Thread: Discussion Skywalker 168cm FPV plane
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Old Jun 09, 2011, 03:48 PM
cmanley_nl is offline
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Skywalker v2 maiden flight remarks

I just flew my Skywalker v2 for the first time today in a non-FPV configuration. To my surprise it flew quite well without any need for trimming.

I noticed 2 problems though that need fixing:
  • The ailerons cause a strong adverse yaw effect as I expected due to the ridiculously wide bevelled gaps. When an aileron goes down, then the huge bevel comes down as a panel that's at almost 90 degrees to the airflow. I'll probably fill the bevelled area with balsa so that only the necessary amount of bevelling is present and tape some white tape over it all. Has anyone done this already?
  • When I throttle up, the nose pitches down immediately, and when I cut the throttle the nose pitches up immediately. I've seen posts here where people have had the opposite effect which seems strange to me. I assume the effect I'm having is because the motor is pointing up slightly and causing the relative airflow at high throttle settings over the stabiliser to give it a higher angle of attack which results in a pitch down. The effect isn't big, but enough to be annoying. Hopefully some washers to make the motor point up less will fix this. The CoG is on the servo wire gaps which from the dive tests seems correct as it has only a slight tendency to pull up which is what I want to happen if I loose radio control.

Then the less important things I noticed:
  • Inverted flying is easy and only a little bit of down stick is required.
  • Rolls are very slow even with moderate amounts of aileron throw.
  • It doesn't want to tip stall which is a good thing.
  • I can slow it down and hold full stick up and put it in a deep stall keeping direction using rudder. This is thanks to it's high wing and very low centre of gravity/mass.
  • I can't get it to spin yet even though I'm using moderate amounts of control throws. In order to spin the rudder must be much more effective and I doubt it will be enough even if it moves out at 45 degrees.
  • I've reinforced the wings with 3 extra carbon strips each (2 below and 1 on top) and the wings still flex in turbulence and when pulling G's so I've been gentle on the controls at high speeds.
  • Flaps aren't really necessary to fly slower, however they may be useful to make it brake and sink faster. They are just so small though, that I have doubts about their effectiveness should I decide to build them in.
  • It is actually possible to perform touch and goes on grass with it.
  • It's possible to fly around using rudder only instead of ailerons. It actually turns much neater this way without the unsightly adverse yaw effect.
  • My Turnigy 60amp ESC gets quite warm under the wing. It's too large to mount outside below the motor, so I guess I'll order a smaller 40 amp ESC and mount it outside.

My setup is:
  • Turnigy 35-36B 1300kv motor and a 9x6 APC-E prop drawing almost 40 amps.
  • 2 * 3S 2200mah 20C Zippy LiPo batteries in parallel so that I can stuff more battery mass up front (effectively a 3S2P pack which is stouter than a 1P 5000mah pack)
  • A chunk of lead substituting the GoPro that still needs to be mounted up front.

I'm still doing research on possible UHF antenna combinations I can use and their placements with my Scherrer UHF receiver which comes with 2 short dipole antennae which I'm afraid are too close to the other noisy electronics (ESC, motor, and cameras). Turnstile looks promising for one. The other will probably be a vertical dipole.

For testing today I just used a 2.4ghz receiver with my 500mw 2.4ghz video transmitter is already mounted (but disconnected) right out on one wingtip and lead in the other.

-Craig
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