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# Intact stability calculation

The mass and centre of gravity of the whole system are input for the intact stability calculation. For this tutorial a very simplified stability calculation is used. The only input value that is required is the moment of area inertia of the waterline area.

• Create a new class in the Knowledge Browser alongside the others that you have made so far: `Intact stability calculation`.
• Create the following parameters in the Knowledge Browser:
 Parameter name Dimension Determined by Reference In Class `BM` [m] USR: User or system/equation Distance between center of buoyancy and metacenter `Intact stability calculation` `GM` [m] USR: User or system/equation Metacentric height `Intact stability calculation` `KB` [m] USR: User or system/equation Distance between keel and center of buoyancy `Intact stability calculation` `KG` [m] USR: User or system/equation Distance between keel and center of gravity `Intact stability calculation` `Moment_of_Inertia` [m^4] USR: User or system/equation Moment of inertia of the water plane area,For this tutorial give a rough estimate `Intact stability calculation`

• Include the following parameters in entity` Intact stability calculation`: `Loa`,`Boa`,`BM`, `COGX`, `COGY`, `COGZ`, `Displacement`, `GM`, `KB`, `KG`, `Moment_of_Inertia`, `Rho`, and `T_design`.
• Create the following relations (either entity relations or normal relations, it does not matter here):

`Loa = ENTITY#(xx).Loa` where “xx” is the `QEntityID` value of entity `Main Dimensions`.

`Boa = ENTITY#(xx).Boa` where “xx” is the `QEntityID` value of entity `Main Dimensions`.

`GM = KB + BM – KG`

`BM = Moment_of_Inertia / (Displacement/Rho)`

`KG = COGZ`

`KB = 0.7*T_design`

`T_design = ENTITY#(xx).T_design` where “xx” is the `QEntityID` value of entity `Hydrostatics`.

`Displacement = ENTITY#(xx).Mass` where “xx” is the `QEntityID` value of entity `Mass calculation`.

`COGX = ENTITY#(xx).COGX` where “xx” is the `QEntityID` value of entity `Mass calculation`.

`COGY = ENTITY#(xx).COGY` where “xx” is the `QEntityID` value of entity `Mass calculation`.

`COGZ = ENTITY#(xx).COGZ` where “xx” is the `QEntityID` value of entity `Mass calculation`.

`Rho = ENTITY#(xx).Rho` where “xx” is the `QEntityID` value of entity `Hydrostatics`.

• To show computed values set attribute @SHOW on `QEntityData`.

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