A guest post from School Rowing New Zealand website  sweep oar gearing Read Part 2 of the article

What is Rowing oar gearing?

Gearing for a rowing boat is roughly analogous to gearing for a bicycle:

• Light/low gears are easy to use at low speed or for comparatively fitter competitors; one stroke of the oar/pedal is easier to do but does not take you very far.
• Heavy/high gears are easy to use at high speed or for comparatively stronger competitors; one stroke of the oar/pedal takes a lot more effort but moves you much farther.

Unfortunately a rower does not have the luxury of changing gear during a race so the boat’s gearing must be chosen with care before the race.

How is a boat put into gear?!

A boat is put into gear by altering the ratio of lengths between three important points on the oar: the blade, the pin and the handle.

The reason these ratios are important is because (as far as physics is concerned) a boat is actually being moved along by levers.

Levers

A lever uses effort (the rower) on an object (the oar) braced against a fulcrum (the water/boat) to shift a load (the boat/water). According to FISA, boats must be propelled by a second order lever, which is one with the load in the middle.

From the shore that is what rowing looks like:

• the rower puts in their effort at the handle end of the oar; and
• the water stays still, so it is the fulcrum, at the blade end of the oar; and
• in between, at the pin, the boat is the load that is being shifted up the course.

However, from the rower’s perspective there is a first order lever in action, which is one with the fulcrum in the middle:

• the rower puts in their effort at the handle end of the oar; and
• the pin does not move so it is the fulcrum; and
• the load is the water being shifted back towards the stern of the boat at the blade end of the oar.

Fortunately, as far as gearing is concerned for coaches, it does not matter which type of lever is in action because the effect of changing the ratios is the same.

Because it is much easier to look at gearing from the rower’s perspective (instead of a shorebound FISA official perspective) we will treat oars as if they are 1st order levers. This also means the arcs traced out by the oar and the limitations on those arcs are easier to follow.

Rigging Arcs

With a 1st order lever you have two complimentary arcs traced out by the ends of the oar rotating around the pin. Gearing is determined by the ratio of the distance travelled by the blade of the oar (outside arc) to the distance travelled by the handle of the oar (inside arc).

When looking at the angle swept out by the arcs there are a couple of considerations.

• The oar is at its most efficient when it is perpendicular to the boat; and
• Rowers have to be able to hold the oar and apply useful pressure to it throughout the arc.

In principal, the angle of the arcs will be limited to the rower’s inside arc and gearing is simply a matter of changing the length of the blade and/or inboard (distance from pin to handle). However, in practice, changing the inboard can involve changing the size of the spread and will usually affect the amount the inside arc overhangs the boat’s keel. Those changes have the following effects:

• Tightening the spread generally increases the angle swept out by the arcs because it makes it easier for rowers to arc the blade behind them at the catch; and
• If the inside arc is too far away from the keel (most historians allow 30cm) this can cause problems with rowers leaning out of the boat to complete their arc [depending on the technique used].

Finally, to add to the confusion, each rower in a crew will have an optimal arc that depends on that rower’s height, strength and ability, the speed of the boat and whether the coach has set the boat up from the catch or the finish (backstop). Then, for the more advanced coach, the idea of the rowers arcing their oars in unison is what rowing is all about.

For the average school coach, faced with sharing oars and equipment, similar arcs are achieved through the placement of the foot stretcher and the compression of the body and legs at the catch – then standard measurements are used for the oars. For coaches with the plant and/or the inclination it is possible to change the leverage for each rower to ensure individual rowers of different shapes and strengths are able to arc together as a crew.

Tomorrow we publish Part 2

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