Toothless Background

Up before the sun, down after the sun

After the success of the Duckasaurus, there was a need for a larger aircraft that can house more payload with a sleeker exterior. Toothless was created to cover that need, using a mold manufacturing procedure that was never performed before. Although Toothless never flew at competition, lessons learned about the manufacturing process and innovative design choices experimented laid the foundation for the next aircraft. Fun fact, the name for Toothless came after we finished the aircraft. Since its skin was carbon fiber, meaning it was completely black, and the weaves reminicising the scales of dragons, Toothless seemed like a fitting name representing the Night Fury from the movie How to Train Your Dragon.

Toothless Design

Toothless was optimized to carry all of the payload and mechanisms required for the competition. The competition during the 2022-2023 academic year included an airdrop task which required teams to drop five water bottles associated with specific targets. This meant that we would have to identify the targets as well with a camera. Thus, an airdorp mechanism and camera gimbal would be needed on top of the normal electrical payload like the batteries and the pixhawk. That being said, all parts had a hollow interior with a carbon fiber skin. There were quite a few differences between Toothless and the Duckasaurus. First of which was the size. Toothless had a fuselage length of about 1.1 meters or about 43 inches, with an added 24 inches roughly accounting for the tail. The wingspan was about 12 ft with an airfoil of 1412 on the root and 1415 on the tip, tapered at 0.45, all data given by our optimization software. Tapered wings allow for faster speeds, less drag and better lift distribution over the wing. The fuselage was designed during the 2020-2021 academic year using an interative process that required Solidworks modeling, ANSYS simulations, data collection and repeatition, however was not inplemented to manufacturing due to the pandemic. 4 double-stacked 1/8 " plywood bulkheads were added into the fuselage to reinforce the skin and to also allow for the landing gear, airdrop mechanism, tailboom and camera gimbal to have places to lock onto and absorb impact forces. Don't ask why we didn't but a bunch of 1/4" plywood. The tail had a symmetric airfoil of 0015 and did not require a taper for the horizontal stabilizer. The vertical stabilizer also had a taper of 0.45 and was attached to the HS by marine epoxy. Marine epoxy has a strong potent odor of fish, hence the name. The tailboom was purchased previously, and the HS and VS were attached to it using a flange design. Specifically, we took another tube with a larger diameter compared to the tailboom and epoxied on a laser cut circular piece with four equidistance holes for fasteners. The tailboom also had a similar flange laser cut and epoxied on at a specific distance from the end of the tailboom, then all that was left to do was align the two flanges and screw them together with a nut. This process was also applied to the aft of the fuselage and the front of the tailboom. The difference was that we used the fourth bulkhead with another piece of wood to sandwhich embedded nuts where the screws would thread to when attaching the front tailboom flange. The wings had to be broken into three 4 ft sections for travel storage. THe wings were connected to each other using L-shaped brackets that were marine epoxied onto the interior of the wing skins. A double balsa wood spar design was also inplemented, with balsa wood also being epoxied into the wing skins specifically to guide the spars into the wings smoothly. An interesting part of Toothless was its unique addition of a detachable mid wing section. The midwing had hinges on the leading and trailing edge that where screwed into the fuselage through embedded nuts layuped onto the fuselage, and when one side was unscrewed, you could lift up the midwing and work on the payload while the wings are still attached.

Toothless Manufacturing

Manufacturing materials included carbon fiber, xps foam, plywood, balsa wood, and epoxy. The fuselage, wings, and tail were created using our new mold manufacturing technique. Please see the Mold Manufacturing page to learn more about the process. Briefly speaking, the wings and tail could by CNC hot wired cut because the way that AFL's MATLAB code functions is by taking airfoil inputs and outputting a G-code for the machine to read. For the fuselage, it was trickier. We had to divide the fuselage into three sections: the nose, the body, and the aft. Then we laser cut templates of each end of the sections and hand hot wire cut the molds by dragging the hot wire through the foam using the templates glued onto the sides of the foam as guides. Then we attached the three sections together to make one mold. After we had the molds we performed our epoxy layer onto the foam molds and completed a carbon fiber layer with two plies. After curing, we attached the two opposite sides together to create the full shape with a hollow interior. This procedure was different from Duckasaurus's manufacturing, as we used the positives of the foam and performed a fiberglass layup over the foam, and in this case we used the negatives as molds. The spars were created by laser cutting balsa wood to fit the shape of the wings, as they are not completely straight. They were then epoxied into the mid wing and into the outer wing pieces with wooden guides within the wings that helps the wings attach together smoothly. The bulkheads were laser cut to the shape of the interior of the fuselage at four specific locations. The control surfaces were cut with a dremel and had epoxied hinges on the edge of the skin.

Photo taken moments before disaster, 1 May 2023