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Oct 27, 2020, 09:12 PM
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Dantiel's Avatar
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Lunala Kite and Solgaleo Kite


thank you john, i wanna fly more with it but its windy season all these days

therefore i made these two circular afghan style fighting kites that are painted as If they were real Pokemon making epic flight battles possible. They fly both fine and manoevrable in light to medium slight strong Wind but i dont have made a record yet of it. The lunala Kite is from book covering mylar and painted by fluophosporescent which means it glows in the dark and when UV light shines on it (will add small LED on the thread) the other is normal acrylic paint on aluminized mylar.

(removed some spars of lunala kite it to finish stormcutter wings)
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Oct 28, 2020, 07:52 AM
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Johns birds's Avatar
Hi Dantiel

You have more experience with ornithopters.
I have some problems with my LiPo batteries.
I use 180 mAh 1S 3.7 V LiPo dual sky brand for my birds.
I realised they last very short time. After only 6 charges
and total flight time 30 min they lost about 50 % capacity
and bird can not climb well as with new one, and Low Voltage Cut off on
my receiver triggers to early too. It happens on third battery
so far so it is not just one faulty. Is there any similar issues
with batteries you use.
Oct 28, 2020, 08:52 AM
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Dantiel's Avatar
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yes well what you refer to is indeed a pain in the buck. when a lipo goes under 20% voltage its chemical cells get destroyed, you can exceed this until 3S lipo is as good as 2S, but often won't work anymore at all or after some time or just become a lower C rating (current capacity it can supply at a time). therefore stop your flight when you notice the lipo starts becoming slightly weaker.
i often drive by 3S by connecting a 1S to a 2S which are not strong enough, by changing the number of cells it can together still supply enough to what is needed, also when using lipos of more cells it is possible that some of the single cells are drained more and one could possibly reassemble them into new functioning lipos
Oct 28, 2020, 06:58 PM
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Johns birds's Avatar
Quote:
Originally Posted by Dantiel
yes well what you refer to is indeed a pain in the buck. when a lipo goes under 20% voltage its chemical cells get destroyed, you can exceed this until 3S lipo is as good as 2S, but often won't work anymore at all or after some time or just become a lower C rating (current capacity it can supply at a time). therefore stop your flight when you notice the lipo starts becoming slightly weaker.
i often drive by 3S by connecting a 1S to a 2S which are not strong enough, by changing the number of cells it can together still supply enough to what is needed, also when using lipos of more cells it is possible that some of the single cells are drained more and one could possibly reassemble them into new functioning lipos
I think also flapping wings make uneven load on the motor and the battery compared to the propeller .
There is big spikes in the load at the beginning of the stroke especially on downstroke .
When I watched slo mo video of my bird flapping, motor literally stops at the end of each stroke.
It is probably not very healthy for battery life span. It seems that we have to live with it and fork out more
money for the batteries then more conventional RC models builders.
Oct 28, 2020, 07:58 PM
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Dantiel's Avatar
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yes flight is more expensive than walking or swimming, all flying animals need a constant supply of food (which they make up by the advantage of flight)... other animals suffice by eating once per year and float around the rest of the time... but its also as i say, try not exceeding the battery life till dead end but only as you see current output changes, then their life span will pass on. many ESC have a low voltage protection just for this reason.
a single stroke won't kill your battery being charged enough.

however try this: maybe you can get a more even stroke by adding spring on the wings that helps normalizing the strokes to mid position, especially for downstroke (just attach thin carbon or glass fibre spar on the wings)
Oct 29, 2020, 07:02 AM
Registered User
Quote:
Originally Posted by Johns birds
Hi Dantiel

You have more experience with ornithopters.
I have some problems with my LiPo batteries.
I use 180 mAh 1S 3.7 V LiPo dual sky brand for my birds.
I realised they last very short time. After only 6 charges
and total flight time 30 min they lost about 50 % capacity
and bird can not climb well as with new one, and Low Voltage Cut off on
my receiver triggers to early too. It happens on third battery
so far so it is not just one faulty. Is there any similar issues
with batteries you use.
I second Dantiel's comments.
30 min flight time within 6 charges => about 5 min per discharge.
Assuming you discharge the battery completely within these 5 min =>
180mAh in 5 min => average current 2,2 Amp
(more reasonably 80% : 180mAh in 5 min => average current 1,7 Amp)

Even the average current of 2,2 A correspond to a C-rating of only 9,6C, well within the capability of this battery (45C).

If the peak current would be well above 2,2 A - I would expect the small motor to die well before the battery.

However, as Dantiel wrote, if the battery is dischared below 20% of its capacity it will be harmed and die.

Try to reduce the flight time by 1 min or change to a battery with a capacity of 220mAh. It does not weigh much more. But it is much more rigid.
Oct 29, 2020, 08:15 PM
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Johns birds's Avatar
Quote:
Originally Posted by Ralf W.
I second Dantiel's comments.
30 min flight time within 6 charges => about 5 min per discharge.
Assuming you discharge the battery completely within these 5 min =>
180mAh in 5 min => average current 2,2 Amp
(more reasonably 80% : 180mAh in 5 min => average current 1,7 Amp)

Even the average current of 2,2 A correspond to a C-rating of only 9,6C, well within the capability of this battery (45C).

If the peak current would be well above 2,2 A - I would expect the small motor to die well before the battery.

However, as Dantiel wrote, if the battery is dischared below 20% of its capacity it will be harmed and die.

Try to reduce the flight time by 1 min or change to a battery with a capacity of 220mAh. It does not weigh much more. But it is much more rigid.
Hi Ralf

Your calculation is all correct. My receiver has built in ESC 2A without overload protection so I can not
overload the battery beyond 45C anyway. If I load ESC with more than 2A, onboard FET will blow, it happened once
on my small bird because motor was faulty and drew more than 2A. My load current is up to 1.8 A. But there is another
problem. My onboard 2A ESC has built in LVC (low Voltage Cut off) at 3.7V. Because of flapping mechanism uneven load
any deep below 3.7V triggers LVC and switches motor off in mid flight. If I briefly close the throttle I can rearm the motor and
make emergency landing. I have switched this option of on my Rx to prevent crash landings. It is possible that I over discharge
the battery. I could try to shorten flight time to extend the battery life, or ignore the problem and replace the battery when
weak. It costs only $9 like two coffees in cafeteria here in Perth (my average daily intake)
Nov 03, 2020, 09:17 PM
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Dantiel's Avatar
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Stormcutter Titan build Wings and tail system finished


Some Progress on the Titan stormcutter. Wings are finished and tail Control System same done as by other stormcutter.

Next is making fuselage covering and painting.
Nov 03, 2020, 09:21 PM
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Dantiel's Avatar
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Quote:
Originally Posted by Johns birds
Hi Ralf

Your calculation is all correct. My receiver has built in ESC 2A without overload protection so I can not
overload the battery beyond 45C anyway. If I load ESC with more than 2A, onboard FET will blow, it happened once
on my small bird because motor was faulty and drew more than 2A. My load current is up to 1.8 A. But there is another
problem. My onboard 2A ESC has built in LVC (low Voltage Cut off) at 3.7V. Because of flapping mechanism uneven load
any deep below 3.7V triggers LVC and switches motor off in mid flight. If I briefly close the throttle I can rearm the motor and
make emergency landing. I have switched this option of on my Rx to prevent crash landings. It is possible that I over discharge
the battery. I could try to shorten flight time to extend the battery life, or ignore the problem and replace the battery when
weak. It costs only $9 like two coffees in cafeteria here in Perth (my average daily intake)
Johnsbird you could try a capacitor it Stores some current and then releases it when a bottleneck of source occurs, i had the same Problem in my butterfly when using stabilize due to the ESC i used and it solved it. When it still occurs you need a bigger capacitor or new battery.
Nov 05, 2020, 04:31 PM
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Dantiel's Avatar
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Stromcutter Titan fuselage covering and painting.


Deepest purple i could find. Next is to try the maiden flight
Nov 05, 2020, 06:06 PM
K Kakuta
Kazu-kaku's Avatar
Quote:
Originally Posted by Dantiel
Deepest purple i could find. Next is to try the maiden flight
Very Good dragon paint!
Nov 07, 2020, 01:05 PM
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Dantiel's Avatar
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Quote:
Originally Posted by Kazu-kaku
Very Good dragon paint!
Thank you Dr. Kazukaku
Nov 07, 2020, 01:07 PM
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Dantiel's Avatar
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Stormcutter Titan Maidenflight at dawn 7.11.20


Stormcutter Titan Maidenflight at dawn 07.11.20 (12 min 33 sec)


Successful flight and good stability, very slow flight is possible by very Low Wing loading. The clicking noises are adjusting trim. However 1000kv 2211 Motor is too weak to Return flapping from glide... Any ideas? Will try to reduce friction a Bit. Didnt find another Motor yet because theres few room for stator
Last edited by Dantiel; Nov 07, 2020 at 01:15 PM.
Nov 08, 2020, 01:27 AM
K Kakuta
Kazu-kaku's Avatar
Quote:
Originally Posted by Dantiel
https://youtu.be/Ss-ld-rtSGw

Successful flight and good stability, very slow flight is possible by very Low Wing loading. The clicking noises are adjusting trim. However 1000kv 2211 Motor is too weak to Return flapping from glide... Any ideas? Will try to reduce friction a Bit. Didnt find another Motor yet because theres few room for stator
Good Flight!! 2211 2300Kv motor is better.
Welcome to HOW TO TRAIN YOUR DRAGON's world.
Last edited by Kazu-kaku; Nov 08, 2020 at 05:42 PM.
Nov 08, 2020, 03:50 AM
Registered User
G-LO's Avatar
Congratulations Dantiel! The great detail, build and flight is in itself very impressive. It flies so efficiently.


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