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About ShadowShadow was my first low-wing design. I wanted to build a real speed demon, so to minimize drag I designed the fuselage to fit tightly around the flight pack and fuel tank. I had a friend at the time who was attending the University of Florida Aerospace program who helped me select an appropriate airfoil. I was a capable pilot at the time, but if this plane were to fly as fast as I wanted it to then there was a good possibility it would be pushing the limits of my skills. For that reason I wanted the plane to be able to fly relatively slowly so that I could bring the throttle back if things got too hairy. My concern there was that it might snap over due to the airfoil and leading edge shape. I also kept the weight down as much as possible. As it turned out, the airfoil was not a good choice for the type airplane I was trying to design. My worries about tip stalls and snap rolls were for naught because the 2412 is a well behaved foil. When I build the next version I'll be using something along the lines of a symmetrical 9% or 10% airfoil and an engine made to go fast. Because I don't plan to race it, I won't be hampered by artificial restrictions imposed by any given class of airplane. We'll see what happens.
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ConstructionThe model was built using conventional techniques. The wing is a D-Tube design using cap strips and a pair of spruce spars with full span shear webs. The first version of the wing had built up balsa tips. When the plane was refinished I replaced them with shaped blocks. The fuselage is a basic box built around the systems installed in it. The battery had to be disassembled and soldered back together to fit inside. When the plane was refinished a canopy was added as well as large wing fillets. The original finish on the plane was SolarFilm. It is very lightweight and pliable, but it also has a nasty habit of sticking to itself. I'm talking about when it's cold. If the adhesive sides get stuck together it's ruined. Pulling it back apart removes the adhesive from one of the parts. The other property that I really don't like is that it turns to rubber in the Florida sun. The stuff would just sag and flop around like a balloon with the air let out of it. Needless to say, I have never purchases another roll of SolarFilm since using it this one time. I completely refinished this model about six months before enlisting in the Army. A canopy was added as were large fillets at the wing root. The fuselage was fiberglassed and the wing was covered with Sig Coverall and dope. The entire aircraft was primed and painted with HobbyPoxy enamels.
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FlyingAerodynamics lessonAirplanes do not care about ground speed. All that matters is how much air is moving across the wing and control surfaces. This means if the wind is blowing and the aircraft is pointed into the wind, it has the same airspeed it would at any other time, but the ground speed is reduced. Therefore, the aircraft can land at a reduced ground speed which will result in less damage if the landing is not perfect. Wind does not prevent me from flying. However, gusty winds are a different matter. When the wind is gusting, the aircraft rises and drops with no warning at low speeds making landing a hazardous proposition, especially with a light aircraft. There is a reason why I mention this... On the day I test flew Shadow the wind was blowing so hard that when the airplane was on the ground, it was sitting on only the main gear - the tail was flying already. My girlfriend and brother were with me that day. Because of the wind, they both tried to drag me back into the car. At one point, I think my brother actually looked in the trunk to find a rope to restrain me with. He was too late because I already had Shadow in the air. Shadow wasn't as fast as I had hoped, but it tracked very well and was an overall smooth flyer. A few weeks later I had an experience with her that I will never forget. Shadow used a K & B .40 engine. On one flight, the engine started screaming about a minute into the flight. Judging from the sound, the engine must have picked up over 1,000 RPM and it wouldn't throttle back. (This is the same K & B .40 that was in my Mantis helicopter.) Because I had no throttle control, I couldn't kill the engine and had to fly large circuits around the field until Shadow ran out of gas. When I landed the plane I found out that the barrel had fallen out of the carburetor, essentially giving the engine twice the air volume. Why the engine did not just quit I have no idea. The engine looked OK inside when I stripped it down. I expected to see a melted piston and scorched liner.
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Epilogue
This aircraft never crashed and was in new condition until Army movers packed it for my move to Hawaii. They packed it in the same box as my bicycle and by the time it arrived it was shredded. The elevator is badly damaged and could never be made right again. The fin is broken and the fuselage is cracked on both sides from the rear of the wing saddle to the tail-post. The parts that have obviously been broken from the plane were missing when my goods were delivered. The wing has dings and dents all over the top and bottom. Because Shadow was not built from a kit, the Army claims officer said the Army wouldn't pay for it because there was no way to determine its value. I went to a local hobby shop and got an estimate from the owner as to what a comparable ARF aircraft would cost. The Army still refused to pay for it. In fact, I was never compensated a dime for any of the many models that were damaged or destroyed in Army moves. In fact, when I was packing to come back to the states from Germany, one of the movers watched me pack my HMMWV in a box. He then took the box and beat it with his fist to force it into another box. When I said something to him about it he flipped me off. Seeing my work and my property destroyed in move after move and then being insulted by weasel Army Claims Officers who refuse to do the right thing was one of many reasons I left the service. There were other reasons as well, but this isn't the place for them. Anyway....<sigh> Shadow is high on my list of planes to build again. I have a lot of ideas for improvements. For one thing, back in the day I did not have the right equipment for this aircraft. All I had was full size "standard" radio gear which made for a questionable installation. Now that there is much larger selection of smaller equipment that is reliable and affordable, I think I'll be able to make this plane what I wanted it to be from the beginning. Hopefully you'll be seeing the next version in the gallery in the next year or two.
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Copyright © 2002 Paul K. Johnson
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