|Mar 10, 2014, 09:16 PM|
Red 5 X-Wing (1.5M quad EDF) build
A long time ago in a state far, far away....
At the age of five I sat on my uncle John's shoulders in the back of a crowded NJ movie theater and saw Star Wars for the first time.
Since then I've wanted an X-Wing.
Judging by the valiant and creative efforts of those RCGers before me and now (KZROL's fun current build included) this is a popular, and by no means easy, topic.
Here's the first thread I can find on an EDF X-Wing, from July 2002
Having put over 40 take-offs and landings (2 ended in cg-based crashes, 3 crashes were pure pilot error :/) on my Radjet-based prototype (super fun and pretty quick flyer) it's time to start construction of a bigger, better, whooshier X-Wing.
Some compromises vis-a-vis the "real" craft are assumed:
- no foldable X-wings. Sorry. A reliable system I can scratch built would be too heavy. And for the flight speeds I'm envisioning (~25-75mph) lift from 4 wings will be necessary.
- no VTOL so LG needs wheels
- Single worm-drive rear LG, since wing-tip wheels only like the prototype would require super-sturdy, super heavy lower wings for the inevitable hard landings.
- wings oversized ~25% to get a calculated WCL of around 12.5 (flying weight 4.5kg with 8-9000mAh of 4S batts).
- no lights. Not even in the R2 unit that'll be chopped off at the shoulders for an almost big enough scale copy
Many sketches and xcel spreadsheets have been done, all the parts are now on hand, and there for sure will be design changes as we go.
BTW One of these excellent 1:29 kits shipped in two weeks from the UK to Texas is great for mic-ing and copying panels and colors:
- four Dr. Mad Thrust 64mm EDF units from HK http://www.hobbyking.com/hobbyking/s...dProduct=21147
I've put 10 flights on a tester in my Stinger. Spits out >1kg thrust with a mostly depleted 4S 40C Zippy Compact 2200mAher. Sweet battery BTW. The fans are nicely balanced and protected by a strong and heavy aluminum shroud. Draw ~55A each at WOT and a fresh pack.
- four HK 60A ESCs http://www.hobbyking.com/hobbyking/s...dProduct=16892
Chunky but smooth throttle and cheap @$20ea
- two 4000mAh Zippy 4S 40-50C LiPos. Have cycled them 4 times so far in the custom 12x10 2-bladed, 820kV HK Donkeyed 1.5M FMS P-51 V6. Great combo.
So far so good, but I'm looking at the Nano-Tech Gold 65-130C 2200's... would buy 6 (X takes 4, with spares) and cycle them first through the Stinger.
8000mAh should give 4 minute flights with an average of 70% throttle usage.
- two sets of Parkzone Apprentice wings @$32 each local hobby shop
Nice since very little dihedral (top X wings would be further from the center line than lower wings by ~2" at tips) and 14mm carbon tube already installed. A tad thicker chord than I'd prefer, but not much.
- various carbon fiber tube and strips for wing and fuse reinforcement from rcfoam.com.
My experience with foamies shows they love a carbon skeleton.
- dual Orange receivers http://www.hobbyking.com/hobbyking/s...dProduct=31224
and extra satellites http://www.hobbyking.com/hobbyking/s...dProduct=46339
I've had great luck with the older versions of these. Use them in all my planes (Jpower P-38, FMS P-51, Dynam PBY, stinger etc) with zero issues.
- five 12g Turnigy MG servos http://www.hobbyking.com/hobbyking/s...dProduct=24763
- beefy retracts http://www.hobbyking.com/hobbyking/s...dProduct=28977
- rear wheel braking http://www.hobbyking.com/hobbyking/s...dProduct=34842
Rather than make the wings strong enough to take a hard landing (like the little X-Wing can) fitting a single large retract in the center, with mag brake for shorter strips. Lower wing tips will have thin sliders to keep her upright on the tarmac.
- closely scaled starfighter figure. May sit in the cockpit for flights.
Here are some pics and full video of an early "little" x-wing flight (landing is at 4:00) :
Now that she's dialed in I don't fly at high throttle so much.
*space reserved for additions/edits*
|Mar 10, 2014, 09:49 PM|
Probably one of the biggest monetary mistakes in George Lucas` career......not creating an X-wing fighter that was easily made aerodynamically viable. The Air Hog version would still be selling and they would have a sticker on the box saying "Billions and Billions Sold!"
But then we couldn`t have had all of the fun trying to make it work. Heck, even Capt Kirk`s Enterprise has been modeled and flown. Good luck with your X-wing!
|Mar 11, 2014, 07:45 PM|
that rad jet is awesome . good luck with the xwing build ,I am a big starwars fan but I am more of a Tie fighter fan , always loved to see and hear them wiz by the xwing
|Mar 12, 2014, 09:18 PM|
The video wasn't up when I chimed in with my first post. Your X-wing pusher flys great. Your scale version should also as long as the wings are spread to the X position. From what I read the problem comes with the lack of yaw stability when the wings are brought together.
One suggestion..... you can probably have plenty of power with just two fans. You might consider powering the lower tubes and leaving the uppers as dummies. Your thrust line would be more controllable when lower. Just a thought.
Good luck. This needs to be done for sure.
|Mar 12, 2014, 10:40 PM|
Hope to fly with you soon bud
Thx Lee and Sandman -
Dual 70mm EDFs may do it, mine would save ~1kg by losing 2 of the 64s but gains 2kg thrust with quads.
It will also be easy to program in differential thrust for a quasi-vectoring effect, but for the maiden at least planning on symmetrical thrust from all 4.
I may run opposite corner EDFs to their own RX so if one RX loses signal for whatever reason she'll still have 2 fans (and one set of wing servos) to bring her in.
After cutting out a few 4" fiber tube intakes from templates made by CAD Jedi and fellow Houstonite/RCGer Jim, I taped up some parts to get a feel for the size and shape of this thing.
Thrust tubes are rolled 8.5x11 0.015" clear plastic sheets, covered in a sheet of paper here but matte white paint and weathering stick well.
Round 12mm CF crossing in the middle is temporary; 2x12mm flat strips fit perfectly in the 14mm existing wing tubes, will extend one out to the wingtips in each and add 2x7mm strips about 4" back to lock all 4 wings together and act as a frame for 1/8" plywood rear fuse (fuse in front of the nose gear mount will be depron and carbon, with a carved foam nose piece).
Magnetic 2.5" rear wheel brake worked well on the bench when mixed with down elev. Pretty heavy though so the front wheel will be a 2.5" foam one that's still in the mail.
Next job is to cut and fab 1/8" plywood cradles for the fan shrouds then get to work modding the wings' shape.
I like it
|Mar 17, 2014, 12:22 AM|
Cut the plywood EDF mounts today, just need to visit the local hobby shop to get some hardware to fit a metal strap over the top then they can go in the wings. Will be careful to align.
Making up a hot-wire foam cutter to do the nose, then will fiber-glass it.
Still on target for ~4.25kgs flying weight. Landing gear contribute ~350g.
There will be pauses in construction for the months of April and July when I'm overseas, but the plan is to finish and test fly before the big electric event in September.
|Mar 19, 2014, 11:14 PM|
how would yall enlarge the wing?
Needs to be about 4" longer at near the root, 0" at the new tip ~3" shorter than stock.
Big elevons will run most of the way.
I'm thinking new carbon spars, thin depron coverings, 3" wide balsa 'vons. But haven't decided how to make the surface finish consistent with EPO.
Now done with all 4 power units. Aluminum straps work well, will beef up the blind nutted cross members for safety.
|Mar 21, 2014, 08:55 PM|
still ruminating on the wings so might as well work on something else...
1st shot at the nose with a home made hot wire cutter and a bit of sanding.
Will make a spare but the first will be close enough to glass and go with.
|Mar 30, 2014, 10:03 AM|
Last update for a little while. Glassed the nose and trimmed the wings.
Still haven't decided if using 4x2200mAh or 2x4000-44000mAh batteries.
|Mar 31, 2014, 12:26 PM|
Shaping up nicely. But you really do need some intake lips for those fans.
Check this out: http://www.velocity-rc.com/cgi-bin/v...d=2&cid=&idx=1
Granted he uses a 70mm to show this, but it applies to all fans.
|Apr 01, 2014, 09:44 AM|
You can see in post #8 that the shrouds do have a decent lip built-in, but I do want to consider the intake area in front of this. The least I can do is try to minimize disturbances i.e. turbulence. The "splitters" ~4" in front of the EDF will introduce
some, but they're quite thin and by tapering the leading and trailing edges it shouldn't be that much. They should also act somewhat as flow "straighteners".
In the second pic of post #6 you can see how the wing more or less blocks the lower half of the 4" outer shrouds (or the upper half for the lower 2 EDFs), and there are gaps on either side of the 64mm shroud.
I read somewhere else that it's actually better for E-Flux speed (and to a lesser extent, thrust) to have a slight negative pressure in front of the EDF. i.e. a smaller area than the full EDF diameter 64mm. I think this is what's being represented in the last diagram in your link.
Any advice or input is appreciated, thanks!
|Apr 01, 2014, 10:47 AM|
Although the shrouds do have a decent lip built-in, does little inside the "pod". It's the L.E. of them that's going to be the issue. If you have ever read testing results done on various fans, with and with-out intake rings, a sizeable difference in thrust. I've read anywhere from 10% to 20% loss.
http://www.rcgroups.com/forums/showp...87&postcount=9 Just came across this!
Some suggest a symetrical lip on the ring, in the link I believe he liked a 2:1 elipse.
As for the "splitters" , there has been some conversation as of late, about wing tubes in front on the fan, and there effect. Different, but simiar.
Good luck .
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