1 Stability criteria in the intact condition
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Statutory Documents - IMO Publications and Documents - International Codes - HSC 2000 Code - International Code of Safety for High-Speed Craft, 2000 – Resolution MSC.97(73) - Annex 7 - Stability of multihull craft - 1 Stability criteria in the intact condition

1 Stability criteria in the intact condition

 A multihull craft, in the intact condition, shall have sufficient stability when rolling in a seaway to successfully withstand the effect of either passenger crowding or high-speed turning as described in 1.4. The craft's stability shall be considered to be sufficient provided compliance with this paragraph is achieved.

  1.1 Area under the GZ curve

The area (A1) under the GZ curve up to an angle θ shall be at least:

where θ is the least of the following angles:

  • .1 the downflooding angle;

  • .2 the angle at which the maximum GZ occurs; and

  • .3 30°.

  1.2 Maximum GZ

The maximum GZ value shall occur at an angle of at least 10°.

  1.3 Heeling due to wind

The wind heeling lever shall be assumed constant at all angles of inclination and shall be calculated as follows:

where:
=
= (see figure 1)
where:
V W = wind speed corresponding to the worst intended conditions (m/s)
A = projected lateral area of the portion of the craft above the lightest service waterline (m2)
Z = vertical distance from the centre of A to a point one half the lightest service draught (m)
Δ = displacement (t)

Figure 1 Intact Stability

  Abbreviations used in figures 1 and 2:

HL 2 = Heeling lever due to wind + gusting
HLT = Heeling lever due to wind + gusting + (passenger crowding or turning)
HL 3 = Heeling lever due to wind
HL 4 = Heeling lever due to wind + passenger crowding
θ m = Angle of maximum GZ
θ d = Angle of downflooding
θ r = Angle of roll
θ e = Angle of equilibrium, assuming no wind, passenger crowding or turning effects
θ h = Angle of heel due to heeling lever HL 2, HTL, HL 3 or HL 4
  • A 1 > Area required by 1.1
  • A 2 > 0.028

  1.4 Heeling due to passenger crowding or high-speed turning

Heeling due to the crowding of passengers on one side of the craft or to high-speed turning, whichever is the greater, shall be applied in combination with the heeling lever due to wind (HL 2).

  1.4.1 Heeling due to passenger crowding

When calculating the magnitude of the heel due to passenger crowding, a passenger crowding lever shall be developed using the assumptions stipulated in 2.10 of this Code.

  1.4.2 Heeling due to high-speed turning

When calculating the magnitude of the heel due to the effects of high-speed turning, a high-speed turning lever shall be developed using either the following formula or an equivalent method specifically developed for the type of craft under consideration, or trials or model test data:

where:
TL = turning lever (m)
V o = speed of craft in the turn (m/s)
R = turning radius (m)
KG = height of vertical centre of gravity above keel (m)
d = mean draught (m)
g = acceleration due to gravity

 Alternatively, another method of assessment may be employed, as provided for in 2.1.4 of this Code.

  1.5 Rolling in waves (figure 1)

The effect of rolling in a seaway upon the craft's stability shall be demonstrated mathematically. In doing so, the residual area under the GZ curve (A 2), i.e. beyond the angle of heel (θ h), shall be at least equal to 0.028 up to the angle of roll θ r. In the absence of model test or other data θ r shall be taken as 15° or an angle of (θ d - θ h), whichever is less. The determination of θ r using model test or other data shall be made using the method for determining θ Z in 1.1.5.3 of annex 6.

Parent topic: Annex 7 - Stability of multihull craft
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