Two terms commonly used in tensioned fabric architecture are Saddle and Facet. Though they are not exclusive of this industry, they each can be used to explain a phenomenon in tensioned fabric.
Saddle: Often said to be the fabric “sucking in,” this effect happens in areas that are under tension but not specifically held by a frame. It most often occurs in the spans between supports where the fabric is allowed to curve inward because of stretch, gravity or a combination of the two. It is almost always an arch shape. The depth of the saddle is defined by a number of factors including elasticity of the fabric, the cutting pattern, tension level and distance between supports. The more stretch a material has, the deeper the curve inward will be without alteration. This gives pieces a uniquely fabric look with graceful inward curves. Shapes that benefit the most from saddling include funnels, sails and ribbons. Fabric can be patterned in a way that promotes exaggerated sucking in of the fabric if desired on these pieces. Saddling offers the reverse effect of air inflated pieces where the framework or support is recessed inward while the air pushes the rest of it out.
If you have never experienced fabric saddling, there are places in nature that you can see a similar result. A bats wings when extended and the webbed feet of ducks have the same arched look between the supports.
Understanding how saddling can benefit your design is important in creating successful projects. There are some shapes that you want to play up the saddling effect.
- Kite shapes
- Custom-looking archways
- Tensioned sails
If you want to minimize saddling there are a number of options:
- Add more frame supports to reduce the unsupported span of the fabric
- Use a less elastic material for construction
- Add a non-stretch stabilizer on the edges such as webbing or aircraft cable
Facets: This is the flat faces on geometric shapes. Fabric like other fluid materials will take the path of least resistance. This creates a flattened area between skeletal protrusions. Borrowed from the gemstone industry, facets showcase angles. Facets can lend a futuristic look to the pieces by creating sharper edges. Lighting at sharp angles can increase the impact.
Think of a crystal with flat edges at various angles, coming together to create unique geometric shapes. Sea salt is a crystal substance most are familiar with that has flat edges with sharper angles. Another way to imagine this effect is to recall the Geodesic domes frequently found on playgrounds. A piece of fabric stretched over this piece will result in a series of triangles rather than a smooth sphere shape. The ways to reduce facets are similar to those that reduce saddling. With the emergence of projection mapping, facets create beautiful areas for vibrant projections.
Facets in fabric can replicate the feel of a number of items in our world; including but not limited to:
- Prisms and Holograms
- Glass, Beads and Crystal
- Stained Glass
Facets and Saddling are not mutually exclusive. Often on large dome like structures there will be a combination of facets and areas with saddling combined in one piece.
Understanding how saddling and facets will impact the design can change the way we expect fabric to behave, allowing it to create amazing unique pieces that can only be accomplished by a substrate with textiles.