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Old Oct 30, 2015, 10:06 AM
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Meltor and bogsan, nice work on the P38s, they look good. You were lucky to pump 43A through a 18A esc without letting out the smoke. Glad you found new motor, prop & battery setup for your plane and were able to fit them without trouble.
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Old Oct 30, 2015, 08:51 PM
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thanks RAFster. my 29g 2800kv motors were pretty much black and stinky when I pulled them but they did manage many flights . the 39g 1200kv with 8x4 props work much better. the new 3s1500mah 40c batteries are much lighter and more well suited than my 3 year old 3s1500mah 25c that I was using. I can make a 4 min. flight easily with a little throttle management. bosang, I just use counter rotating multi copter props they are out there in many sizes and are inexpensive. I am really glad to see your progress, I have my props counter rotating to the outside so sitting in the cockpit of the model the left motor is counter clock wise and the right is clockwise.
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Old Oct 31, 2015, 11:04 AM
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Although it would probably not make a huge difference at that scale, the prop on the right side from the pilot view should be turning counterclockwise and the prop on the left should be turning clockwise.

The only reason why some full size airplane have counter rotating propeller is to help prevent loss of control in case of an engine failure. The problem is that when an aircraft is flying at a lower speed with a higher angle of attack, the down going prop is meeting the air at a higher angle of attack than the up going prop and therefore the down going prop is producing more thrust. If the right engine is turning clockwise that means more thrust is created farther from the centerline of the aircraft which will result in a difficult to control yawing moment in case the left engine quits and possible loss of control. That is why aircraft without counter rotating propellers have a critical engine as things are worse when they loose the left engine as most light airplanes have engines turning clockwise from the pilot point of view.

The way you did set up your P-38 you have 2 critical engines in case of an engine failure...
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Old Oct 31, 2015, 01:10 PM
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i think the guys @ Lockheed knew what they were doing so
I set up my model just like the full scale p-38s that I have seen. it seems to work well and is very smooth on take off especially. you may see for yourself in the flight videos i have posted in this thread.
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Old Oct 31, 2015, 05:50 PM
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Quote:
Originally Posted by meltor View Post
i think the guys @ Lockheed knew what they were doing so
I set up my model just like the full scale p-38s that I have seen. it seems to work well and is very smooth on take off especially. you may see for yourself in the flight videos i have posted in this thread.
Actually the guys at Lockheed tried it the other way around first but it caused stability problems. The solution was to reverse the rotation and just live with the consequences of two critical engines. Thus the P-38 has a pretty nasty reputation for being a widow maker in low speed, engine out situations. While I am a pretty hard core scale fanatic this is definitely one area where I would deviate from scale if I were to build a P-38 model.

The prototype

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Old Oct 31, 2015, 06:40 PM
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wow! interesting stuff. I suppose then that I wouldn't really know the difference until I loose a motor. with my dynam BF110 both props turn clockwise if you were sitting in the cockpit. I think it is also a great flying model and really haven't noticed any alarming pull or problems from it so like shotgun said maybe there would be little difference in a model of this scale.
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Old Jan 10, 2016, 08:07 PM
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i had made this video last fall to show how the 1200KV 2822 39G motors preformed with 8x4 props on 3 cell. this is with an 1800mah battery and as you can see there is no room for anything bigger. AUW was @ 32 oz. but the model flew well. i since have been using a new 3s1500KV 40c battery that saved some weight and flight times are still around 4 min. with throttle management.

i wasn't happy with the video as it was getting dark and on landing i thought i chipped a prop but it just scratched it. with the full metal retracts with suspension it allows the props to just strike the surface under full compression but with this landing it was really a guess as to where i was setting down. i was totally blinded by the sunset. this a robust model i have flown it allot and many landings have been dead stick and short in the grass.
anyways i was hoping to get better footage @ some point but we ran out of season so this spring i hope to come up with a good video .
until then we can while away a cold winter day and dream of good flying in the months to come.
Guillows P-38 R/C test flight (3 min 32 sec)
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Old Jan 11, 2016, 05:22 AM
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Hi meltor,
I'm guessing the original 1800 mah pack was a 3s s well so the only change was the AUFW?

cheer s- Phil
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Old Jan 11, 2016, 02:34 PM
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hi phil, yes the only change was with AUW. here are the 3 batteries that i have ran in this model. 3s 1500mah 25c gforce is battered and puffed. the first setup with the 2800kv motors and 7" props was just not right and really cooked this 1500mah it weighs 112 G. the new 3s 1500mah 40c battery is working really well with the 1200kv motors and 8x4 props. it weighs 103G and is just warm to the touch after a 4 min. flight.
the 3s 1800mah 30c is the largest battery i could fit in the model and weighed in @ 149G. so there is a difference in how the model feels on a day with lighter winds. in the wind like on the day of this video the model really flew well with 45 grams of extra weight. so as of right now the 1200KV motors and 8x4 props seem to work well and give the best flight times. origonally the model flew on 2800kv motors with 8x4 props and a 2s 2200mah 30c battery and would barely make 3 min.
it has been a learning experience
but still i think there is a better set up that would achieve 5-6 min flights. maybe on the next p-38 build.
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Old Jan 11, 2016, 05:58 PM
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Quote:
Originally Posted by meltor View Post
i think the guys @ Lockheed knew what they were doing so
I set up my model just like the full scale p-38s that I have seen. it seems to work well and is very smooth on take off especially. you may see for yourself in the flight videos i have posted in this thread.
Great job and I hear you bro. Being someone who actually builds these Guillows jobs and other similar models, I refrain from throwing over-analyzing technical theoretical advice at someone who has your level of success with a subject like this.

You're reminding me that I need to fly the inspiration of the P38, the AG Crusader. Built one a few years ago. Never flew it, but the Miles Aerovan twin built right afterwards flew well, without counter rotating props.
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Old Jan 11, 2016, 11:53 PM
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hi Anti, thanks for your support. it is interesting what comes up in these build logs and i do thank everyone who posts their comments. of nearly 14,000 views and only 114 comments in this thread i would really be interested what other advice is out there. i try to keep things simple and apply tried and tested methods that i have found in these forums and have figured out myself. miles per pound had a big inspiration on this p-38 build. i would still just adore a pair of vario 3 blade props and spinners like he used.

Phil, i have really been looking over your B-29 super fortress build log, a real masterpiece. recently i had the good fortune to purchase a complete kit and have been selecting parts for the build. so far i have motors , servos , and retracts. i am really hooked so @ some point there may be a build log.
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