Trevor Gardner

A fluid dynamic investigation of the Big Blade and Macon oar blade designs in rowing propulsion

Abstract The purpose of this investigation was to examine the fluid dynamic characteristics of the two most commonly used oar blades: the Big Blade and the Macon. Scaled models of each blade, as well as a flat Big Blade, were tested in a water flume using a quasi-static method similar to that used in swimming and kayaking research. Measurement of the normal and tangential blade forces enabled lift and drag forces generated by the oar blades to be calculated over the full range of sweep angles observed during a rowing stroke. Lift and drag force coefficients were then calculated and compared between blades. The results showed that the Big Blade and Macon oar blades exhibited very similar characteristics. Hydraulic blade efficiency was not therefore found to be the reason for claims that the Big Blade could elicit a 2% improvement in performance over the Macon. The Big Blade was also shown to have similar characteristics to the flat plate when the angle of attack was below 90°, despite significant increases in the lift coefficient when the angle of attack increased above 90°. This result suggests that the Big Blade design may not be completely optimized over the whole stroke.

A mathematical model of the oar blade – water interaction in rowing

Abstract Our aim was to present a mathematical model of rowing and sculling that allowed for a comparison of oar blade designs. The relative movement between the oar blades and water during the drive phase of the stroke was modelled, and the lift and drag forces generated by this complex interaction were determined. The model was driven by the oar shaft angular velocity about the oarlock in the horizontal plane, and was shown to be valid against measured on-water mean steady-state shell velocity for both a heavyweight mens eight and a lightweight mens single scull. Measured lift and drag force coefficients previously presented by the authors were used as inputs to the model, whichs allowed for the influence of oar blade design on rowing performance to be determined. The commonly used Big Blade, which is curved, and its flat equivalent were compared, and blade curvature was shown to generate a 1.14% improvement in mean boat velocity, or a 17.1-m lead over 1500 m. With races being won and lost by much smaller margins than this, blade curvature would appear to play a significant role in propulsion.

Optimization of oar blade design for improved performance in rowing

Abstract The aim of the present study was to find a more optimal blade design for rowing performance than the Big Blade, which has been shown to be less than optimal for propulsion. As well as the Big Blade, a flat Big Blade, a flat rectangular blade, and a rectangular blade with the same curvature and projected area as the Big Blade were tested in a water flume to determine their fluid dynamic characteristics at the full range of angles at which the oar blade might present itself to the water. Similarities were observed between the flat Big Blade and rectangular blades. However, the curved rectangular blade generated significantly more lift in the angle range 0 – 90° than the curved Big Blade, although it was similar between 90 and 180°. This difference was attributed to the shape of the upper and lower edges of the blade and their influence on the fluid flow around the blade. Although the influence of oar blade design on boat speed was not investigated here, the significant increases in fluid force coefficients for the curved rectangular blade suggest that this new oar blade design could elicit a practically significant improvement in rowing performance.

Numerical Modelling of the Flow Around Rowing Oar Blades (P71)

Recent experimental studies have presented the lift and drag coefficients for a range of oar blades. However, these studies were not able to provide insight into the mechanisms of lift and drag generation. The aims of this study, therefore, were to model the flow around an oar blade using computational fluid dynamics (CFD), and to validate this model against experimental data.

A review of propulsive mechanisms in rowing

This paper reviews the fluid dynamic mechanisms that are fundamental to the rowing stroke. Complex interactions occur between the oar blade and water, and over the last 30 years our understanding of the mechanisms that govern rowing propulsion has developed significantly. The oar blade was once believed to rip through the water, generating a drag force acting normal to the blade. Current research indicates that the oar blade acts as an aerofoil making use of lift forces to propel the boat through the water early and late in the stroke, with drag being the dominant propulsive force when the oar is perpendicular to the boat. Early on-water research showed variations in the fluid dynamic behaviour of different oar blades. Recently, more controlled laboratory tests have isolated the oar blade from the rower—boat—water system to obtain blade characteristics. The isolated nature of recent oar blade studies and the complex nature of the oar blade—water interaction have led to suggestions that computational fluid dynamics (CFD) may be used to advance understanding of oar blade behaviour as a precursor to a more informed design process. By integrating a dynamic CFD model with a mathematical model of rowing mechanics, a full optimization of rower technique, boat rigging, and equipment design could be performed.

Simulating the fluid dynamic behaviour of oar blades in competition rowing

This study examines the hydrodynamic behaviour of rowing oar blades using computational fluid dynamics (CFD). For initial validation of the modelling technique, the lift and drag coefficients of the Big Blade oar design and a flat rectangular oar were compared against previously published experimental data carried out on quarter-scale blades held stationary at a number of angles of attack to the oncoming flow. The CFD model was in agreement with the experimental data, predicting the lift and drag coefficients within 0.14 and 0.34 of the measured values respectively, although the degree of correlation was found to be sensitive to the particular turbulence model applied. The simulations provided predictions of the fluid—blade propulsive forces of lift and drag over the range of angles of attack used in rowing, and they characterized the features of hydrodynamic flow around the blade. To investigate the performance of currently available oar blades at full scale, a second series of simulations was carried out over a range of blade velocities commonly used in rowing. The CFD model provided much insight into the fluid dynamic behaviour of rowing oar blades and showed great potential as an aid to oar blade design.

The influence of stretcher height on posture in ergometer rowing

Abstract The aim of this investigation was to determine the effect on rower posture of raising the stretchers. Nine male university rowers completed a single 30-s trial at each of three stretcher heights on an ergometer, at 30 strokes min−1. The first ten strokes with complete data were averaged and data for four time points during the stroke extracted: catch, mid-drive, finish, and mid-recovery. Ankle angle was shown to increase significantly at all points during the stroke (P<0.01) as the stretchers were raised. Knee angle was only significantly increased into a more extended posture at mid-drive (P<0.05) and mid-recovery (P<0.01) for the higher stretcher positions, hip angle was significantly reduced into a more flexed posture at the catch (P<0.05) and at mid-recovery (P<0.05), and the trunk was significantly extended at the catch (P<0.01), finish (P<0.01), and mid-recovery (P<0.05) as the stretchers were raised. Our results show that the increase in stretcher height caused the rowers body to rotate posteriorly in the sagittal plane. This we suggest reduced the vertical component of stretcher force, thus achieving a more mechanically effective position, which could have led to the slower rate of fatigue reported previously for the two raised stretcher positions (Caplan & Gardner, 2005). The increased flexion of the hip should not be ignored, however, as this may lead to overstretching of the hip extensors if the stretchers are raised too high. Further research is required to determine the extent to which the stretchers can be raised in on-water rowing.