Oar Span in Rowing: Measurement, Optimal Settings, and Performance Impact

How do you measure span rowing?

Measuring "span rowing" primarily refers to the precise measurement of oar span (also known as rigging span or spread) on a rowing shell, a critical rigging parameter that dictates the leverage applied to the oar. This measurement, taken from the boat's centerline to the oarlock pin, directly impacts a rower's biomechanics, power transfer, and overall efficiency on the water.

Understanding Oar Span (Rigging Span)

Oar span, often simply called "span," is a fundamental rigging dimension in competitive rowing. It defines the horizontal distance from the boat's longitudinal centerline to the pivot point of the oarlock (the pin). This measurement is crucial for several reasons:

• Leverage and Power Transfer: The span, in conjunction with the oar's inboard and outboard lengths, determines the effective leverage ratio. A wider span increases the load per stroke but can allow for more power application, while a narrower span reduces the load, potentially increasing stroke rate.
• Biomechanics and Ergonomics: The correct span ensures that a rower can achieve an optimal catch, drive, and finish position without undue strain or awkward angles. It influences the rower's reach, the arc of the oar through the water, and the comfort of the stroke.
• Symmetry and Balance: In sweep rowing, matching the span on both sides (port and starboard) is vital for maintaining the boat's balance and preventing steering issues. In sculling, consistent span on both sides ensures symmetrical power application.

Tools Required for Measurement

Accurate measurement of oar span requires specific tools and attention to detail:

• Rigging Tape or Ruler: A rigid, accurate measuring tape, preferably a specialized rigging tape that can extend across the boat.
• Spirit Level: To ensure the boat is perfectly level and stable before measurements are taken, preventing skewed readings.
• T-Square or Rigging Square: To ensure that the measurement from the centerline to the pin is taken perpendicularly, avoiding angular errors.
• Marking Pen (Optional): To lightly mark the centerline if not already present.

Step-by-Step Measurement Process

Precise execution is key to obtaining accurate span measurements.

1. Preparation of the Boat:

   • Place the rowing shell on a stable, level surface (e.g., slings or trestles) indoors or in calm conditions.
   • Use a spirit level to ensure the boat is perfectly level both longitudinally and transversely. Any tilt can introduce errors.
   • Ensure the oarlocks are securely tightened in their gates and are in their standard, upright position.

2. Identifying the Centerline:

   • Locate or mark the exact longitudinal centerline of the boat. This is typically the keel line. If not clearly marked, measure the width of the boat at various points and find the midpoint.

3. Identifying the Pin Center:

   • The measurement point on the oarlock is the precise center of the pin around which the oarlock pivots. This is where the oar's shaft theoretically pivots.

4. Performing the Measurement:

   • For Sweep Rowing: Measure from the centerline of the boat to the centerline of the oarlock pin on each side (port and starboard).
   • For Sculling: Measure from the centerline of the boat to the centerline of each oarlock pin.
   • Technique:
     • Hold the rigging tape or ruler taut and perfectly perpendicular to the centerline.
     • Use a T-square or rigging square to ensure the measurement is taken at a 90-degree angle from the centerline to the pin. This eliminates parallax errors.
     • Read the measurement precisely to the nearest millimeter or sixteenth of an inch.
     • Record the measurements for both sides.

Optimal Span and Adjustments

The "optimal" span is not a universal fixed number but rather a dynamic setting tailored to the individual rower and specific boat.

• Factors Influencing Optimal Span:

  • Rower's Body Dimensions: Arm length, torso length, and overall height.
  • Strength and Power Output: Stronger rowers may tolerate a wider span.
  • Boat Type: Single sculls, doubles, fours, eights all have different hull characteristics.
  • Oar Length and Blade Type: These interact with span to define the overall gearing.
  • Water Conditions: Rough water might necessitate slight adjustments.

• Typical Ranges (Approximate):

  • Sweep Rowing (eights, fours): Often ranges from 84-88 cm (33-34.5 inches) per side.
  • Sculling (singles, doubles): Typically ranges from 158-162 cm (62-64 inches) from pin to pin, meaning 79-81 cm per side.

• Effects of Incorrect Span:

  • Too Wide: Can lead to over-reaching, reduced effective power, excessive strain on the shoulders and back, and difficulty achieving a strong finish.
  • Too Narrow: Can restrict the stroke length, cause the oar handle to hit the body too early, and limit the power that can be applied.

• Iterative Adjustment: Rigging is an iterative process. Small adjustments to the span (e.g., 0.5-1 cm) should be made methodically, followed by on-water testing to assess the feel, efficiency, and performance impact.

Related Concepts: Inboard and Outboard Length

While span measures the distance from the boat's centerline to the oarlock, the oar's dimensions complete the leverage equation:

• Inboard Length: The distance from the center of the oarlock to the end of the oar handle. This is the portion of the oar inside the boat.
• Outboard Length: The distance from the center of the oarlock to the tip of the oar blade. This is the portion of the oar outside the boat.
• Total Oar Length: Inboard + Outboard.
• Leverage Ratio (Gearing): The ratio of the outboard length to the inboard length. This ratio, combined with the span, determines the overall "gearing" of the boat, influencing how much effort is required per stroke and how fast the blade moves through the water.

Adjusting span, inboard, and outboard lengths allows coaches and rowers to fine-tune the "feel" of the stroke and optimize the mechanical advantage for maximum speed and efficiency.

Measuring Rowing Performance (Beyond Rigging Span)

While oar span is a crucial rigging measurement, "measuring rowing" in a broader sense often refers to assessing a rower's performance and physiological output. This typically involves:

• Key Performance Metrics:

  • Distance and Time: Total meters covered in a given time, or time to cover a set distance.
  • Split Pace (Watts/500m): The average time it takes to row 500 meters, a common indicator of intensity and power output. Often expressed in watts.
  • Stroke Rate (SPM): Strokes per minute, indicating the tempo of the rowing.
  • Heart Rate: Physiological response to the effort, used for training zone management.
  • Power Output: Measured in watts, especially on ergometers, reflecting the force applied.

• Technology Used:

  • Ergometers (Rowing Machines): Provide real-time data on distance, time, split, stroke rate, and watts.
  • GPS and Stroke Coaches: On-water devices that track distance, speed, stroke rate, and sometimes power.
  • Lactate and VO2 Max Testing: Advanced physiological assessments to determine aerobic and anaerobic thresholds.

These performance metrics are used for training progression, race strategy, fitness assessment, and comparing performance over time.

Conclusion: Precision for Performance

Measuring oar span is a fundamental aspect of rowing rigging that directly impacts a rower's biomechanics, comfort, and ability to generate power. It is a precise process requiring specific tools and careful execution. While seemingly a small detail, accurate span measurement, in concert with other rigging parameters like inboard and outboard lengths, is paramount for optimizing a rowing shell's efficiency and maximizing a rower's on-water performance. Regular checks and adjustments, often with the guidance of experienced coaches, are essential to ensure the rigging is always perfectly matched to the athlete and the conditions.