Oar length: are shorter oars really faster?

What is certain is that as rowers get faster, oars are getting shorter. In fact, they have been shortening up for at least a century and the pace of change has only sped up in recent decades. But as rowing’s elite coaches and athletes search for precious fractions-of-a-second, one millimetre of oar length at a time, how much shorter can oars realistically get?

New research from the laboratory of hydrodynamics at the École Polytechnique in Paris, France has taken a hi-tech approach to answering this question. World Rowing spoke with Dr Jean-Philippe Boucher about the team’s findings and why he believes that there is a limit to how short an oar can be.

“What we see is that the current length is very close to the optimum,” says Boucher. “Depending on parameters, it could be smaller, but the thing is when you decrease the length of the oars, it has an effect on the stroke rate and there is a physiological limit that dictates a shortest possible length for oars.”

Working with a team of sports physics researchers, Boucher and his colleague Dr Romain Labbé, the study’s lead author, earned their doctorate degrees in a large part due to this innovative work. Together, the team developed rowing robots to understand the physics behind some of rowing’s biggest questions.

When it comes to oar length, “we wanted to see why this evolution was taking place,” says Boucher. To do this, the team built a crew of “row bots” and placed them in a scaled down rowing shell in the university’s swimming pool to take a look at how oar length effected boat speed.

“The experiments give us some ideas about how the velocity of the boat changes with the length of the oars,” says Boucher. “We are looking at the mechanical optimum. To get the results for real rowing, we did numerical simulations.”

It turns out that while shorter oars do make the boat go faster, each stroke takes more and more energy the shorter you go.

“If you want to be as fast as possible without caring so much about how much energy you spend, shorter oars are better,” Boucher says. Fortunately for rowers looking for top speed over 2000m or less, “the cost of lower energy efficiency is not as great as it is for longer distances, so shorter oars are most effective.”

“For longer distances,” Boucher adds, “we think that efficiency comes into play and longer oars would work better. But if you want to have a high stroke rate then maybe longer oars would not be so easy to use.”

Interestingly, although the overall length of oars is getting shorter, one part of the oar has remained pretty much the same for a long time. “The inboard length [distance from the oarlock to the end of the handle] over the years has stayed almost constant,” Boucher says. “What we have observed is that the oars are getting shorter because of a decrease in outboard length [distance from the oar lock to the outside edge of the blade].”

The physics of rower-oar interaction that drive these design changes have been looked at time and time again over the years, spurring on each new tweak to one of the sport’s most iconic pieces of equipment. Yet Boucher’s work is unique in eliminating the human element.

“The thing we wanted to do with this study was to decouple the physiology from the mechanics,” he says. “That way we could really concentrate on the mechanics as in this study where we looked at oar length.”

This isn’t the first time the row bots have made headlines. In 2017, the team’s first iteration of row bots made internet headlines with their findings on asymmetrical rowing. Read World Rowing’s coverage here.

As for what’s next, Boucher hopes that the robot rowers can inspire more studies in future. With his doctorate in hand, Boucher has teamed up once more with fellow row bot researcher, Labbé to put their experimental knowledge into practice developing the next generation of sport measurement and performance instrumentation.

“We are now trying our sensors with top-level French athletes,” says Boucher of their newly launched company, Phyling. Soon, he hopes their products will be available to the larger performance sports community in France and beyond.

 For more information on Phyling here.