A bridging structure for a deforming foil, such as a morphing wing, that provides a fluid-dynamic surface throughout foil deformation that forms a curved fluid-dynamic surface with a relatively low drag. A high extent of foil deformation can be provided, with lower actuation force, providing a fluid-dynamic surface with a simple or complex curve in one direction, by providing a set of rail-mounted members that are joined at one end to a deforming sheet. By coupling the members with high elongation, resilient bodies, adjacent members can support each other, while permitting extension, and accommodating curvature.