Making It Safe- Testing our net products
Gavin Smith
When we design and build our net products such as aerial nets, flying trapeze nets, fall arrest, debris and cargo nets we always take the opportunity to destruction test our prototypes and validate the design before moving into the production phase.
What that means is we get to break things on a regular basis, and when things break it gets pretty exciting to see how and where they break and how close our theoretical calculations are to the real thing.
Our Aerial nets have been developed over decades of research, development and performance experiences. We have developed the unique process of machine overlocking the edges to prevent fraying and provide a structural rigging point anywhere along the ridge or border of the net. The evolution of hand sewn and reinforced corners are still used for some of our aerial nets but we find generally the aerial artists enjoy the freedom of rigging the nets anywhere along the edge of the net and corners.
Nets are a very complex product for us to build, the possibilities of augmenting a flat piece of netting into a 3 dimensional shape really gets our thinking caps on. The mathematical component of net building is the key to understanding how a net can be constructed and how it behaves under load. For example, when we select a new net mesh to construct a flying trapeze net or fall arrest net, we measure the mesh squares either on the stretched diamond or on the square, a T90 mesh (measured on the stretched diamond) is actually 45mm x 45mm on the square and the twine size could be 5mm diameter and constructed with 210 ply yarn. If that’s not confusing enough try ordering a bail of net mesh on the diamond and turning it around on to the square.
If you have ever noticed, an old flying trapeze net will always have a small diagonal join on the bed where the net mesh has been joined, that’s because when net mesh used to be made only on the diamond you had to cut it on the square and stitch a piece to fill in the gap. Net beds are usually mesh on the square and aprons on the diamond. Nowadays you can buy 45 mm x 45 mm x 5 mm net mesh on the square at widths of 4 metres or greater, perfect for flying trapeze nets and less work and less waste to build them.
Back to the destruction testing! How do we test nets? There is a standard test for the actual mesh which can indicate the strength of each intersecting mesh join, this test lets us know how much each square can be loaded before it breaks, this amount varies with each type of fibre, such as nylon, polypropylene, and the construction, such as knotted or knot-less and the ply or amount of yarn that has been used to weave the net.
We use this data from the individual destruction test of the net mesh squares and apply it to the entire net, the formula used to calculate the Work Load Limit (WLL) of a net is basically the number or net squares in the X direction multiplied by the number of net squares in the Y direction. We then take the net or a sample net and apply force until it breaks, for this we have built a test plate that is placed in the centre of the net and connected to our test bed.
Our dedication to safety and quality assurance means our products and services are the highest quality anywhere on the market.