Lakeroadster's X-Wing Alpha Build Thread

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I modeled the X-Wing Alpha on Open Rocket today. It's my first attempt at using Open Rocket. Seems like an awesome program.

I added a bit of weight to the bottom of the nose cone for stability.. and I haven't added the cockpit... and not sure how to add the tube fins on the tips of the x-wings.

I've attached the .ork file, anybody care to take a look and share their thoughts?

Thanks!

In OR you can put tubefins on regular fins with a "phantom body tube"- a zero mass, zero thickness tube with the diameter of the fins. You then put your tubefins on that. The sims don't like it, and it sometimes messes up the zoom, but it looks decent.
 
Your PM caught me in the few minutes between eyes open, and out the door to work. It'll be 12 hours minimum before I can start to collaborate with you. However, it looks like you've got a good grasp on the beginnings of the project.

A quick idea on how to visually (not flight performance wise) sim the tubes on the wingtips. Use internal body tubes that have been offset to the correct place. For more on that, download any of my payload rockets with larger diameter forward body tubes, and look at how I moved the launch lugs out to the ends of the standoffs. The Estes Omega would be a contender for that kind of reverse engineering.

The standard OR release (15.03) currently doesn't support pods. And they're still working on the update that does.

HTH
Jim
 
Thanks fella's.

Open Rocket Model Accuracy

If adding the wing tip mounted tubes to the open rocket simulations doesn't do anything but make it visually more accurate I'll just leave them off. My goal with the simulation is more for a performance evaluation, not so much visual accuracy.

Chute Deployment

It appears the 5 second delay of the D12-5 ejects the parachute when the rocket is at a pretty slow velocity.

Is right after apogee ideal or do some folks want the rocket to fall closer to the ground? Seems like the shock cord could damage the body tube in that scenario?


Your PM caught me in the few minutes between eyes open, and out the door to work. It'll be 12 hours minimum before I can start to collaborate with you. However, it looks like you've got a good grasp on the beginnings of the project.......
Jim

Thanks for the reply.

I added the cockpit, launch lug and let the program optimize the ballast for the x-wing. Seems to be more stable now.

I await your input. :handshake:

Open Rocket 3D Model.jpg

View attachment X-Wing Alpha.ork

Open Rocket X-Wing Simulation.jpg
 
+ or - 1 second of apogee is considered to be the maxium amount early or late of apogee you want otherwise the rocket may be travelling to fast and the airframe be zippered by the shockcord.
 
You folks that have used Open Rocket.. you pretty comfortable with the actual in-field comparisons of simulations vs actual flights?

I dropped the vertical stabilizers, optimized the ballast and the rocket is still stable. maybe because of the faux engine pods that act as tube fins?

Thanks in advance.

Open Rocket 3D Model No Vert Stabilizers.jpg

Open Rocket X-Wing Simulation No Vert Stabilizers.jpg

View attachment X-Wing Alpha No Rudder.ork
 
You folks that have used Open Rocket.. you pretty comfortable with the actual in-field comparisons of simulations vs actual flights?

I dropped the vertical stabilizers, optimized the ballast and the rocket is still stable. maybe because of the faux engine pods that act as tube fins?

Thanks in advance.
Actually the X configuration fins are surprisingly stable, the Binder Dragonfly is a kit that uses a similar fin config and they fly beautifully. Dan Feller even built a 12" upscale of the D-fly, its something to see.
 
BMS directed the local mail lady to deliver the X-Wing Alpha hardware yesterday....:clap:

Super impressed with the packaging job by BMS. They used 2 priority mail boxes, the second box was empty.. simply taped back to back with the other box to provide for strength / durability.

Nicely done.

001.JPG

002.JPG
 
Actually the X configuration fins are surprisingly stable, the Binder Dragonfly is a kit that uses a similar fin config and they fly beautifully. Dan Feller even built a 12" upscale of the D-fly, its something to see.


Yeah... but, then there's this flight...

[video=youtube;ogYrvEEM0Ts]https://www.youtube.com/watch?v=ogYrvEEM0Ts[/video]
 
What's the delta between the CG and cp locations? It looks close you might want to plan for some extra margin, if you wind up tail heavy it may put your lateral stability at risk, just because the sim doesn't tumble you may be marginal in some wind. It's fairly short and you'll have glue down on all those fiddly bits at the rear. You may consider doing a boilerplate with the verticals and then trimming down to confirm you are good.
 
You folks that have used Open Rocket.. you pretty comfortable with the actual in-field comparisons of simulations vs actual flights?

Open Rocket is very accurate at sub-sonic speeds, but it does assume perfect construction outcomes.
That rarely applies in the real world (at least not to me), so expect your paint to be less than perfectly smooth, the fins to be less than perfectly aligned and airfoiled, and additional drag from less than perfect glue joints and fillets. Than there is the ~10% thrust variance from the commercial motors....

I get 10-15% lower flight altitudes in real life vs. simulated, with most flights.

I dropped the vertical stabilizers, optimized the ballast and the rocket is still stable. maybe because of the faux engine pods that act as tube fins?.

That absolutely does help. You are WAY over-winged with this model.
If you want even larger stability margin, move the fins further back, in-line with the tail end of the motor mount, and you should pickup another 0.25 of a caliber.

Also, your launch rod is configured to be 39.37" in length for the simulation. That's short-to-average rod size.
If yours is longer (if not, get a longer rod from Home Depot), that will instantly give you higher off-rod sped and stability margins!

a
 
Yeah... but, then there's this flight...

Wow.. looks like they used Velcro to hold it together until launch :surprised:

What's the delta between the CG and cp locations? It looks close you might want to plan for some extra margin, if you wind up tail heavy it may put your lateral stability at risk, just because the sim doesn't tumble you may be marginal in some wind. It's fairly short and you'll have glue down on all those fiddly bits at the rear. You may consider doing a boilerplate with the verticals and then trimming down to confirm you are good.

It was much closer until I added ballast in the nose. I like the looks of the vertical stabilizers.. adds to the WWII paint theme. Good idea about leaving them and then trimming them down later after a few flights. Thanks.

Open Rocket is very accurate at sub-sonic speeds, but it does assume perfect construction outcomes.
That rarely applies in the real world (at least not to me), so expect your paint to be less than perfectly smooth, the fins to be less than perfectly aligned and airfoiled, and additional drag from less than perfect glue joints and fillets. Than there is the ~10% thrust variance from the commercial motors....

I get 10-15% lower flight altitudes in real life vs. simulated, with most flights.



That absolutely does help. You are WAY over-winged with this model.
If you want even larger stability margin, move the fins further back, in-line with the tail end of the motor mount, and you should pickup another 0.25 of a caliber.

Also, your launch rod is configured to be 39.37" in length for the simulation. That's short-to-average rod size.
If yours is longer (if not, get a longer rod from Home Depot), that will instantly give you higher off-rod sped and stability margins!

a

Thanks for the tutelage, much appreciated. :handshake:
 
Yeah... but, then there's this flight...

[video=youtube;ogYrvEEM0Ts]https://www.youtube.com/watch?v=ogYrvEEM0Ts[/video]

Wow.. looks like they used Velcro to hold it together until launch :surprised:

Oh... I found the un-retouched version of the launch...

[video=youtube;BDk_W5boWts]https://www.youtube.com/watch?v=BDk_W5boWts[/video]
 
You could also consider clear polycarbonate fins as well and trim them down, and leave them clear or cover them if you like the look.
 
A quick idea on how to visually (not flight performance wise) sim the tubes on the wingtips. Use internal body tubes that have been offset to the correct place. For more on that, download any of my payload rockets with larger diameter forward body tubes, and look at how I moved the launch lugs out to the ends of the standoffs. The Estes Omega would be a contender for that kind of reverse engineering.

The standard OR release (15.03) currently doesn't support pods. And they're still working on the update that does.

HTH
Jim

I tried and was successful at adding the wingtip tubes... Thanks.

Also did some more fine tuning in Open Rocket, .ork file attached. I was surprised that simply changing the fins from square to round yielded an additional 300 feet of altitude.

Open Rocket 3D Model.jpg

Open Rocket 3D Model Rear.jpg

View attachment X-Wing Alpha - Vert Stabilizers - Chute.ork

Open Rocket X-Wing Simulation.jpg
 
lakeroadster: This thread reminded me of an X-Wing I was building some time ago (not on a far far away galaxy...) I was also inspired by the same Centuri Rocket Times X-Wing Fighter Design. I only used the cockpit template to do mine and customized the rest of the rocket to look "sorta like" the ones in the movies. I also used an Alpha III Nose cone but I customized it also... here is what I did. Yours is looking very good. Love the CAD sheets. Thanks for sharing.

R-R

R_R X-Wing NC.jpg
 
lakeroadster: This thread reminded me of an X-Wing I was building some time ago (not on a far far away galaxy...) I was also inspired by the same Centuri Rocket Times X-Wing Fighter Design. I only used the cockpit template to do mine and customized the rest of the rocket to look "sorta like" the ones in the movies. I also used an Alpha III Nose cone but I customized it also... here is what I did. Yours is looking very good. Love the CAD sheets. Thanks for sharing.

R-R

Sweet. Any photos of the rocket?

I added the weapons to the weapons tubes in OpenRocket... really love that program!

Open Rocket 3D Model Rear.jpg

Open Rocket 3D Model.jpg
 
.... So, how did you finally get the weapons positioned?

I followed the advice of a guy I know by the name of Jim...

A quick idea on how to visually (not flight performance wise) sim the tubes on the wingtips. Use internal body tubes that have been offset to the correct place.

Jim

Basically they consist of concentric internal tubes, located via offsets.

And they did affect the flight sim's... lost about 20 feet in apogee.

Thanks again Jim
 
Only due to their weight. They are not accounted for in terms of drag and CP.

They affected the stability.. had to add a bit more weight to the nose. So isn't that related to CP?

In regard to drag... I may make the weapons removable and fly the X-Wing with just open weapons tubes.... unless I spot undesirables in the area ;-)
 
They affected the stability.. had to add a bit more weight to the nose. So isn't that related to CP?

In regard to drag... I may make the weapons removable and fly the X-Wing with just open weapons tubes.... unless I spot undesirables in the area ;-)
They brought the CG further aft, closer to the CP thus diminishing the stability margin.
 
Actually the X configuration fins are surprisingly stable, the Binder Dragonfly is a kit that uses a similar fin config and they fly beautifully. Dan Feller even built a 12" upscale of the D-fly, its something to see.

Thanks for the plug, Rich!

Our Dragonfly is very stable, it actually starts to backslide at apogee. We get almost zero rotation as well, which makes for a great camera platform.

Our fins are in a 60/120 degree spacing, yours look to be a bit closer/farther spaced. One nice thing about the X-Wing design is that it allows the Dragonfly to fit through a 30"door, even with our 60" span.

In case you want to see the rocket:

https://youtu.be/ygMil4CAt34

More onboard video from a different launch:

https://youtu.be/HCuR_UPI9KI
 
Thanks to everyone for their comments, advice and links. Great group of folks here.

Only due to their weight. They are not accounted for in terms of drag and CP.

Neil's right with this one... Internal tubes are not factored into the computation of drag (and presumably CP).

So in an attempt to get Open Rocket to evaluate the wingtip mounted tubes during flight I modified the model by adding a large body tube equal in diameter to the wingspan, then added the tubes as tube fins.

It looked great, see below, but resulted in a crash and burn unstable design.. even with the large body tube having no thickness, and no length.

I'm assuming it's the big body tube (that's not really even there) that's throwing off the program and not that the rocket will indeed be unstable?

When I "Assume" things they often get out of hand ..... well, let's let Benny explain it.. https://www.youtube.com/watch?v=R6jaKkE0RsI

Open Rocket 3D Model Alternate Weapons Pod.jpg

View attachment X-Wing Alpha - Vert Stabilizers - Chute - Alternate Weapons Pods.ork
 
So in an attempt to get Open Rocket to evaluate the wingtip mounted tubes during flight I modified the model by adding a large body tube equal in diameter to the wingspan, then added the tubes as tube fins.

It looked great, see below, but resulted in a crash and burn unstable design.. even with the large body tube having no thickness, and no length.

I'm assuming it's the big body tube (that's not really even there) that's throwing off the program and not that the rocket will indeed be unstable?

Looks fine to me... What does OR say? Check the CG/CP spacing in inches- if it says something like 0.2 cal, it may just be confused by the large "diameter".
 
Thanks for the reply.

Looks fine to me... What does OR say? Check the CG/CP spacing in inches- if it says something like 0.2 cal, it may just be confused by the large "diameter".

Stability: 0.369 cal
CG: 5.289 in
CP: 8.217 in
Check out the accelerations and velocities below.... looks like a wild ride for only 7.25 seconds. :fly:

Open Rocket X-Wing Simulation Alternate Weapons Pods.jpg
 
OR considers the diameter to be some 7+ inches, because it considers the phantom body tube you have there to be a real one. And so, you can see you have 3" between CG and CP, which should be fine. The flight simulation result is likely nonsense. Phantom body tubes are good for visualization but wreck simulations.

Oftentimes for complex designs you need to change the design to something "equivalent" to get a decent sim. For some designs I maintain two ORK files, one for visualization and part specification, and the other for simulation. For your X wing, the first thing to do would be to move the pods to the main body tube and delete the 7" phantom tube. Your stability jumps to 2.98 and it now shows 700 ft on a D12-5. Is that accurate? Certainly not perfect, but it should be in the right ballpark at least.
 
Sorry I forgot to mention the problems with PBT's better. I've been pulling some long shifts (12 hour days), and doing report cards (on one occasion until 1am), and I've just been shackled with two one on one students with vastly split class times on what used to be my time off. I'm a little tired.
 
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