An odd picture of an improvised device to measure the available lift of our balloon. Constructed by tying 2.375" TrussSteel screws along a string, as the balloon exerts more or less upward pull, the device responds by allowing a greater or lesser number of screws to lift off of the floor. Our 16 candle test showed a steady state lift of 10 screws, with a peak lifting force of 12 screws. A box of 1500 screws weighs 45 pounds, so we figured we could safely lift just under 0.3 lbs of additional weight (fuel).