Biomimicry is the science of copying nature to produce more efficient and useful products. Biomimicry makes use of the millions of years in which evolution has been slowly perfecting various aspects of natural life. For example, when the Shinkansen Bullet Train in Japan goes through tunnels, it creates a large thunder clap from the air pressure differences it creates in the tunnel. Looking at animals that moved elegantly at high speed though different mediums produced a train modeled after the beak of a Kingfisher, a bird that dives headfirst into water to catch prey but makes a minimal splash. The Biomimicry Institute reporting on the study noted that “modeling the front-end [sic] of the train after the beak of kingfishers… resulted not only in a quieter train, but 15% less electricity use even while the train travels 10% faster.” [1]

Dr. Frank Fish, founder of Whale Power, first noticed the strangeness of tubercles on the tail of the humpback whale when he was in a gift shop. He saw a model of a tail and assumed that the artist got the model wrong because there were tubercles on the front of the tail, not the back like he expected. When he found out that the tubercles did actually go on the front, he was fascinated because he knew that they must have evolved like that for some purpose. After some testing, Dr. Fish found that humpback whales have evolved tubercles on their tails in order to increase efficiency while swimming [2]. The whale tubercles improved the effective angles of the fin without stalling, reduced drag, and increased lift. When the humpback whales search for food, they have to take relatively tight turns in order to move underneath their prey [3]. The benefits from the decrease in stalling angles means that the whale can position its fin at sharp angles without losing the ability to push itself through the water. The increase in lift from the tubercles means that with each push from the fin, more power is generated. The decrease in drag means that as the whale moves along, there is less resisting force to its movement. Drag is the term for friction between a solid object and a liquid or gas object. Just as a hockey puck will slide across ice easier than wood because the friction between a hockey puck and ice is less than that of a hockey puck and cement, the tubercles act as a type of “ice” or a way to reduce friction between the whale and the water. The tubercles work by creating vortices behind the bumps on the fin. In turn, the different parts of the fin change the distribution of pressure over the fin. This pressure distribution means that these different areas would stall at various times, but as a whole, the fin maintains its stability through a wide breadth of angles [4]. The same principles could be applied to turbine blades: friction between the air and blade would be reduced, operating angles would be broader, and less wind would be required to turn a turbine. As a result, Dr. Fish founded the company Whale Power, which has pioneered tubercle technology. They have developed various fans and wind turbines based on tubercle design, all of which have shown improvements in efficiency.

Tubercles could possibly improve any type of blade or fin moving through some sort of medium, be it water or air. Helicopter blades fit this exact criteria. We wondered if they could also be made more efficient by the addition of tubercles, thereby contributing to the Green Earth movement. We wanted to design something that could save fuel and reduce emissions while being able to fly, maneuver, and accelerate at the same, if not better, level and quality.

This research study was made in the hopes that more efficient helicopter blades can be developed. Adding tubercles to the RC Helicopter blades was hypothesized to produce a higher wind speed than regular blades under the same conditions. A higher wind speed would indicate a higher efficiency because a higher wind speed at a base energy input implies the idea that equal wind speeds could be produced by the new blades on a helicopter using less energy than conventional means.

Testing on a real helicopter is prohibitively expensive so we used a high quality RC Helicopter as a model. The Double Horse 9056 RC Helicopter fit the requirements for price limit, size, and accuracy. We decided to make the tubercles out of FIMO Soft Clay, which is not porous and would allow for the least air resistance. It is also easy to mold and to attach to the blades. The design of the tubercles had to go on the front of the blade like the whales’ did. They also had to lie low enough so as to reduce extra air resistance while spinning. We varied the number of tubercles to see what effect that would have but kept them evenly spaced so that they covered the length of the blade.

The results partially support the hypothesis that adding tubercles to helicopter blades would increase their efficiency. On one hand, the 8-tubercle blades showed an increase in output across the board, creating between a 1.54% to 4.20% increase in average windspeed per input level. On the other hand, the 4-tubercle blades had a decrease in output, creating between a 1.44% and 3.38% decrease in average windspeed per input level. These results match what is known about tubercles. Our data suggests that the closer the tubercles are together, the better the outcome. This correlation can be tied to the fluid dynamics physics that apply to tubercle-blades. If tubercles are too far apart, the vortices that create the differentiating air pressures on the blade become impossible to create. These results point to the need for tubercles to be close together. It also helps to show that there is a point at which the tubercles stop helping but actually decrease efficiency.