Downen Scaled Replicas

The panel line wash worked well to highlight the control surfaces and the panel lines on the top and bottom of the fuselage. 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. If you look down the inlet and exhaust nozzle you can just see the engine fan and mixer peeking out! 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. When completed, the model is 17.5 inches wingtip to wingtip! 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 Thanks for tuning in. This has been a fun and rewarding build. I wish that I would have done this years ago!

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. 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. 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.

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

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.

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...

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. 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. 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: 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. 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: 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. 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. 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. The engine mixer inserts into the exhaust duct snugly. The engine fan face is next. Just a few drops of thin CA glue fix those parts in place. 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. 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… The wings are joined, everything is primed, and finally it’s starting to look like a Darkstar! Adding some color (such as it is) will be the next step…

Thank you! I appreciate it. This was an enjoyable build.

Wings and fuselage are both decaled and ready for flight! The decals perform okay overall. They’re thick enough to withstand some rough handling during application, but not so thick that they don’t settle down well around details and in panel lines. My process includes using Micro Sol and Set, plus Solvaset in stubborn areas. This kit is such a monster (33 inches from wingtip to wingtip!) that it was best for me to pose it in flight. I did not plan to design and print new wings, but it quickly became obvious that the kit wings with their built-in droop just would not work for me. So, I really like the effect given by the new in-flight wings which are now available for other modelers who might like to pose their Global Hawk in flight as well: www.DownenScaledReplicas.com A complete video of this build is also available on YouTube: https://youtu.be/_apXWqjZIeg The 1/48 Global Hawk posed next to my 1/48 scale Lockheed RQ-3 Darkstar. This is an original design and is currently also available at the website: www.DownenScaledReplicas.com The Global Hawk kit is not a bad build. Overall the fit is good (be prepared to work on those seams, though) and the decal performance is average. I probably spent about 30 hours on the build itself, plus the time it took to design and build prototypes of the new wings which I had not originally planned to do. Happy modeling everyone.

Thanks dnl42 and CaptainObvious! I do really like the look so far. Some white on the upper surfaces of the wings and gunship gray on the bottoms. I wasn’t sure just where the white and gray intersected on the wings, but several photos I was looking at seemed to indicate that the white might wrap under the leading edge of the wing. It also made things easier to mask while painting! It’s hard to see in the previous photo the different shading that I did on the fuselage parts which are composite. I ended up masking and painting those parts straight dark gray, then coming back with a very thin / highly diluted overspray of the gunship gray to blend things together. Overall I’m happy with the look, but a few clearcoats and decals will really serve to tell if the effect works.

Back on the Global Hawk after taking a short break. The fit of the V-tails is not as positive as one might prefer; they can be installed at different angles so I held them against the grid on my cutting mat to ensure that I got both tails at the same angle. The base of the tails could use some work to blend them in. Lots of interesting details on the top and side of the engine nacelle. I had to replace one of the antennas with a styrene disk because I sanded off the molded detail. I cut a styrene rod to replace the nose gear bay doors; the kit parts were not going to fit well in the closed position. All primed up and ready to go with the new wings. And back to those wings. I made a few design tweaks to the original set and printed a new set which will actually go on the model. They are printed in three parts per side (six parts for a total wing set). When fresh from the printer they look like this (this is the left hand side wing only): I will make these available very shortly via my website (www.DownenScaledReplicas.com), and when ordered the wings will already have the supports “rough trimmed”, so they’ll look like this: You can see the support stubs still visible on the trailing edge of the wing parts and a few on the main gear bay fairing. All of these stubs are easily trimmed with a pair of sprue cutters, a hobby knife and/or sandpaper. The resin material is very easy to work with, so I recommend 400 grit sandpaper; anything rougher than that and you might find that you’ve gone through more material than you realize. After about 10 minutes or so of cleaning up the support stubs, you’ll have a root wing section, mid section and outboard section that fit together with tab/slot joints. I’ve also designed-in a channel for a 1/16 inch diameter brass rod to help stabilize the wing over time and ensure that it does not droop (although I don’t believe there is much risk of that anyway). You can see the brass rod and trimmed parts in this photo: The brass rod is 5-1/2 inches in length and spans from the inboard to the outboard section. The wing root has been designed to match the kit’s root airfoil, and will slide right into the fuselage slot without any modifications to the kit (and this means that the wings will be removable for transportation): When assembled, the kit wingspan is approximately 33 inches. WOW! (Camera perspective makes it look longer, but when measured it is 33 inches.) Now everything is primed and ready for color. I’m going to do the traditional overall gunship gray with white upper wing surfaces. Hopefully I’ll have that soon.

Yes, the paints are lacquers. They flow very well and give a great, tough surface for sanding, decals, etc. I use Mr. Color and like them as well. Lacquers are my preferred paint if I can get hold of them to use. It's becoming more and more difficult to get them in the States.

Some really cool progress to report today. First, I’ve mentioned that I’m not happy with the kit wings due to the droop and because I’m planning to pose the Global Hawk in flight. So, I modeled some new “flight” wings showing the 4-foot flex at the wingtip (full scale) designed into the wings for cruise flight. I printed them overnight and here are the first pictures. Top (planform) view (dark gray is the new 3D printed wing, light gray is kit wing): The white lines show where the parts join; I had to print them in three parts due to the size limit of the 3D printer. BTW, these are SLA-printed, so the print lines are minimal and barely noticeable to the naked eye (the camera always over-emphasizes them). The camera angle in the photo also makes the new wings appear to be longer than the kit wings. This is not the case. Bottom view showing the main gear bay fairing and gear door outline. With these new wings, Droopy McCool has now become Joe Cool… (LOL): These are designed to be plug-and-play with the kit (no modifications required), and can be removed when transporting the model. I am super-happy with the new wings, but I have a few tweaks to make to the design based on this prototype, then the wing set will be available for purchase at DownenScaledReplicas.com. One more bit I accomplished this weekend was to paint the engine inlet and nozzle and get those parts installed so that I can close up the fuselage. I used the MCW paints and I’m really impressed with how well these airbrush. They are easy to apply (no thinning required) and go on with a smooth finish that will be perfect for decals when I get to that point. I can’t wait to put these on the entire model; they are going to look GREAT!

Paints have arrived! This will be my first time using the MCW brand of paints so I’m anxious to get started with them. On the far left are the two colors for the Global Hawk: Gunship Gray and White. The remainder of the paints are for upcoming UAV projects. I’ve been working the wings with a heat gun and there is some improvement, but I’m not overly happy with the result. It was suggested that the wings be made removable for transport. I like that idea AND it will give me the option of replacing them later if opportunity arises (more on that in a minute). Meanwhile, you can see in the picture how the wings are “trapped” between the lower and upper fuselage parts via four pins that fit into the wing roots. I have cut slots into the wing roots so that the wings can slide in and out of the fuselage. Because I’m not happy with the wing droop on the Global Hawk, and because I really want to pose it in flight with the wings flexed up, I’m considering designing and 3D printing replacement wings for the kit. I’m starting to work with a 3D SLA printer which can print fine details in high resolution. I’ve designed a companion for the Global Hawk, a 1/48 scale Lockheed DarkStar, and now I’m starting to think that I might need to print a few things for the Global Hawk as well. Flight wings, perhaps an engine for a maintenance diorama… I’ll see. Visit the Downen Scaled Replicas website or Facebook page if you want to see more about the DarkStar. Meanwhile, I need to start sanding on the Global Hawk… Thanks for watching. More soon...

Hey dnl42 and skyhawk174, thanks for the alerts on the main gear wheels. I'll do this one gear up, hence the preoccupation with the wing droop. I'll take a look at those wing walk decals... mirror image text, eh? Great! I worked a bit last night on the wing droop. I anchored the wings to a slightly curved surface (curved them up) and hit them (gently) with a heat gun. SOME improvement from that effort. I also worked inside the fuselage to ensure that the wing root attach point did not permit any droop. I actually gave them just a teensy bit of dihedral. Together, both of those efforts appear to have given me wings that are level. I agree that a spar of some sort - even just a brass rod - would not be a bad idea. These wings are light, so it does not have to be very beefy.

Droopy McCool... LOL