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Method 3 alternative 1.

The extracted factor can be used directly to determine a correction in tones to apply to the final displacement.

Correction (tone) = factor x TPC x hog/sag (cm)

Where: hog/sag (cm) = (DM-AMD) x 100

 

Method 3 alternative 2.

The graph or table itself may be adapted to give a correction table directly in tones (i.e. factor X TPC) for each centimeter of hog or sag. This would give a correction to apply to the final displacement by entering the table with the AMD and the hog/sag in CMS.

 

Other alternative methods.

These require additional draught/freeboard measurements at points other than perpendiculars and midships, along the vessels length. This is very difficult to establish.

 

CORRECTION FOR TRIM

There may be a total trim correction table included in the stability information book. This will normally combine the following 1st.and 2nd.corrections. Find out what it includes, and examine the ships stability data carefully before conducting a survey.

First trim correction (Correction for Layer)

The displacement scale is normally calculated on the assumption that the vessel is lying on an even keel. The first trim correction is to correct the draught midships to the true mean draught, at the center of flotation. This correction is known as the correction for layer (or layer correction).

 

AP Midship FP

 

W1

LCF

W L

Layer Correction Trim

TMD

TMD

L1

LBP

AP aft perpendicular FP forward perpendicular

TMD true mean draught AMD arithmetical mean draught corrected for hog or sag

LCF longitudinal center of flotation LBP length between perpendiculars

Layer correction (metros) = (distance LCF to midships) x trim/ LBP

Then TMD = AMD +/- layer correction

1st trim correction (tones) = layer correction x TPC x 100

Metric: 1st trim correction (distance LCF to midships) x TPC x trim (cm)

LBP

Imperial: 1st trim correction (distance LCF to midships) x TPI x trim (inches)

LBP

Actual displacement = tabulated displacement +/- 1st trim correction

Sign convention: Trim LCF forward of midships LCF aft of midships

Aft negative (-) positive (+)

Forward positive (+) negative (-)


Date: 2016-01-03; view: 613


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