What is Velocity Ratio (VR)
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 | ft2 | 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 [1] standard, where the sail area is defined as (P*E + I*J)/2. where:
P:
E:
I:
J:
References