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Author Topic: Optimization of Flight Parameters  (Read 2342 times)

Offline Matt Piatkowski

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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

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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

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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

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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

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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

Online Vitalis Pilkionis

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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

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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


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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.

Online Vitalis Pilkionis

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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

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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

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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

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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,

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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

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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.

Online Vitalis Pilkionis

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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

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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

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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

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Re: Optimization of Flight Parameters
« Reply #17 on: July 16, 2018, 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?

Online Vitalis Pilkionis

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Re: Optimization of Flight Parameters
« Reply #18 on: July 16, 2018, 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

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Re: Optimization of Flight Parameters
« Reply #19 on: July 16, 2018, 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
 


   

Online Vitalis Pilkionis

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Re: Optimization of Flight Parameters
« Reply #20 on: July 17, 2018, 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

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Re: Optimization of Flight Parameters
« Reply #21 on: July 17, 2018, 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

Offline Fred Underwood

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Re: Optimization of Flight Parameters
« Reply #22 on: July 17, 2018, 07:37:35 PM »
Fred
352575

Offline TDM

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Re: Optimization of Flight Parameters
« Reply #23 on: July 27, 2018, 07:01:52 AM »
Matt I saw you are using a MVVS 8 which tips the scale at 233g. The OD of the motor is 36mm.
I use a Joker from Lindinger on my bird. The motor is a 4250 510KV it runs great on same exact stuff you have in your plane (Jetti Igor 6S2800). Right now is turning a Igor under cambered 11x5 3B. Back in the pack after a 5min 30 sec flight is a max of 1405mAh. Yup the average amp draw is 15.27A. On top of it this motor is 210g. If you have room for a 42mm diameter motor I would think you might want to go in that direction. It also matches the 25mm B.C. 4 holes pattern in many of the motors. Here is the kicker they cost 36 Euro plus shipping.
IMHO big motors are a good thing. They are easy on batteries easy on ESC use far less energy and even though you have a increase of motor weight the batteries get lighter so overall you have a net weight decrease.
I just received the new motors and I will test them soon. The thing is I do not know if I will make the change yet because we have already  invested in the 6S batteries and we have a bunch of them.

Batteries are happy in a certain charge range. Because chemistry they get damaged easily if you over discharge them or over charge them or keep them fully charged for prolonged periods of time. Hard to overcharge them because the charger is taking care of the, but you can definitely over discharge them so there comes the 20% rule. This is something we need to be aware when we fly electric. Long story short is charge the day you fly and at the end of the day if you do not plan to fly for a few days store charge and set aside till you are ready to go again and fly.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Online Vitalis Pilkionis

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Re: Optimization of Flight Parameters
« Reply #24 on: July 27, 2018, 08:27:59 AM »
I use a Joker from Lindinger on my bird. The motor is a 4250 510KV it runs great...

Hi TDM,

does Joker 4250 have 2 ball bearings or 3?


Vitalis

Offline TDM

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Re: Optimization of Flight Parameters
« Reply #25 on: July 27, 2018, 08:47:30 AM »
Vitalis I don't know if it has 2 or 3 bearings. I don't care a hole lot either because I mount the motor from the front not the back. So far so good and even if it goes bad I can buy three of these with the money I put in an AXI. My take is get two and keep on e in the tool box in case. By the way I have an Igor AXI in my box too. The bigger motor balances the plane better and responds to throttle faster than the AXI too.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline Matt Piatkowski

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Re: Optimization of Flight Parameters
« Reply #26 on: July 27, 2018, 01:35:04 PM »
Latest report from the field:
1. Active timer Target Throttle = 164 ( gives the ground RPM = 10,880 on Igor's 12x5x3 blade narrow carbon composite electric)
2. Max Throttle = 190
3. Min.Throttle = 070

Flight time: 5 min. 5 seconds
Spin66 ESC setup: Max RPM=10,900, min. RPM=7600.

Lap time: 5.13-5.15 sec. on 19.40 meters long (eye-to-eye) Solomianikov "golden" lines.

MVVS timing = 19 degrees.

Very good RPM boost when the nose goes up and no problem flying the pattern in ~6 m/s wind ( ~13 miles/hour). One mile =1609 m.

The best news: 6S Thunder Power 2800 mAh 25C I am using is drained 19-20 % after pattern.

I am staying with this setup until I complete 200 patterns on it.

Greetings from the MP Stunt Academy in Toronto.
Regards,
M


 

Offline Matt Piatkowski

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Re: Optimization of Flight Parameters
« Reply #27 on: July 28, 2018, 07:07:03 AM »
Correction:
In my last post have written: "6S Thunder Power 2800 mAh 25C I am using is drained 19-20 % after pattern".

I should have written: ""6S Thunder Power 2800 mAh 25C I am using is drained 80-81 % after pattern".

Matt


Offline Christoph Holtermann

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Re: Optimization of Flight Parameters
« Reply #28 on: July 31, 2018, 03:04:19 AM »
1. Active timer Target Throttle = 164 ( gives the ground RPM = 10,880 on Igor's 12x5x3 blade narrow carbon composite electric)


Hi Matt,

thanks for telling us the measured ground rpm on Igor's 12x5N prop.

I see that your ground rpm is approx. 1000 rpm higher than on my plane and that for sure explains your higher consumption compared to what the others have. At what altitude above sea level you fly?

With this prop I fly 5.2 sec laps at 19.6m length. So now the question is, why you need so much more rpm.

Is your rudder so much deflected to the outside or are your lines so much back?

Igor mentioned his trick with the markers on fuselage and wing tip.  When my plane was new I put the marker on the fuselage and the one on the wingtip was positioned at 1.5 back. That's how I fly. A yawing fuselage could explain some of the extra mAh's you use.

Christoph

Offline Matt Piatkowski

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Re: Optimization of Flight Parameters
« Reply #29 on: July 31, 2018, 04:57:15 AM »
Hi Christoph,
I am in Toronto, Ontario, Canada. The altitude of the circle I use for flying is about 180 m. above see level therefore the air density cannot be blamed.

Yes....10,880 RPM on the ground is high but I could not get 5.15 sec./lap with lower RPM. I measure the time of 10 horizontal laps and divide the result by 10 so I believe the result is more accurate.

The rudder is about 5-7 deg. outside and the rudder area in this plane is relatively small.
I will hang the model using the leadouts and check the equilibrium.

The thing that bothers me the most is the fact that the maximum RPM range set on Spin66 is 10,900 and this is practically the same as the Target Throttle RPM. How is this possible that the active timer adds the RPM in flight when the nose goes up? I can feel it and I can hear it. The graph in the active timer manual clearly shows that the range of regulation of timer sits somewhere in the middle of the absolute RPM range defined by the Spin66.
setup. It would be nice to receive some advice from Igor.

Regards,
M





 

Offline Christoph Holtermann

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Re: Optimization of Flight Parameters
« Reply #30 on: July 31, 2018, 06:42:10 AM »
Morning Matt,

180 above sea level is not the reason for this high target rpm, I agree.

5-7 degree of rudder are also not a lot but just try flying without rudder offset. I think with some backward leadouts you will still have enough yawing to maintain proper line tension. At 5.15 sec line tension shouldn't be a problem especially when the nose goes up and the timer boosts in.

What you describe as "what bothers you" should not bother you  :) I asked Igor exactly the same question some weeks before Landres because I also recognized that the ground target rpm was exactly what I programmed as max. rpm in the Spin-66. He mentioned the important thing is the regulation curve, not absolute numbers. Ergo, I think we better ignore these absolute settings in Jeti-Spin and fine tune with the timer. But this is just an interesting side-effect and not the reason for your high consumption respectively the high rpm.

Christoph

Online Vitalis Pilkionis

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Re: Optimization of Flight Parameters
« Reply #31 on: July 31, 2018, 08:31:05 AM »
Have you performed a calibration flight after you changed propeller, settings in esc and in timer ?



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Offline Matt Piatkowski

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Re: Optimization of Flight Parameters
« Reply #32 on: July 31, 2018, 09:17:18 AM »
Hi Christoph,

I am pleased to hear that you asked the same question. This means that we both recognized the potential issue that was not addressed before.

Please see the attached. The yaw angle in the position shown on the photograph is 2.5 degrees. Red, thin string represents the vertical direction.
There is also 1.5 degrees thrust line offset to the outside.

I will set the rudder straight.
I will change 2.5 to 1.5 degrees but I doubt this change will lead to saving, say, 5% more capacity of the batteries.
I will not change the thrust line angle at this moment.

Then...please see my response to Vitalis below.

Hi Vitalis,
No!  I have not.  I have never performed the calibration flight.

Igor writes the following in the active timer manual:

" 5/ Set calibration parameter to 1 and do calibration flight. Model will start and keep
wanted speed several minutes. Pilot must do whole flight in level altitude. Model will
stop the motor after calibration itself. It will ignore flight time, so be prepared to earlier
or later landing. It will add a power for short time before landing. It is warning before
motor stop. Choose a calm day if possible. Controller will automatically clear calibration
parameter to 0, so next flight will be normal. If you later feel that model changes lap time
after changing sensitivity parameter, if you change line length, if you change target
throttle (because of different prop etc.) do the calibration again."

I will perform the calibration flight ASAP.

Guys,
You are helping a lot. Thank you!
Regards,
M



Online Vitalis Pilkionis

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Re: Optimization of Flight Parameters
« Reply #33 on: July 31, 2018, 09:27:25 AM »
Calibration flight is implemented there for controller to find centrifugal force value at level flight. It is highly recommended to perform it if lap time has changed for any reason - other propeller, other line lenght, etc.

And my other recommendation - put color strips (markers) on your model's fuselage (at CG) and wing tip (leadout point). That will open your eyes a little: you will be able to see how model reacts to side wind and what your inputs to rudder offset, motor thrust line and leadout position actually change.


Vitalis

Offline Matt Piatkowski

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Re: Optimization of Flight Parameters
« Reply #34 on: August 01, 2018, 11:59:51 AM »
Latest report from the field:
1. I have done the calibration flight. It lasted nine level laps with the Target Throttle = 160 (ground RPM=10,350-10,400).
In the tenths lap the RPM went up for about 1/4 of the lap and the motor stopped.

2. Then, I have done four full patterns. The RPM boost provided by the system in the nose up configuration became a bit shorter than before. I gather that the calibration process changed the length of the RPM boost without changing it's value.

3. The horizontal lap time was 5.22-5.25 sec. It seems a bit slow for me because I am used to faster lap times.
4. The lines tension overhead decreased a bit but seems to be sufficient in erratic, a bit gusty wind (average wind speed during flying was 3.0-3.5 m/sec.)

5. Batteries: the batteries temperature just after landing was 45 deg. C. It took about 20 minutes for the battery to cool down to the ambient temperature (24 deg. C). All batteries were drained 78-80 % what was checked two hours later when they fully recovered.

Comment: the flight time was 5 minutes and 5 seconds what allowed for six spare laps. I fly 2.5 laps between the hourglass and the OH eight. I feel I can decrease the flight time to 5 minutes and start making 1.5 laps between hourglass and the OH eight. This will save two laps and probably 2% of the batteries capacity.

Regards,
M

Offline Christoph Holtermann

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Re: Optimization of Flight Parameters
« Reply #35 on: August 02, 2018, 02:55:21 AM »
Hi Matt,

that already sounds good. Did you also change leadouts or decrease rudder offset to see whether this saves you some mAh's?

The lap-time of 5.2 sec is good and if you lack overhead line tension or speed then just increase the max. throttle in the timer. If that doesn't have an effect, probably because the limiting factor is the max. rpm in the controller, then you must increase the max. rpm in the controller by let's say 100 rpm. Maybe then you need to decrease again the target throttle to reach your 5.2 sec laps. If your boost on top is too much you can take the max. throttle in the timer down.

Where I fly (60m above sea level) I feel very comfortable with 5.3 sec laps and adjust the max. throttle so far that the speed at 45 gives me a good feeling and/or the the plane has enough speed in the hourglass for the third corner. Flying that slow results in a pattern of 4:50 min with 6 laps after launch until start wingover until the exit of the fourleaf clover. I set the motor run time to 5:10 min to have at least 4 laps after the clover.

Last but not least, check if your motor is well ventilated. I made some changes yesterday on the air intake area on my motor that resulted immediately in a 6 cooler temperature after the flight compared to the previous setting. What you learned regarding intake and outlet area on IC-engines also applies to electric motors. Your nose construction looks that a lot of air goes into the engine compartment but is it also guided directly into the Stator or can it bypass easily around the bell? And is the outlet area large enough to generate a low enough pressure in the engine compartment? The cooler the motor the lower the mAh's consumed. My Cobra is 50C measured at the stator and 44C measured at the bell immediately after flight. It was 25C yesterday here.
Your battery temperature of 45C after flight is ok.

Christoph

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Re: Optimization of Flight Parameters
« Reply #36 on: August 03, 2018, 04:12:58 AM »
Hi Christoph,
I have changed the leadouts angle to 1.5 degrees and set the rudder to zero before the calibration flight.
I have also changed the Target Throttle from 164 (10,880 ground RPM) to 160 (10,350 - 10,400 ground RPM) before the calibration flight. In this situation, I cannot properly assess the impact of each change but I feel the Target Throttle change is the main one. In other words: slightly less battery drain is probably the effect of the Target Throttle change.

I am flying again today to verify again the overall "pattern feel", the overhead maneuvers lines tension and the gyroscopic moment effects in corners. There will be two people with me and I have asked them to watch the tendency to yaw in the bottom corners of squares and the square eight. This will probably allow to decide if the rudder deflection is needed or not.

I will set the flight time to exactly 5 minutes, will count the laps after the cloverleaf and, as
suggested by you, I will watch the plane at the 45 deg. angle and in the top corners of the hourglass.

Motor ventilation: the air inlet is quite sizeable and the outlet is almost 4 times larger. The ESC is sitting in the direct air flow that is of course very turbulent but I feel the proper cooling is there. It is only slightly warm after the pattern anyway. The motor may not receive good cooling, though. It is mounted to the fiberglass firewall and there may be a pocket of the circulating hot air around the motor. The air that cools the ESC flows about 20-25 mm. above the motor and may only brush the circulating pocket of the hot air that surrounds the motor. At this moment, I do not see the solution to this problem except adding the aluminum heat sink with fins that will be exposed to the main air flow. This will add about 5 - 6 grams. The effect of this extra weight can be compensated by moving the battery a bit back.

Another solution is to add the scoops for the incoming air and direct this air to the motor. Zbynek Kravcik built such scoops-inlets in his red plane. In order to build such scoops, I would have to cut through the firewall to the fuselage connection and I am a bit reluctant to do it because this will decrease to stiffness and strength of this critical connection.

Perhaps the remaining strength will be ok but....who knows?

Going flying now.
Regards,
M

 

Offline Christoph Holtermann

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Re: Optimization of Flight Parameters
« Reply #37 on: August 03, 2018, 05:02:31 AM »
Good flights this morning!! I am pleased to see you work so hard on the plane and the powertrain. Sure it will be rewarding.

Don't forget: Don't trim your plane to save battery but trim it to fly well. If it uses more battery than others, so then be it that way.

I scrolled through the thread but maybe didn't find how much mAh's you effectively charge back into a battery after flight. The "percentage" respectively the voltage after a flight might not necessarily be a criteria for mAh's consumed during the flight.

My set of batteries aged a lot during the week in Landres/France and when I had 20-30% remaining in spring, the same batteries now show between 10-20%, simply because they are older now and have been squeezed out in hot air and turbulence. The mAh's charged back in spring and now are the same, in spring even more because air was cool and overall drag of prop and plane higher than in thinner and warmer air.

My oldest battery now has 52 cycles on it and only 8% remain after flight. You see, I don't count with many cycles but the Zippy's are cheap.

Seeing Orestes' air intakes in his Shark however convinced me that air really must be pressurized through the motor, the stator.

Good further luck!

Christoph

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Re: Optimization of Flight Parameters
« Reply #38 on: August 03, 2018, 02:56:35 PM »
Hi Christoph,
Do you have the photos of Orestes air inlets?

I will install the aluminum heat sink ( 1.3 mm. thick 60xx series Aluminum, weight right now = 7 grams but 6 grams when finished with fins bend the proper way and polished) and fly with the same parameters I have now. I will send you the detailed photo of the installed heat sink ASAP.

My five 6S ThunderPower 2800 mAh 25 C have about 35 patterns on each and I do not see any indication of the IR increase or swelling. They charge easily using the Revoletrix GT500 charger and the Revoletrix parallel charging board.

I am charging the batteries now in order to fly tomorrow morning.
Regards,
M

 

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Re: Optimization of Flight Parameters
« Reply #39 on: August 04, 2018, 02:44:58 PM »
Heat sink was a good idea. Please see the attached.
The motor was about 6-8 degrees C cooler after landing and the heat sink fins were very warm - clear sign that the conduction worked well between the motor and the heat sink plate.

The batteries drain after pattern stabilized on 80%. All five batteries used today (sunny, 29 Deg.C and humid ) showed the cells voltages in 3.72-3.75 V./cell range. The time of flight now is 5 minutes with 1.5 laps before the OH eight. There are five spare laps after the clover.

The plane grooves well but it is lively and corners are reasonably good. The hourglass is very good, no problem in the top corners.

Regards,
M

 

Offline Christoph Holtermann

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Re: Optimization of Flight Parameters
« Reply #40 on: August 06, 2018, 02:30:49 AM »
Congratulations! It seems that you have found a good solution to keep the motor cool and the batteries healthy.

There isn't a lot more I can say apart from: Practise, practise, practise!  :)

No, I didn't take a picture of Orestes plane and the cooling inlets but remember he used the cowling cheeks of his Shark and also the lower cheek to guide air into the cutouts of the stator.

Good luck!

Christoph

Offline Matt Piatkowski

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Re: Optimization of Flight Parameters
« Reply #41 on: August 06, 2018, 04:55:32 AM »
Hi Christoph,
I have to go back to 2.5 laps between the hourglass and the overhead eight as this is required by the rules.
Also, the rudder must be deflected about 5 degrees to counteract the yawing caused the gyroscopic moment in really tight corners.

To sum it up: I am pleased with the progress, I have four spare laps and well flying plane. I am planning to fly as much as I can until the snows come to Toronto.

Future tasks:
1. I will try 5S ThunderPower 2800 mAh. batteries with Cobra 3520/12 (Kv=820) and Plettenberg Orbit 15-18 or 15-20. This will save some weight and will decrease the inertia of the model. I am also very curious how the active timer works with the 5S battery. Many people flying with the active timer say that it must have 6S battery. I will see.

2. I will replace the glass laminate pushrod with the carbon composite, thin walled, tapered tube. Weight loss: 7-10 grams.
 
3. I will move the landing gear 1" back to improve landing on the hard surface. Current landing gear attachment points will be used for grass.

4. I will finish the original Max Bee I am building and will compare both planes.

Are you using Solomiannikov's lines? They are much stiffer in tension than SIG's having similar diameter but they rust. Hmm...

Regards,




Offline Christoph Holtermann

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Re: Optimization of Flight Parameters
« Reply #42 on: August 06, 2018, 07:57:51 AM »
Hi Matt,

I also want to check the 5s Thunderpower battery (I got one as present in Landres) within my plane but with the Cobra 3515/18. I expect no difference to my 6s batteries as both batteries have approx. the same Wh's and weigh the same.

Instead of moving the landing gear back you may simply install a higher tail wheel. That also reduces bouncing on hard surfaces because the main landing gear touches ground with less AoA. I have two different tail gears. One for grass: The model sits with more AoA on ground and one for tarmac where model is nearly parallel to ground.

My lines are the PAW Stay Straites from Tony Eifflander (UK). From elasticity they are as per Frank Wadles' tests as stiff as the Ukrainian brass coloured lines but I think (subjective impression) they have less drag in the air. But the Solomianikov or Ruslan lines are fine as well and I think somewhat cheaper than the Staystraites.

Enjoy!

Christoph

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Re: Optimization of Flight Parameters
« Reply #43 on: August 06, 2018, 10:33:45 AM »
Christoph,
I have five 5S ThunderPower 2800 mAh 25C and weighted them one by one. The weight of a single battery with EC3 connector is 302-303 grams.
I have also five 6S ThunderPower 2800 mAh 25C and each weights 362-363 grams with the same connector. The difference of weights is, therefore, about 60 grams - the weight of one cell.

Cobra 3515/18 is a good motor but:

1. The maximum continuous current is probably really 36 Amps. as shown by the Innov8tive Design website. I have made more than 50 patterns on one of my Cobras 3515/18 and finally burned this motor, despite the fact that the average in-flight current was 28 Amps on 6S. When the active timer was used, the momentary current, lasting 2-2.5 seconds, was reaching higher values in maneuvers. I could not record the current's amplitude during the entire pattern, because my EagleTree eLogger conflicts with either active timer or Spin66 or both. After 50 patterns, the cumulative effect of more than 500 short current spikes of unknown value finally burned the enamel on the copper wires and the motor died in the air. I was lucky flying wheels down at this moment and landed. 

2. Orestes Hernandes plane suppose to be "light", therefore he can use Cobra 3515/18 drawing less average current, maybe 24 Amps. or even less. I hear that he also flies with the two blade carbon prop. that is more efficient than three bladers. Is "light" 1700 grams RTF or less? At this moment I do not know. I will write to Orestes with questions and, perhaps, he will be willing to share the technical data.

I believe, after my experience with Cobra3515/18, that this motor may work longer and better with 5S, without the active timer and in the plane that is truly feather like.

3. Cobra 3515/18 has two bearings of debatable quality and I had to replace both after 45 flights.

Like I wrote, I will keep experimenting with 5 and 6 S and various motors. Perhaps I will learn something new?

Very nice trick with the tail landing gear! I will give it a try.

Thanks and Regards,
M


Offline Howard Rush

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Re: Optimization of Flight Parameters
« Reply #44 on: August 06, 2018, 11:15:23 AM »
This will save some weight and will decrease the inertia of the model.

How would it decrease inertia?  Would it allow you to remove tail ballast?
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Offline Matt Piatkowski

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Re: Optimization of Flight Parameters
« Reply #45 on: August 06, 2018, 02:48:53 PM »
Hi Howard,
Each time we add weight or remove weight from the model at the distance r from the C.G., we are also changing the rotational (pitching) inertia measured w/r to the C.G.
Only if we add the weight at the C.G, there is no increase in the pitching inertia Ip=m x r^2 because r becomes zero.
 
If I, say, replace the MVVS 8.0 weighting ~228 grams (about 8 oz.) with Plettenberg Orbit 15-20 weighting about 180 grams (6.4 oz.), it will be easier for the model to pitch. "Easier" means that the energy needed to pitch will be smaller and the corner will be tighter assuming the same handle input.

The fundamental assumption made here is that the pitching movement is always about the C.G. Because the C/L model flight dynamics is very complex, it is not exactly true but good enough to understand why less weight away from C.G. is good.

I do not have the tail ballast - it was never needed. I move the battery FWD or AFT instead. Kv=755 Plettenberg Orbit 15-20 needs 5S battery that must be moved FWD 0.60" w/r to the current, 6S battery position to maintain the C.G where it was with MVVS 8.0 and 6S battery.

Regards,
M

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Re: Optimization of Flight Parameters
« Reply #46 on: August 07, 2018, 12:22:31 AM »
Looks like I missed something here, so:

1/ Calibration

it is tool so tell timer what is standard centrifugal force at standard speed in level flight (at target rpm). That value is stored and then timer measures what is happening, dedicides what is necessary to do, multipies it by sensitivity and adds that number to target throttle.

That means that if you have stored standard centrifugal force different than it should be in level flight (if model flies slower for example - mean target throttle slows it down from standard speed) and if you change sensitivity, then that permanent offset from standard centrifugal force will be also multiplied by sensitivity and thus lap time will be changed. So if you want change sensitivity often, and you do not want compensate that change by target throttle, it is necessary to do calibration when you decide to change lap time. For example if you normally fly 5.2 and for some reasons you decided go to 5.1 because of altitude or another prop or whatever, then adjust target throtte to set that new lap time and do the calibration. If you do not change sensitivity at all (like myself) you not need to do calibration. I do not do it at all, timer has stored "some" value which will be close to usual model.

2/ 4s vs 5s vs 6s
That depends only on prop and motor. Motor which has higher rpm/v or prop with higher pitch will work also with 5s (or even 4s) without problem. The only rule is that the combo must be able to reach highes set RPM (means Max rpm in ESC) with discharged battery. Means it must have enough power to boost uphill also in last leg of 4leaf. However it also means the motor will take the same energy and thus battery must have it, so if you go from 6s to 5s you will need larger capacity (MAH) because you have smaller voltage and at lower voltage you need larger current make the same power and larger batery capacity to store the same energy. So you will not save anything.

3/ staic RPM or RPM measured by ESC
Simply forget those numbers. Static RPM is in regime when timer wants something to do and it is limited by some value in saturated regime. Simply watch what it does in flight and adjust if necessary.  Also measured value can be off, either by overregulation in PID regulator, or "atomization" of input parameters etc.


4/
Matt, if you balance model with heavier battery closer to CG, you will get LOWER moment of inertia, not larger. So lighter battery will make it smaller only in case that you remove some tail weight as Howard mentioned  ;D
   

Offline Howard Rush

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Re: Optimization of Flight Parameters
« Reply #47 on: August 07, 2018, 01:01:04 AM »
I decided that I was wrong, but then I got confused by too many variables.  If I am correct, it's an accident.
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Offline Howard Rush

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Re: Optimization of Flight Parameters
« Reply #48 on: August 07, 2018, 02:44:31 AM »
This gets more interesting. 

Configuration 1:
Motor weight = 8 oz.
Battery weight = 12.7 oz.

Configuration 2:
Motor weight = 6.4 oz.
Battery weight = 10.6 oz.

Configuration 1 cg = Configuration 2 cg
Distance from cg to motor, Lm, is the same for both configurations.
Distance from cg to battery in Configuration 2 = Distance from cg to battery in Configuration 1, Lb, + 0.6 inch.

Assuming motors and batteries are point masses (which looks like a bad assumption, but figuring the real moments of inertia is left to the reader as an exercise),

6.4 Lm - 8 Lm + 10.6 (Lb + 0.6) - 12.7 Lb = 0
-1.6 Lm = 12.7 Lb - 10.6 Lb -6.36
-1.6 Lm = 2.1 Lb -6.36
Lm = (2.1 Lb - 6.36) / -1.6
Lm = -1.3125 Lb + 3.975 inches

It's a small airplane.  For both the battery and motor to be forward of the cg, the motor must be less than 3.975 inches from the cg, and the battery of Configuration 1 must be less than 3.03 inches from the cg. 

Using the moment of inertia calculator below, I calculated the table on the right from which the graph is drawn.  Delta Iyy is the change in pitch moment of inertia from Matt's first configuration to the second.  If Lb is less than about .85 inch, moment of inertia decreases; if Lb is greater than about .85 inch, it increases.
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Offline Matt Piatkowski

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Re: Optimization of Flight Parameters
« Reply #49 on: August 07, 2018, 05:14:25 AM »
Hi Howard,
Yes. This is how it works.
The plane has 60" wings span with very spacious motor and battery compartment and is ideally suited for the testing of motors and batteries I am going to do.

Hi Igor,
I was going to write to you about my discussions with JETI people. Rather hopeless. Some guy responded but the only thing I have learned was that Spin66 Measure option does not fully work. Some measurements stored by Spin66 in flight are wrong and some suppose to be right but the JETI guy did not specify which are wrong. At this moment, I feel the RPM stored by Spin66 in flight are wrong, total time from powering up, time of flight, voltages and the ESC max. temperature are correct.

Thank you for explaining the details of the active timer calibration process.

Re: 4s vs 5s vs 6s: I will not use 4S for this plane. I will try to use 5S ThunderPower 2800 mAh. 25 C with Cobra 3520/12 (Kv=820) and Plettenberg Orbit 15-20 (Kv=755). If, for the reasons specified by you, I will start draining the batteries too much after pattern, I will go back to the present configuration.
I am in touch with Nicolas Chapoulaud who flies his Gee Bee R3 with 4S Zippys 3700 mAh, using MVVS Kv=980 and three blade Barry Robinson's, wooden prop. Nicolas uses your active timer. This trend, namely using the 4S batteries having larger capacities with lighter motors having higher Kv for the full size competition planes is very interesting. I know that Nicolas' plane weights RTF ~ 1700 grams - the weight very difficult to achieve without buying the F2B plane from Yatsenko.

Re:static RPM: these are RPM on the ground measured by the properly calibrated tachometer so they are reasonably correct.

Thanks,
M

 


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