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P-82 Power

Old 04-26-2013, 07:46 PM
  #1  
Scottyd
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Default P-82 Power

Thanks for all the feedback on the Exceed motor I posted earlier.

The P-82 I am converting is from World Models:

Wing Span:70.5 in / 1790 mmWing Area:734 sq in / 47.4 sq dmFlying Weight:9.5 lbs / 4300 gFuselage Length:49.6 in / 1260 mmEngine Required:2 x 2-stroke 0.40 - 0.46

Converted weight will likely be slightly over the 9.5 lbs.

I'm leaning toward the Turnigy SK3 - 4250-500kv.

Any thoughts?
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Old 04-26-2013, 08:05 PM
  #2  
fhhuber
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I've had very bad results with Turnigy motors...
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Old 04-26-2013, 08:08 PM
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Oh crap. I just purchased two 3536/8's for my P-38 (Richmodel 51.6").

What should I beware of?
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Old 04-26-2013, 08:35 PM
  #4  
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My Turnigy motors all failed due to bad glue holding the magnets in.

Running at well under rated power with good cooling.

if that failure happens its cureable.
I put the motor bells in the oven at 140 F and slid the magnets all out.
Cleaned the glue out
Reinstalled the magnets with J B Weld.

Its a project...

Its kid of silly to put the magnets in a motor with low temp hot-melt glue.
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Old 04-27-2013, 12:23 AM
  #5  
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I couldn't help myself.

Stupidity on my part. Did not realize what a p-82 was. Here is the two prop result.

Airframe Details
All Up Weight (oz) 152
Number Of Wings 1
Wingspan (in) 70.5
Total Wing Area (sq in) 734
Number of Propellers 2
Maximum Prop. Size (inches) 12
Flight Mission Fast sport aerobatics
Desired Top Speed (mph) 87
Desired Thrust (oz) 152
Desired Flight Duration (minutes) 7
Motor Efficiency (%) 80
Select battery chemistry & cell count below 6S LIPO
Battery Voltage (V) 21.6
Desired current per motor (A) 35.5
Motor Kv (rpm/volt) 500 Kv


WebOCalc Results:
Flies Like: Fast Aerobatic/Sport model
Power Level:
(with white highlighted prop) Excellent. Long vertical lines.
Might hover.
Thrust/weight about 1.2:1
Minimum Pilot Skill Needed: Advanced Intermediate.
Minimum Flying Field Size: 1800 x 1300 feet.

Per Motor:
Minimum Battery Size: 6S, 2100 mAh, 17 C, lithium polymer.
Estimated Flight Duration: 5 to 9 minutes depending on pilot.
Will vary with throttle usage.
Suggested ESC Rating: 46 A to 53 A.
Power Into / Out of Motor: 766.8 watts in / 613.4 watts out.

Power To Weight Ratio: 80.72 watts/pound.
Estimated Stall Speed: 26.7 mph.
Wing Loading: 29.82 oz/square foot.
Cubic Wing Loading: 10.42 oz/cubic foot.

SUGGESTED PROP
APC-TE 12 x 10
8657 rpm
82.4 mph Vpitch
Direct drive

Last edited by dgholmes59; 04-27-2013 at 09:17 PM.
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Old 04-27-2013, 06:01 AM
  #6  
starcad
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Wow! Sorry fhhyber you had such a bad experience with Turnigy motors. I have 7 of them and have been using them for the last three years with no issues. Only thing I don't like is some of the motors I have are now discontinued and I'd like another.


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Old 04-27-2013, 07:20 PM
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Yes, sorry to hear of your Turnigy issues as well. I guess you get what you pay for.. Hopefully the manufacturer is using a better adhesive now. I do see a number of feedbacks on the distributors website regarding magnet glue failure. Perhaps they were counting on centrifugal force to hold the magnets in?

Thanks for the WebOcalc idea. I believe I understand the mission of the software; more for model performance vs a motor calculator. The first thing that jumped out from the data above was the single prop selected as opposed to the twins the P-82 will have.

To my surprise WebOcalc didn't change the watts or prop selection between 1 or 2 props. It did change the plane performance, however.

I attempted to dig further into the tool, in order to avoid more stupid questions, but alas, it appears more stupid questions are yet to come:

Is the power into/out of motor the total for both motors? Is the battery per motor or shared? Mute point if watts are total, but with two motors and identical props, the flight time should be significantly shorter (around 1/2?), and it is not.

Perhaps I am expecting too much from the tool. I guess that's why I am asking the forum for your advice. My level of experience with electric's is pretty limited. An electric cub with the brushed motor it came with and the Electra (I believe the electric version of the Gentle Lady) is pretty much the extent of my experience and that was quite a few years ago. The Cub was fine, the Electra didn't glide or power well.

My goal at this point is to use China motors (Turnigy? - knowing the risks) and have "excellent long vertical flights" with hovering not a necessity. The info I am seeking help with is motor, prop and LiPO selection. Keeping in mind the Turnigy SK3's are not recommended for 6S. I am open to other motor ideas, however. I have only purchased the Turnigy D3536/8 motors for the P-38 and have not flown them yet.

thanks for any help you can offer.

Scott
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Old 04-27-2013, 08:47 PM
  #8  
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Getting better results with Dynam motors (First found at Polks Hobbies, now get them through Nitroplanes.com)

I have some Dynam outrunners that have given over 8 years of service. I have never had a problem with a Dynam motor. Their earlier ESCs were junk. The newer ones are looking better.

bphobbies motors seem good so far too... I haven't had those very long though.
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Old 04-27-2013, 09:12 PM
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dgholmes59
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Originally Posted by Scottyd View Post
Thanks for the WebOcalc idea. I believe I understand the mission of the software; more for model performance vs a motor calculator. The first thing that jumped out from the data above was the single prop selected as opposed to the twins the P-82 will have.

To my surprise WebOcalc didn't change the watts or prop selection between 1 or 2 props. It did change the plane performance, however.

I attempted to dig further into the tool, in order to avoid more stupid questions, but alas, it appears more stupid questions are yet to come:

Is the power into/out of motor the total for both motors? Is the battery per motor or shared? Mute point if watts are total, but with two motors and identical props, the flight time should be significantly shorter (around 1/2?), and it is not.

Perhaps I am expecting too much from the tool. I guess that's why I am asking the forum for your advice. My level of experience with electric's is pretty limited. An electric cub with the brushed motor it came with and the Electra (I believe the electric version of the Gentle Lady) is pretty much the extent of my experience and that was quite a few years ago. The Cub was fine, the Electra didn't glide or power well.

My goal at this point is to use China motors (Turnigy? - knowing the risks) and have "excellent long vertical flights" with hovering not a necessity. The info I am seeking help with is motor, prop and LiPO selection. Keeping in mind the Turnigy SK3's are not recommended for 6S. I am open to other motor ideas, however. I have only purchased the Turnigy D3536/8 motors for the P-38 and have not flown them yet.

thanks for any help you can offer.

Scott
I edited the webocalc results for two motors. This is the first time I have used it for two props. Looks like the data is less than half now indicating per motor. It also changed the props from a 15 x 10 to a 12 x 10. First time I have tried it on a two prop plane.
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Old 04-28-2013, 04:07 PM
  #10  
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dgholmes59,

Thank you very much for taking the time to update WebOCalc (and the intro to the program).

I will attempt to apply the results to an appropriate motor.

I was hoping someone might have a similar setup or motor advice. Oh well; at least I'll be making a more educated guess now.

thanks again,
Scott
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Old 04-28-2013, 05:07 PM
  #11  
dgholmes59
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Originally Posted by Scottyd View Post
dgholmes59,

Thank you very much for taking the time to update WebOCalc (and the intro to the program).

I will attempt to apply the results to an appropriate motor.

I was hoping someone might have a similar setup or motor advice. Oh well; at least I'll be making a more educated guess now.

thanks again,
Scott
Would be neat if someone has done one of these to see how close the theoretical (webocalc) is to actual. It is such a quick way to get all the data needed for powering a plane. Takes about 5 to 10 minutes. It did recommend the 500 kv motor that you are using as well.
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Old 04-29-2013, 05:01 PM
  #12  
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The recipe I used for the P-38 (not yet flown) came from a forum member, beavenx5.

For grins I plugged his info into WebOCalc. The motor watts, suggested battery and flight characteristics were dead-on with the model as described by beavenx5.

I feel more confident in the motor selection for the 38 now. I'm also forwarned that it will be a "heavy warbird". I'd better brush up a bit before flying it.

The P-82 is another animal, however. I am still having difficulty choosing the correct motor. Web surfing yields a few combos that people have used or suggested: AXI 4120/14 or 2826/10 or 12 (expensive and this application is just a guess by the author), Turnigy SK3 4240-530KV (no battery info), G46 670KV 4SLipo.

Thoughts?
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Old 04-29-2013, 08:14 PM
  #13  
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By the way, that P-38 I recently purchased was only $69 from these guys: http://www.generalhobby.com/richmode...lane-p-70.html It's closing out soon. My buddy was over when it arrived and he had me get one for him to hang in his office. I know it's not totally scale with the flat fuse, but you just have to love that Devilish profile!

I couldn't resist getting the huge 73" de Havilland Mosquito as well. There's some forum activity on converting this to electric (some time ago). I believe it's close to closing out as well.
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Old 04-29-2013, 08:27 PM
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There you go... pointing me at another plane to drool over ...

But I got no room for it
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