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Old Feb 19, 2014, 12:26 PM
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Scratch build Star Wars X-Wing EDF [Help Needed]

I've been working on a design for an EDF X-Wing from Star Wars. I currently have several 3D CAD models that I've put together in SolidWorks and am working on designing the balsa pieces.

After much searching on the internet I haven't found anyone who has made one that is truly scale and actually flies. I've seen a number of pusher prop designs but, I want to make a 4 EDF design with each fan fitting in the engine nacelles.

I also want to make the S-foils(wings) expand and collapse with a servo and am working through several thoughts on how to do that...
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Old Feb 19, 2014, 12:35 PM
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Well give us some specs you have come up with:

Length, WS, what sized EDF's and ESC's and batteries.

After that, where is the balance point?
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Old Feb 19, 2014, 12:38 PM
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Really cool project. I also want to see a Star Trek Enterprise ship with EDF for power.
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Old Feb 19, 2014, 12:49 PM
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Length:36 inches
Wingspan:33 inches (closed), 30 (open)
I'm looking at 50mm EDFx4 and using one of the (new?) Q Brain quadcopter 20 A ESCs. For the battery I have a 3s 4000mAh 40C battery from a different project.

I've made a foamboard and hot glue glider that I threw around my yard to figure out the CG and it was 1 inch back from the leading edge when it flew the best. Which is 28.5 inches back from the nose
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Old Feb 19, 2014, 01:12 PM
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Here's my best guess on what to do for expanding/collapsing the s-foils.

I'm thinking a grooved gear that posts from each wing spar will fit into. When you rotate the gear (not sure how yet) it should spread the wings apart. If designed properly it should keep both sets of s-foils synchronized.

My main reason for thinking about this system is that it'd keep the wings from torquing the servo directly so it should be less prone to breaking.
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Old Feb 19, 2014, 02:03 PM
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Quote:
I've made a foamboard and hot glue glider that I threw around my yard to figure out the CG and it was 1 inch back from the leading edge when it flew the best. Which is 28.5 inches back from the nose
Although I don't know what you exact components are-- ie, which fans, battery, I do know the weigh on the Q Brain quadcopter 20 A ESCs. (112g)

I used 4- Changesun 50mm EDF 11 blade w/ motors, ( 130g) and a Nano Tech 4000 mAh-- 3s.(335g) Total weight around 33 oz.

So how do you figure the balancing when adding the components??
And where for each?

Pretty hard to mount them all on the CG. I think this where most have ran into the problems on the CG/balance .
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Old Feb 19, 2014, 06:44 PM
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Right now my Solidworks model is slightly aft CG of where it needs to be (about an inch) without the engine pods, canopy, nose cone, or lasers. Since I don't know what I'm going to make those out of yet I don't know how much they'll weigh so I don't know how they'll affect the CG.

I was thinking of mounting the battery up in the top of the fuselage in an oversize tray so I can move it around until I find the best place for it. It'll probably be slightly aft of the CG.

The EDF units I'm thinking will be right on the CG.

The electronics (minus servos) will be right below the canopy to counteract the battery.

As for calculations on all of this...
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Old Feb 19, 2014, 08:02 PM
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Wow nice project I wish you the best luck! I thought about this same project once but I just don't have the computer skills it would take.

Sub'd for sure!
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Old Feb 20, 2014, 01:13 AM
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Very cool project! I'll be watching this unfold
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Old Feb 20, 2014, 01:46 AM
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Malaysia, Selangor, Kajang
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With that much side area and zero vertical stabilizer you'll have issues with yaw stability. It will fly as long as you don't turn. Which means that it will take off and climb just fine but the first time you touch the ailerons you'll completely lose control of it. This is what happens to planes with lots of side area in front of the CG but not enough behind the CG:
A strange RC model crashes at Tokoroa airfield (1 min 47 sec)


I once considered an X-wing completely impossible to fly due to this but someone on the scratchbuilt foamy forum managed to build and fly an X-wing like plane. His secret: the CG is about 2 inches in front of the leading edge.

With the CG in front of the wing that makes the wing act as two very large V tails joined together giving the aircraft yaw stability. Of course this makes the plane extremely nose heavy but you know the saying about nose heaviness. If you make the bottom of the plane flat then you can have the fuse provide a little lift so that the plane acts like it has very-very small canards. Canards have CG exactly where it should be for this plane - in front of the leading edge of the main wings.

Oh, and don't close the X-wing. If you do it reduces the side area behind the CG and you lose yaw stability.
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Old Feb 20, 2014, 11:06 AM
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Quote:
Originally Posted by slebetman View Post
With that much side area and zero vertical stabilizer you'll have issues with yaw stability. It will fly as long as you don't turn. Which means that it will take off and climb just fine but the first time you touch the ailerons you'll completely lose control of it. This is what happens to planes with lots of side area in front of the CG but not enough behind the CG: http://www.youtube.com/watch?v=5H8IBfQbkus

I once considered an X-wing completely impossible to fly due to this but someone on the scratchbuilt foamy forum managed to build and fly an X-wing like plane. His secret: the CG is about 2 inches in front of the leading edge.

With the CG in front of the wing that makes the wing act as two very large V tails joined together giving the aircraft yaw stability. Of course this makes the plane extremely nose heavy but you know the saying about nose heaviness. If you make the bottom of the plane flat then you can have the fuse provide a little lift so that the plane acts like it has very-very small canards. Canards have CG exactly where it should be for this plane - in front of the leading edge of the main wings.

Oh, and don't close the X-wing. If you do it reduces the side area behind the CG and you lose yaw stability.
I am currently thinking of using split elevons (duckerons) for the control surfaces. So it will have yaw control if not yaw stabilization...

Along those lines, what is a good way to get a stabilization module to work with a heavily mixed control scheme? I'm worried that if I use a unit that doesn't talk back to my Tx it won't be able to send a properly mixed control signal. For the record I've got a Futaba 14sg Tx.

I am also considering using a quadcopter control board for the EDF control and giving that a rudder and elevator input to get 2 axis differential thrust as a supplemental control method. If I used a board with stability control would that be of much benefit in this situation?
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Old Feb 20, 2014, 04:11 PM
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Quote:
Originally Posted by KZROL88 View Post
I am currently thinking of using split elevons (duckerons) for the control surfaces. So it will have yaw control if not yaw stabilization...
Duckerons work quite well for yaw stability. Especially if you have the ability to open both at once to get an auto-stabilize feature (maybe configured to a 3 position switch like flaps?).

Check out this completely tailless plank:

http://www.rcgroups.com/forums/showt...8#post22132667

I believe his CG is roughly where you're planning to have yours. But you still have significantly more forward area than his plane. On the other hand, you have two sets of wings. So that may tip the scales back in your favor.

I guess the best way to test the CG is to build a smaller model as a chuck glider and use a lump of clay to shift the CG around until you get it to fly. I've tried that myself several years back but never managed to get my X wing to glide without entering a flat spin at the end of the glide. But that was before I saw the nose heavy X-wing build that worked.

Quote:
Originally Posted by KZROL88 View Post
Along those lines, what is a good way to get a stabilization module to work with a heavily mixed control scheme? I'm worried that if I use a unit that doesn't talk back to my Tx it won't be able to send a properly mixed control signal. For the record I've got a Futaba 14sg Tx.

I am also considering using a quadcopter control board for the EDF control and giving that a rudder and elevator input to get 2 axis differential thrust as a supplemental control method. If I used a board with stability control would that be of much benefit in this situation?
I've never used a flight control board myself so I can't really say. I guess the multirotor guys have the most experience with them. The open source multirotor boards like the multiwii are also extremely configurable. I've seen people program them to fly everything from fixed wing airplanes to VTOL planes complete with transition. Though I believe the VTOL project used a modified firmware with custom software changes.
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Old Feb 21, 2014, 06:49 AM
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Interesting project!
Keep us posted.
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Old Feb 22, 2014, 12:16 PM
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Yep! Very interesting, subscribed!
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Old Feb 24, 2014, 02:34 PM
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Here's the flight control on the prototype:


X-Wing Flight Controls (0 min 28 sec)


My EDFs arrived late last week so I decided to slap them on my foamy prototype and give it a go.

Saying that the "flight" was disappointing would be a gross understatement. Immediately upon release it nosed up and almost turned completely around and fell tail first.
Tried again...same result.

Tried releasing it from a moving 4-wheeler...this time it just rammed straight into the ground.

I can think of several reasons for this behavior.

1. All of the added weight was at or above the line of thrust (and it was a significant amount of weight added)
2. To attach the EDFs I boxed the interior of the wings in which probably had a huge impact on the lift of the wings and added a lot of drag.
3. I didn't try gliding it with the added weight so I have no idea if it might have flown at all.

And here's one of the failed attempts at flying:

X-Wing flight fail (0 min 12 sec)
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