Formula issues

Many (most!) formulas refer to 'Sail Area' of a sailboat without defining what they actually mean by the sail area. Which sails is the calculation based on?
- mainsail and fok?
- mainsail and genoa? And if 'yes', which genoa?
It is obvious that using different value for the sail area will result in different result

Mitigation:
In our calculations, we 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.

Advantages:
- A well recognized international ISO definition is used.
- The calculation are well defined.
- Since the same definition is used for all boats, similar boats can be compared.

Disadvantages:
- Looking at a specific calculation for a specific boat, the calculation is not entirely fair as no boat has precise this sail area. The area of the standard jib might be ok, but the main sail will typically be a bit larger.

Many (most!) formulas refer to 'Displacement' of a sailboat without defining what they actually include in their displacement.
Examples:
- Is the weight of the motor included? and what about the fuel?
- Are the weight of the crew included?
- What about water, food and the like?

To highlight the displacement issue, the International Standard ISO 12217-2^[2] operates with 6 (six!) different definitions for the displacement of a boat:

m	Mass of the boat, used where more than one loading condition is considered
mEC	Mass of the boat in the empty craft condition
mLC	Mass of the boat in the light craft condition
mMO	Mass of the boat in the minimum operating condition
mLDC	Mass of the boat in maximum load condition
mLA	Mass of the boat in the loaded arrival condition

Mitigation:
In our calculations, we use the m_EC or equivalent mass condition.

Advantages:
- A well recognized international ISO definition is used.
- Since the same definition is used for all boats, similar boats can be compared.

Disadvantages:
- Looking at a specific calculation for a specific boat under sail m_EC cannot be used. In this scenario, the displacement must also include crew, fuel, and cargo. For a boat under sail m_MO or m_LDC would be a better choice.

Most people consider length as loa (Length over all). Unfortunately the term 'loa' is not well defined. In the good old days, the loa was measured as the length of the hull (L_H). The loa did not include the pulpit, bathing ladder, and the like. When you look in sales brochures nowadays, the loa includes these exterior items because the boat will appear longer. We believe that it is the old interpretation of the loa (i.e. L_H) that is intended to be used in the formulas.

Mitigation:
Therefore - in order to avoid any confusion - we use the length of the hull (L_H) as defined in ISO 8666^[1] in our calculations as this is consistent with the old interpretation of the loa.

Advantages:
- A well recognized international ISO definition is used.
- Is well aligned with length defined by international sailing rules and provided by measurers.
- Since the same definition is used for all boats, similar boats can be compared.
- The value is often easy available.

Disadvantages:
- None identified.