We should be able to increase boat speed by taking full advantage of this favorable area of propulsion by biasing the stroke toward the catch, extending it as much as is biomechanicaly possible and using a blade shape whose size, shape and orientation work well in this area.
There are two or three ways to achieve this: The first is to recruit athletes that are naturally able to row a long arc favoring the catch. These are athletes with broad shoulders, long arms and long upper bodies. Unfortunately this is a small percentage of the general population. If you are one of these, thank your parents. The rest of us are left with the option of emulating these rare people by trying to duplicate their catch angles.
The first option is to row through the pin as far as possible. You get about 1 degree more angle at the catch for each centimeter through the pin. It is now common practice to see 10 and 11 cm through the pin. This results in a higher load at the catch, which requires using shorter outboard length oars to get back to the same, load or ‘FEEL’ at the catch. In international rowing over the last ten years we have seen average scull oar length reduce by 4 to 6 cm. Average spreads and inboards have remained about the same. Another option is to reduce the spread. This will increase the arc and lengthen the stroke, but you then need to reduce the inboard for clearance and reduce the outboard further to preserve the original ratio of inboard to outboard that gives the same load or “feel” at the catch.
Below is an example of calculations to try to get back to the same load (ratio) when changing the spread. For example if we start with a current big blade Apex scull blade used with 160 cm. spread and sculling oars set at 288 cm. length with 88.5 cm. inboard we will have a load or RATIO of 2.21 if we divide the true outboard of 177.1 cm. by ½ the spread which is 80 cm.
Apex-R Scull Blade Spread/Oar Length Example Calculations:
The problem that you run into when reducing the spread thereby lengthening the stroke is that the catch still feels heavier due to the increasing acute angle or “pinching”. As you get near 25 degrees or less to the centerline of the boat you need a smaller blade shape to get the same feel at the catch. Trying to design the optimum blade shape and size is difficult because the blade moves through the water sometimes acting as a wing and sometimes acting as a parachute. The ideal blade shape would have to morph from a small elliptical shape with the blade depth greater than the blade length at the catch to a large circle when the shaft is perpendicular to the boat.
The Apex-R (round) blade shape is a compromise as all blade shapes must be. It is not completely round, but more oval in shape, the area is less than the Apex big blade and it’s width or blade depth is 3 cm. more than the Apex sculling blade. It’s designed to favor the first third of the stroke where we are able to generate the most force and which should result in the most speed. To take full advantage of the Apex-R blade shape it is best if maximum distance through the pin, minimal spread and shorter inboard and outboard dimensions (shorter oars) are tried. The common remark that “these oars release so clean and effortlessly” is a side benefit of the round tail end of the blade. The other design features are identical to our Apex big blade – minimun FISA allowable thickness, rounded edges, blade spline in line with the water flow and smooth attachment to the shaft. All these design features are there to offer the least impediment to water flowing back and forth over the blade during the stroke. The center of pressure or “centroid” of the blade area is identical to the Apex big blade and is 20.9 cm. from the blade tip.
The Apex-R Sweep Blade:
Identical boats with the same number of rowers but twice the number of smaller bladed oars with more angle at the catch are considerably faster, for example: a heavyweight men’s quad as compared to a heavyweight men’s straight four. Sculling boats using the same number of blades, but half as many people as sweep boats (4x vs. 8+ for example) are too close in speed to explain using increased boat surface area alone. If we look at the sculling motion versus the sweep we see that the symmetric sculling motion enables us to generate over 10 degrees more angle at the catch with each scull than with one sweep oar. We think that significant gains in boat speed could be realized if the catch angle of the blade seen in sculling could be approached in sweep rowing. When designing the Apex-R sweep blade we canted the blade back about 9 degrees from the centerline of the shaft to emulate the sculling blade angle at the catch. This increase in the “cant angle” will of course result in an increase load or “feel” at the catch.
The same recommendations as regard to the Apex-R scull blade are encouraged: increased through the pin dimensions and reduced outboard oar length. The Apex-R sweep blade profile is similar to the scull blade, but because of the difficulty in reaching the same catch angle as seen with sculling, the sweep blade aspect ratio (ratio of length to width) is different. It is slightly longer relative to its width when compared to the Apex-R scull blade.
Below is an example of calculations to try to get back to the same load (ratio) when changing the span. For example if we start with a current big blade 55 Apex sweep blade used with 84 cm. span and oars set at 374 cm. length with 114 cm. inboard we will have a load or RATIO of 2.761 if we divide the true outboard of 231.9 cm. by the span which is 84 cm.
Apex-R Sweep Blades Span/Oar Length Example Calculations:
by James Dreher (12/12/03)
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