When using a digital inclinometer to measure the pitch of a boat propeller, the "Blade Angle × Constant" method is a straightforward approach used by the Buckshot Racing #77 Formula 1 Tunnel Boat Racing Team.

The constant is typically related to the propeller's diameter and the point at which the measurement is taken, which in this case is at 75% of the radius.

We've included a proprietary Buckshot Racing #77 Calculator Sheet to make these instructions below much simpler, but included the detail for those who want to take a deeper dive into the math.

### Tools You'll Need:

Digital inclinometer

Ruler or tape measure

Calculator (Print the Buckshot Racing #77 Calculator Sheet)

### Steps to Calculate Pitch Using Blade Angle × Constant:

**Position the Propeller:**Place the propeller on a flat, stable surface.

**Set the Measurement Point:**Identify the point that is 75% of the way from the hub to the tip of the blade. This is done by measuring the propeller's radius (half of the diameter).

For example, if the propeller diameter is 14 inches, the radius is 7 inches.

75% of this radius is 0.75 × 7 = 5.25 inches. Mark this point on the blade.

**Measure the Blade Angle:**Place the digital inclinometer flat against the blade at the 75% radius mark.

Read and record the blade angle shown on the digital inclinometer.

**Determine the Constant:**The constant is derived from the diameter and the position at which the angle is measured.

For simplicity, the constant can be approximated as: Constant=Propeller Diameter×π360∘\text{Constant} = \frac{\text{Propeller Diameter} \times \pi}{360^\circ} Constant=360∘Propeller Diameter×π

This accounts for the propeller’s diameter and translates the angle into a linear distance.

**Calculate the Pitch:**Use the formula: Pitch=Blade Angle×Constant\text{Pitch} = \text{Blade Angle} \times \text{Constant}Pitch=Blade Angle×Constant

Substitute the angle and constant into the formula to calculate the pitch.

### Example Calculation:

**Propeller Diameter:**14 inches**75% of Radius:**5.25 inches**Measured Blade Angle:**20 degrees

### Calculate the Constant:

Constant=14×3.1416360=0.1223 inches per degree\text{Constant} = \frac{14 \times 3.1416}{360} = 0.1223 \text{ inches per degree}Constant=36014×3.1416=0.1223 inches per degree

### Calculate the Pitch:

Pitch=20∘×0.1223=2.446 inches\text{Pitch} = 20^\circ \times 0.1223 = 2.446 \text{ inches}Pitch=20∘×0.1223=2.446 inches

The pitch of the propeller, based on these calculations, would be approximately 2.446 inches per revolution.

### Notes:

**Calibration:**Ensure that the inclinometer is properly zeroed before measuring.**Average of Multiple Blades:**For accuracy, measure the blade angle at the same point on each blade and take the average.**Blade Variations:**Account for any variations in the blade angles by averaging them if necessary.

This method provides a simplified yet effective way to calculate the propeller pitch using a digital inclinometer.

Download our Free how-to-measure-prop-pitch-calculator-sheet, kindly reference Buckshot Racing #77 when sharing.

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