Making big ships beyond 50m was problematic in OFP because there was the 50m geometry limit, geometrys just didn't work on objects (p3d models) larger than 50m. ArmA still has this same limitation, so any big ship you're going to make, you need to build it in 50m x 50m pieces.

Create the pieces as you like and when you prepare the config, do it like this. First a model.cfg:

class CfgSkeletons
{
	class Default;
	class NimitzBones: Default
	{
		isDiscrete=1;
		skeletonInherit="";
		skeletonBones[]=
		{
			"nm_alt",""
		};
	};
};

class CfgModels
{
	class Default
	{
		sections[] = {""};
		sectionsInherit="";
	};
	class Ship;
	class bridge: Ship
	{
		skeletonName="NimitzBones";
		sectionsInherit="";
		sections[]={ "clan","clan_sign","zasleh" };
	};
	class USS_Nimitzback1 : bridge{};
	class USS_Nimitzback : bridge{};
	class USS_Nimitzfront1 : bridge{};
	class USS_Nimitzfront : bridge{};
	class USS_Nimitzlata : bridge{};
};

And then a config.cpp:

class CfgVehicles
{
	class All;
	class Static:All
	{
		class UserActions;
	};
	class building: Static{}; 
	class uss_nimitzbase : building
	{
            	vehicleClass="Ship";
		unitInfoType = "UnitInfoShip";
		nameSound = "ship";
		cost = 10000000;
		accuracy = 1000;
		side = 1;
		icon = "";
		armor = 30000;
		scope = 1;
		class EventHandlers
		{
			killed = "(_this select 0) exec ""\hwk_uss_Nimitz\script\fire.sqs""";
		};
	};

	class uss_nimitzback : building
	{
            	vehicleClass="Ship";
		unitInfoType = "UnitInfoShip";
		nameSound = "ship";
		cost = 10000000;
		accuracy = 1000;
		side = 1;
		icon = "\hwk_uss_Nimitz\icon.paa";
		model = "\hwk_uss_Nimitz\USS_Nimitzback";
		armor = 30000;
		scope = 2;
		displayName = "USS Nimitz";
		destrType = "DestructEngine";
		mapSize = 360;

		class EventHandlers
		{
			init = "_this execVM ""\hwk_uss_Nimitz\script\build.sqf"";";
		};
	};
...
};

The above config is just an example, not complete usable config!

As you see the model is setup as house class object. Next is the build.sqf script that createVehicle's the 50m ship blocks together. The key there is to take the initial mission editor placed object and set it and the rest of the objects into 0.2 elevation.

For further discussion, check making big ships topic. PMC would like to thank [APS]Gnat for providing this information.