How to calculate required thrust for take-off knowing gross weight and L/D?
http://www.dept.aoe.vt.edu/~lutze/AOE3104/takeoff&amp;landing.pdf

This source has been really helpful for me in calculating takeoff time and takeoff distance. In this method, the author uses thrust as an input to calculate takeoff distance, but obviously you could re-arrange the equations to calculate for thrust if you knew the other variables. You will likely need to know the static thrust (zero speed thrust) of your engine and then can calculate for thrust required at takeoff. I would recommend putting the equations into an excel spreadsheet where you can then play with all the inputs until you reach a desired result. Hope this helps!