I'm making a quick mock-up of a panel air filter, which uses a wave type design for the filter element.

Example: http://www.potn.co.uk/watermark1~POTN~images/kandn/33-2201-425x425.jpg

I'm having some trouble drawing this, I tried using a spline but cannot get it to work accurately so that I can extrude it as I need to add thickness to it, and offsetting the line didn't want to work...

Attached is a quick sketch of what I'm trying to produce (cross section). Needs around a 1mm thickness.

Any ideas?