your kayak.
When Do You Need a Rudder or a Skeg?
As a general rule, you should consider a rudder or skeg if you are paddling in windy conditions or plan on covering large distances. If you are touring in windy areas, then a rudder or skeg is a great idea. Kayaks under 14 feet do not typically need a rudder or skeg, since they are already maneuverable on their own. Once you get above 14 feet, a rudder or skeg becomes more valuable because long boats do not turn well.