Maximum altitude??
05-10-2014, 11:31 AM
#126
I have just read all through this thread - very interesting.
As a very significant part of your flight will be climbing weight is your enemy.
With electric you can't do much about the LiPo batteries.
You will have to find the motor prop combination that gives you the best specific performance but again with commercial units there is little opportunity for further development.
The bit that you can do something about is the airframe. Finding the best compromise between aerodynamic and structural efficiency for the most efficient climb rate is very complex indeed. Every item in the whole structure has to be made just strong enough.
All I can say is that to climb you need an excess of power. To get the greatest excess from a specific amount of energy the airframe needs to have the lowest possible power requirement to fly. This means the lightest possible airframe with the lowest possible gliding sink rate.
Note a high performance glider is intended to fly the greatest distance for given height (best possible lift to drag ratio). The power its uses whilst doing it is not of primary importance, however the design is a bit different if the object is to use as little power as possible whilst descending and where the distance travelled is not an issue. In effect aerodynamic efficiency is compromised for structural efficiency.
A good target for low power level flight would be 10W/lb. If you can achieve this then any more power and you will be climbing.
I have an electric RC plane that can maintain level flight on a bit less than 10W/lb.
As a very significant part of your flight will be climbing weight is your enemy.
With electric you can't do much about the LiPo batteries.
You will have to find the motor prop combination that gives you the best specific performance but again with commercial units there is little opportunity for further development.
The bit that you can do something about is the airframe. Finding the best compromise between aerodynamic and structural efficiency for the most efficient climb rate is very complex indeed. Every item in the whole structure has to be made just strong enough.
All I can say is that to climb you need an excess of power. To get the greatest excess from a specific amount of energy the airframe needs to have the lowest possible power requirement to fly. This means the lightest possible airframe with the lowest possible gliding sink rate.
Note a high performance glider is intended to fly the greatest distance for given height (best possible lift to drag ratio). The power its uses whilst doing it is not of primary importance, however the design is a bit different if the object is to use as little power as possible whilst descending and where the distance travelled is not an issue. In effect aerodynamic efficiency is compromised for structural efficiency.
A good target for low power level flight would be 10W/lb. If you can achieve this then any more power and you will be climbing.
I have an electric RC plane that can maintain level flight on a bit less than 10W/lb.
