News:
2018----><---- T Shirt




  • July 17, 2018, 08:49:18 PM

Login with username, password and session length

Author Topic: Optimization of Flight Parameters  (Read 552 times)

Offline Matt Piatkowski

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 401
Optimization of Flight Parameters
« on: July 10, 2018, 05:30:27 PM »
Hello,
I have made about 120 pattern flights in Europe using the stunt model (attached) weighting RTF 1,815 -1840 grams (64 - 65 oz.). 64 oz. setup used Cobra 3515/18 and 65 oz. setup used Black Tiger 4230 C that is heavier.

The batteries: 6S Thunder Power 2800 mAh 25C.
ESC: SPIN66
Timer: Igor's active timer.

Propellers: 11.5x6 3 blade carbon composite Pol-Prop and 11x6 3 blade (narrow) carbon composite Pol-Prop.

11.5x6 3 blade carbon composite Pol-Prop was too much for Cobra 3515/18 - the level laps were too slow (5.6 sec.) and the battery drain too high ( 92% after 5 min. 10 sec. flight ). There was not enough lines tension for the pattern so the "flight" included only level flight, wide inside loops and inverted flight. The lines length: 19.40 m. (64 ft. eye-to-eye)

After the prop was changed to 11x6 3 blade narrow carbon composite Pol-Prop, the level lap time dropped to 5.1 sec. and the pattern became possible. The battery drain after 5 min. and 10 sec. full pattern was 78% with the cells voltages were in the 3.73-3.75 V/cell range.

Please note that the SPIN 66 and the active timer setup remained the same.

Then, I have installed the Black Tiger 4230 motor using the same, 11x6 3 blade prop. The lap times and the battery drain after full pattern remained roughly the same.

Again, SPIN 66 and the active timer setup remained the same.

I am looking for the convincing and properly justified explanation why the change of the prop only caused such positive change, namely, decrease of the lap time by 0.5 sec. and much lower battery drain.

I will be soon using MVVS 8.0, Kv=680 motor in this plane and then there will be enough spare power to use not only 11.5x6 3blade Pol-Prop but also Igor's 12x5 3blade electric carbon composite props.

Regards,
Matt   




Online Motorman

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 3966
  • Millville NJ PDQ Flying Clown Country
Re: Optimization of Flight Parameters
« Reply #1 on: July 10, 2018, 07:07:37 PM »
The narrow prop has more pitch. Nice plane, I like the air intake around the spinner. I am running a similar set up using my 12.5 x 6 with Hubin timer which I believe uses less battery.
There will be a sunny day and we will fly our airplanes.

Offline Matt Piatkowski

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 401
Re: Optimization of Flight Parameters
« Reply #2 on: July 11, 2018, 05:24:20 AM »
Hi Motorman,
The narrow prop has the same pitch (6").

The measured on the ground RPM are 9,420-9450 for 11.5 x 6 3 blade and 11 x 6 3 blade and for Cobra 3515/18 and Black Tiger. These RPM are controlled of course by the active timer setup. This timer modifies the current draw and RPM
depending on the model position in space. When the nose goes up - RPM go up, nose down - RPM down.
In level flight, however, RPM stay constant and are controlled by one of the parameters selectable in the active timer menu. The timer and the ESC are programmed using the JETI box.
 
I know that the 11.5 x 6 3blade prop. draws more current in flight because it has slightly larger diameter and wider blades.
This explains larger battery drain for this prop.

In order for the model to fly faster on the 11 x 6 3 blade prop., the in-flight thrust had to go up. In order for the thrust to go up, the RPM had go up. In order for the RPM to go up, the current draw had go up again. The current "thing" can be understood as follows: the change of prop. to 11x6 3blade narrow blades ,assuming the same RPM, makes the current smaller but the RPM increase needed for faster flight requires more current. Somehow the net result gives smaller (and acceptable) battery drain after pattern.

I do not understand, however, where the additional RPM come from. Perhaps the active timer allows for higher RPM in level flight when the overall prop. resistance goes down? I will talk to Igor after he returns to Bratislava from the C/L World Championships in Landres.

The plane is take-apart with 1520 mm. wing in one piece.
Thanks,
M



 

Offline Christoph Holtermann

  • 2017
  • Trade Count: (0)
  • New Pilot
  • *
  • Posts: 23
Re: Optimization of Flight Parameters
« Reply #3 on: July 11, 2018, 05:36:44 AM »
Hello Matt,

nice green model and wow: 120 flights during your Europe trip is a lot!!

Your fellow Marek Niescioruk showed me these Pol-Props in Bitterfeld, early May and I think he and also Michal Kaminski flew them there on this competition. They looked good but I am astonished that you report such high battery consumption on such a large battery. The Cobra 3515/18 is a good motor and runs very efficient. So probably the target rpm on the larger 11.5x6 prop was set too low. How much rpm does it turn in level flight to achieve a proper lap-time?

The 12x5N from Igor runs at approx. 9800 1/min and this results in approx. 5.2 sec/lap, depending where you fly (altitude). My Cobra 3515/18 with this prop uses approx. 80% of battery capacity but on a 2200 mAh, 25C, 6 cell battery. Your battery is much larger so where does all this energy go to? Probably the motor gets quite hot.

With higher rpm (on your 11x6prop) you probably needed to increase target throttle, correct? At higher rpm the motor runs more efficient and the internal cooling works better. I currently fly Igor's 11x5prop at approx. 11.000 rpm and at this "high" rpm the internal cooling of the Cobra 3515/18 is so good that the motor temperature after the flight is as low as battery temperature, max. 50C.

I still think that if you intend to continue with Igor's 12x5N prop then the Cobra is just fine and also lighter than the MVVS. Maybe you could also fly with one cell less (TP, 5s, 2800 mAh) and save another 60 grams as well.
Igor's 12x5 UCT prop works also with the Cobra, at least in my models but my small batteries then are at their limits. With a slightly heavier battery (2200mAh, 6s, 45C) it is fine again. BTW: target rpm with the 12x5 UCT is the same as with 12x5N, thus, very easy to make back-to-back test flights.

For your comparison: My modell flies with 19,6m line length (eyelet-eyelet) and I set the run time also at 5:10min as you. Weight 1620-1680 grams, depending which of above batteries I use.

Good further luck with your tests!

I'll drive to Landres tomorrow evening and hope that all I have written above still proves correct in France as well.

Christoph

Offline Matt Piatkowski

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 401
Re: Optimization of Flight Parameters
« Reply #4 on: July 12, 2018, 05:42:00 AM »
Hi Christoph,
I also do not understand why the batteries drain was and is so large.

The only plausible explanation is that my motors and prop. combination working on 6S is inefficient, generating a lot of heat.

I have burned one Cobra 3515/18 already and the other one is on a verge of burning.

Yesterday, I have made three pattern flights using Black Tiger 4230C motor (Kv=750, maximum current unknown) and the batteries drain was 85%! - not good. After landing the motor was hot and the batteries very warm but I could hold them in my palm for 30 seconds. I was using 11x6 3blade narrow Pol-Prop turning on the ground at 9,200 RPM., measured by the properly calibrated tachometer. The lap time on 19.40 m. long eye-to-eye lines: 5.0-5.1 sec. but there was no sufficient power overhead. The active timer was working but this effect was sort of weak. Max Throttle:190, Target Throttle:150, Min.Throttle:070, sensitivity:65. Spin 66 RPM range:7,000-10,000.

You wrote " So probably the target rpm on the larger 11.5x6 prop was set too low. How much rpm does it turn in level flight to achieve a proper lap-time?"

In my first three flights in Poland, the Target Throttle was set to 170 on 11.5x6 3 blade Pol-Prop, Cobra 3515/18 and 6S Thunder Power 2800 mAh., 25C batteries.
The Max. Throttle was 187 and Min. Throttle 070. The lap times were....5.6 - 5.7 sec. and the batteries drain after flying mostly level was 91% (!!).

We figured out that 11.5x6 3 blade Pol-Prop was simply too much for Cobra 3515/18 and changed it to 11x6 3 blade narrow Pol-Prop. The lap times dropped instantly by ...0.5 second and I could fly the entire pattern but the batteries drain was still large, 78-83%.

I know Marek and other F2B fliers in Poland but nobody could figure out what to do with my setup. Consequently, I flew in the Hradec Kralove and Zarnovica competitions using the setup I had.

Now, I am back in Toronto, Canada and I will experiment until I understand what was and is going on.

Perhaps the 6S ThunderPower I got have low quality? Perhaps they are not 2800 mAh.? Perhaps...who knows?

Good luck in Landres!
Regards,
Matt

Offline Vitalis Pilkionis

  • Trade Count: (0)
  • Lieutenant
  • ***
  • Posts: 67
Re: Optimization of Flight Parameters
« Reply #5 on: July 12, 2018, 07:27:52 AM »
Hi Matt,

I think both motors you have chosen for 6S operation are not right. Cobra has too much Kv value, so its efficiency is optimized for higher rpm. This is what you actually found when switched to lower diameter prop.  And that Black Tiger is simply too small and can't provide you with enough power.
Go for Axi 2826/13 if you want to save some weight on the nose, or Cobra C-3520/14. Both motors will turn PolProp 12x5 or 12x6 with ease.

Greetings,
Vitalis

Offline Matt Piatkowski

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 401
Re: Optimization of Flight Parameters
« Reply #6 on: July 12, 2018, 09:56:07 AM »
Hi Vitalis,
Are you one of the Latvian guys I met in Wierzawice?
I have MVVS 8.0 Kv=680 and can use it in my model (RTF weight ~1840 grams).
Polish F2B flier "Kuba" Haszczynski uses this MVVS in his 1850 grams F2B plane with 2 blade and 3 blade props.
Best Regards,
Matt (Maciek) Piatkowski


Online Motorman

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 3966
  • Millville NJ PDQ Flying Clown Country
Re: Optimization of Flight Parameters
« Reply #7 on: July 12, 2018, 10:09:09 AM »
Hi Motorman,
The narrow prop has the same pitch (6").

What makes you think they are the same?
There will be a sunny day and we will fly our airplanes.

Offline Vitalis Pilkionis

  • Trade Count: (0)
  • Lieutenant
  • ***
  • Posts: 67
Re: Optimization of Flight Parameters
« Reply #8 on: July 12, 2018, 11:49:14 AM »
Hi Vitalis,
Are you one of the Latvian guys I met in Wierzawice?
I have MVVS 8.0 Kv=680 and can use it in my model (RTF weight ~1840 grams).

No, Matt, I'v never been in Wierzawice. Maybe next year...  ::)

I am sure MVVS 8.0 /680 is the right motor for 6S and a model of 1840 grams. Ofcourse it is a bit heavier, so you propably will have to adjust a battery's position for the right CG.

Good luck,
Vitalis

Offline Matt Piatkowski

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 401
Re: Optimization of Flight Parameters
« Reply #9 on: July 12, 2018, 12:52:14 PM »
Hi Vitalis,
I have just discovered that the Black Tiger motor is 12 pole. Cobras are 14 pole motors and Spin66 was set for 14 poles.

I reset the Spin66 for 12 poles and will fly tomorrow with three different props to assess the effect.

By the way: I could not find the specs. for the Black Tiger motor. This would definitely help if the RSM Distribution that sold this motor published such specs.

If I cannot find some reasonable compromise using Black Tiger, I will install the MVVS 8.0 motor. The weight increase of 40 grams w/r to Cobra 3515/18 and 18 grams w/r to Black Tiger can be easily compensated - I will simply remove the extra lead weight that is used now to properly balance the model.

Hi Motorman,
I believe the guy who produces these props. The average pitch is between 5.9 and 6".
Regards,
M

Offline Rogerio Fiorotti

  • 2017
  • Trade Count: (0)
  • Lieutenant
  • *
  • Posts: 92
    • Control Line by Fiorotti
Re: Optimization of Flight Parameters
« Reply #10 on: July 12, 2018, 01:18:23 PM »
Dear Matt,

At the moment I will not know about your setup set, but to do a comparative I am using COBRA engine 3520/14 700kv - Battery 6S 2800 Thunder Power - Propeller 12x5 UCT Igor.

Lap time at 5.15 sec - flight time 5:10 - final flight battery 28%.

My model flies with 19,4m line length (eyelet-eyelet). Weight 1880 grams.

So far I have not found setup better.

Rogerio Fiorotti

Offline Matt Piatkowski

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 401
Re: Optimization of Flight Parameters
« Reply #11 on: July 12, 2018, 04:39:10 PM »
Hi Rogerio,
What are your ground RPM before take off?
Are you using Igor's active timer?

If yes, what are your " throttles"?

Target Throttle?
Max. Throttle?
Min.Throttle?

Are you using SPIN66 ESC?

If yes....what is the ESC RPM range? Is it 7,000 to 10,000?
Thank you for sharing,
Best Regards,

Online Motorman

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 3966
  • Millville NJ PDQ Flying Clown Country
Re: Optimization of Flight Parameters
« Reply #12 on: July 12, 2018, 08:17:52 PM »
Hi Rogerio,
Are you using Igor's active timer?

Rogerio Fiorotti makes his own active timer. I would also like to know the settings as I now have the same motor/battery/prop.
There will be a sunny day and we will fly our airplanes.

Offline Rogerio Fiorotti

  • 2017
  • Trade Count: (0)
  • Lieutenant
  • *
  • Posts: 92
    • Control Line by Fiorotti
Re: Optimization of Flight Parameters
« Reply #13 on: July 12, 2018, 08:30:51 PM »
Matt,

I do not use the Igor setup.

Manufacture the C / L Timer that is also active with accelerometer, the operating principle is the same but the settings values are different.

I am currently using ESC Castle Talon 60 and it has faster response than Castle Edge, but not as fast as SPIN.

The RPM that is set before takeoff is at 9600.

I think his problem is in the efficiency of the engine versus propeller as spoken by Christoph Holtermann, Orestes Hernandez uses the 3515/18 and 12x5 UCT Igor propeller, but with 5S and his plane is very light.

The 3520/14 is 38gr heavier but more powerful and with more tranquility flight below the motor limit. Think about it!

Rogerio.

Offline Vitalis Pilkionis

  • Trade Count: (0)
  • Lieutenant
  • ***
  • Posts: 67
Re: Optimization of Flight Parameters
« Reply #14 on: July 13, 2018, 03:06:09 AM »
Hi Rogerio,
What are your ground RPM before take off?
Are you using Igor's active timer?
If yes, what are your " throttles"?

Target Throttle?
Max. Throttle?
Min.Throttle?

Are you using SPIN66 ESC?

If yes....what is the ESC RPM range? Is it 7,000 to 10,000?

I use Igor's active timer with SPIN66 and 6S lipo. Propeller is Polprop 3blade 12x5 electric, motor Axi 2826/13.
ESC rpm range is set 7000 to 11000 rpm.

For air density 1.200 kg/m3:
Target throttle is 165
Max throttle is 180
Min throttle is 1


Greetings,
Vitalis

Offline Matt Piatkowski

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 401
Re: Optimization of Flight Parameters
« Reply #15 on: July 13, 2018, 08:41:52 AM »
Vitalis, Rogerio,
I appreciate your help.
Best Regards,
M

Offline Matt Piatkowski

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 401
Re: Optimization of Flight Parameters
« Reply #16 on: July 14, 2018, 05:07:31 AM »
Hello,
Black Tiger was replaced by MVVS 8.0 Kv=680 with 11,5 x 6 3 wider blade carbon composite Pol-Prop.
The weight of the RTF model with 6S ThunderPower is now 1837 grams as I have removed 40 grams of lead placed in the nose.

This lead was needed to properly balance the model with Black Tiger that weights 207 grams. MVVS weights 228 grams.
I have used Scorpion long prop. adapter as it fits the 5 mm. dia. MVVS shaft. The factory provided MVVS prop adapter is slightly heavier and can be used too.

The static tests run for 30 seconds gave 9,670 RPM on the above mentioned prop. The Igor's active timer Target Throttle is 155.

I set the flight time for 2 minutes to clock the lap times and I am going to fly now.

Please expect another report in the afternoon.

M


Offline Matt Piatkowski

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 401
Re: Optimization of Flight Parameters
« Reply #17 on: Yesterday at 12:24:24 PM »
Hello,
The lap time 5.15-5.2 sec. (on 19.40 m., eye-to-eye, Solomianikov 0.014", 4 stranded, "golden" lines) was achieved using the following setup:
SPIN's 66 ESC RPM range: 7,700 - 10,700 RPM.

Active timer Target Throttle: 162. This is equivalent of 10,400 RPM on the ground using 11.5x6 3blade Pol-Prop.
Max Throttle: 200, Min. Throttle: 070.

There is only 300 RPM. difference between the Target Throttle (162==10,400 RPM. static ) and the upper limit of the SPIN's 66 RPM range.

This 300 RPM seems to be sufficient to give the acceptable RPM boost and to maintain the lines tension when the nose of the model is up and in the overhead maneuvers.

The battery drain after 5 minutes and 10 seconds flights including the pattern and six spare laps is unfortunately 84%.

At this moment I do not see the solution. If I decrease the target throttle to, say, 158 ( RPM equivalent to about 10,250 -10,300) and the SPIN's 66 ESC upper RPM limit range to 10,500, I may be able to save the desired 4% of the battery capacity but the lap time will go up to 5.35-5.4 seconds. This is too slow for me, especially in windy conditions.
I will be trying Igor's 12x5 3 blade carbon composite electric prop. next. This prop is lighter and has better aerodynamic quality, and therefore efficiency, than the Pol-Prop so maybe the elusive 4% can be found this way.

Perhaps I have to shorten the flight time to 5 minutes?
Perhaps I have to shorten the lines?

Any other ideas?

Offline Vitalis Pilkionis

  • Trade Count: (0)
  • Lieutenant
  • ***
  • Posts: 67
Re: Optimization of Flight Parameters
« Reply #18 on: Yesterday at 01:50:20 PM »
Hi Matt,

Igor sells two versions of 12x5 props - UCT and N, which one are you going to test?

BTW, I have the same battery drain with my system, but I don't bother alot about it, while voltage in cells stays at 3.69-3.70V after flight.
The lap time I usually fly is ~5.4s with 19.5m lines. I don't like too much of speed and excessive line pull.


Vitalis

Offline Matt Piatkowski

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 401
Re: Optimization of Flight Parameters
« Reply #19 on: Yesterday at 04:32:12 PM »
Hi Vitalis,
The cells voltages in my 6S stay in the 3.69-3.72 V range after 5 minutes and 10 seconds pattern flight.
I am considering changing this time to 5 minutes to save a little more capacity but, at this moment, I like the comfort of having seven spare laps to account for the wind changes during the pattern.

Please see the attachment - Igor's 12x5 prop. on the left, Pol-Prop I am using now - on the right.

I do not know if the Igor's prop is UCT or N. Maybe you can see which one it is?

Regarding batteries use again: do you know where the 20% capacity limit is coming from?

Regards,
M
 


   

Offline Vitalis Pilkionis

  • Trade Count: (0)
  • Lieutenant
  • ***
  • Posts: 67
Re: Optimization of Flight Parameters
« Reply #20 on: Today at 01:19:09 PM »
Yes Matt, it is definitely N (narrow) prop. This prop is considered by Igor as less power hungry than UCT, thus it better suits to axi 2826 motor, which in our application operates at the edge of power capabilities.


Greetings,
Vitalis

Offline Matt Piatkowski

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 401
Re: Optimization of Flight Parameters
« Reply #21 on: Today at 04:35:42 PM »
Hi Vitalis,
Which AXI 2826 is used with this narrow 12x5 3blade prop to get the best efficiency?
There are several different AXI 2826 motors available.
What battery? I know the answer depends on WHICH AXI 2826 is used.

5S goes of course with HIGHER Kv and the motor is lighter.
6S goes with LOWER Kv and the motor is heavier.

Thanks,
M

Online Fred Underwood

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 424
Re: Optimization of Flight Parameters
« Reply #22 on: Today at 07:37:35 PM »
Fred
352575


Tags: