Front-loaded versus back-loaded catch.              

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1. Introduction

A drive with a front-loaded catch means that the maximum blade force is reached early after the catch. A back-loaded catch means that the maximum blade force occurs much later in the drive phase. (I think the terminology is due to Valery Kleshnev)

The aim of this chapter is to shed some light on the question whether one kind of catch has an advantage over the other.

 

2. Parameters

The force-oar angle curve has approximately a trapezoidal shape. For all cases considered the stroke angle is 110o. The catch angle = -70o and the finish angle = +40o.

The maximum blade force is obtained after an angle s following the catch angle. s has been chosen equal to: 10, 20, 30, 40, 50 and 30 degrees. In all cases the maximum blade force remains constant over an interval w = 30o. Power input is 400W.

This results in blade force curves as displayed in Fig 2.1.

 

 

 

Fig  2.1

Blade force curve

s = 10, 20,….60 degr

w = 30 degr

 

 

 

 

3.Results

The shell velocity curves are not very different for the various values of s. See Fig 3.1

 

 

Fig 3.1

Shell speed during one stroke.

Note: The front loaded catch has the minimum speed loss after the catch.

 

 

 

Table 3.1 displays a summary of the other results. The variation in time to cover the 2000m is very small. The same for the other results. The variations are of the same order of magnitude as the accuracy of the calculations.

 

 

Table 3.1

 

 

Fig 3.2 displays graphically again how the 2000m time varies with the parameter s.

If a maximum really exists is quest able.

 

 

Fig 3.2

Time for 2000m as function of s.

 

4. Conclusion

From the analysis as presented above it is very difficult to draw a firm conclusion but Fig 3.2 shows a very small advantage of the front loaded catch. Another conclusion might be that very little profit can be obtained by varying this aspect of the drive. But note: this might be valid for this purely mechanical system. The human rower might very well be shaped to perform best with a certain shape of the drive curve.

 

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