| Part of a series on vessels'
Vessel have different framing systems depending on the mission profile of the vessel, no one framing system is perfect for every ship type and to save weight and increase strength the framing system will need to be optimized by the structural designer.
The direction (transverse, longitudinal) of a vessels framing system is chosen based upon the structural loads it will be subject to, the ability to run the structural members uninterrupted over great lengths, localized considerations for vibration, and the ability to form frames to the hull form. As vessels approach 90 meters in length, longitudinal strength requirements become dominate - favoring full or partial longitudinal framing. For icebreaking vessels, transversely applied hull plate pressures dominate, favoring transverse framing. For larger icebreakers, unstiffened panel size is minimized by utilizing both types of framing simultaneously (i.e., a grillage structure) which runs in both directions.
Transverse framing is the traditional framing system. Individual frames run across the breadth of the vessel. Spacings are denoted longitudinally. Transverse framing is particularly good for small ships, ships subject to repeated impact loading, and to ships with a lot of shape to their hullform.
Longitudinal framing is ideal for longer vessels. Individual frames run lengthwise to the vessel. The longitudinal members provide a modest bump to longitudinal strength, and can save steel weight. Longitudinal framing is ideal for plate with little curvature, such as in vessels with significant parrallel middlebody.
Grillage framing uses mutually supported transverse and longitudinal primary structure. Grillage framing is typically used to minimize structural intrusion, as it can be demonstrated that grillage structures are always heavier than traditional framing methods. They are also more labour intensive to construct. Grillage structures tend to be found in the bow sections of icebreakers and in some naval vessels.
Combination framing is used in situations where a vessel can benefit from longitudinal framing systems, but areas remain of loading, outfit, or hull shape where transverse is more suited. A vessel with parrallel middlebody, but a cruiser stern may switch to transverse framing in the aft end; or a vessel fitted with a bulbous bow may transition to transverse frames forward. It is also possible to frame decks longitudinally, and shell transversely; particularly when transitioning from one type of framing to the other.