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SteveT |
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Latest blog entry: My hangar...
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nice video Bonedoc!looked like you kicked it when you punched it.
also power came in handy for the "on purpose fall out of hover to drag rudder on ground" move..nice
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Latest blog entry: Lil repair work.
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Flagstaff, Arizona
Joined Oct 2004
398 Posts
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Mr. Stoops,
Are you or have you used the Reaper Xl recommended for this plane at altitude yet? I am slightly higher than you and am used to a lack of power, I just don't want to buy a few motors until I get it right. I feel 1900 watts should work, even with 15-20% loss of power, but I thought I would ask anyway. Thanks! Bryce |
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Rob |
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WI
Joined Mar 2001
808 Posts
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Maybe I’m full of it,
but it seems to me it would take –more- power to hold the same weight object up in thinner air? So equal power in does not equal power out needed at the prop for a given weight? [edit] I may have gravity and air density confused. Hopfully you'll get the full scoop from Stoops. Kevin |
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I set up the ICE 100 today. Direct soldered, soft cutoff, and 2 samples per second for data logging (for 22 minutes of logging.) I have the auto calibrate throttle but don't like the idea of having to waste full power milliamps for 4 seconds on the beginning of every flight to calibrate it. I may set the endpoints but the way that it was explained in the manual sounded a little confusing.
I wonder if using a throttle curve for the low end and high end would just work. I have the JR X9303 Heli version. I took amp readings on the ground and with the built in logger. It seems like the logger is about 20 amps higher and 300 watts more than my e-flite watt meter. The watt meter is capable of reads over 100 amps and over 2000 watts. I am not sure if it is because the logger can sample every 2 seconds vs me looking at the meter for the highest # seen or something else. I was very happy with the throttle response and timing on the ICE 100. It was cool the entire time of testing! Hope the weathers good Thursday. Fall has arrived in Colorado and it has been windy as well. Joe |
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That being said I still think that the same plane at sea level with the recommended prop is a little more powerful out of a hover than the same plane with the increased pitch and diameter at 5200ft. I don't think with electric there is any reason to go to a bigger motor at higher altitudes. Just match the prop to the amps and watts that are recommended. Gas planes suffer much much more at high altitudes. With gas planes a bigger motor may be necessary but also adds weight which increases wing loading in already thin air. Not a good combo. Any technical stuff Scott would be better to answer. Joe |
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Joined Apr 2008
440 Posts
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In hover and vertical pull-out, you need the same power from the motor regardless of altitude, because the motor is supplying the lift (discounting secondary effects like efficiency and prop wieght).
In more horizontal flight, when the wing is suppling the lift, the plane seems heaver because the wings supply less lift because of thie thinner air. However, in a hover, when the motor is doing the lifting, proping-up is like making the wing bigger, to give you equivelant lift and power output. |
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Sorry, I got nerdy there for a minute .
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WI
Joined Mar 2001
808 Posts
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I guess the key is that the thinner air loads the motor less and causes it to draw less current with a given prop, compared to sea level. A bit of a brain teaser there for my pea sized brain
Was also thinking of the loss of lift while more horizontal. Does that lift not also come from the motor altimatly, since the motor is also pulling the wing forward? I'd better stop thinking about this now before I blow up Kevin |
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