“Do you also want to build it?” project leader Julian Kupski had asked. He was referring to the ultra-lightweight biplane that the group of ten students had just designed for their end-of-bachelor Design Synthesis Exercise (DSE). It was a radical design, and all of them wanted to see it fly.
Transportable by bike
Ten students spent ten weeks full-time designing the AERGO, the next generation hydroplane. It was an idea pitched to the DSE committee by Julian Kupski, PhD candidate in the Structural Integrity and Composites group. Two of the students, Aydin van den Bergh and Lander Callens, explained that the aim of the project was to design a recreational ultralight water-aircraft that is transportable by bike, and that is license-free for the recreational user (due to its low weight.) And, at 100 meters distance, it should make less noise than the hum of a refrigerator. A single person should be able to operate, assemble and maintain it. “On our first project day, we chose for the AERGO to be a biplane,” said van den Bergh.
A balancing act
A plane needs lift in order to fly, and forward speed to create lift. Steering is also a must have. But the actual design process is much more complicated than that. The students quickly sub-divided into subgroups related to Aerodynamic, Hydrodynamics, Propulsion & Performance, Stability & Control, Materials & Structures and Operations. “The basics of nearly all these disciplines were covered in the bachelor’s phase, but we had to seriously delve into detailed theory,” said Callens. “Even the plane floating on water turned out to be a major design problem,” van den Bergh added. “We had to balance stability versus water resistance during take-off, also considering the pilot shifting weight. We used the knowledge available within TU Delft, for example at maritime engineering.”
One step forward, two steps back…
Airplane performance was leading, but everything in the design process was interconnected. “Take-off speed, cruising speed and cruising altitude demanded a certain wing area,” said van den Bergh. “The aerodynamics group then selected a wing shape (airfoil). But stability during flight led to design choices that were detrimental to stability when floating before take-off or after landing. It was a continual negotiation and back-and-forth between the different disciplines and we all had our own stakes and concerns.” Because of the noise constraint, the group had decided to use battery-powered propellers early on in the design process. According to van den Bergh “take-off power was the driving factor for engine design, while the power needed for cruising speed and range determined the battery design. Their weight had major influence on the required lift and, because of how it influenced the centre of gravity, on overall stability.”
“For airplane roll we decided to use wingwarping instead of flaps, just like the Wright brothers did 114 years ago,” Callens said. “It keeps the design simple.” Nevertheless, they first made a scale model in Lego Technic to fully understand the steering mechanism. Their final report at the end of the ten weeks covered all design aspects. It even considered the proper shape and weight of the paddle.
Building a glider
“Our design, the AERGO, is unique. There simply is no competition from existing one-man flyers,” said van den Bergh. “So, when Julian suggested we actually build it, we were eager to do so.” After a presentation by the students, professor Rinze Benedictus provided budget and workspace. He also made the students pick a deadline and a clear goal. “The most radical design aspect are the wings, that weigh only 600 grams per meter of wingspan. So, we decided to build the glider, to be ready at the start of the academic year,” said van den Bergh. The glider is the AERGO with a reduced wingspan, also lacking propulsion and a boat, but it does have all required steering integrated.
A crash course
Kupski provided a crash course in practical skills, such as laminating carbon tape. The students then spent many hours, and much of the summer holiday, building their glider. Van den Bergh and Callens would recommend this to all students. “Can I make this? How can I make this?” asked Callens. “Manufacturing your design arouses the true engineering spirit as you run into many unexpected problems,” van den Bergh added. “The bachelor phase covers conceptual design, but we noticed that there is quite a gap between theory and practice.”
The final validation tests, mid-August, were related to the steering mechanisms. After that, all that was left was to have one of the ten students pick up the 15 kilogram glider, run down a dune and glide. Two weeks before their projected deadline they hauled the glider to the ‘Zandmotor’ near The Hague, driving a car and trailer over private roads and bicycle paths. “The sun had already set when we started our test flights,” said van den Bergh. “Our third run was successful. There had never been a better example of people smiling from ear to ear
Where will you go
The students describe their AERGO as a worthy successor of the Wright Flyer I. “It’s basically the same plane, improved with a century of knowledge and technological innovations,” Callens said. “We use composite material with a carbon tape coating, rather than wood and cloth.” Now that the prototype glider has been field tested, the students intend to continue building the AERGO. “It’s ideally suited for the Dutch market,” added van den Bergh. “We may even create our own start-up company.” But for now, he has a more poetic view of their future destination:
The AERGO is slow
flies silent and low
leaving the question
where will you go?