What is Velocity Ratio (VR)?

The Velocity Ratio is attempt to estimate the velocity of a given sail boat.

The VR for a good relatively fast boat will be about 1.0. A full-blown race boat will be in the range 1.5 to 1.8.

The VR for a good relatively fast boat will be about 1.0. A full-blown race boat will be in the range 1.5 to 1.8.

How to calculate the Velocity Ratio (VR)?

Velocity Ratio = 1.88*lwl^.5*sail area^.33/disp^.25 / (1.34*lwl^.5)

Velocity Ratio formula

Velocity Ratio formula

Abrev. | Unit | Description |
---|---|---|

lwl | ft | Length of the boat in the waterline |

SA | ft^{2} | Sail Area |

Displacement | lbs | Displacement of the boat in pounds |

Problems with the formula?

The main problem with the formula is that "sail area" and "displacement" are not clearly defined.
This means that the SA/D calculation may result in different values for the same boat.

Sail area:

Which sails is the calculation based on?

- mainsail and fok?

- mailsail and genoa? And if 'yes', which genoa?

Displacement:

- Is it the displacement for an empty boat?

- Is the motor included and what about the fuel?

- Are the weight of the crew included?

- What about water, food and the like?

In our reviews - when comparing boat types - we have decided to use the nominal sail area as defined in the ISO 8666^{[1]} standard, where the sail area is defined as (P*E + I*J)/2. where:

P:

E:

I:

J:

Sail area:

Which sails is the calculation based on?

- mainsail and fok?

- mailsail and genoa? And if 'yes', which genoa?

Displacement:

- Is it the displacement for an empty boat?

- Is the motor included and what about the fuel?

- Are the weight of the crew included?

- What about water, food and the like?

In our reviews - when comparing boat types - we have decided to use the nominal sail area as defined in the ISO 8666

P:

E:

I:

J:

References