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Downen Scaled Replicas

1/48 RQ-3 Lockheed Darkstar

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There are a number of UAVs that are not available as commercial kits that I would really like to build. The Lockheed RQ-3 Darkstar is among them.

 

48 Darkstar 01a

The Lockheed RQ-3 Darkstar was developed as part of DARPA’s High-Altitude Endurance Unmanned Aerial Vehicle (HAE UAV) program in the 1990s. This Advanced Concept Technology Demonstration (ACTD) program was intended as a means for the rapid, cost-effective demonstration of new capabilities and systems for the military services.

 

Two air vehicles were developed for HAE UAV: a conventional configuration (Tier II+) designed by Northrop Grumman (RQ-4 Global Hawk) and a low-observables configuration (Tier III-) designed by Lockheed which was designated as the RQ-3 Darkstar.

 

The RQ-3 incorporated stealth aircraft technology to make it difficult to detect, which allowed it to operate within heavily defended airspace, unlike the RQ-4 Global Hawk, which is unable to operate except under conditions of air supremacy. The Darkstar was fully autonomous: it could take off, fly to its target, operate its sensors, transmit information, return and land without human intervention.

Darkstar system development efforts began in 1994 with first prototype flight in 1996. Four units were built prior to program termination in January 1999. The first prototype crashed on its second flight in 1996; the remaining three airframes are displayed in museums in the United States.

 

Enough background: let’s build!

 

I designed my own Darkstar using the Fusion360 CAD program and printed it in 1/48 scale on a stereolithography printer. The resin material is firm but easy to work with (cut, sand, etc.) and requires the use of CA (“super”) glue or epoxy glue.

 

48 Darkstar 02

 

The vehicle is printed in the following seven parts:

 

  • Fuselage upper and lower halves with complete inlet duct (no nasty seams to clean up) and mounting hole designed into the lower fuselage to accept a 5/32 inch diameter rod.
  • A separate exhaust nozzle duct; the seam will be difficult to see and the separate part makes painting the inside of the duct easier
  • The Williams FJ44 engine is represented with a fan (correct number of blades for those blade-counters among us) and exhaust mixer
  • Right- and left-hand side wings

 

Straight out of the printer, this is what the parts look like with supports still attached:

 

48 Darkstar 01

 

The wing design correctly represents the wing dihedral as well as the 2-degree wing incidence and resulting trailing edge “joggle” at the wing root. The unusual symmetric wing airfoil and wing tip blend are also represented and are accurately designed based on publicly-available technical information.
 

48 Darkstar 17

 

Access panels and gear bay doors are represented with finely engraved lines. No landing gear have been designed and I have not designed decals since photos indicate few markings (a few photos show “USAF” on the upper fuselage which most of us will have in our spares box).

 

I’ll make copies of the unbuilt kit available to anyone who may have an interest (www.DownenScaledReplicas.com).

 

I don’t expect everyone to clean up all of those supports on the raw parts straight out of the printer, so I’ll do a rough trim first and the parts will look like this when made available:

 

48 Darkstar 18

 

There are a number of support stubs remaining on the parts. The resin material is very easy to work with and those stubs can be cleaned up with sprue cutters, a hobby knife and/or sandpaper. I would recommend 400 grit sandpaper or finer since this resin is easily removed and you may find yourself removing more material than intended if you use rougher grits.

 

Most supports have been placed in areas where they won’t be seen or where they can easily be removed with a sanding stick. Probably one of the trickier spots is inside the exhaust duct, but a smaller sanding stick can get those stubs without too much trouble.
 

48 Darkstar 03

 

In about 30 minutes I have a set of parts that are ready for assembly. Note that not all support stubs need to be cleaned up since some are hidden inside the assembly.

 

48 Darkstar 19

 

48 Darkstar 02a

 

Part of the aft nozzle exhaust duct is separate, so I painted the inside black and then installed it in the upper fuselage half with some thin CA (“super”) glue. Note the “DOWN” text on the part which should still be visible when installed.

 

I do suggest painting the engine fan and mixer (aluminum or such), inlet duct (white or whatever your base color will be) and the exhaust nozzle (black, per photos) before you install them in the upper fuselage half.

 

48 Darkstar 20

 

The engine mixer inserts into the exhaust duct snugly.

 

48 Darkstar 04

 

The engine fan face is next. Just a few drops of thin CA glue fix those parts in place.

 

48 Darkstar 05

 

Here you see the lower fuselage half, which sits inside a recess in the upper fuselage. I’m not holding the parts together in this photo so the fit appears poor, but a gentle press will get the upper and lower halves fitting together well. Again, thin CA glue run around the perimeter will fix those parts together in no time. You can clearly see the 5/32-inch hole in the lower fuselage for mounting the UAV in-flight.

 

48 Darkstar 06

 

My next step will be to put some filler along the perimeter joint to help disguise it. Again, I’m using 400 grit wet/dry sandpaper to clean up joints; I might use 320 grit in just a few stubborn spots, but use it gently!

 

A bit of filler on the lower fuselage joint with the upper, and things are starting to look good…

 

48 Darkstar 21

 

The wings are joined, everything is primed, and finally it’s starting to look like a Darkstar!

 

48 Darkstar 22

 

 

Adding some color (such as it is) will be the next step…
 

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Very nice!!  Can you tell us how you did this in Fusion? I have not had a lot of success in doing curved streamlined shapes with it. 

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7 hours ago, Major Walt said:

Very nice!!  Can you tell us how you did this in Fusion? I have not had a lot of success in doing curved streamlined shapes with it. 

 

Major, I can say that I did this with a lot of difficulty and trial and error. LOL

 

Mostly lofts that follow rails. Clearly the wings are easiest: two airfoils (splines) that are lofted following leading edge and trailing edge rails. The fuselage is composed of four lofts (and I only draw the left hand side of the UAV - mirror to the right): upper front, upper aft, lower front and lower aft. All follow rails that define the upper and lower surface centerline contours (it's important to have side views of the UAV to follow) as well as a second rail that follows the plan view (top view) of the fuselage curve. Believe me, I spent HOURS experimenting until I found (stumbled across?) combinations that worked. But it really is just a series of lofts w/ rails...

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The result was worth the effort. What you have produced is indisputable from an injection molded kit.

 

I know very well the trial and error of 3D modeling. It is painful but rewarding at the same time. I’ve gone the hard route with Blender and have gotten good results but wish I’d started with Fusion 360 instead 😎

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3 hours ago, Major Walt said:

The result was worth the effort. What you have produced is indisputable from an injection molded kit.

 

I know very well the trial and error of 3D modeling. It is painful but rewarding at the same time. I’ve gone the hard route with Blender and have gotten good results but wish I’d started with Fusion 360 instead 😎

 

I gave Blender a shot but turned to Fusion360 after reading a number of positive reviews of the software package. It's free - for those who don't know - and I must say that I'm really happy that I decided to go with Fusion. My recommendation to everyone starting out with CAD: start with something easy to model so that you can learn the basics. I started with JATO bottles. Then go for something a bit more challenging: a wing, perhaps.

 

I appreciate the compliment, Major Walt.

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Wow ma'an!

 

Awesome build.  

I'd like to know what printer you used... the resolution is outstanding.

 

Keep up the great work, and thanks for sharing.

 

Ernie A.

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6 hours ago, modelmax said:

Wow ma'an!

 

Awesome build.  

I'd like to know what printer you used... the resolution is outstanding.

 

Keep up the great work, and thanks for sharing.

 

Ernie A.

 

Ernie, the printer is a FormLabs Form 2. It's stereolithography (SLA) which uses a laser to solidify a liquid resin polymer. I did a lot of research before purchasing the printer and so far I'm really happy with the results. --Troy

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I’m going to do a hypothetical operational scheme on this model using Light Ghost Grey, similar to what would be seen on a Predator or Reaper UAV. I’m using Model Car World’s military line of lacquer paints for the first time. I really like the way they airbrush easily and dry quickly. A bit later I’ll use a light gray enamel panel line wash from AMMO MiG.

 

48590793651_f01d180c22_b.jpg

 

I’ve used a black-basing technique for the paint scheme. I painted the entire model a dark gray (but oftentimes black will be used) and then gone back over the dark color with the top coat color (Light Ghost Gray) using a random squiggle movement to leave a patchy finish of lighter and darker areas all over the model. A final overall coat of thinned Light Ghost Gray helps to blend the patchy paint job. It helps to break up an otherwise monotone paint scheme with a bit of variety and interest. I also gave the model a really good coat of Alclad Gloss Kote in preparation for decals.

 

48590793776_1f885d81e6_b.jpg

 

I dug through my decal bin for spare markings that might work well for an operational scheme. Between a leftover 1/72 scale Predator sheet and a set of stars-and-bars from SuperScale, I think I can put something together.

 

48590937397_1b1b2e6809_b.jpg

 

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The panel line wash worked well to highlight the control surfaces and the panel lines on the top and bottom of the fuselage.

 

48 Darkstar 12

 

As I mentioned, I scrounged through my leftovers and found a set of USAF markings that I thought would work well for what a Darkstar might have looked like if it had been placed into service. Overall I’m very happy with the look of the completed model.

 

48 Darkstar 13

 

If you look down the inlet and exhaust nozzle you can just see the engine fan and mixer peeking out!

 

48 Darkstar 24

 

I’ve built two prototypes as I worked through tweaks to improve the build. The first build was painted with a white top / black bottom to resemble the test articles that I’ve seen in museums.

 

48 Darkstar 15

 

When completed, the model is 17.5 inches wingtip to wingtip!

 

48 Darkstar 14

 

And displayed next to my 1/48 scale Global Hawk from Skunk Models. I’ve designed new wings for the Global Hawk, which you view on the website (and also purchase Darkstar kits): https://downenscaledreplicas.com

 

48 Darkstar 16

 

Thanks for tuning in. This has been a fun and rewarding build. I wish that I would have done this years ago!

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