Crossbracing

Related categories : Gear Technologies

What is a Cross Brace Tri-cell?
Cross Brace Tri-cell means the cell is divided into three chambers instead of two, with the chambers diagonally braced to force each cell back into shape. Viewed from the front, a canopy normally has a zigzag appearance. The cells are deformed due to a lack of internal support, with only a free floating, non load bearing rib between them. But if you look at the front of a Cross Brace Tri-cell, both the upper and lower surfaces appear smooth.

Where did the idea come from?
Performance Designs originated the idea with a parachute called the Excaliber, in the late 80's. It was a rectangular, F-111 Cross Brace Tri-cell, and in its day it was awesome. The Excaliber out performed anything else available at the time. It was eventually superseded by Zero-P parachutes, which out performed the Excaliber using only conventional construction.

What are the advantages?
There is less drag because there are less lines for more chambers. This improves the shapes of the surfaces without adding more line and creating more drag.

The canopy is more rigid in flight. Due to the triangulation of the cell structure the cells are 'locked' into position rather than being free floating and able to breathe.

The canopy surfaces are less distorted. A ram air canopy inflates to form a wing; ideally one that is smooth and straight like an airplane wing. But rather than being a rigid structure, a canopy wing is made from an inflating membrane with surfaces that distort; significantly reducing their effectiveness.

See Distortion for a further explanation.

Disadvantages of this canopy design
There are a couple of unavoidable trade-offs with this design, and jumpers went through the same issues when ZP canopies first appeared. Pack volume and price will undoubtedly put a few people off.

1.Pack volume - A regular 9 cell canopy consists of 40 different panels. A 7 Cell cross braced like the JFX or the Velocity consists of 53 different panels and an increased amount of material is required to support the cell structure. Consequently a 104 sqft cross brace tri-cell will pack up about the same as a 125 sqft regular ZP canopy - an approximate 20% increase in pack volume. You will undoubtedly go down in canopy size but you probably will not want to go down 20% to get the equivalent pack volume (unless you were intending a reduction anyway). So you will probably end up with a bigger rig than with another canopy.

2.Price - Material and construction time involved is significantly increased when manufacturing a cross brace tri-cell. It can take up to twice twice as long to manufacture compared to a conventional canopy. Finally, as there can be less lines the loading is a little higher on each attachment point so reinforcing can be different.

Examples of canopies using the Cross brace technology

 * JFX
 * JVX
 * JPX-Petra
 * Matrix II
 * Velocity
 * Xaos 21
 * Xaos 27