As noted in the excerpt from the RASAero II Users Manual, the differences between the Barrowman Method and the Rogers Modified Barrowman Method are:
1) The CNalpha of the combined Nose Cone and Body Tube at low angles of attack is included, versus the Barrowman Method where only the Nose Cone is included. Again, this is the CNalpha through zero degrees angle of attack. The effect of adding the Body Tube to the Nose Cone at low angles of attack is the CNalpha is increased, and the Center of Pressure of the Nose Cone/Body Tube combination at low angles of attack is moved aft towards the bottom of the Nose Cone/top of the Body Tube. Note this is not the increased CNalpha with angle of attack from viscous crossflow (Galejs), which is covered below.
2) The Body in the presence of the Fins Interference Factor (Kbf), which was left out of the Barrowman Method, is included.
3) The viscous crossflow increase in CN with angle of attack is included. This is what was described by Galejs in What Barrowman Left Out. In fact we used some of the Galejs Planform Areas and Planform Area CP's. (Thanks you Galejs.) We used a more advanced method, Jorgensen Viscous Crossflow, for the CN calculations.
Charles E. (Chuck) Rogers
Rogers Aeroscience