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Old Nov 18, 2012, 03:03 PM
Praying for better weather
Coyote64's Avatar
Joined Dec 2007
4,103 Posts
Quote:
Originally Posted by VizBizTas View Post
X8 up for 3rd flight with correct CG.
Onboard video and also from a chase plan... Enjoy...

http://www.youtube.com/watch?v=yvmqLJixDJ4&sns=em

Please also join my x8 build on face book if you have not yet done so.
www.facebook.com/groups/projectbigbird

Thanks.
What CG point did you end up going with may I ask ?
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Old Nov 18, 2012, 10:38 PM
Team Park Pilot - Airborne
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Australia, NSW, Sydney
Joined Nov 2006
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This would be very cool for the X8

Bat 3 UAV Autonomous Catapult Launch (0 min 11 sec)
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Old Nov 19, 2012, 12:08 AM
Opt
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New Zealand, Auckland
Joined Oct 2010
388 Posts
Whoa, found this random vid on yt of a guy stalling his X8 from quite high up... Only positive is we can confirm using the motor when stalled makes things worse!

Fpv X8 wing Crash (7 min 53 sec)
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Old Nov 19, 2012, 12:12 AM
Opt
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New Zealand, Auckland
Joined Oct 2010
388 Posts
Recently finished doing a few upgrades on my X8. Not sure of they will have any effect but i plated the front bulkhead with plywood to reduce the flexing in the central section, added thin fibreglass spars along the top and bottom of each wing and covered everything in 3M high gloss vinyl.
It still flexes a bit so I suppose I will wait and see how it flies before deciding that was all worthless.
Weight is 2.9kg ready to fly with 6600mah 4S, gopro and radio gear, but without fpv camera and tx. Prob will be exactly 3kg with that
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Old Nov 19, 2012, 12:24 AM
Team Park Pilot - Airborne
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Australia, NSW, Sydney
Joined Nov 2006
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That was pretty amazing - Opt.. thanks for posting this.

I don't see a stall as such. You can hear the throttle cycling and I think it sound more like loss of RX signal. As I posted some pages back. there is a right way... a wrong way... and a fatal way to try and recover from BOTH types of a stall. One is a standard stall... the other a flat stall. BOTH require power but neither whist is the rotation. What I suspect here is a full power opposite deflection attempt at recover. Bad mistake.

To recap - stall recovery is:

Throttle to minimum

Stick full forward

FULL opposite rudder

rotation will stop...

stick to center

recover from dive.


NEVER NEVER pull up in a spin or add power... this will simply make the spin tighter and you will eather break that plane or ride it all the way to the ground.
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Old Nov 19, 2012, 12:45 AM
What goes up, must come down
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United States, MI, Midland
Joined Sep 2009
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In the case of the X8 you actually want to apply full forward in the direction of the spin, (in the case of this video, full left/down) this ads maximum deflection of the aileron on the wing that is partially flying, then once the nose drops and it begins to fly again just add full down, build speed, pull out. (no rudders on the X8 )

Crazy1

Quote:
Originally Posted by G-Forced View Post
That was pretty amazing - Opt.. thanks for posting this.

I don't see a stall as such. You can hear the throttle cycling and I think it sound more like loss of RX signal. As I posted some pages back. there is a right way... a wrong way... and a fatal way to try and recover from BOTH types of a stall. One is a standard stall... the other a flat stall. BOTH require power but neither whist is the rotation. What I suspect here is a full power opposite deflection attempt at recover. Bad mistake.

To recap - stall recovery is:

Throttle to minimum

Stick full forward

FULL opposite rudder

rotation will stop...

stick to center

recover from dive.


NEVER NEVER pull up in a spin or add power... this will simply make the spin tighter and you will eather break that plane or ride it all the way to the ground.
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Old Nov 19, 2012, 01:05 AM
Team Park Pilot - Airborne
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Australia, NSW, Sydney
Joined Nov 2006
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Agreed - I should of highlighted the fact that in conventional 3 axis aircraft this is standard but when we are talking spoilers / flying wing configuration we need to take in to account it is a blended control action. Ie: rudder and aileron are connected but still maintain their respective duties.
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Old Nov 19, 2012, 01:58 AM
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There's no "rudder" action at all, so it's just not applicable in this context.
On a flying wing you have ailerons and elevator combined into elevon, and if you apply full
down + full opposite roll (opposite the spin direction as you're implying by
suggesting an analog to rudder input) and look at the control
surfaces, you'll find the one on the outside wing (the only one flying) is level or even above
level (depending on relative aileron/elevator rates) which is exactly
the wrong way it needs to be. It needs to be below level as far as possible, so
this one flying wing can pitch the nose down to built airspeed, get the other wing flying, and
then you can center the stick and pull out. The only way to get it into that state is full down
elevator and roll input *into* the spin direction. No power is necessary at any time during X8
spin recovery, and will make the situation worse.

Just to be clear, the control inputs do not resemble a conventional aircraft spin recovery, at all.
It's not the intuitive thing to do either which means you have to think about what you're
doing, and get it right, or it *can* just spin all the way to the ground.

ian
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Last edited by Daemon; Nov 19, 2012 at 02:08 AM.
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Old Nov 19, 2012, 02:08 AM
Team Park Pilot - Airborne
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Australia, NSW, Sydney
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Ian - fully appreciate your X8 experience here and love your videos. mine is still in its box.

So I can explain this more Ian, A rudder has the SAME purpose if it used in a conventional 3 axis layout, a canard, or flying wing. a rudder as in - A vertically hinged plate that can be build of foam, metal, fiberglass, or wood mounted for effecting horizontal changes in course.

Rudder is a rudder mate.
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Old Nov 19, 2012, 02:10 AM
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And the X8 doesn't have a rudder. Period.
It doesn't have any vertical moving surface that acts as a rudder. Got it yet?
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Old Nov 19, 2012, 02:12 AM
Team Park Pilot - Airborne
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Australia, NSW, Sydney
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Quote:
Originally Posted by Daemon View Post
And the X8 doesn't have a rudder. Period.
It doesn't have any vertical moving surface that acts as a rudder. Got it yet?

I understand but... we were talking about " the effects of rudder used AS spoilerons ( rudder mix ) to recover from a spin buddy..
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Old Nov 19, 2012, 02:26 AM
What goes up, must come down
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United States, MI, Midland
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I'm not taking any sides BUT they are more "winglets" and because they are so close to the CG on a flying wing, the affectivly do nothing in a spin,, or to help recover,, even in level flight, the X8 will still "wing wag" because of the lack of rudder authority. but hey, they look cool!

Crazy1
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Old Nov 19, 2012, 02:27 AM
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Lakewood, Colorado
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Quote:
Originally Posted by G-Forced View Post
I understand but... we were talking about " the effects of rudder used AS spoilerons ( rudder mix ) to recover from a spin buddy..
It doesn't have spoilerons, or the function of spoilerons either. Spoilerons are
a combination of spoilers (a lift killing function + aileron function).
Again, a flying wing has Aileron function + elevator function, and they are combined
together into one control surface type called an Elevon. It's unique to flying wings
(planks, etc).

When a conventional plane spins, you center the ailerons, push down elevator and opposite
rudder (left rudder, for a right hand spin). The rudder is useful, because it's a large
control surface on the end of a long lever arm, that can provide a directional change
at airspeed below that which all the other flying surfaces are stalled.
A flying wing doesn't have any equivalent to the rudder function. It has no
yaw inducing capability.

When the X8 spins, you push full down elevator, and roll *into* the spin direction.
As explained above, this is because it's the only way to combine roll inputs
and pitch inputs together in a single elevon, to drop the elevon on the *one* flying
wing half on the outside of the spin (inside wing half is at center of spin with no airspeed)
in order to cause the front of the wing (and thus the whole plane) to pitch forward (nose down).
If you were to pretend that your roll function were equivalent to a "rudder" and
rudder against the spin, you'll find the elevon on the outside wing is at or above
center, and will pitch that wing up, keeping the spin going forever.

ian
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Last edited by Daemon; Nov 19, 2012 at 02:52 AM.
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Old Nov 19, 2012, 02:29 AM
Registered User
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Quote:
Originally Posted by crazy1pilot View Post
I'm not taking any sides BUT they are more "winglets" and because they are so close to the CG on a flying wing, the affectivly do nothing in a spin,, or to help recover,, even in level flight, the X8 will still "wing wag" because of the lack of rudder authority. but they look cool! 8)

Crazy1
Winglets are vertical stabilizers. They're not rudders. A rudder is a movable vertical
surface that can induce a yaw change, not just point the plane straight. The stock
X8 doesn't have em. People have built em with rudders, but it's very rare
and mostly useless unless you use em together as drag brakes.

ian
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Old Nov 19, 2012, 02:32 AM
What goes up, must come down
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United States, MI, Midland
Joined Sep 2009
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That's what I am saying,, because there is no movable control surface that can induce yaw, they are affectivly "verticle stabilizers" but because they are blended so beautifully with the wing,, they are pretty much winglets.

(by winglets I made the assumption they don't move)

Crazy1

Quote:
Originally Posted by Daemon View Post
Winglets are vertical stabilizers. They're not rudders. A rudder is a movable vertical
surface that can induce a yaw change, not just point the plane straight. The stock
X8 doesn't have em. People have built em with rudders, but it's very rare
and mostly useless unless you use em together as drag brakes.

ian
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