I have been looking for the most energy efficient setup in RC flight. The goal is to sustain a glider in flight for the longest time possible on a single charge.
Here are some base specifications that may help
Weight (2.5-4.5lb)
Folding Propellers
1.) Voltage (3s, or 4s batteries)
2.) Propeller (Stay with recommended prop, or is there a more efficient option {decreases x traits for efficiency})
3.) Motor brands (any well known companies with higher quality magnets or products)
4.) Motor kV (which is the most efficient kV for a glider? Higher, lower, medium {800kV large prop vs 1600kV small prop})
5.) ESC (are there certain types that are more efficient, companies or higher quality brands. Should I use a higher amperage ESC if the weight is the same?)
6.) Throttle (What is the best throttle percentage for efficiency, {like a car getting best mpg with slow acceleration, should I keep the throttle between 40-60% when running for example or 80%-90%?})
7.) Servo Motors (What will yield the best efficiency for constant use, or is this minimal consumption in the glider. Again, any companies, brands or styles?)
If there is any point that may increase efficiency on a glider electrically speaking, let us know. Pick a number if you want and discuss the best options for a specific topic in efficiency. This will help me and the entire community find the best option for the better flight times and more advanced builds!
With solar panels + dynamic soaring you can keep flying practically forever.
With dynamic soaring you can potentially turn generate electricity if you use your propeller like a wind turbine.
The best throttle percent will depend on motor, esc, and propeller.
>Learn to thermal, scrub
Failing that
>1.) Voltage (3s, or 4s batteries)
Makes little difference as long as you have the restraint to pull the throttle back on 4s
2.) Propeller (Stay with recommended prop, or is there a more efficient option {decreases x traits for efficiency})
Stick with the recommended range for your motor. Choose a prop from within that range based off the flight envelope of your plane.
3.) Motor brands (any well known companies with higher quality magnets or products)
Meh
4.) Motor kV (which is the most efficient kV for a glider? Higher, lower, medium {800kV large prop vs 1600kV small prop})
Large, slow-turning props are more efficient, especially at low speed (and as seen from the increasing prevalence of big geared folders in F5B and now even F5D, are capable of going very fast as well).
5.) ESC (are there certain types that are more efficient, companies or higher quality brands. Should I use a higher amperage ESC if the weight is the same?)
I can't say I fully understand the differences, but I've seen a good bit of variation in wattage, efficiency and effective kV just from different ESCs. Not sure why it happens, perhaps it's related to motor timing. Now, I've also read that the ESC itself is only a minor source of energy loss (1-5%) but if it's changing the way your motor behaves (and assuming you don't change props or motors accordingly), that CAN have a more significant impact on the efficiency of your propulsion.
>6.) Throttle (What is the best throttle percentage for efficiency)
As little as it takes to fly, period. More for climbs, less for descents. I'm often able to get about twice the "usual" flight time out of many of my models since I prefer not to fly at WOT.
7.) Servo Motors
Minimal draw. Digital servos draw over twice as much as analog for some reason. Don't be stupid with your control surfaces and linkages; the servo will draw more if it constantly has to exert force to hold position.
>>998351
Is modyfying the wing/fuselage an option? Because lift distribution and aspect ratios can be a pretty big deal.
Not really as it is composed of carbon fiber... But any improvement is huge, even if it is a few watts
I dunno whether you're using a fixed amount of batteries or not, but one of the most obvious ways to get more endurance, provided thrust alone is being used to sustained flight (i.e. no thermals or ridge lift) is by adding more batteries. More batteries means more energy onboard, which for a given power draw means more endurance. However, this only works to a point, since more batteries means more power is needed to fly. After this point, the power increase required by the additional weight of the batteries exceeds the energy increase of adding more batteries.
According to an analytic optimization I ran a while back, this optimum occurs when the weight of the batteries is 2/3 of the overall aircraft weight (that is, two pounds battery for every one pound everything else), provided battery quantity is the only independent variable (if the airframe must be strengthened or the motor must be enlarged to carry the additional weight, then these assumptions go out the window) and that the aircraft is trimmed and flown for the same AoA and L/D regardless of weight, which means that speed and power setting will depend on weight (if a constant speed or a specific power setting must be maintained regardless of battery quantity and weight, then this goes out the window).
Note that, even well before the optimum, there is a very clear trend of diminishing returns - over 90% of the optimum endurance can be achieved with just 50% battery weight (i.e. 1 pound battery for 1 pound everything else), and 70% at 33.3% battery weight (i.e. 1 pound battery for 2 pounds everything else). Pic related (x is battery weight/total weight).
However, since it is a glider, if conditions are favorable then it's possible to shut the motor off entirely and continue flight indefinitely (or at least as long as conditions allow), PROVIDED that it's light enough to sustain without power. Under these circumstances, weighing the glider down with gobs of batteries will likely conflict with this approach.
>>998901
Forgot my pic. Again, x = (battery weight)/(total weight). y is normalized to the optimum, which itself will depend on the airframe (and particularly it's L/D, efficiency of the propulsion system, it's size, and it's non-battery weight including any payload).
>>998901
>>998905
Holy shit, you're actually right. I did the math and found that the mass of the batteries is 2/3th of the total mass.
But what surprised me the most is that the result is completely independant of things like the air density, angle of attack, L/D and even the energy density of the batteries. Everything canceled out in the end.
Pic related is the equation i started from, where mb is the battery mass and mf is the mass of everything else. Q is the energy density of the batteries.
>and that the aircraft is trimmed and flown for the same AoA and L/D regardless of weight
This condition is not necessary. There will be an optimal AoA but this does not influence the optimum for the battery mass.
Flight time = infinite.
Check out thin film solar panels
http://www.powerfilmsolar.com
Also it would have to be fairly large to reach an ideal surface area ( for the panels) to weight.
>>998901
OP here, I have been busy in the recent days but I am here. This sounds incredible! It does have a plan of motor bursting in which the plane will fly to its height before gliding back down... hopefully gliding quite far. The batteries added will be what I can hold in terms of charging capacity from solar panels which are coming from a company who will custom build and cut them. they currently hold the world record in non mirrored solar panels at 28.9% vs. the 2nd place 22.5%
I am also using batteries with 4 times the energy density of normal lipo batteries. This will expand flight time to the highest possible.
I will definitely not go past the drop off point of 2/3 weight in batteries, but I will stay as close as I can while maintaining gliding abilities.
Use a drone motor with large diameter and very low KV. Maybe use a longer shaft to be able to mount it fartehr back from the nose as the nose of most fuselages is to narrow. Then use a very big propeller. This way, you have more efficiency. Also use ESCs with active freewheeling. Hobbyking's YEP line has it. Use brand name propellers as Aeronaut Cam Carbon, or Freudenthaler.
>>999147
>I did the math and found that the mass of the batteries is 2/3th of the total mass.
>Pic related is the equation i started from, where mb is the battery mass and mf is the mass of everything else.
Yep. Sorta a fun little exercise, isn't it?
>But what surprised me the most is that the result is completely independant of things like the air density, angle of attack, L/D and even the energy density of the batteries
Yeah, provided each of these things are held constant.
>This condition is not necessary. There will be an optimal AoA but this does not influence the optimum for the battery mass.
My point was that the AoA in question, whatever it is, must be maintained from battery configuration to battery configuration. If you're going to run at 60% power regardless of how heavy the aircraft is, or if you must maintain 20 m/s regardless of weight, then that assumption goes out the window.
