Ballast Displacement Ratio Calculator

| Added in Miscellaneous

Understanding Ballast Displacement Ratio

The Ballast Displacement Ratio is a critical metric for evaluating boat stability and sailing characteristics. This ratio represents the proportion of a vessel's total weight that is dedicated to ballast, which directly impacts how the boat handles in various conditions.

Formula

[\text{BDR} = \frac{\text{Total Ballast}}{\text{Total Displacement}}]

Where:

  • Total Ballast is the weight of the ballast (in lbs or kg)
  • Total Displacement is the total weight of the boat (in lbs or kg)

Example Calculation

For a sailboat with:

  • Total Ballast: 6,000 lbs
  • Total Displacement: 15,000 lbs

[\text{BDR} = \frac{6000}{15000} = 0.40]

This means 40% of the boat's total weight is ballast, which is typical for a moderate cruising sailboat and provides good stability characteristics.

Frequently Asked Questions

The Ballast Displacement Ratio (BDR) is a measure of a boat stability, calculated by dividing the total ballast by the total displacement. It indicates what portion of the boat weight is ballast, which affects stability and performance.

The ratio is calculated using the formula: BDR = Total Ballast / Total Displacement. The calculator converts kg to lbs if needed and displays the result as a decimal ratio.

For cruising sailboats, a BDR between 0.35 and 0.45 is typical. Racing boats may have lower ratios (0.25-0.35) for lighter weight, while heavy cruisers may have ratios above 0.45 for maximum stability.

Yes, the calculator allows you to select units (lbs or kg) independently for each value. It will automatically convert to a common unit for the calculation.

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