# Spacer Properties
This defines the properties of a spacer chain made up of a series of spacer elements. Each individual spacer chain has its own unique spacer property number. The properties determine how the nodes along the spacer chain are controlled during the form-finding process.
Spacer elements are only used in form-finding analysis. They are ignore in all other solutions.
# Definition
Name
The name is only used as a convenient way of identifying a spacer property.
Spacer Axis
The axis number, which is only used when the spacer leg length type is “Projected Ratio”. (Global or user defined axis, local axis is not available.)
Type
The types are
- Geodesic – Geodesic spacers will reposition the nodes in 2 directions within the tangent plane. The tangent plane is defined by the normal vector of the node on a 2D fabric surface.
- Free – Free spacers will reposition the node in only one direction; the tangent direction is defined by the two legs of the spacer connected to the node.
- Bar – Bar spacers will reposition the nodes in all three directions. Bar spacers can be imagined as Tie elements except the spacer element length will be adjusted during form-finding analysis to meet the nodal spacing requirement.
Spacer Leg Length Type
The spacer leg length types can be defined as
- Proportional – Final spacer leg length will be proportional to the original leg length.
- Ratio – Final leg length of the spacer elements will form a geometric series using the ratio defined in the Spacer leg ratio column.
- XY plane projected ratio – Final projected leg length of the spacer on the xy plane of the Spacer Axis will form a geometric series with the ratio defined by the spacer leg ratio.
- X axis projected ratio – Final projected leg length of the spacer on the x Spacer Axis will form a geometric series with the ratio defined by the spacer leg ratio.
Spacer stiffness
If the spacer is imagined as a Tie element, the spacer stiffness is equal to EA (where E is the Young’s modulus and A is section area). If zero is specified, a default value will be used in form-finding analysis.
Spacer leg ratio
This is only used when spacer leg length type is Ratio or Projected Ratio. For example,
where