Study the dimensions of an existing rocking chair that you like. Take note of what you do and do not like about the chair so you can design a personalized version.
Design the width and depth of the chair. A good width for a rocking chair is at least 4 inches wider than the width of the intended user. If you are designing a rocking chair for a child, allow room for the child’s growth. When designing the depth of the chair, keep in mind that chair back can take up to 2 inches. The front edge of the rocking chairs seat should be designed so a user does not feel a harsh angle under her legs.
Determine the span of the rocking rails. The rails are the bottom, curved pieces that make the chair rock. Rails that are too long pose a tripping hazard, and those that are too short can cause a rocking chair to tip. Good rocking chair rails extend 2 inches past the front of the seat and no more than 6 inches past its back edge.
Design the arc of the rails and angle of the chair legs. The rails should have a gentle curve that does not make the rocking chair tilt back quickly once you sit in the seat. The legs of a rocking chair generally extend from the seat at a 5-degree angle and enter the rails at the same angle. It is important to remember that the legs on a rocking chair are shorter than those of a traditional chair because of the height provided by the rails.
Create a comfortable seat back design. After deciding if you want a solid back on the chair or one that has rails, you can further design the chair to follow the curves of the intended user or have a back that is slightly angled.
Select the wood. When deciding on the wood to use on a rocking chair, woodworker Scott Morrison states that you should pay particular attention to the direction of the wood grain to help maximize its strength and minimize creaking noises. The grain of the chair’s front and back legs should follow the curves. The wood at the locations of the joinery should be as flawless as possible.