Aeroguy,

The reason that I do all the calculations for Ct is that the Thrust programs available do not account for the Blade Angle of attack very well unless the pitch/diam ratio is around .6 to .7. Most of the time the values are over by 10 to 30 percent. Something like a 12x4 prop will give way over inflated thrust calculation using the program. I guess to keep it very down and dirty you could just use pitch/diam relationship to adjust the Cf in the program.

EX. 4/12=.33 - .65= -.32
if you divided this by 2 (-.32/2=-.16)

The program also does not take into account body and wing interferance so I always take .10 percent away for this. So on the 12x4 prop I would reduce the cf by .26 or cf=.74.

About the smallest glow engine I've run is a .049 with a 6x3 prop if I remeber right 10,000 rpm probably about 5 oz of thrust. By the time you add the prop and fuel I think this was around 2.5 oz to 3 oz so probably to big for your application.

Good luck on the project and good luck on finding a job. I have alway hated job hunting!