how to calculate thickness distribution between upper and lower surface and how does +/- t(x)

Hi there,

Any ideas on how to have an equation that defines the mid position of the fitted curve along its length and then to have another that defines a thickness distribution along the length about this mid thickness position. Basically, to find the curve of the mid point between upper and lower surface and tehn how does +/- t(x) varyExept for the equation I would like to visualise this...Something similar to the approach used to define aerofoil shapes. I am attaching an example.

Thanks!