What is the purpose of this span wise "false spar" on Affordaplane wings? This is the wing of an Affordaplane Ultralight,what is the use of those spanwise foam boards between the foam ribs,I know it's not for aesthetics.
If you push up on the rib from below, it will eventually start to deform sideways, along its least stiff axis, and collapse.  The pieces in between them are just braces that prevent sideways deformation, and making the rib stronger.