All in all, I made around 21 different test wing sections (each 78mm wide and 100mm long) before coming up with a satisfactory design. The first few prints were attempts to improve upon the initial spar-and-rib build from the previous post, which I based on more conventional metal and wood airplane wings from around the internet:
However, there were many problems with these wings. Not only were they incredibly heavy (clocking in at over 40 grams each) due to their thick shells (about 5mm initially), but the small rib holes were not providing the air with enough space to circulate and cool the plastic evenly, which led to warping along the edges. I tried remedying this by making the ribs more hollow, and the shell less thick, but to no avail. In addition, it became apparent that the spar was simply not sturdy enough to support the entire structure, and snapped off in the third wing section on the right. So, I began experimenting with different internal structures more suited to working well with plastic, and finally decided on implementing a lattice design on the inside of the wing with male and female connection points on each side:
The first such design had the lattice crosses completely filled in, and the female holes plus wing trailing edge were warped in:
So, I decided to add holes in the lattice structure. In addition, I noticed that there were only two connection points at the male-female joints, and decided to add a third for improved structural stability:
Next I tried slowly decreasing the wing thickness to see if I could cut down on unnecessary weight, but often found that there would be inconsistencies, misprints, and disconnecting of components during the whole process. All in all, this was probably the most frustrating part of the whole build since there were so many issues with the design, and I wasn't sure how to tackle them:
As a result, I often did not print entire wing components because the printer would mess them up early on. Finally, I realized that all these problems were originating in CATIA, where I had modeled the wing shell as a thick volume rather than an extruded surface. By making this simple change, along with setting the nozzle temperature to 230 degrees Celsius (which seemed to print better wings) each build began to get better and better:
With the basic internal structure complete, I began focusing on perfecting the male-female connections.
At first the male and female components were quite thick and wide, and did not have a surrounding bed on which glue could be applied to make them stick to one another. So, I played around with the design by slightly decreasing the male/female thickness while adding more surface area on the sides for better contact. With that, the design process was complete, and I decided to print out larger wing components (x2 the height) to see how they scaled up:
Overall, I was very satisfied with how sturdy they were, and how solid the connection felt when they were attached to one another. I also quickly designed and printed out caps for the edges of each wing, which were simply a filleted extrusion of the profile of the wing. These were also quite sturdy, but required me to fill the tops in with a hot glue gun due to the printer not being able to create that layer of the cap. Finally, after doubling the length of the wing section in CATIA (so that I didn't have to print four small pieces for each wing), I created the final wings for the airplane, complete with caps on each end:
Each wing measures about 315mm long, 100mm wide, and have a maximum thickness of 12mm. They also weigh in at 47 grams a piece, the same as the very first wing section I made despite being 4 times as long! Next up I'll begin working on the final component of the wing, which will connect the two parts displayed above with the fuselage of the plane itself, before moving on to design the tail section.
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