Metric Formula

[power boater]

Gentlemen

On How to Design a Boat, by John Teale, there is the formula to find Draft as Displacement(in lb)/(L x B x Cb x 64), my question is the metric formula as Displacement(in KG)/(L x B x Cb x 1025) ?
Are there any other methods or formulas to optain Draft?
Thank you in advance.

 

[fredrosse]

In English Units Draft(feet) = Displacememt (Lb) / (Length(ft) x Beam(ft) x Cb x 64(Lb seawater per ft^3) ),
In Metric Units Draft(Meter) = Displacememt (kg) / (Length(Meter) x Beam(Meter) x Cb x 1025(kg seawater per Meter^3) ),

"my question is the metric formula as Displacement(in KG)/(L x B x Cb x 1025) ? " :the answer, YES you are correct

"Are there any other methods or formulas to optain Draft?"
The fundamental equations shown above relate the submerged volume of sea water to the weight of sea water displaced, this is a fundamental, there is no other way. Although determining the factor "Cb" can have many complicated mathematical forms, it is just a factor = 1 for a pure rectangular badge hull, and a number significantly less than 1 for streamlined hulls.

 

[TANSL]

In reality, this formula is not used to obtain the depth, but on the contrary, once the depth and the rest of the dimensions are known, this formula gives us the block coefficient. The draft is obtained, with forms already defined although provisional, by calculating the weight of the boat. It may also be that you determine the draft by some other requirement that the ship must meet, or by comparison with similar ships, and that conditions its shapes and everything else.

 

[sharpii2]

Use consistent, directly connected units in your measurements.

For example, if you are describing your displacement in metric tons, use meters as your standard unit.

If you are describing your displacement in kilograms, use delimiters (10ths of a meter). A cubic decimeter of water is a kilogram.

 

[Heimfried]

Use consistent, directly connected units in your measurements.
[...]

Right, but the examples you give are not appropriate to the formula given in the OP.

Displacement(in KG)/(L x B x Cb x 1025)

As 1025 is used for sea water density it has the unit kg/m³. For this reason the input of lenght and breadth is in meters and the result (draft) is also in meters.

@power boater
An additional remark: The block coefficient Cb is calculated for the design water line (zero trim and list). This involves a design displacement. In case of different displacements this formula won't give you the correct draft.