GHS BULLETIN

GHS BULLETIN GHS LIMIT commands based on Navy stability criteria

Rev. 06/2018

Intact severe wind and wave:

  HMMT WIND /C2
  ROLL = 25
  LIM RISE > 0.667
  LIM RESIDUAL RATIO FROM ROLL TO RA0 > 1.4

Lifting, Crowding & Turning:

  HMMT = x /CS
  LIM RISE > 0.667
  LIM ABS ANGLE AT EQU < 15
  LIM ABS RATIO FROM EQU0 TO RA0 > 1.667                `* conservative approximation

Towline adds to Lifting:

  LIM ANGLE FROM MAX TO ABS 40 OR FLD > 0
  LIM ABS RATIO FROM EQU0 TO ABS 40 OR FLD > 1.667      `* conservative approximation

`* Use DDS079 wizard for precise evaluation of A1/A0 which requires two righting arms

Damage:

  LIM ABS ANGLE AT EQU0 < 15
  LIM RESIDUAL RATIO FROM ROLL TO ABS 45 OR RA0 > 1.4
  LIM RESIDUAL RATIO FROM ROLL TO FLD OR RA0 > 1.4
 `roll angle depends on displacement
  LIM RA AT MAX > 0.25  `(units must be feet)

These interpretations of the Navy criteria are not necessarily appropriate for every type of vessel in every loading condition and in all types of service. Additional limit commands and/or changes to the parameters as shown above may be needed in order to guarantee adequate stability.

A value attained for the RISE limit (A) can be converted to the value of the ratio of righting arm at equilibrium to righting arm at max (B) as follows:

  B = 1 / (1 + A)

For example, A = 0.667 yields B = 0.6.

A value attained for the ABS RATIO limit (A) can be converted to the value of the ratio of residual area to total area (B) as follows:

  B = 1 - 1/A

For example, A = 1.667 yields B = 0.4.

To allow for off-center weights, the transverse center of gravity can be set to an appropriate value. If it is desired that the transverse center of gravity of the total weight (including tanks) be 0.05, the following command can be used:

  WEIGHT (TOTAL) *, *, 0.05, *

This will set the transverse componenet of the light ship CG such that the overall TCG comes out to be 0.05. Since the MAXVCG command ignores the TCG (as well as tank loads), this will not affect MAXVCG curves.

For a run file that calculates the Rollback Angle for damage stability:
Click here

If you would like to see another bulletin created regarding a specific topic, please email Creative Systems, Inc. at support@ghsport.com.