The cutter on the CYPRES is strong…much stronger than you think! Though the job of the cutter is to cut through the reserve closing loop, people are amazed that it can cut through steel!
A major ‘aha’ moment for inventor Helmut Cloth came in 1987 when he patented his idea of having a cutter initiate the opening sequence of the reserve container by cutting the reserve loop. The brilliance of this design was that it was a separate function from a skydiver initiating emergency procedures which pulls the ripcord pin out of the closing loop.
What makes the CYPRES design excellent is it takes a set of complicated calculations within a microprocessor and is housed in a simple design reducing the amount of mechanical components. The cutter is a great example of this as it has been reduced to a single movable piston in the release unit. The piston only has to move 5mm in order to activate and cut the reserve loop.
Another part of the innovative design is the V shape of the cutter itself. This is a major detail that most jumpers never see, but a detail that every skydiver should know about because it could literally save your life. The V-Cut design only cuts the loop one time. This is an important detail because it reduces the error rate of the closing loop having an unclean cut and then possibly jamming. To our knowledge, the CYPRES cutter has never failed to sever the reserve closing loop when the loop has been routed correctly.
Other cutter designs use a circular knife shape. The circular design does not rule out the possibility of the loop becoming jammed within the housing of the cutter. Below is an example of other cutter designs using the circular cutter. The second illustration demonstrates that the loop must be cut twice and there is a small gap which exists between the knife and cutter case.
This may not sound like a big problem until you see the potential outcome. Below: two images from an AAD competitor (non-CYPRES brand) demonstrating what can happen if the reserve loop is not completely severed.
Take four skydivers on a rainy English day and mix it with a dose of skepticism. Can CYPRES really do as it claims… only using a 4mm thick piece of steel wire? They were as astonished as you’re about to be!
WARNING: Please do not try this. Cutting steel with a CYPRES may result in serious injury.