Tench745
Master member
I have this train of thought I am currently following and I thought maybe some others might want to weigh in on it. It's a theoretical and number crunching problem.
As many know, wing loading is a terrible way to compare how aircraft of different sizes will fly. To compare models of different size we use cubic wing loading, which gives us a number we can compare pretty universally across all sizes of aircraft. They fall somewhere in the following categories:
Slow-flyers and Gliders: under 4
Trainers and Parkflyers: 5 to 7
Aerobatics: 7 to 10
Scale: 10 to 15
Warbirds and Racers: 15 and over
When sizing motors we have compare watts/pound depending on the type of flying you want to do. The categories are something like the following, depending on who you ask:
50 -70W/lb. …....Trainers and slow flyers
70-100 W/lb. .....Basic aero/sport flying
125 W/lb. …........Precision aerobatics
150+ W/lb. …...…Extreme 3D performance
My current line of thinking is: why do we compare power to weight directly? Would there be any benefit to comparing power to cubic wing load?
I crunched a few numbers to start a comparison. All data for the given aircraft are from Wikipedia based on rated power and maximum weights, so they don't necessarily reflect actual use cases of a given aircraft.
- A full scale Cessna 172R has about 160hp(119312W) and a gross weight of 2450lbs, for a power to weight of ~49W/lb. At gross weight a 172R would have a cubing wing loading(WCL) of 17.1.
- A Zivko Edge 540 has 310hp(231167W)and a max aerobatic weight of 1550lbs, for a power to weight of 149 W/lb. At its aerobatic weight the Zivko Edge 540 has a WCL of 22.7.
- A J-3 Cub has 65hp (48470.5W) and a max weight if 1220lbs for a power to weight of 39.7W/lb. Its WCL at max gross is 8.2.
As many know, wing loading is a terrible way to compare how aircraft of different sizes will fly. To compare models of different size we use cubic wing loading, which gives us a number we can compare pretty universally across all sizes of aircraft. They fall somewhere in the following categories:
Slow-flyers and Gliders: under 4
Trainers and Parkflyers: 5 to 7
Aerobatics: 7 to 10
Scale: 10 to 15
Warbirds and Racers: 15 and over
When sizing motors we have compare watts/pound depending on the type of flying you want to do. The categories are something like the following, depending on who you ask:
50 -70W/lb. …....Trainers and slow flyers
70-100 W/lb. .....Basic aero/sport flying
125 W/lb. …........Precision aerobatics
150+ W/lb. …...…Extreme 3D performance
My current line of thinking is: why do we compare power to weight directly? Would there be any benefit to comparing power to cubic wing load?
I crunched a few numbers to start a comparison. All data for the given aircraft are from Wikipedia based on rated power and maximum weights, so they don't necessarily reflect actual use cases of a given aircraft.
- A full scale Cessna 172R has about 160hp(119312W) and a gross weight of 2450lbs, for a power to weight of ~49W/lb. At gross weight a 172R would have a cubing wing loading(WCL) of 17.1.
- A Zivko Edge 540 has 310hp(231167W)and a max aerobatic weight of 1550lbs, for a power to weight of 149 W/lb. At its aerobatic weight the Zivko Edge 540 has a WCL of 22.7.
- A J-3 Cub has 65hp (48470.5W) and a max weight if 1220lbs for a power to weight of 39.7W/lb. Its WCL at max gross is 8.2.