Regulation 38 - Sheer
Clasification Society 2024 - Version 9.40
Statutory Documents - IMO Publications and Documents - International Conventions - Load Lines, 1966/1988 - International Convention on Load Lines, 1966, as Amended by the Protocol of 1988 - Annex I - Regulations for Determining Load Lines - Chapter III - Freeboards - Regulation 38 - Sheer

Regulation 38 - Sheer


  (1) The sheer shall be measured from the deck at side to a line of reference drawn parallel to the keel through the sheer line amidships.

  (2) In ships designed with a rake of keel, the sheer shall be measured in relation to a reference line drawn parallel to the design load waterline.

  (3) In flush deck ships and in ships with detached superstructures the sheer shall be measured at the freeboard deck.

  (4) In ships with topsides of unusual form in which there is a step or break in the topsides, the sheer shall be considered in relation to the equivalent depth amidships.

  (5) In ships with a superstructure of standard height which extends over the whole length of the freeboard deck, the sheer shall be measured at the superstructure deck. Where the height exceeds the standard, the least difference (Z) between the actual and standard heights shall be added to each end ordinate. Similarly, the intermediate ordinates at distances of 1/6L and 1/3L from each perpendicular shall be increased by 0.444Z and 0.111Z, respectively. Where there is an enclosed poop or forecastle superimposed on the superstructure, sheer credit shall be allowed for such a poop or forecastle, according to the method of paragraph (12) as shown in figure 38.1.

Figure 38.1

  (6) Where the deck of an enclosed superstructure has at least the same sheer as the exposed freeboard deck, the sheer of the enclosed portion of the freeboard deck shall not be taken into account.

  (7) Where an enclosed poop or forecastle is of standard height with greater sheer than that of the freeboard deck, or is of more than standard height, an addition to the sheer of the freeboard deck shall be made as provided in paragraph (12).

 Where a poop or forecastle consists of two layers, the method shown in figure 38.2 shall be used.

Figure 38.2

 In figures 38.1 and 38.2, the following definitions apply:

Z = is as defined in paragraph (5); and
Zv = is the end ordinate of a virtual standard parabolic curve taken through the point "X". If Zv is greater than (Z + h), the end ordinate shall be (Z + h), in which case point "X" shall be disregarded and curve (2) not taken into account.

 When the length of the first tier superstructure is greater than 0.5l, the virtual standard parabolic curve shall commence at amidships as indicated in figure 38.1.

Standard sheer profile

  (8) The ordinates of the standard sheer profile are given in the following table:

Table 38.1 Standard sheer profile (where L is in m)

  Station Ordinate (in mm) Factor
After half After perpendicular 1
L from A.P. 3
L from A.P. 3
Amidships 0 1
Forward half Amidships 0 1
L from F.P. 3
L from F.P. 3
Forward perpendicular 1

Measurement of variation from standard sheer profile

  (9) Where the sheer profile differs from the standard, the four ordinates of each profile in the forward or after half shall be multiplied by the appropriate factors given in the above table of ordinates. The difference between the sums of the respective products and those of the standard divided by 8 measures the deficiency or excess of sheer in the forward or after half. The arithmetical mean of the excess or deficiency in the forward and after halves measures the excess or deficiency of sheer.

  (10) Where the after half of the sheer profile is greater than the standard and the forward half is less than the standard, no credit shall be allowed for the part in excess and deficiency only shall be measured.

  (11) Where the forward half of the sheer profile exceeds the standard, and the after portion of the sheer profile is not less than 75% of the standard, credit shall be allowed for the part in excess. Where the after part is less than 50% of the standard no credit shall be given for the excess sheer forward. Where the after sheer is between 50% and 75% of the standard, intermediate allowances may be granted for excess sheer forward.

  (12) Where sheer credit is given for a poop or forecastle the following formula shall be used:

s = is the sheer credit, to be deducted from the deficiency, or added to the excess of sheer;
y = is the difference between actual and standard height of superstructure at the after or forward perpendicular;
L' = is the mean enclosed length of poop or forecastle up to a maximum length of 0.5 L; and
L = is the length of the ship as defined in regulation 3(1).

 The above formula provides a curve in the form of a parabola tangent to the actual sheer curve at the freeboard deck and intersecting the end ordinate at a point below the superstructure deck a distance equal to the standard height of a superstructure. The superstructure deck shall not be less than standard height above this curve at any point. This curve shall be used in determining the sheer profile for forward and after halves of the ship.


  • (a) Any excess in the height of a superstructure which does not extend to the after perpendicular cannot be regarded as contributing to the sheer allowance.

  • (b) Where the height of a superstructure is less than standard, the superstructure deck shall not be less than the minimum height of the superstructure above the virtual shear curve at any point. For this purpose y shall be taken as the difference between the actual and minimum height of the superstructure at the after/forward perpendicular.

  • (c) For a raised quarterdeck credit may be given only when the height of this quarterdeck is greater than the standard height of ’other superstructures’ as defined in regulation 33, and only for the amount by which the actual height of the raised quarterdeck exceeds that standard height.

  • (d) When a poop or a forecastle has sloping end bulkheads, the sheer credit may be allowed on account of excess height. The formula given in paragraph (12) shall be used, the values for y and L’ being as shown in figure 38.3.

Figure 38.3 Sheer credit S for excess height

Correction for variations from standard sheer profile

  (14) The correction for sheer shall be the deficiency or excess of sheer (see paragraphs (9) to (11) inclusive), multiplied by

where S 1 is the total length S of enclosed superstructures as defined in regulation 34 without trunks.

Addition for deficiency in sheer

  (15) Where the sheer is less than the standard, the correction for deficiency in sheer (see paragraph (14)) shall be added to the freeboard.

Deduction for excess sheer

  (16) In ships where an enclosed superstructure covers 0.1L before and 0.1L abaft amidships, the correction for excess of sheer as calculated under the provisions of paragraph (14) shall be deducted from the freeboard; in ships where no enclosed superstructure covers amidships, no deduction shall be made from the freeboard; where an enclosed superstructure covers less than 0.1L before and 0.1L abaft amidships, the deduction shall be obtained by linear interpolation. The maximum deduction for excess sheer shall be at the rate of 125 mm per 100 m of length.

 In applying this paragraph, the height of the superstructure shall be related to its standard height. Where the height of the superstructure or raised quarterdeck is less than standard, the reduction shall be in the ratio of the actual to the standard height thereof.

Copyright 2022 Clasifications Register Group Limited, International Maritime Organization, International Labour Organization or Maritime and Coastguard Agency. All rights reserved. Clasifications Register Group Limited, its affiliates and subsidiaries and their respective officers, employees or agents are, individually and collectively, referred to in this clause as 'Clasifications Register'. Clasifications Register assumes no responsibility and shall not be liable to any person for any loss, damage or expense caused by reliance on the information or advice in this document or howsoever provided, unless that person has signed a contract with the relevant Clasifications Register entity for the provision of this information or advice and in that case any responsibility or liability is exclusively on the terms and conditions set out in that contract.