The Research
Where the idea came from, and what it's trying to answer.
That's the premise behind Wobble. Stability in a rowing shell is widely understood to matter. A wobbling boat loses speed, disrupts timing, and makes consistent technique harder to develop. But it's rarely measured in any systematic way. Coaches can see it. Rowers can feel it. But there's usually no number attached to it.
Wobble is a research project aimed at changing that. By attaching an iPhone to the craft and computing a continuous stability score (the Wobble Factor), teams gain something concrete to observe, discuss, and work toward improving. Stroke rate and speed are displayed alongside it, so the team can see how stability relates to other key metrics in real time.
The Wobble Factor is a derived stability metric calculated from the iPhone's motion sensors (accelerometer, gyroscope, and magnetometer via Apple's Core Motion framework). It's a single number that reflects how much the craft is moving in unwanted ways. Lower is more stable.
The goal isn't to reduce wobble to zero; some motion is inherent to rowing. The goal is to give teams a shared reference point so they can compare sessions, experiment with technique, and track whether changes are actually helping.
The Wobble Factor reflects not just the crew's technique, but the environment they're rowing in. Wind, waves, and current all introduce motion that the sensors will capture. A rough day on the water will naturally produce a higher Wobble Factor than a calm one. Boat type and hull design play a role too, as does the number of rowers and how the crew is seated. The number is most meaningful when compared within sessions or across similar conditions, rather than as an absolute score.
A practical concern with phone-based sensing is that mounting geometry varies by boat type, rigging, and what's convenient. Wobble addresses this directly: it automatically detects how the phone is oriented when attached to the craft and compensates accordingly. You don't need to mount it in a specific position or tell the app how it's configured. Just attach it and go.
Wobble doesn't interpret what it sees or tell you what to change. It shows the team the Wobble Factor in real time, and lets the team figure out what to do with that information. That's intentional. The research question is whether having a live stability metric changes how teams train. That question only has meaning if the teams are the ones doing the interpreting. The app is free to download with no subscriptions.
In most rowing shells, the coxswain is already watching, calling, and steering, making them the natural user of Wobble. With the phone mounted where the cox can see it, the Wobble Factor becomes part of their feedback loop in real time. Rather than calling "sit the boat" on instinct alone, the cox can see the stability number respond as the crew makes adjustments and report back what actually moved the needle.
As a research project in active development, Wobble is beta software. The core measurements (Wobble Factor, stroke rate, and speed) are functional, but the app will continue to evolve as more is learned from real-world use. In particular, the calculation of the Wobble Factor itself is an area of active research. The underlying model will be refined as more data is gathered from a wider range of boats, crews, and conditions. I'm releasing early because the best way to improve the models is to get the tool on the water. I'm very grateful to those teams that give it a try.
Wobble is an active solo development project. The current focus is the core measurement and display loop: getting a reliable, meaningful Wobble Factor in front of a team on the water. Future work will explore session recording, historical comparison, and what the data can reveal about different boat types and crew configurations.
If you're a coach, rower, or researcher interested in the project, the Support page is the best way to get in touch.
Questions or feedback? Visit the Support page or reach out directly.