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Did you know that… Randall foils do not increase rowing efficiency or improve performance. They increase blade drag, making rowing feel heavier and more energy-demanding. While this may lead to higher force and power output in isolated sections, it is unlikely to translate into improved racing performance.
Recently, several questions regarding the efficiency of Randall foils were raised on the BioRow expert chat (https://biorow.com/chatbiorow/ ). As this topic has not been addressed in our previous publications, AI-generated responses were ambiguous. Here, we present results from our 2017 study.
“Randall foils” are pieces of plastic attached to the top edge of the blade at a right angle to its surface. This design was claimed to prevent the blade from sinking too deeply during the drive, improve blade efficiency, and increase rowing speed. Two pairs of identical sculls (WinTech RDS) with spoons similar to Concept2 Big Blades were equipped with handle force sensors. Randall foils were attached to the blades of one pair. Four national-level junior scullers performed a 1500-m continuous test in their own singles, consisting of six 250-m sections with increasing stroke rates: 20–24–28–32–36–40 spm. All boats were instrumented with the BioRow system measured 2D oar angles, body segment movements, and boat motion.
Scullers were tested in pairs simultaneously: one with Randall foils (RFB) and one with normal blades (NB) without foils, ensuring identical weather conditions. The scullers then swapped oars and repeated the test simultaneously, eliminating effects of rower size, technique, boat quality, and fatigue.
The average stroke rate across all samples was slightly lower with Randall foils. Average rowing speed (v) was slightly 0.23% higher with foils (equivalent to 1.0 s over 2 km), while rowing power (P) increased significantly by 2.34% with foils, resulting in a 1.66% higher gross drag factor (DFgross = P/v³). Thus, rowing with foils was more energy-consuming, and at equal power output, foils would reduce speed by 0.55% (2.65 s over 2 km).
The higher rowing power with RFB was primarily due to a 2.7% higher average force and a slightly longer stroke length (+0.7%), resulting in a 2.6% higher HDF “burden factor”. These findings were consistent with athletes’ subjective reports that “rowing with foils felt significantly heavier”.
Using the BioRow method of averaging biomechanical curves, the mean force curve with foils was compared to that without foils. The additional force associated with foils occurred primarily in the middle of the drive, while force at the beginning and end remained unchanged.
Analysis of blade work revealed that foils reduced catch slip by 14.2%, but increased release slip by 24.5%, shortening the effective angle with a fully covered blade by 3.59%. Scullers reported: “Foils made it more difficult to insert the blade into the water after the catch, and especially to extract it at the finish.” To compensate, they applied greater efforts at blade entry and maintained shallower blade positions before the finish.
Blade efficiency differed by only 0.08%, indicating negligible changes in slippage. Variation in boat speed during the stroke cycle was 0.11% higher with foils, suggesting increased acceleration during the drive, but greater deceleration during recovery. Maximal handle velocity during recovery was 6.5% lower with foils. Combined with the higher DFgross, this supports the hypothesis that foils increase aerodynamic drag during recovery, when feathered blades position foils to move directly against the air stream with a high speed resulted as a sum of blade and boat movements. Athlete feedback—“rowing with foils made oar movement more difficult during recovery”—corroborates this finding.
These results indicate that Randall foils do not improve rowing efficiency or performance. Foils increase blade drag during both drive and recovery phases, making rowing more energy-intensive. The increased perception of “heaviness” may stimulate rowers to generate higher force and power, which can result in slightly higher speed in some segments. However, in a race scenario, it is unlikely that athletes would have sufficient energy reserves to overcome the additional drag and achieve higher overall speed.
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©2025 Dr. Valery Kleshnev