|Jun 08, 2014, 12:02 PM|
Joined May 2014
Just a video of my Sean Kinkade Slow Hawk
A few weeks back I purchased this bird used. On my first flight I snapped the wing spar at the shoulder ferrule. After repairing, I flew a bit more cautiously and all is great. It actually flies best at 1/3rd throttle! When flying into a small headwind, I can maintain level flight with a flap rate of about one flap per second; insanely slow.
This video doesn't show that so well, but there are some spots where I slow down and you can see how smooth it flies. (1800ma 2-cell battery, by the way.)
My son is doing the video and commentary.
|Jun 09, 2014, 12:26 AM|
Palo Alto, California, United States
Joined Jan 2003
If you install a data recording speed controller (ESC) you can measure the flap frequency by plotting the variation of Watts vs. time in the recorded data. You can also use frame-by-frame on the original video to count the number of frames per flap cycle and knowing the frame rate of the video recorder you can get the period for one flap cycle and then calculate the frequency. You might be surprised to find out that what seems like 1HZ is often closer to 2 or more HZ. Every time I fly one of my home made designs I make these measurements because I'm interested in flapping efficiency, something that all ornithopters are currently pretty bad at when compared to a bird or a conventional propeller.
Here's a video of my model taken from the ground and with an on-board camera. I measured the minimum flapping rate to be approximately 2.25HZ during the segments 0:57-1:07 and 2:23-3:50. When I'm flying it seems like 1HZ but the data doesn't lie, it's roughly double that. Keep in mind that my model weighs 5lbs and has a 7 ft wingspan, so it's nothing like a SlowHawk which is much more lightly loaded for its size.
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