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Electric Stunt => Gettin all AMP'ed up! => Topic started by: Dennis_Bieber on November 19, 2016, 05:17:13 PM
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Somewhere in a post that I cannot find Brett said most guys have gone back to conventional rotation. I was under the impression using pusher props was the best thing since Corn Flakes. What are you guys using???
Thanks Dennis
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Igor only sells his props in conventional rotation, so that is what I run :)
When I was using 12x6 APC I tried LH props, all it did was make the line tension less in different parts of the pattern than you normally get in a conventional prop.
For example overhead 8, usually lighter in the outsides, with LH lighter on the insides.
It was not better or worse, just different. Too different for me, I went back to RH.
Pat MacKenzie
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I can report getting very solid line tension at all points in the pattern, inside, outside, overhead, using reverse-rotation APC 12-6 "F2B" prop. Model is Legacy, a large stunter in 680 inch range. Most electric flyers in NorCal are using reverse rotation, but in the Pacific NW it seems to be conventional rotation. I guess it depends on the model, line diameter, trim, and pilot experience, and maybe prevailing wind characteristics. I will be using the full Igor electronics system on nearly finished China Clipper, so may work best with conventional rotation. We will find out pretty soon. This seems like something that would be a good field test for flyers that really know what they are doing and why one thing works and another doesn't, which I am not one of. Also would be useful to know how rotation direction affects the trimming techniques that have been learned for conventional rotation IC engines over the last 60 years. In-thrust rather than out-thrust? And everything else?
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I wrote answer several times here. Yes, different rotation makes some maneuvers with better tension and others worse as Pat wrote, so going to pusher is not universal answer, even som pilots reported better line tension "somewhere" but it failed "elsewhere". Solution for that is proper trimming and use of well selected prop.
But the real point is that our conventional models ater 50 years of evolution (flying left, landing gears down, trust line over the wing) are simply compatible with righ rotating prop. The reason is precession which pushes nose up during flight (therefore thrust line over the wing and landing gears drag compensates for that). So many pilots learned lesson that model is easier and better trimmable with classic right rotation prop (tractor).
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But the real point is that our conventional models ater 50 years of evolution (flying left, landing gears down, trust line over the wing) are simply compatible with righ rotating prop. The reason is precession which pushes nose up during flight (therefore thrust line over the wing and landing gears drag compensates for that). So many pilots learned lesson that model is easier and better trimmable with classic right rotation prop (tractor).
Hi, Igor. I'd appreciate your theoretical analysis of an in-line airplane with retractable landing gear in general and the effect of left/right prop rotation in this particular case. I have such a new airplane ready to go now and I thought it would be good to know what to look for in the upcoming trimming process.
Thanks
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I used pusher props on my electric models for several years but always had trimming and tracking issues. I asked the question regarding tracking problems here a while ago and received many helpful replies. I tried everything (almost) that was suggested and many worked to some degree without total success. The only thing that worked really well for me was changing to a tractor prop.
As Igor said then and now we have developed aerobatics models aver a period of 50 or so years always with tractor props. If you change that all trimming options change too.
So just use a tractor prop and all the trimming tricks you already know can be utilised.
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Hi, Igor. I'd appreciate your theoretical analysis of an in-line airplane with retractable landing gear in general and the effect of left/right prop rotation in this particular case. I have such a new airplane ready to go now and I thought it would be good to know what to look for in the upcoming trimming process.
Thanks
All inline model, without landing gears and symetrical rudder and nose, will clearly have problem with precession, which must be compensated some way (motor angular offset or tail deflection, so really neutral model will need everything symmetrical and also conter rotating props).
If I HAVE to choose pusher or tractor prop on such model, I will probably use pusher, it can give some advantage on top of hourglass when line tension goes down. However Rabe rudder can solve also that problem. But I do not think the difference will be visible.
I still think well designed LEFT flying and well trimmed model with ONE prop will have tractor prop, thrust line over the wing and landing gears down - means calassic configuration.
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Pusher props an aid when the lines go slack.
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I think we are only scratching the surface of what is possible. Most of what we are flying are IC designs converted to e-power. Per Igor's comments I think the birds we design specifically for electric will have enhanced layouts that take advantage of what electric power has to offer.
We can be successful using either CCW or CW props. For me, I am using CW props exclusively.
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All inline model, without landing gears and symetrical rudder and nose, will clearly have problem with precession, which must be compensated some way (motor angular offset or tail deflection, so really neutral model will need everything symmetrical and also conter rotating props).
If I HAVE to choose pusher or tractor prop on such model, I will probably use pusher, it can give some advantage on top of hourglass when line tension goes down. However Rabe rudder can solve also that problem. But I do not think the difference will be visible.
I still think well designed LEFT flying and well trimmed model with ONE prop will have tractor prop, thrust line over the wing and landing gears down - means calassic configuration.
Thank you, Igor.
As I in fact now have the airplane sitting here on my desk I will, weather permitting, carry on flying it with the not too heavy (27 Gr.) APC 12 x 6 E Pusher at constant 9'300 RPM, looking for precession induced yaw in corners while bearing in mind the 1.5° motor-out I've built in. I appreciate your comment on the Rabe rudder, too, because I was , in case yaw would become a serious problem, thinking of retrofitting a symmetrically operating one.
Rgds.