Blank

Contents

The Blank component has no shape. It is a coordinate frame -- an origin and a set of axes -- placed in the model like any other component, and drawn in the 3D view as an axis triad at its origin (red $X$, green $Y$, blue $Z$), with one triad at each symmetric copy. With Pick on in the Geom Browser, click the triad to select the Blank.

What a Blank Is For

A Blank gives a model a frame that belongs to no part of the airframe. It is used to:

• Hold a group of components together. Components attached to a Blank move with it, so an engine installation, a cockpit or a payload bay built under a Blank is moved or turned by changing the Blank alone. Put a Blank at the top of any assembly whose origin should not be on one of its parts.
• Carry a mass that has no shape, such as equipment, fuel or passengers (see Point Mass).
• Mark a point for components that refer to a point rather than a surface. A Routing point on a Blank lies at the Blank's origin, so a route can run through free space. An Auxiliary super cone or rotor fragment zone hung from a Blank sits at the Blank's origin with the Blank's axes, which is more flexible than the origin of the component it describes.

A Blank has no surface, so it is left out of every analysis that works on shape (CompGeom, DegenGeom, CFD meshing, export). Children attached to it by UW, RST, LMN or $\eta$MN coordinates fall back to its origin and axes. A Blank cannot be flipped: its axes always stay right-handed.

Point Mass

A Blank's only mass is the concentrated mass of the Specified Mass Properties on the Mass tab (see Mass); the density, priority and thin-shell settings are greyed, since a Blank has no volume or area for them to act on. The center of gravity is measured from the Blank's origin in its own axes, so a Blank placed at an item of equipment carries that item's mass with its center of gravity at zero. While the Blank is selected and has a mass, the 3D view marks the center of gravity with a blue point.

Shared Tabs

The Gen, XForm and Mass tabs are common to every component; see Gen, XForm and Mass. A Blank has no Sub tab, since it has no surface to carry sub-surfaces.

Scripting

A script adds a Blank with AddGeom( "BLANK" ) and sets its point mass through the parms PointMass, CGx, CGy, CGz and Ixx to Iyz in the group Mass_Props.