Hi all,
As I experiment a little more with APM in my Skyfun, I wonder if there's a suite of attributes we could use to compare airframes and get a good idea of where one airframe performs better over another. Just for starters, example attributes could be:
Performance
Stall speed
Max level speed
Max climb rate at flight-ready weight
Max climb rate at maximum weight
Efficiency
Max power draw
Power draw at optimum speed
Endurance at maximum speed and weight
Endurance at optimum speed and flight-ready weight
Physical
Dimensions
Dry weight
Flight-ready weight
Max payload
Avionics bay dimensions
Number of control axes
CoG thresholds (balance limits)
Each of the outputs of the above is then weighted based on a bias of vehicle requirements (eg: Speed vs Endurance vs Payload) and you end up with a rank for each airframe.
These quantitative attributes could be supplemented with qualitative data from users (eg: Beware tip-stall...! or Suitable for belly-mounted camera).
I'm not sure how to implement this - Perhaps an Excel or something, but am interested in people's thoughts...
Replies
[quote]
Performance
Stall speed
Max level speed
Max climb rate at flight-ready weight
Max climb rate at maximum weight
Efficiency
Max power draw
Power draw at optimum speed
Endurance at maximum speed and weight
Endurance at optimum speed and flight-ready weight
Physical
Dimensions
Dry weight
Flight-ready weight
Max payload
Avionics bay dimensions
Number of control axes
CoG thresholds (balance limits)
[/quote]
Instead of stall speed you could have stall constant and it be understood the actual stall speed is its weight * stall constant.
Instead of max speed there could be a max speed constant that can be used in a simple formulat with motor thrust to give max speed.
Continue doing the rest for the other stats.
I have already done a physical airframe spreadsheet that I update when people post up information or an airframe they are interested in. That way all the data can be verified and proven with manufacturers specifications not peoples choices of servos, motors etc thereby making the effectiveness skewed.
As efficiency and performance is dependent upon personal preferences you would end up with an enormous spreadsheet just for an Easystar let alone anything else.
Rupert, As part of my mission to (possibly) use the Skyfun as a high-altitude glider, I'm doing some relatively simple math modelling of the airframe at high density altitudes to see at what altitude it will begin to fly, what the terminal speed might be etc. At the moment I'm using assumed values for stall speed, mass, Cd/Cl etc, but if you already have some data from your Skyfun that you're prepared to share, I'd really appreciate it!
Andrew