Setup for longest flight time
02-13-2016, 09:18 AM
#1
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Setup for longest flight time
Any help would be appreciated.
I'm doing a slow stick strictly for long flight time and don't need anymore power than stock.
I've searched around and get a lot of old threads so I thought I'd rekindle the discussion.
Looked at radical RC but there is no way to get in contact with them to ask questions.
Would like a 2S brushless motor and maybe a gearbox. Any opinions on what to buy?
I'm doing a slow stick strictly for long flight time and don't need anymore power than stock.
I've searched around and get a lot of old threads so I thought I'd rekindle the discussion.
Looked at radical RC but there is no way to get in contact with them to ask questions.
Would like a 2S brushless motor and maybe a gearbox. Any opinions on what to buy?
Last edited by gordyd4; 02-13-2016 at 03:45 PM.
02-14-2016, 09:20 AM
#2
gordyd4
The question really should be what aspect of the Slow Stik are you trying to improve to gain longer endurance?
Obviously a bigger capacity battery is the simplest way but it follows the laws of diminishing returns as the extra battery weight requires the use of more power. Eventually even if it has enough power to fly it will virtually impossible to take off and even if it does it will be hard to control.
Bigger slower revving propellers can be more efficient but a gearbox tends to absorb much of the efficiency gained so an appropriate lower kV motor matched to a suitable prop is the best way of using the power.
Finally there the airframe weight and drag. Both absorb power just to maintain level flight. How much you do about either depends on how 'original' you wish to keep your Slow Stick.
I acquired a Hobby King Slow Stick and managed to significantly improved its performance & duration by:
Cutting the stiff foam hinges and replacing them with top surface tape for the ailerons and 'Barbie' hinges for the elevator and rudder which enabled tiny 3.7g servos to be used in place of the original 9g.
Burying the rudder and elevator servos in the fin and tailplane saved the weight of two long snakes and the drag of the servos stuck on the sides of the fuselage stick.
Carefully fairing the 2s 2200mAh battery, motor and prop adapter.
Using a suitable diameter and pitch (9x6) prop to suit the low motor revs.
Even the tail end of the two part fuselage stick was replaced with a much lighter glass fibre tube along with a lighter tail wheel assembly.
Complete.
It now flies rather better than it did and has an economical cruise at low power approaching 45 minutes or to put it another way, longer than I really want to fly in one go!
The question really should be what aspect of the Slow Stik are you trying to improve to gain longer endurance?
Obviously a bigger capacity battery is the simplest way but it follows the laws of diminishing returns as the extra battery weight requires the use of more power. Eventually even if it has enough power to fly it will virtually impossible to take off and even if it does it will be hard to control.
Bigger slower revving propellers can be more efficient but a gearbox tends to absorb much of the efficiency gained so an appropriate lower kV motor matched to a suitable prop is the best way of using the power.
Finally there the airframe weight and drag. Both absorb power just to maintain level flight. How much you do about either depends on how 'original' you wish to keep your Slow Stick.
I acquired a Hobby King Slow Stick and managed to significantly improved its performance & duration by:
Cutting the stiff foam hinges and replacing them with top surface tape for the ailerons and 'Barbie' hinges for the elevator and rudder which enabled tiny 3.7g servos to be used in place of the original 9g.
Burying the rudder and elevator servos in the fin and tailplane saved the weight of two long snakes and the drag of the servos stuck on the sides of the fuselage stick.
Carefully fairing the 2s 2200mAh battery, motor and prop adapter.
Using a suitable diameter and pitch (9x6) prop to suit the low motor revs.
Even the tail end of the two part fuselage stick was replaced with a much lighter glass fibre tube along with a lighter tail wheel assembly.
Complete.
It now flies rather better than it did and has an economical cruise at low power approaching 45 minutes or to put it another way, longer than I really want to fly in one go!
02-14-2016, 01:49 PM
#4
Gordyd4
The problem is a brushless motor is already pretty efficient over quite a wide power range so the best you can hope for is a few percentage points improvement in motor/prop efficiency.
If you want to stick with the standard motor (as I did) but run on a 2s (as I did) the best you can do is load the motor so it keeps about the same maximum current as it did with a 3s. This is achieved by increasing the pitch of the prop to compensate for the 1/3 reduction in the motor rpm and possibly increasing its diameter as well.
It will take some experimenting with different props and a Watt meter to even begin to identify the best combination and it would have to be followed by accurate flight testing to 'prove' any benefit.
My own guess is that with the same motor and weight of battery you are likely to find it hard to achieve more than a 5% improvement in endurance compared to using the standard prop and a 3s.
Do keep posting as I would be very interested to hear about you results.
The problem is a brushless motor is already pretty efficient over quite a wide power range so the best you can hope for is a few percentage points improvement in motor/prop efficiency.
If you want to stick with the standard motor (as I did) but run on a 2s (as I did) the best you can do is load the motor so it keeps about the same maximum current as it did with a 3s. This is achieved by increasing the pitch of the prop to compensate for the 1/3 reduction in the motor rpm and possibly increasing its diameter as well.
It will take some experimenting with different props and a Watt meter to even begin to identify the best combination and it would have to be followed by accurate flight testing to 'prove' any benefit.
My own guess is that with the same motor and weight of battery you are likely to find it hard to achieve more than a 5% improvement in endurance compared to using the standard prop and a 3s.
Do keep posting as I would be very interested to hear about you results.
