F22 Epp/Depron Parkjet modification from pusher to tractor

by animan | June 27, 2012 | (5) Posted in Projects

After flight testing myF22 Parkjet I decided to try and see if a modification from pusher to tractor would improve the performance numbers of the battery flight time. To my surprise, a 25% increase in motor run times was seen. I went from an 8 minute flight to a 10 minute flight time.

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COMMENTS

3dRCrazy on July 3, 2012
Im doing the same thing on my raptor, I havent gotten to fly it yet. My plane is still tail heavy with the battery as far foward as possible. Can it fly tail heavy?
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animan on July 3, 2012
If it is a little off, you will be alright. If it is way off (more than 1" form Cg, then you might have to put in some down elevator. For these types of flying wings, it is way better to be nose heavy and then add up elevons. I know if you keep it tail heavy (even adding some down elevons) you will effect negatively the stall characteristics of the plane. Hope it all works out for you.
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colorex on June 27, 2012
Wow... That's a big increase in efficiency! But do you think maybe the prop was reversed? Reversed props can cause lots of thrust loss. Sorry if you already know that.

Glad you got it working better!
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animan on June 27, 2012
Hello. The prop was in the correct "pusher" direction. If it was not, The jet would not even have flown and it would make a horrible sound. I am going to do refuter testing. I have designed 15 airplanes over the years and every time I do a pusher arrangement, I seem to lose efficiency, even though the motors can work both directions and the prop should not have efficiency differences. I am perplexed at this.
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colorex on June 27, 2012
Wow... certainly needs some investigation!
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animan on June 30, 2012
I did some internet searching today to see any input on pusher vs. tractor configurations. Looks like the difference in efficiency really depends on the airplanes overall airflow to and exiting the prop. In most applications, a pusher vs. a tractor ends up in an efficiency wash. The weird thing is if you go to APC website, they do sell pusher electric propellers but do not state what the difference is. just adds more to the confusion. In any case, the best route is to experiment for your own application.
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bmsweb on June 28, 2012
I really wouldn't have thought it would have made any difference but I'll try to test this out when I get time. Thanks for sharing your findings
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animan on June 28, 2012
If you do any testing, please post your results on this webpage. Thanks.
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Teilchen on June 27, 2012
Hi there!
I do not want to spoil the fun, but you are using a different prop in this tractor setup. This might actually be the main reason for this performance increase you observe. Some props are more efficient then the others, even with the same parameters... I'll just mention EMS and APC...
What do you think?
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animan on June 27, 2012
I did not show that orange prop in the first video- but that was the prop I collected all my flight data with. I just went out today and put in 6 more flights and I stand by that number of 25%. In fact, some flights went from 7 minutes to 11 minutes duration, same prop, same battery set, same wind conditions...
I wish I had an explanation for this, but at this point, I am glad I made the modification from pusher to tractor.
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Teilchen on June 27, 2012
Thanks for that update!
I will try this out during my next build...
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Teilchen on June 27, 2012
Thanks for that update!
I will try this out during my next build...
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F22 Epp/Depron Parkjet modification from pusher t...