SkySNATCH fra Squirrel
SkySNATCH fra Squirrel er lidt en evolution i pilotskærms design. Læs her hvad firmaet selv beskriver om den:
The SkySNATCH is an evolution in pilot chute design. The three dimensional partial toroidal shape is the most technically advanced design being used in skydiving today. Simply put, the SkySNATCH is the most efficient, stable, and symmetrical pilot chute available.
The SkySNATCH is a kill-line pilot chute system for skydiving. It comes standard with an 8′ bridle (from pin to PC attach-point, 11′ in total), attachment mallions, and a carbon fiber handle. The SkySnatch is designed to work with D-bags with a bottom grommet size of #4 or #5 only.
The Snatch project began after a conversation between Squirrel Co-designer, Will Kitto, and CRW expert, Jim Rasmussen. Although the toroidal design concept has been used extensively in parachutes for over 40 years (it is also known as an annular or pulled-down-apex (PDA) design), it has never before been put into production for skydive pilot chutes due to the complexity of the design. The Snatch has rapidly become the new standard in BASE jumping pilot chutes, where PC stability is critical. The new SkySNATCH is designed for skydivers who seek the highest quality PC available.
The SkySNATCH’s three dimensional partial toroidal shape is joined together with two mesh cones. The torus shape, like a donut cut in half, has a very high drag coefficient. “Traditional” skydiving pilot chutes are a very loose approximation of this same shape. Traditional PCs are two circles sewn together around the edges, typically one of ZP and one of mesh, with a piece of line or webbing connecting the center of each circle together at a specific distance. When pulled from the center of the mesh circle and dragged through a fluid, it inflates into a rough approximation of a pulled-down-apex shape, but with a large amount of distortion and error, with a wrinkled and asymmetric circumference. Imagine crumpling up a single piece of paper until it forms the 3D shape you want to design – it won’t look good, nor be an accurate representation of a 3D surface. Yet that is the current basis of traditional PCs: an approximate and inefficient 2D design meant to perform a task that requires a 3D shape.
The SkySNATCH’s design achieves a specific 3D shape when inflated by using multiple panels (gores), each with a mathematically calculated 3D shape. The design is similar to the way that round parachutes are designed from multiple gores to form a hemispherical shape when inflated.
A torus is made by rotating an ellipse around a center axis. For this design, we used an ellipse with a ratio of 7:10 (height : width) with an axis offset from the ellipse by 20% of its width. Mesh cones meet with the outside and inside edges of the partial torus at an exact tangent to its curve, ensuring a smooth transition from mesh to ZP, which maintains a smooth and error-free perimeter of the pilot chute. The difference between a SkySNATCH and a traditional PC design is immediately apparent when handled or inflated by any experienced jumper.
HOW IT WORKS BETTER
The inherent imperfection of the standard double circle pilot chute design means that there is a significant amount of randomness in its inflated shape. There is a constant tug-of-war between air pressure forcing it into a 3D shape, and the fabric trying to remain a 2D shape. Across its surfaces there are sections of high and low stress, where there is too much material in one section and not enough in another, causing “stretch and sag”. This can contribute to the pulsing and surging we see in traditional pilot chutes in freefall. A toroidal design minimizes the randomness and helps to ensure that the inflation is more consistent and predictable. Once inflated, the pilot chute is not searching for alternative shapes: it inflates to its intended shape and stays there. There is no pulsing, and instead only a clean inflated shape.
WHAT THIS MEANS TO YOU, THE JUMPER
Per square millimeter, the SkySNATCH pulls with more stability than a traditional PC. Wind tunnel and field testing have shown superior stability in all applications, from CRW to Wingsuit use.
WHAT SIZE SHOULD I CHOOSE?
The SkySNATCH is not necessarily more or less powerful than other PCs of similar size. The main difference is stability. For example, if you find that your 30″ PC is functioning well for wingsuit use currently, then a 30″ SkySNATCH will work similarly depending on the design factors specific to your current PC. If you are using an older 0-3fcm (F-111) PC for skydiving currently and are happy with the extraction force it is providing, then you may need to choose a smaller size of SkySNATCH.
SkySNATCH BRIDLE LENGTH
The SkySNATCH bridle length is 8′ from pin to PC (11′ in total, but we don’t measure the start of our pony tail at our foreheads). The optimum bridle length for skydiving and BASE jumping has been debated many times. The SkySNATCH bridle length is chosen based on the burble size of an average wingsuit pilot flying at a responsible and acceptable speed and angle of attack for deployment. Extending the length beyond 8′, in our opinion, only provides a crutch for pilots in irresponsibly slow or inefficient deployment configurations, and also increases the risk of bridle/PC entanglement. More bridle does not increase the inherent safety of the system and in fact decreases it (in our opinion, based on extensive field testing in the BASE environment).
WEIGHT & BALANCE, AND MATERIALS
We believe pilot chute weight to be a critical safety factor. For over a decade now, the BASE community has known that hacky-sack-handles are bad, and contribute to PC/bridle entanglements because of their weight. Yet there are still countless PCs in use today which feature heavy and bulky PVC handles and overbuilt/clumsy construction. Evidence suggests that lighter is better, and for that reason we have created the lightest design that we could without sacrificing durability. A lighter PC is less likely to entangle with the bridle: it tumbles less, and is carried downstream at rates more similar to the bridle. A heavier PC can be carried downstream at a slower rate than the bridle, which can cause the heavy PC to then tumble and mix with the bridle in the jumper’s burble.
HEXAGONAL CARBON HANDLE
The hexagonal carbon-fiber handle design is very light. It provides a distinct easy-to-feel shape, with minimum weight. The carbon hex is standard on all SkySNATCHes. We do not offer other handle options.
QUALITY AND PRECISION
Each SkySNATCH is guaranteed to be symmetric in construction. PC symmetry is critical – while there are many factors that can cause a pilot chute to exhibit unstable behavior, ensuring that your PC is built symmetrically is important to ensuring stable parachute extractions.
WHY WE ARE OPEN SOURCING THE DESIGN
The toroidal concept was not invented by Squirrel, and has been in use in the military and civilian parachute industries for decades. In addition to that, we feel that the benefits of this design are such that all parachutists should consider using it. For that reason, patterns for certain sizes of the SNATCH can be downloaded for free. Just email us to request 2D patterns ready to be printed or plotted, and sewn. The files available can be opened with all common CAD programs, many of which can be found for free online.