Calculations for building 3 rail cabinet door with raised or shaker panels
I would appreciate some guidance on the calculations for building tall pantry doors that will require 3 rails instead of 2. It will have 2 floating panels, but require a horizontal rail in the center of the door for structural integrity to prevent bowing under the weight of the tall door. For example, the door height is about 68 inches and the 3 rails will be about 23 inches. How do I calculate the dimensions of my floating panels for the cabinet door, assuming that the rails and stiles are 2 1/4 inches wide, with a standard 3/8 inch mortise depth and a 1/16 inch expansion gap on each side of the 3 tenons. Thank you.