Post by crawfishes on May 22, 2012 23:39:03 GMT -6
Trent and Nick,
Recent member and enjoy watching the show. A few questions though. I know something about the cross country trip, but not sure where you are in the development of that process with regard to the episodes. I'd like to offer input (not that is would be needed) but uncertain what phase of the project the show is in. Could I suggest integrating a timeline and milestones into the progression of the show?
In terms of aircraft, what are you trying to achieve? If I were building a plane for the trip, I would have a very specific set of performance goals defined. Example: If you're following a car, you should be able to keep at least 60-70 mph airspeed on the aircraft at all times. The speed of the trip is more related to the number of battery swaps than airspeed however which makes endurance a big player. For RC (I think) endurance=battery power/quantity so I would be looking to haul the most weight (batteries) while still keeping 60-70 airspeed. What throttle settings equal the longest endurance, etc. (I tend to ramble). If you're just looking for a testbed for the APM, I wouldn't recommend the Shrike however. Flying wings are inherently unstable (just do some research on the career of Jack Northrop) and not a good stable platform for testing of avionics. I would recommend something more like the Nova for that. Again, all good designs begin with a very specific list of performance goals, and form follows function.
With regard to episode 66 and your aileron trim problem, I think Nick is mostly right. Do some reading on P factor and torque. At high angles of attack (not incidence), low airspeeds and high torque, this P factor will induce a roll moment. All of which fit your description of 'flying like a truck'. Most airplanes account for this with the vertical tail at the rear of the airplane and the application of opposite rudder on takeoff as flight at higher airspeeds are not as severe. However, since flying wings don't have conventional tails............. May I suggest putting a few spacers on the engine mount to move the center of thrust away from the aircraft centerline. In your case, angle it to the right. Lots of small aircraft do this as a simple solution which does not add much weight to the aircraft. Other reasons for the trim could be asymetrical wing construction/design (especially at the tips), weight distribution and aileron rigging. Please do NOT add weight to the other wing to compensate. Adding weight to fix a problem is breaking the cardinal rule of aircraft design.
Keep up the good work.
Dustin
Recent member and enjoy watching the show. A few questions though. I know something about the cross country trip, but not sure where you are in the development of that process with regard to the episodes. I'd like to offer input (not that is would be needed) but uncertain what phase of the project the show is in. Could I suggest integrating a timeline and milestones into the progression of the show?
In terms of aircraft, what are you trying to achieve? If I were building a plane for the trip, I would have a very specific set of performance goals defined. Example: If you're following a car, you should be able to keep at least 60-70 mph airspeed on the aircraft at all times. The speed of the trip is more related to the number of battery swaps than airspeed however which makes endurance a big player. For RC (I think) endurance=battery power/quantity so I would be looking to haul the most weight (batteries) while still keeping 60-70 airspeed. What throttle settings equal the longest endurance, etc. (I tend to ramble). If you're just looking for a testbed for the APM, I wouldn't recommend the Shrike however. Flying wings are inherently unstable (just do some research on the career of Jack Northrop) and not a good stable platform for testing of avionics. I would recommend something more like the Nova for that. Again, all good designs begin with a very specific list of performance goals, and form follows function.
With regard to episode 66 and your aileron trim problem, I think Nick is mostly right. Do some reading on P factor and torque. At high angles of attack (not incidence), low airspeeds and high torque, this P factor will induce a roll moment. All of which fit your description of 'flying like a truck'. Most airplanes account for this with the vertical tail at the rear of the airplane and the application of opposite rudder on takeoff as flight at higher airspeeds are not as severe. However, since flying wings don't have conventional tails............. May I suggest putting a few spacers on the engine mount to move the center of thrust away from the aircraft centerline. In your case, angle it to the right. Lots of small aircraft do this as a simple solution which does not add much weight to the aircraft. Other reasons for the trim could be asymetrical wing construction/design (especially at the tips), weight distribution and aileron rigging. Please do NOT add weight to the other wing to compensate. Adding weight to fix a problem is breaking the cardinal rule of aircraft design.
Keep up the good work.
Dustin
