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  1. 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…
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