What is a common type of patch used for repairing plywood skin?

Scarfed patches are commonly used for repairing plywood skin because they allow for a smooth transition between the original plywood and the new patch, thereby maintaining the structural integrity and aerodynamics of the aircraft. This type of patch involves cutting the edges of the damaged area and the patch at an angle, creating a gradual slope that allows for better bonding and load distribution. The angled cut enhances the mechanical strength of the repair and reduces the likelihood of stress concentrations that could lead to further damage.

In contrast, other patch types, though they may have specific applications, do not provide the same effectiveness for plywood repairs. Jump patches, for instance, may be used in some instances, but they do not provide as seamless a transition and can create weak points in the structure. Rivet patches rely on mechanical fasteners which can introduce additional weight and points of stress. Adhesive patches may not offer the durability required for an airframe's stresses and are typically not recommended for structural repairs in wood. Therefore, scarfed patches are the preferred choice due to their ability to strengthen the repair while maintaining the integrity of the plywood skin.