Every rower needs a rowing computer

An outline graphic depicting a stopwatch All the critical training data you need on an easy-to-read screen.
An outline graphic depicting a rowing course With touch up and go — you can accurately time races hands free.
An outline graphic depicting a crew winning a race Its affordable enough for crews, so every seat in the boat has one.
A rower in a single scull with a Scullr GPS rowing computer on an adhesive mount.
The new Scullr firmware features an intuitive interface and a host of class leading features.

How effectively can you train if you have no idea of how fast you're going or how efficient your technique really is?

My approach to coaching has been to give kids performance visualization tools so they motivate themselves. With this aim I developed the Scullr GPS rowing computer to make rowing performance feedback simple and affordable. I did this so everyone I coach could have a rowing computer in the boat with them every time we train.

Only $173

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Simple Practical Features:

Intelligent hands free operation

Refined over the past year and a half the Scullr rowing computer has a rich feature set to address the specific needs of school and club rowing programs with a particular emphasis on single, double scull and sweep pair training, where intelligent hands free operation is essential.

A low cost design, manufactured in Bundaberg

Scullr rowing computers were designed to meet a price. To keep costs down I decided to use off-the-shelf hardware and components; like the case which is a repurposed industrial junction box. This is what makes Scullr rowing computers so affordable, because there are none of the sunk costs in molds and tooling that need to be amortized. Unlike most electronic products which are manufactured in China, Scullr rowing computers are made here in Bundaberg in batches to meet demand on a just-in-time basis with lead times of 1-3 weeks. This keeps inventory costs down and ensures that each unit can be individually tested before delivery.

Change the way you train

Scullr rowing computers have transformed the way we train. Whether its singles, doubles or quads, the crews I coach are often spread out along the Burnett river, so I can't be along-side every boat at once. With rowing computers at every seat my crews can perform the same training drills independently, they get live feedback on how technique and economy affect boat speed, and they can review race data to see how pacing affects their finish times [1]. They love data and use it to analyse their performance after every race, comparing their times with previous results stored on the computer. It’s a totally different training vibe, very performance orientated and naturally competitive — yet I never have to push them.

Standardized flexible workouts — no programming required

When your trying to coach a crew and get them working together — programming custom workouts just leads to distraction. Seriously, do you really what to custom program the same workouts onto a dozen rowing computers without making any mistakes, because all you need is one kid to fiddle with something, press the wrong button and you're all getting frustrated wasting precious time on the water. We tried this and had little success.

Scullr GPS rowing computers have a standard set of training modes, each with a standard set of flexible workouts. The crew simply selects the same mode and then the same workout and they are ready to go. In my experience this saves a lot of time, making training sessions more productive and freeing you up to focus on coaching rather than herding crews. See the Scullr online manual for further details.

Racing mode

An outline graphic depicting the different race mode distances Hands free virtual timing gate

The Scullr rowing computer features a hands free virtual timing gate for 250m, 500m, 1000m, 1500m, 2000m and 4000m distances. The computer recognizes a race has commenced when 15 or more consecutive strokes are detected at a rating of at least 16 strokes per minute. Prior to the race start, any touch up strokes are ignored, so rowers can line up at the start and focus on their race, rather than manually resetting their rowing computer. Once underway the race is timed with the distance counting down to zero at the finish line.

Post Race Summary

When the race distance is reached and rowing stops the Scullr rowing computer switches to a race summary screen which includes the finish time along with a quintile performance breakdown with each segment's stroke rate, speed, length-per-stroke and percentage variance. Having this summary appear automatically as soon as the race ends is particularly useful for training sessions because it allows rowers to review their performance and reflect on how they paced themselves while the race is still fresh in their memory. Nominal quintile pacing [2] should be around: +3%, 0%, -1%, -1% and -0%. Any significant deviation from this may require remediation. For example, in the race summary below, the rower held back a little after the start and possibly could have gone a bit harder.

Previous race results stored on the Scullr rowing computer can be reviewed at any time by pressing and holding the black Mode Button in Race Mode.

River Courses

An outline graphic depicting a winding river course Races can follow the turns of a river

Races timed using the hands free virtual timing gate can follow turns in a river. Regardless of any heading changes the total distance actually traveled is accumulated over the course of a race. This means you can run practice races almost anywhere with boats lined up side-by-side, single file, or even using staggered starts.


The Scullr rowing computer's accelerometer samples movement at 50Hz to accurately detect each rowing stroke. The rating, which is calculated from the time the previous stroke was detected is displayed at the end of each drive phase. The stroke detection algorithm uses an adaptive matched filter to reduce the occurrence of false signals from the oars hitting chop in rough conditions. It has taken some time to prefect this algorithm, but now we are really happy with its reliability in adverse conditions. Nevertheless, sometimes when rowing against the tide into a strong headwind and chop the algorithm can struggle to detect a weak stroke signal amongst the background noise. This can cause the algorithm to skip or double count.

Scullr vs Actual race results

At ratings of 20-30 SPM (Strokes Per Minute) the GPS module samples boat speed and position 10-15 times per stroke. The high sample rates of the GPS and accelerometer, along with error reduction provided by the adaptive matched filter all work to increase virtual timing gate accuracy.

At the 2018 QLD Schools Championship Regatta in conditions that were extremely unfavorable (high winds and rough water) the Scullr rowing computer reported race results that were on average within 2 seconds of the officially timed results.

Boat config Day Distance Scullr Time Official Time Difference
1x Saturday 7:39 am 1000m 4:25 4:27 -2s
1x Saturday 8:48 am 1000m 4:40 4:42 -2s
2x Saturday 10:46 am 1000m 4:05 4:07 -2s
2x Saturday 11:45 am 1000m 3:41 3:44 -3s
1x Saturday 2:44 am 1500m 7:00 7:00 0s
1x Saturday 4:01 am 1000m 5:47 6:01 -4s
1x Sunday 1:13 am 1000m 4:15 4:15 0s
1x Sunday 2:53 am 1000m 4:03 4:07 -4s
4x Monday 9:36 am 1000m 3:58 4:01 -3s

Differences between the rowing computer and timed results are caused by the accumulation of variance from:

So while Scullr race results may not be as accurate as timed results between known start and end points, the hands free virtual timing gate provides a measurement of race distance that is reliably accurate to within a few seconds (generally under rather than over). This is particularly convenient for training, benchmarking and racing.

Training mode

Long slow distance rowing is a foundational component of successful training programs [3]. To keep track of session statistics the Scullr rowing computer's Training mode displays rating, speed, stroke count, accumulated distance and accumulated time spent rowing — all on a single easy to read screen. We found that crews really like to know how far they row regardless of the other drills and exercises they do — because it helps keep them motivated — so regardless of which other modes are accessed during a session, training data for the entire session continues to accumulate on the Training mode screen. Likewise, the companion odometer screen tracks the number of training sessions, total time and total distance rowed over a season.

Castle Mode

An outline graphic depicting the hard vs easy strokes in castle mode

High Intensity Interval Training (HIIT) has been shown to strengthen rowers' cardio vascular systems and improve VO2 Max [4]. To keep track of interval training sets the Scullr rowing computer features a duty cycle counter. In this mode, the red button can be used to cycle between 10/20, 20/20, 30/30, 40/40, 50/50 and 60/60 easy vs hard strokes. The addition of a repitition counter simplifies the design and implementation of high-intensity interval training sessions using this mode.


With high-intensity interval training the idea is to cover approximately twice the target race distance at race pace. To make this achievable the distance is broken down into more manageable intervals of race pace and light recovery rowing. Over time, crews work towards longer duty cycles with less reps, yet the total distance covered at race pace during each training session remains the same. This limit is intended to mitigate the risk of injury from overtraining.

Intervals Race (m) 500 1000 1500 2000
20 / 20 Reps 6 11 17 22
30 / 30 Reps 4 8 11 15
40 / 40 Reps 3 6 9 11
50 / 50 Reps 3 5 7 9
60 / 60 Reps 2 4 6 8

Depending on the age group and training volume, high-intensity interval training is most effective once or twice a week, with long slow distance rowing and strength and conditioning at the gym done in between [4].

No threshold training?

'Available evidence suggests that combining large volumes of low-intensity training ( <2 mmol·L−1 lactate ) with careful use of high-intensity interval training ( >4 mmol·L−1 lactate ) throughout the annual training cycle is the best-practice model for development of endurance performance' [4]. In successful young elite rowers we see a polarization of training intensity with 95% at low-intensity, only 5% at high-intensity and very little in between. The 'polarization observed demonstrates a form of intensity management discipline (keeping hard training hard and easy training easy) among the most successful athletes' [3]. So with counterindicating emperical evidence there seems little need to support threshold training.

Ladder Mode

An outline graphic depicting a rating ladder

Rating ladder training sets are used to train crews to throttle ratings up and down during races and to adapt technique to higher speeds. The Scullr rowing computer features a ladder counter which steps the rating up and down in four one minute increments, i.e. the 21-30-21 sequence spends one minute at 21, 24, 27, 30, 27, 24 and back to 21 strokes per minute, then the sequence repeats. In this mode, the red button is used to cycle the ladder counter between 18-24-18, 16-25-16, 22-28-22 and 21-30-21 sets.

Length-Per-Stroke Mode

An outline graphic depicting the length of a stroke

Recent research contributions by Dr. Valery Kleshnev, the leading researcher in rowing biomechanics have substantially expanded our understanding of rowing biomechanics and the drivers of performance — 'The effectiveness of rowing technique is related to the magnitude and timing of the acceleration of the rower's center of mass' [5 Section 2.4.2]. To help rowers work on their technique, identify optimal ratings [6] and gain an understanding of how changes in technique improve rowing economy the Scullr rowing computer features a Length-Per-Stroke mode that measures the distance between puddles.

It turns out that rowing becomes less efficient the faster you row. Using this mode, live feedback at target speeds and ratings can reveal how improvements in rowing economy reduce velocity fluctuations of the boat relative to the water [7]. The idea is to row at race pace while matching the prognostic rating and observe how changes in technique (force timing) effect efficiency — like middle loading the drive with an upper body pivot. Positive feedback from improved technique raises confidence in its benefit.

Coaching tools

Autonomous training exercises

As a coach one of the greatest benefits I get from training with Scullr GPS rowing computers is I can give my crews a training program including castle, ladder or length-per-stroke exercises, and without involvement from me they set up these modes on their computers and get to work. I don't have to keep the boats grouped together, or cruise behind them with a stop watch and loud hailer barking out orders. This frees up my time to focus on the individual boats and crew members that need my attention.

Performance tracking

Every time a race is completed, a new race record is created. Race records include a lot of detail, specifically: race date, time of day, and distance, average and maximum speed, average and maximum rating, finish time, and quintile splits of rating, speed and time.

Flexible mounting

The mounting bracket takes a Velcro strap for wing riggers. There is also GoPro hardware support for adhesive mounts. The case is watertight with NEMA 4X and IP66 ingress protection, and the whole unit floats if dropped in water.

Extended battery life

The rechargeable 16850 battery gives the Scullr rowing computer about 50 hours of battery life (25 hours when the LCD backlight is used). With a training schedule of 10 hours a week the unit only needs to be recharged once a month. The Scullr rowing computer automatically powers-off after 20 minutes of inactivity to conserve battery life.


The Scullr rowing computer case has a functional industrial aesthetic with a clear polycarbonate cover and ABS base. School and club rowing can be tough on gear, accidents happen and gear invariably gets broken. I chose this case to make the Scullr rowing computer serviceable. The polycarbonate cover, 16850 battery and ABS base — including switches — can all be replaced if damaged.


A few years ago my son and daughter started rowing here in Bundaberg and their school asked if I was interested in coaching. I had rowed as a schoolboy in Sydney in the early 80s where I had benefited from the expert coaching of ex-olympic rowers. My father, grandfather and great grandfather all rowed. My grandfather also coached at Sydney rowing club where he was involved in the development of the first calibrated ergometer at Sydney University (below right). The eight he coached won the 1949 Kings Cup (below left) and went on to win gold at the 1950 empire games in New Zealand. With five generations of rowers in my family — clearly rowing is in our blood.

Taking on a coaching role for a small regional school in Queensland I wanted to know if we were training competitively enough to do well at the Queensland State Championships. To achieve this I knew we needed data from GPS rowing computers to compare against historic race times. Yet after a quick review of the rowing computers on the market I couldn’t find one with the features and price/performance I was looking for. The NK SpeedCoach and Active-Tools CoxOrb are fine products, but these GPS rowing computers are relatively expensive here in Australia. From my observation most rowing coaches at schools and particularly clubs don’t trust kids with them, so parents either purchase one for their child, or the cox gets to use one occasionally at regattas. The Coxmate GPS is less expensive but the screen is small and at least to me, the case doesn't feel robust enough. I wanted something that could withstand the rough and tumble of daily school and club use, so I decided to build my own.

My solution would have a particular focus on sculling — which I felt was missing from the other devices — along with features that would assist coaching. I also wanted a more affordable price point so coaches would see this as a standard piece of equipment, rather than a luxury. I am an experienced hardware and software engineer having lived and worked in Silicon Valley from 1995-2003. I have a PhD in behavioural science — specifically the behavioural influences that trigger innovation uptake — and I consult as a design engineer in the development of sporting goods manufactured in China.

So, after a bit of Google research I realized I could design and build 10 rowing computers using Atmel AVR’s and off-the-shelf components used in drones — all for less than the cost of a single GPS SpeedCoach. The proof of concept was hand wired and tested on a breadboard. A week later I had designed a prototype PCB, had it manufactured and was sourcing parts from international suppliers. While waiting for the parts to arrive I used a data logger to collect acceleration data from several rowing sessions. I used the R statistical package to write a matched filter stroke detection algorithm that improves on exiting implementations [8]. When the PCB’s and parts arrived I hand soldered the boards together and programmed my algorithm into the AVR controllers.

Over the subsequent months as we got stuck into training with these new GPS rowing computers, my observation of how the kids used them helped to refine the feature set and user interface. I really hadn’t taken it much further than that when I started getting enquiries from other coaches about what we were using. Obviously in the back of my mind I had considered selling these units as a product, however knowing from first hand experience how school and club rowing gear can get dropped and broken, I realized that these rowing computers would need to be easily repaired. With this in mind I redesigned the whole unit to make it modular and serviceable. Now simply unscrewing the four plastic bolts on the cover, then unplugging the LCD and CPU modules, allows the entire unit to come apart for the repair or replacement of its parts.

Scullr has been a labour of love for the past two years and I think you will be pleased with the functionality and pragmatic features of this design — the kids love training with them, its the first thing the grab after taking their oars down to the pontoon.


  1. Kleshnev, V. (2001) Racing strategy in rowing during Sydney Olympic Games. Australian Rowing, 24: 20–23. Google Scholar [PDF]
  2. Garland SW. (2005) An analysis of the pacing strategy adopted by elite competitors in 2000m rowing. Br J Sports Med, 39 (1): 39–42. Google Scholar [PDF]
  3. Guellich, A., Seiler, S., & Emrich, E. (2009). Training methods and intensity distribution of young world-class rowers. International Journal of Sports Physiology & Performance, 4(4): 448–460. Google Scholar [PDF]
  4. Seiler, S., & Tonnesen, E. (2009). Intervals, thresholds, and long slow distance: The role of intensity and duration in endurance training. Sportscience, 13: 32–53. Google Scholar [PDF]
  5. Kleshnev, V. (2016). The biomechanics of rowing. Wiltshire: Crowood Press. Google Scholar [Preview]
  6. Kleshnev, V. (2001) Stroke rate vs. distance in rowing during the Sydney Olympics. Australian Rowing, 25(2): 18–21. Google Scholar [PDF]
  7. Baudouin, A. and Hawkins, D. (2002). A biomechanical review of factors affecting rowing performance: A review. British Journal of Sports Medicine, 36: 396–402. Google Scholar [PDF]
  8. Hermsen, H. (2013). Using gps and accelerometer data for rowing race tracking. Dept of Artificial Intelligence. University of Groningen, The Netherlands. Google Scholar [PDF]