Air resistance / density / humidity changes ?
Posted: May 20th, 2013, 11:03 am
Last week was our first trip to nationals, and we had a great time (thanks to all of the events supervisors) but our helicopter times were disappointing.
At home (Phoenix, AZ) we had tuned our helicopter using thin 3/32" rubber to allow us to use a long band with over 2000 turns and keep the motor weight down. We were getting times of about 2:45 with a flat 8" ceiling, but at nationals we only got 1:19. We later found some damage to one of the helicopter blades, but both helicopters had similar low flight times so we think that the change in humidity between AZ and Ohio was the biggest factor.
We also had a weight gain (one helicopter added 0.14g) and some of the balsa glue joints broke, lifting the surface layer off the balsa motor stick rather than the joint itself. Again we believe that this was the humidity.
We can keep the helicopters sealed with desiccant to reduce the weight gain, but that won't enable us to test or adjust for the change in flight times.
Given that next year will be in Orlando (and hoping that we win state again) how do other groups manage this variability ? Do you just go early with extra kits and retune or are there better solutions ?
At home (Phoenix, AZ) we had tuned our helicopter using thin 3/32" rubber to allow us to use a long band with over 2000 turns and keep the motor weight down. We were getting times of about 2:45 with a flat 8" ceiling, but at nationals we only got 1:19. We later found some damage to one of the helicopter blades, but both helicopters had similar low flight times so we think that the change in humidity between AZ and Ohio was the biggest factor.
We also had a weight gain (one helicopter added 0.14g) and some of the balsa glue joints broke, lifting the surface layer off the balsa motor stick rather than the joint itself. Again we believe that this was the humidity.
We can keep the helicopters sealed with desiccant to reduce the weight gain, but that won't enable us to test or adjust for the change in flight times.
Given that next year will be in Orlando (and hoping that we win state again) how do other groups manage this variability ? Do you just go early with extra kits and retune or are there better solutions ?