"Gunderfighter" Control Surfaces Test Aircraft
This project was started in the summer after my Freshman Year of College, when I did not have an internship. I was curious about the joint operation of leading and trailing Edge flaps to effectively modify camber (like used in the F-18 and F-16), and I wanted to build an aircraft that had that same functionality. I was also interested in programming a flight controller that would manage the surfaces independently. Ultimately, as you will see, it was really good experience. That said, it is the sort of project that I am glad I did, but I would not re-do, because I learned so much doing it that I realize how wrong I initially was about almost everything.
Gunderfighter 1:
Version 1 was a disaster in most respects (but a tremendous learning experience). I began construction in summer 2016, and the aircraft was done the following spring (it took so long because it was my first balsa design and school got in the way). In retrospect, the whole design was not very good. It worked, but the wing was not aerodynamically effective or structurally efficient because it was modeled after the airfoil on an F-16. The wing was far too thin for either. I did not quite realize at the time that the aircraft is low-subsonic, and that wing shape was wholly unnecessary. Also, some of the effects I was trying to model (such as strong lifting vortices from Leading-Edge Root-Extensions) were not present at such a low reynolds and mach numbers. The fuselage was also not a very structurally reliable design (it was entirely stressed-skin balsa with minimal reinforcement). It was also difficult to build. In the rush to get it flying, I decided to opt for not having a a forward wing bolt (so that it was only held on by dowels in the front and bolts in the aft). On the aircraft's second test flight, the balsa in the fuselage that secured the forward-wing-mounting-dowels broke free, and the fuselage and wing separated. The wing and tail surfaces mostly survived, but the fuselage was a total loss.
Gunderfighter 2:
After this, I had learned so much about the project that I almost did not re-build it. Finally however, during my time in Virginia (as an intern at NASA LARC) I fixed the wing and designed a new fuselage that would be stronger, simpler, and easier to build. Also, instead of having all-moving Horizontal Tails, I had more conventional (but still mechanically independent) elevators. Learning from the mistakes of the previous versions, I did not leave out a forward wing bolt and the forward dowels connected to the 3d-printed ABS firewall rather than some epoxied-on balsa. As a credit to the simplicity of the new design, construction and mating of the new fuselage was finished over about a 3 - week span in January 2018.
First flight happened successfully just before the spring semester. The second flight successfully demonstrated use of all the control surfaces intended, with an improved capability for low-speed and/or high-load-factor flying. The aircraft, in this final configuration, also had decent flying characteristics despite a mediocre aerodynamic shape. On its third flight, I damaged the landing gear because of poor visibility on the final approach. It would have been easily repaired, but I felt that the project had achieved its goals and could be retired.
Gunderfighter 1:
Version 1 was a disaster in most respects (but a tremendous learning experience). I began construction in summer 2016, and the aircraft was done the following spring (it took so long because it was my first balsa design and school got in the way). In retrospect, the whole design was not very good. It worked, but the wing was not aerodynamically effective or structurally efficient because it was modeled after the airfoil on an F-16. The wing was far too thin for either. I did not quite realize at the time that the aircraft is low-subsonic, and that wing shape was wholly unnecessary. Also, some of the effects I was trying to model (such as strong lifting vortices from Leading-Edge Root-Extensions) were not present at such a low reynolds and mach numbers. The fuselage was also not a very structurally reliable design (it was entirely stressed-skin balsa with minimal reinforcement). It was also difficult to build. In the rush to get it flying, I decided to opt for not having a a forward wing bolt (so that it was only held on by dowels in the front and bolts in the aft). On the aircraft's second test flight, the balsa in the fuselage that secured the forward-wing-mounting-dowels broke free, and the fuselage and wing separated. The wing and tail surfaces mostly survived, but the fuselage was a total loss.
Gunderfighter 2:
After this, I had learned so much about the project that I almost did not re-build it. Finally however, during my time in Virginia (as an intern at NASA LARC) I fixed the wing and designed a new fuselage that would be stronger, simpler, and easier to build. Also, instead of having all-moving Horizontal Tails, I had more conventional (but still mechanically independent) elevators. Learning from the mistakes of the previous versions, I did not leave out a forward wing bolt and the forward dowels connected to the 3d-printed ABS firewall rather than some epoxied-on balsa. As a credit to the simplicity of the new design, construction and mating of the new fuselage was finished over about a 3 - week span in January 2018.
First flight happened successfully just before the spring semester. The second flight successfully demonstrated use of all the control surfaces intended, with an improved capability for low-speed and/or high-load-factor flying. The aircraft, in this final configuration, also had decent flying characteristics despite a mediocre aerodynamic shape. On its third flight, I damaged the landing gear because of poor visibility on the final approach. It would have been easily repaired, but I felt that the project had achieved its goals and could be retired.
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