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Old Aug 24, 2011, 05:10 AM
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takeoff2's Avatar
Romania
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Quote:
Originally Posted by troynh View Post
This isn't an FPV flight but thought I'd post anyway... I've had this SW kicking around for close to 6 months + and I just got around to putting it together. I scavenged the wing spars from the kit for another project a month or so ago. So, Instead of using the original wing, I'm using an Easy Glider wing. The maiden was tonight and everything went very well. The AUW is around 54 ounces. The motor is an old Rimfire 35-30-1450 spinning a 9x3.3 SF. One 3s 2650. It was getting dark and it shows in the GoPro footage but that was shot in the R5 1080P mode.

-Tim
Super flight, where CG is in this case?
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Old Aug 24, 2011, 06:30 AM
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Quote:
Originally Posted by brifa View Post
i don't think so
without fy21 i had to put CG on the servo wire and it flies well... finally...
then i used fy 21 with that CG and no issues...
According to the manual the CoG should be 75mm from the leading edge. I measured that today and if I put my CoG there its about 6mm FORWARD of the servo leads.

I measured 30mm aft of the servo leads, and if I were to put the CoG there that would be way too tail heavy. In fact my first flight resulted in uncontrolled collision into terrain because the battery moved back 3/4 inch. I couldn't even hand launch with CoG there far back.
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Old Aug 24, 2011, 06:33 AM
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Quote:
Originally Posted by nyc863 View Post
ardupilot mega has a LOT of PID tuning parameters
the defaults are not going to suit your setup. have you tried tuning them?
I used the Skywalker.params that is provided. I was however surprised why the Pitch P was set for 3.3 when the default is 0.8. I was playing around using XPlane for hardware in loop and I had to dial it down to 0.4.

The problem with using ardupilot mega is that I have to drag my laptop down to the field to tune the PIDs, and right now my skywalker needs stablisation, so I'm installing the FY21AP II now, as everyone's telling me it works well.
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Old Aug 24, 2011, 08:40 AM
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Originally Posted by Daemon View Post
The plane (any/all planes) does not need any more power to fly upwind at the same
airspeed as it flies downwind. The only thing that can cause it to stall
is you at the sticks, choosing to slow it down when you turn downwind
because it *appears* to be going too fast from the ground.
You wouldn't have this problem if you were actually piloting it FPV
and simply letting it fly the speed it wants to.

It'll fly with the CG anywhere from the servo slots to about 35mm behind the servo
slots. 30mm is optimal but control throws must be reduced.

ian
@Daemon, upon reflecting over the last 8 flights of the SW, I think its too tail heavy as the CoG is too far toward the aft. So this is my recollection of the flights.

Flights 1-6 where done with 4S 6000MaH battery and ReadyRC Camera pod canopy. Flights 7+ done with standard foam canopy and undercarriage. Flight 9-10 done with 4S 5000MaH battery.

Flights 4-6 where the most successful flights.

Flights 1 - 3 CoG was aft of flights 4 - 6.
Flights 7 - 10, weight was removed from the front (ie. FPV pod and going to smaller battery), therefore I assume CoG moved aft compared to flights 4 - 6.

These are the results of each flight:
Flight 1. Ground take off, nose up, plane banks left, full right aileron, plane still is banked left with nose up attitude, powered off, crash landing, landing gear torn off.

Flight 2. Hand launch, flys straight but fails to maintain level flight refuses to gain altitude, belly landing

Flight 3. Hand launch with flaps down, maintaining straight and level @ 1m AGL but can't climb, flaps up, plane lands.

Discover that the battery pack has moved 3/4 inch rear, move battery pack forward and secured it.

Flights 4 to 6, successful hand launch and completed a number circruits. Battery only lasted about 15 mins with throttle needed to be 3/4 to full for most of flight.

Flight 7. Change to foam canopy, had to abort one take off due to not lifting off. Hand launch successful, aircraft seems to be fighting the wind, full power required most of flight.

Discovered prop on backwards.

Flight 8. Take off on half throttle, much more power. Still fighting the wind. Aircraft almost rolls past 80degs on turn to crosswind. Aircraft enters spin on turn to base leg.

Flights 9-10. Change battery to 4S 5000MaH. Climbing well on take off, turn cross wind fighting the wind as it wants to roll me over. Turn to downwind, can not maintain height, losing height on full power. Power off, nose into wind, glide landing
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Old Aug 24, 2011, 08:47 AM
No thrust...It'll bust...
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Troy, NH
Joined Sep 2006
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Quote:
Originally Posted by takeoff2 View Post
Super flight, where CG is in this case?
Start at the standard (Easy Glider) 70mm from the leading edge and move up from there. I'll have to load it back up and find where mine landed last night. It's well in front of the standard 70mm mark.

Also, I added a 1/4" piece of of basswood to the LE to give the wing roughly 2 degrees of incidence.

-Tim
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Old Aug 24, 2011, 09:01 AM
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I've just done some balance checks with the load out of my SW from the previous flights. It looks like with the FPV pod the CoG with 4S 6000Mah is just foward of the servo leads. Without the pod and using foam canopy the CoG has moved aft of the servo leads. That explains how come flight performance started getting bad when I started flight with the foam canopy.

Now tested with today's configuration 4S 5000MaH with the foam canopy, and the CoG is again aft of the servo leads but more so than with the 4S 6000Mah. This correlates with the performance getting worst. When I put on the FPV pod the CoG is on the servo leads. Now I move the 4S 5000Mah all the way to the front, and the CoG is now on the 75mm line recommended in the manual.

I will test fly tomorrow and post results to see if they validate my theory.
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Old Aug 24, 2011, 09:02 AM
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Quote:
Originally Posted by htran View Post
@Daemon, upon reflecting over the last 8 flights of the SW, I think its too tail heavy as the CoG is too far toward the aft. So this is my recollection of the flights.

Flights 1-6 where done with 4S 6000MaH battery and ReadyRC Camera pod canopy. Flights 7+ done with standard foam canopy and undercarriage. Flight 9-10 done with 4S 5000MaH battery.

Flights 4-6 where the most successful flights.

Flights 1 - 3 CoG was aft of flights 4 - 6.
Flights 7 - 10, weight was removed from the front (ie. FPV pod and going to smaller battery), therefore I assume CoG moved aft compared to flights 4 - 6.

These are the results of each flight:
Flight 1. Ground take off, nose up, plane banks left, full right aileron, plane still is banked left with nose up attitude, powered off, crash landing, landing gear torn off.

Flight 2. Hand launch, flys straight but fails to maintain level flight refuses to gain altitude, belly landing

Flight 3. Hand launch with flaps down, maintaining straight and level @ 1m AGL but can't climb, flaps up, plane lands.

Discover that the battery pack has moved 3/4 inch rear, move battery pack forward and secured it.

Flights 4 to 6, successful hand launch and completed a number circruits. Battery only lasted about 15 mins with throttle needed to be 3/4 to full for most of flight.

Flight 7. Change to foam canopy, had to abort one take off due to not lifting off. Hand launch successful, aircraft seems to be fighting the wind, full power required most of flight.

Discovered prop on backwards.

Flight 8. Take off on half throttle, much more power. Still fighting the wind. Aircraft almost rolls past 80degs on turn to crosswind. Aircraft enters spin on turn to base leg.

Flights 9-10. Change battery to 4S 5000MaH. Climbing well on take off, turn cross wind fighting the wind as it wants to roll me over. Turn to downwind, can not maintain height, losing height on full power. Power off, nose into wind, glide landing

Something is horribly wrong here.

I fly with CoG about 25mm behind servo leads.
4S 9x6 prop 1400kv motor
I can take off at 20 amps no problem, if I juice it more than that it wants to jump out of my hands.
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Old Aug 24, 2011, 09:08 AM
RTFM
octane81's Avatar
Antarctica
Joined Oct 2010
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I usually give about 10amp (4S lipo) at takeoff , no more is needed... and then just give it a gentle throw.. away it goes!
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Old Aug 24, 2011, 09:18 AM
Nakelp
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United States, NJ, Union
Joined Sep 2004
6,793 Posts
Hey guys, since there are so many options and questions regarding motor/prop/ESC and other electronics would it be beneficial for all to group all the options in a separate thread for Skywalker instead searching individual posts here?
Something like this:

http://www.rcgroups.com/forums/showthread.php?t=1494373
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Old Aug 24, 2011, 09:36 AM
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Quote:
Originally Posted by BushmanLA View Post
Something is horribly wrong here.

I fly with CoG about 25mm behind servo leads.
4S 9x6 prop 1400kv motor
I can take off at 20 amps no problem, if I juice it more than that it wants to jump out of my hands.
Ok, maybe your servo leads are in a different position than mine (I have v4 SW). The only real point of reference is the leading edge.

How far back from the leading edge is your CoG?
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Old Aug 24, 2011, 10:33 AM
RTFM
octane81's Avatar
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Quote:
Originally Posted by htran View Post
Flights 4 to 6, successful hand launch and completed a number circruits. Battery only lasted about 15 mins with throttle needed to be 3/4 to full for most of flight.
That is very wrong ! and i dont think thats an CoG issue
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Old Aug 24, 2011, 10:33 AM
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Quote:
Originally Posted by Crist Rigotti View Post
Ian,
Where iis the center of lift located on the Skywalker?
lift acts at the CoP (Centre of Pressure)
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Old Aug 24, 2011, 10:35 AM
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Quote:
Originally Posted by octane81 View Post
That is very wrong ! and i dont think thats an CoG issue
@Octance, it is very correct, as per my post, I later discovered the low flight time was due to the prop behind mounted backwards, which after fixing resulted in flights 7+ using very little battery, and being able to take off at half throttle in 1/3 the distance.

It all starting getting worst when I started removed weight from the front
Changing from FPV canopy to standard foam and then and even more worst when I went from 4S 6000 to 4S 5000
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Old Aug 24, 2011, 10:59 AM
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United Kingdom
Joined Jun 2009
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My CoG is currently about 25mm behind the servo wires (on a v2)

I think you'll find the SkyWalker has a very wide range it can accept and still fly because of teh large underhanging fuselage.

I started on the recommended point and moved it back 5mm at a time, adjusting the elevator each time so it would fly hands off level.

Then it's a case of getting it as close to the point wher eit doesn't pitch up or down under the various throttle settings
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Old Aug 24, 2011, 11:01 AM
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Quote:
Originally Posted by Shikra View Post
My CoG is currently about 25mm behind the servo wires (on a v2)

I think you'll find the SkyWalker has a very wide range it can accept and still fly because of teh large underhanging fuselage.

I started on the recommended point and moved it back 5mm at a time, adjusting the elevator each time so it would fly hands off level.

Then it's a case of getting it as close to the point wher eit doesn't pitch up or down under the various throttle settings
Shikra, how far back from the leading edge is your CoG?

Also, planes should pitch up when you increase throttle, that's how you'r suppose to climb. Sounds a bit weird to setup a plane not to pitch up when throttle is increased.
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