RC Aircraft
Learn To Fly
It’s impressive what a few engineers with a pot of coffee can do, even a group as young as ours was. Our group of five mechanical engineers and two electrical engineers competed with 86 collegiate teams and finished 18th. The goal of the competition was to carry as much weight as possible around the course using the same power supply and same dimension limitations. Our 9’ wingspan, 11 lbs RC aircraft successfully carried 24 lbs around the course. The 1st place team carried 32 lbs around the course. Competition was close.
Building an RC Aircraft
Design
Our first semester together was spent mostly designing. We divvied our group up into smaller teams: Project Lead, Aerodynamics, Structures, and Controls. I led our Structures team and worked closely with our Aerodynamics team. My job was to design the internal structures to realize Aero’s ideal form. Many times, we had to find a compromise between what was structurally stable and aerodynamically preferable.
Manufacture
Our team was young and largely inexperienced with manufacturing. We had access to our college’s shop, which was well-equipped albeit crowded. We used the shop’s laser cutter to cut the thin balsa ribs and CNC machine to carve out our aluminum base. I created a jig to hold the main wing’s ribs in place while installing the spars which made manufacturing the wing much easier, quicker, and precise. We were amateurs, but we were fast learners.
Performance
It was windy in Sugar Land, TX when competition day had arrived. Our nervous team sat on deck and watched the group before us. As their aircraft raced down the runway, they huddled together, eyes for nothing else. Just as the plane took off, the full weight of the aircraft suspended in air, the wings collapsed in perfect unison, and months of work went crashing into the ground. They stared in horror. It was our turn…
Design
I was in charge of analyzing the forces on the wings provided from our Aero team and creating the internal structures to sustain these loads. After studying older planes and going through a couple of designs, I settled with a box spar for the main spar that cut off before the wing tip, a full length rear spar just before the ailerons, and stringers to support the wing tip.
This was my final main wing design which I created in Solidworks. The main spar is highlighted in yellow, the stringers in green, and the rear spar in purple. The leading edge is covered in a thin balsa wood sheet to maintain its all important shape.
I then used Excel to calculate the stresses in each member along the length of the wing. Initial designs had the stresses exceeding the Sitka yield stress, which began an iterative process of the aero team shortening the wingspan and lengthening the chord until the wing structures could withstand the stresses.
We followed a similar process for the Horizontal and Vertical Stabilizers. Click on the picture for a link to the structural PowerPoint presentation.
Manufacture
Performance
A Motley Crew
Unfortunately, I don’t have any video from our competition, and we didn’t even take very many pictures. But that day and that team will forever be a part of my memory. We were a ragtag team with little experience, but we were a determined bunch. We finished 18th, and I couldn’t be prouder.
Back Row: Nicole Trosclaire (E.E., Controls), Leon Chen (M.E., Structures), Sean Walsh (M.E., Aerodynamics)
Middle Row: Robert Levy (M.E., Project Lead), Sam Bossier (M.E., Aerodynamics), Collin Gillen (M.E., Structures)
Front Row: Alex Young (E.E., Controls)
Skills Used During This Project
Engineering
AutoCAD for laser cutting
Solidworks for structure design
Excel for structural calculations
Shear Force and Bending Moment Diagrams
Manufacturing
Simple woodworking
Applying Monokote
Laser Cutting
Creating a Jig