Regulation 38 - Sheer
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Statutory Documents - IMO Publications and Documents - International Conventions - Load Lines, 1966 - International Convention on Load Lines, 1966 - Annex I - Regulations for Determining Load Lines - Chapter III - Freeboards - Regulation 38 - Sheer

Regulation 38 - Sheer

  General

  (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 ⅙ L and ⅓ L from each perpendicular shall be increased by 0.444 Z and 0.111 Z respectively.

  (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) of this Regulation.

  Standard Sheer Profile

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

Standard Sheer Profile
  (Where L is in metres)  
  Station Ordinate
(in millimetres)
Factor
After half After Perpendicular 25 1
⅙ L from A.P. 11.1 3
⅓ L from A.P. 2.8 3
Amidships 0 1
Forward half Amidships 0 1
⅙ L from F.P. 5.6 3
⅓ L from F.P. 22.2 3
Forward Perpendicular 50 1
Standard Sheer Profile
  (Where L is in feet)  
  Station Ordinate
(in inches)
Factor
After half After Perpendicular 0.1 L+10 1
⅙ L from A.P. 0.0444 L+4.44 3
⅓ L from A.P. 0.0111 L+1.11 3
Amidships 0 1
Forward half Amidships 0 1
⅙ L from F.P. 0.0222 L+2.22 3
⅓ L from F.P. 0.0888 L+8.88 3
Forward Perpendicular 0.2 L+20 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 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 per cent of the standard, credit shall be allowed for the part in excess; where the after part is less than 50 per cent of the standard no credit shall be given for the excess sheer forward. Where the after sheer is between 50 per cent and 75 per cent 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:

where
s = sheer credit, to be deducted from the deficiency or added to the excess of sheer,
y = difference between actual and standard height of super-structure at the end of sheer,
L' = mean enclosed length of poop or forecastle up to a maximum length of 0.5 L,
L = length of ship as defined in Regulation 3 (1) of this Annex.

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.

  Correction for Variations from Standard Sheer Profile

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

where
S = is the total length of enclosed superstructures.

  Addition for Deficiency in Sheer

  (14) Where the sheer is less than the standard, the correction for deficiency in sheer (see paragraph (13) of this Regulation) shall be added to the freeboard.

  Deduction for Excess Sheer

  (15) In ships where an enclosed superstructure covers 0.1 L before and 0.1 L abaft amidships, the correction for excess of sheer as calculated under the provisions of paragraph (13) of this Regulation 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 0.1 L before and 0.1 L abaft amidships, the deduction shall be obtained by linear interpolation. The maximum deduction for excess sheer shall be at the rate of 125 millimetres per 100 metres of length (1 inches per 100 feet of length).


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