CoroCub - a little bigger one.
11-05-2007, 01:56 AM
#76
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RE: CoroCub - a little bigger one.
We flew today again - it is so much fun. We took some measurments and I am very confused. There was a little crosswing but we still decided to take two speed measurments (both directions). Measuring the sound of the engine I calculated 7620 rpm (on MA 16x8 Classic). Now the weired thing is, that when I put the data into doppler formula I got the ground speed 70 mph. But at that rpm 8 inch pich prop will move no more than 58mph. What the heck? Maybe the MA prop does have more than 8 inch pich?
The frequency were: In = 140Hz, Center=127Hz, Out = 117Hz. It was low fast pass.
I measured the sound wave from that video clip using all available tools. When the airplane was exactly in front of us the recording indicated 7620 rpm (127Hz).
Anyway, I flew a little later with APC 16.5x5. I did not read the rpm, but it was noticable faster. The plane flew better too. I think I will leave this APC on it.
The frequency were: In = 140Hz, Center=127Hz, Out = 117Hz. It was low fast pass.
I measured the sound wave from that video clip using all available tools. When the airplane was exactly in front of us the recording indicated 7620 rpm (127Hz).
Anyway, I flew a little later with APC 16.5x5. I did not read the rpm, but it was noticable faster. The plane flew better too. I think I will leave this APC on it.
11-06-2007, 05:15 AM
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RE: CoroCub - a little bigger one.
This might help.
Here is a link to a Doppler Speed program thread at spadworld.net
http://spadworld.net/forum/viewtopic.php?t=14713
Jeff
Here is a link to a Doppler Speed program thread at spadworld.net
http://spadworld.net/forum/viewtopic.php?t=14713
Jeff
11-06-2007, 08:13 AM
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RE: CoroCub - a little bigger one.
the prop pitch doesn't take into account the lift produced by the prop itself. Its very possible to get a much higher speed than the prop pitch at a specified rpm, provided the airframe's nice and slippery in the air.
11-06-2007, 01:22 PM
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RE: CoroCub - a little bigger one.
ORIGINAL: ChrisSpad
Its very possible to get a much higher speed than the prop pitch at a specified rpm, provided the airframe's nice and slippery in the air.
Its very possible to get a much higher speed than the prop pitch at a specified rpm, provided the airframe's nice and slippery in the air.
11-06-2007, 04:14 PM
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RE: CoroCub - a little bigger one.
its probably more aerodynamic than you'd think - the biggest cause of drag is the wing, and the cub has a very long skinny wing - much like a glider, which has very little drag.
11-06-2007, 07:15 PM
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RE: CoroCub - a little bigger one.
Now it's time to paint it. I will get it like Pipers used as corp dusters after WWII in Poland. See the picture below. The nose is blue, fuselage light grey-silver (I will leave it white), Polish checkboard on the ruder and PLL-LOT text on the fin.
11-23-2008, 02:04 PM
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RE: CoroCub - a little bigger one.
Unfortunately I have not been flying for last couple months - to busy [:@] And the Cub is still the same hape except it received Spectrum receiver (I converted my Futana 8US to Spectrum using 109 dollars deal from Horizon).
But next month I will officially pass the presidency of my club to the new elected president (I mean the MASM President, not USA) so I hope being a simple member I will have more time for hobby. I have so much backlog in RC.[
]
But next month I will officially pass the presidency of my club to the new elected president (I mean the MASM President, not USA
) so I hope being a simple member I will have more time for hobby. I have so much backlog in RC.[]
