Vortex Edge Development 2

Oars - Theory and Testing: On Water Testing
Presented by Pete & Dick Dreissigacker at the XXIX FISA Coaches Conference, Sevilla, Spain 2000

The real fun begins when we take a theoretical idea and get it on the water. We began systematic testing with the development of the Big Blade shape in 1991. Over the last 9 years, we have gathered test results on over 200 days of testing. That adds up to over 1,250 timed pieces. The odd thing is, we still enjoy this part the best.

We use the following test procedure:

  1. Row at least six pieces switching between the two oars each piece. We want to maximize the number of changes between oars to see if a pattern evolves.
  2. Do not change anything other than the oars being tested. If you change two things you will not know which change made the difference.
  3. Row all pieces at maximum effort. It is easier to be consistent if the pieces are rowed at maximum effort. Longer pieces require some degree of pacing and, as such, are subject to mentally controlling the effort.
  4. Timing accuracy is critical. We set our speed-meter to give us 10 strokes to get up to speed then start recording speed data for the next 40 strokes. Timing a fixed number of strokes is the most accurate method. If you are timing a distance, it should be at least 500m to minimize the end effects. End effects can be expected because the piece may not begin and end during the same place in the stroke cycle.
  5. Do not look at any results until all pieces are completed. Knowing the results while doing the test may effect your performance. We cover the speed part of the display with a piece of tape.
  6. Only test on days with calm conditions. Row all pieces in the same direction with the wind. Changes in a tail wind will have less effect than a head wind.


We apply the following principles to evaluating results:

  1. Graph results and calculate the difference in speed as a percentage.
  2. Do not compare the speed achieved from one day to the next because day to day variation is too great.
  3. Test the same variable several days before making a conclusion.
  4. Test results only directly apply to the crew doing the testing.


Here are some examples of results from three different days of testing: November 6, 1996
This test was between the Big Blade and the Smoothie. The idea behind the Smoothie was to make a truly asymmetrical blade, designed to fit the path of the water during the first part of the stroke. Typically, blades had been made symmetrical about the shaft. We also adjusted the curvature and tip angle. Here is the graph of the speeds of the test pieces. Big Blade is red, Smoothie is black. The Smoothie pieces were faster by 1.2%.

October 12, 1999
This test was between the Smoothie and a Smoothie with a rounded tip. Most of our testing in 1999 was to investigate the delta wing effect. We tried various delta tip shapes over the season, which led us to this one. This gave us the best results of the delta tip trials. Here is the graph of the speeds of the test pieces. Round tip is red, Smoothie is black. The speed of these two designs were the same in our tests. It is interesting to note that the feel of the oar was greatly changed by the tip profile. With the rounded profile, the oar was rowed one centimeter shorter and still felt like a heavier load during phase 2. This would suggest improved efficiency in phase 2. The lack of a speed increase may be due to a decreased effectiveness in other parts of the stroke, perhaps phases 1 and 3.

October 4, 2000
This test is between the Smoothie and the new Vortex Edge blade. The Vortex Edge is an attempt to gain a phase 2 improvement with some taper along sides without losing efficiency in other parts of the stroke. We have also added vortex-generating features on the low-pressure side of the tip to increase efficiency during phase 1. The Vortex Edge is black, Smoothie is red. The pieces with the Vortex Edge were faster by 1.3%.

The important thing to remember is that these results are from our testing only. We believe that if we are faster with a particular design that at least some other crews will be faster as well. The burden then falls on the individual or crew to test and determine what is fastest for them. This is not always easy because testing can get in the way of a training plan. But, the benefits can be well worth the effort.

There are lots of reasons why a blade that is faster for one crew may not be faster for another.

This is an example of a power curve overlaid onto the four phases of the stroke. The rower's effort is not evenly distributed across the four phases.

By changing the shape of the curve the rower can move some of the effort from one phase to another.

Notice that the red curve moves effort from phase 2 to phase 1. It is then possible for a blade design that is more efficient in a particular phase to work well for a rower with one force profile but not so well for a rower with a different force profile. Likewise a change in rigging that alters the catch and finish angles could have a similar effect.

The blue curve represents rigging the rower further through the pin so they reach out to a greater angle at the catch. This results in more of the rower's effort spent in phase 1.

This brings us back to the three ideas that we wanted you to take away from this presentation.
  1. There ARE performance differences between different blade shapes.
  2. These performance differences may be DEPENDENT on various factors such as rigging, catch angles, power application, etc.
  3. Crews need to determine for THEMSELVES what works best for them.