I've modelled a Lotus racing car wheel that has a waveform web something like the wave that you want, except that it's got compound topography. It's commonly known as the "wobbly web" wheel. I made it by drawing a spline like yours about a focus, then copying the spline successively about the focus, scaling x and y uniformly, varying z, then translating the splines in z. For yours, scaling a fractional copy uniformally in x and y, unit factor in z, and lofting a surface between them, then either thickening it or using offset surfaces and solidifying them would probably be more manageable than trying to control a bend. As far as I understand it, bend is single axis, you want two axes.