FOC calculator-notice problems

[tradwannabe]

I tried Rob D.'s foc calculator (how to resources) but found when i put in 32"long, 530 grains weight, no insert, 175 grains broadhead then change the broadhead weight, nothing happens. FOC should change as i add weight to the broadhead. Maybe my numbers are outside of the parameters? (real numbers by the way-ash shafts)

[Greg Owen]

I have never tried his calculator but from a glance it looks like you have to enter in the balance point too.  The FOC calculation only uses the arrow length and the balance length.  So it won't change unless you change one of those numbers.