Draft and Displacement Survey Instructions

CroMark

Croatian patent HR P20010731A

DRAFT AND DISPLACEMENT SURVEY INSTRUCTIONS

The procedure for ships with CroMark draft marks

OIL PRODUCT/CHEMICAL CARRIER

m/t “STINICE”

Figure 1. The CroMarkdraft marks

Main Particulars: Loa=188,90 m, Lpp=180,00, Bmld=32,20 m, Hmld=19,15 m

T=11.20 m, Tscant= 12,20 m, DWT= 40 398, DWTscant= 45 000 t

Classification ABS

The very first vessel on the world with CroMark draft marks

Built 2002 by: BRODOSPLIT – BRODOGRADILIŠTE d.o.o.

SPLIT - CROATIA

Yard No. 431

The basic CroMark procedure

The basic CroMark procedure employs only two draft readings at positions where the observed drafts coincides with the equivalent drafts (Fig. 1.):

• The CroMark draft observed aft:
• The CroMark draft observed forward: .

The CroMark equivalent draft at the position LCF (Longitudinal Center of Flotation) is defined as: .

The CroMark standard equivalent draft at once provides the input draft for displacement calculation from standard hydrostatic data, accounting simultaneously for sensible hull hogging or sagging, as well as trim, as follows:

Note that for intermediate data in the Table 1, linear interpolation can be applied.

Example: The CroMark draft readings aft and forward are and .

The CroMark standard equivalent draft directly follows as .

The displacement accounting simultaneously for hull hogging or sagging and trim from ship's hydrostatic data (Table 1), is obtained for CroMark equivalent draft as follows:

.

The auxiliary CroMarkprocedure for ships fitted with optional CroMark draft at LCF

The fitting of auxiliary CroMark draft marks at the position LCF (Longitudinal Center of Flotation) is optional, Fig. 1. If fitted, the draft reading on the at once provides displacement assessment for negligible hogging or sagging, accounting for sensible trim corrections only, as:

For excessive hull deflection, theCroMark hogging or sagging is defined by employing the observed CroMarkdraft and the equivalent draft , both at the position LCF, as follows:

.

The probable maximal hogging or sagging at the position of LCF, can be assessed by employing , the draft correction factor (Table 1) and the CroMark deflection as .

Note and are considered positive for hogging and negative for sagging condition.

Normally, the amidships deflection does not differ significantly of the deflection at LCF, moreover, the difference even cannot be practically measured.

The actual displacement of a deflected ship hull can be assessed by using the waterplane area and the specific gravity of the sea , as follows:

.

Note that for intermediate data in the Table 1, linear interpolation can be provided.

Example:

The auxiliary CroMark draft reading observed at LCF is .

The CroMark sagging is obtained as .

The CroMark probably maximal sagging is assessed for at draft (Table 1) as

.

The actual displacement of a deflected ship hull is assessed by using the waterplane area (Table 1) and the specific gravity of the sea , as follows:

.

For details see the attached CroMark‘Draft and Displacement Survey and Explanatory Notes’.

Additional CroMark procedure for ships fitted with CroMark draft marks

The additional CroMark calculations apply to trim and drafts, as well as to hogging or sagging relative to perpendiculars and amidships. The following data are required (Fig. 1, Table 1):

The CroMark longitudinal distance from the 1/4 between perpendiculars:

The CroMark longitudinal distance from the 3/4 between perpendiculars:

The overall longitudinal distance between the aft and forward CroMark draft marks: .

Calculations:

The CroMark trim in meters is defined as: .

The CroMark angle of trim in radians is obtained as .

The trim with respect to the perpendiculars in meters is obtained as follows: .

Note the positive trim is by bow, negative otherwise.

The aft draft and the forward draft at the perpendiculars accounting for the hull trim and deflection, are calculated as follows:

.

The mean draft is .

The amidships draft is calculated as. .

The amidships hogging or sagging can be assessed as: . Note is positive for hogging and negative for sagging condition.

Example:

The CroMark distance from the 1/4 between perpendiculars (Table 1): .

The CroMark distance from the 3/4 between perpendiculars (Table 1): .

The longitudinal distance between the CroMark draft marks (Table 1): .

The CroMark trim: .

The CroMark angle of trim: .

The trim with respect to the perpendiculars: .

The aft and forward drafts at the perpendiculars can be calculated as presented next:

.

The mean draft is .

The calculated draft amidships is calculated next:

.

The amidships sagging, relative to perpendiculars, amounts to:

.

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TABLE 1. BRODOSPLIT YARD No. 431 m/t "STINICE OIL PRODUCT/CHEMICAL CARRIER

Main Particulars:Loa=188,90 m, Lpp=180,00, Bmld=32,20 m, Hmld=19,15 m, T=11.20 m, Tscant=12,20 m, DWT=40398, DWTsc=45000 t

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