A 3-D printed replica of a pelican wing sits inside the Cal Poly wind tunnel. Students and faculty are studying how the wings operate to create efficient airplane models. | Graham Doig/Courtesy Photo

Aerospace engineering students and faculty are studying how bird wings can help make better airplane wings. They can’t stick live birds in Cal Poly’s wind tunnel, so they are using 3-D printed replicas.

Putting live birds in the wind tunnel is probably not the best way to conduct the study, according to David Martin, the aerospace engineering graduate student who is using the bird study as his master’s thesis.

“It would be incredibly difficult and ethically questionable to test a live bird in the wind tunnel, though I think it has been done before with smaller birds,” Martin said.

Birds can glide effortlessly without exhausting all of their energy, even on a windy day, said Graham Doig, aerospace engineering assistant professor. Studying how birds efficiently use their wings can help improve airplane wing efficiency.

The team chose a brown pelican and California condor wing for the study from the Natural History Museum of Los Angeles, Martin said. Condors glide more and fly higher than other birds. Pelicans glide close to the water for long periods of time without losing energy. Large gliding birds are the best to study because their wing shapes are similar to airplane wing shapes, he said.

“The wing and feathers may have one shape for gliding, but a completely different one for diving. Aircraft wings also change shape for different flight movements such as landing and reducing speed,” Martin said.

By collecting detailed data on the two bird wings, the team is hoping to find a new way to create better types of airplane wings, Martin said. Scanning and printing technology and laser sensors allow the team to collect new data on bird wings.

“Our study is mostly trial and error at this point since the amount of details going into this project has never really been done before, especially with the technology we have available to us,” Martin said.

The complex details of the wings create many steps in the study, said Martin’s research assistant and aerospace engineering senior Brandon Baldovin.

“In order to mimic the wings, we have to replicate and manufacture the curvature, thickness and exact geometry of the wings, which is very hard to do,” Baldovin said.

The pelican wing was the first to be scanned. Doig did that last summer. The wing was placed on a rotating table so the wing could be scanned at different angles, he said. A laser measured each point and groove of the wing and its feathers.

In order to capture the exact texture and grooves of the feathers, high resolution had to be used, Doig said. The higher the resolution, the better the 3-D printing job turns out.

“Scanning takes about an hour, which is a longer scanning time, due to the higher type of resolution that we use,” Doig said.

After the scans were done, the team moved on to the printing part of the project. Each scan showed the feathers, fibers and bumps from different angles, Doig said. The scans were put together to create the 3-D copy of the whole pelican wing.

Doig, Martin and Baldovin printed the pelican wing in three pieces. The bird has a 6-foot long wingspan. It was easier to work with than the condor’s 10-foot long wingspan. The team created a 3-foot long wing, a ½ scale copy of the pelican wing.

“Since our printer is small and can only print up to 10 inches at a time, we can only print the wing in parts,” Doig said.

The three parts are made out of plastic called ABS, Doig said. The 3-D printing machine creates layers of liquid ABS that dry and set instantly once sprayed from a nozzle.

Printing takes a long time because of the size of the printer and the need to create a high-resolution copy, Martin said. The pelican wing took about three months. While 3-D printing can be a lengthy process, it helps produce incredibly accurate reproductions, he said.

David Martin watches the 3-D printer produce a faux pelican wing. | Graham Doig/Courtesy Photo
David Martin watches the 3-D printer produce a faux pelican wing. | Graham Doig/Courtesy Photo

The wind tunnel is where the project comes alive, Baldovin said. The 3-D printed wing part sticks up from a baseplate on the floor. For the team’s experiment, the wind tunnel’s speed only goes up to 11 mph, a slow speed for Cal Poly’s wind tunnel.

“This is because we are trying to model bird flight in a gliding scenario and that glide speed is pretty slow,” Baldovin said.

The team can track the air moving past the 3-D printed wing in the wind tunnel, Doig said. It’s like a moving car. A person can’t understand how a car moves without considering the wind’s effect on the car, he said.

“We put the bird wing scan into the tunnel to study the effects of the air movements along the feathers since we cannot fully study the wing without the speed of its movement matching the speed of the wind,” Doig said.

The wind tunnel recreates air movements as if the bird wing is in flight, Doig said. A laser measures the air movements in the tunnel. These measurements are used to see how air moves along the feathers.

The wind tunnel also tracks how the wind moves between certain wing and feather structures, Baldovin said. Pelican and condor wings are the best to study in terms on the specific feather anatomy. That is why the team picked the two birds.

There are two types of wings — standard and split. Standard wings have all the feathers together, Baldovin said, holding his fingers closed together. Split is just what the name suggests — feathers that are individually split when flying, he said spreading his fingers.

A 3-D printed pelican wing. | David Martin/Courtesy Photo
A 3-D printed pelican wing. | David Martin/Courtesy Photo

A theory being tested in the wind tunnel is the idea that split wings lead to better reduction in drag. Less drag allows airplanes to use less energy while flying, Doig said.

“What we’re trying to address here is the gap in knowledge about split wings and how that applies to aircrafts,” Martin said.

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