CYPRES cutter placement?

[ernokaikkonen 0]

A question to the riggers(or anyone else who knows...):

Why is it that on some rigs the CYPRES-cutter is placed on the bottom of the reserve container, and on some rigs it's on one of the reserve closing flaps?

The way I see it it would be a better choice to install it on the bottom of the container: The reserve is (slightly) easier to close, and you don't have to route the cable along the flap(less kinks in the cable, less likely to fail). There must be some advantage in installing the cutter on the flap, but I can't think of any right now...

[slotperfect 7]

On rigs with an external pilot chute, like a Javelin, the cutter will be placed on the bottom. On rigs like a Vector II with an internal pilot chute, it will be on the closing flap, otherwise when the closing loop is cut, the pilot chute spring will have to fight the friction of dragging the cut loop through all the grommets to get free.

That's what they tell me . . .

Arrive Safely

John

[ernokaikkonen 0]

Ok, that makes sense. Thanks!

[Hooknswoop 19]

Any friction from a cut loop would be negligible.

I don't have any idea why manufacturers put the cutter where they do. I'm sure Bill Booth could give a great answer though.

Hook

[riggerrob 558]

I think it is a question of how many grommets the loop has to wiggle free of afte you have scared your Cypres.
On a simple rig (like a Javelin) that only has 3 grommets before the pilotchute is free, you can place the Cypres cutter almost anywhere.
On a more complicated rig (like a Vector) where the loop must clear 5 grommets before the pilotchute can launch, you have to be more careful in Cypres cutter placement.
Mind you, Racer completely blows my theory to shreds. Racers have their cutters installed in the pack tray, so the severed loops must clear 10 grommets before the pilotchute can launch.
If you ignored written instructions (voiding TSO etc.) and installed the cutters on a Racer's side flaps, then the loops would still have to clear 6 flaps before the pilotchute could launch. Later in the deployment sequence another 4 freebag grommets would have to clear the severed loops before the freebag could lift out of the container.
I suspect that Racer cutters are positioned to be as close as possible to the ripcord pins to mimic ripcord deployments.
One pin Pop Tops are only marginally better in that respect. Once a Reflex wearer scares his Cypres, the severed loop still has to clear 6 grommets before the pilotchute can launch.
t
ll theory aside, they all seem to launch about the same. Rigger skill becomes a greater variable in practice. For example, a really long loop will slow deployment in any container because it has farther to wiggle past all the grommets. Heaven forbid if yoiu install anything but a Cypres loop because any other loop will be thicker, stiffer and slower to wiggle out of the way.

[billvon 2,400]

>One pin Pop Tops are only marginally better in that respect.

I'd argue that the dynamics are a bit different.

On a single pin poptop, once the loop is free, the force of the spring is trying to pull the loop out of the grommets, and that's a straight pull. If the grommets are even close to lined up (which they were at one point, if you use a hard bodkin or T-handle) then the pull takes the closing loop in a straight line, with the force of the spring behind it.

On something like a Vector, the spring does not pull the closing loop out. Instead, it just presses against the flaps. Once the loop is free, the spring tries to push the flaps open sideways, and as they move sideways, they drag the loop sideways until its free end clears the grommet and allows the flap to open. Once all flaps are open, the PC begins launch.

Javelins are sort of a mix of these two dynamics.

[riggerrob 558]

billvon,
We agree on one issue, but disagree on the other issue.
On the one hand, I have never used a steel bodkin to close a one-pin Pop-Top (i.e. Reflex or Teardrop) and quit using steel bodkins on Racers shortly after Cypres were invented. A learning disability makes it incredibly difficult for me to pack a Cypres-equipped Racer with the factory-recommended tools, so difficult that i found it easier to develop my own tools. Hint, a German rigger gave me the original concept and another local rigger named John Davies came to a similar conclusion by himself.
I can pack a Pop-Top quicker with one homemade tool than the 3 or 6 recommended in the manual and it vastly simplifies the final tool count.

Fortunately, billvon and I agree on the second point. I do believe that single-pin Pop-Tops (i.e. Reflex) and semi-Pop-Tops (i.e Javelin) allow the loop to slip free much easier after you have scared your Cypres. Even the Talon, with its Cypres cutter on top of the pilotchute, is a better installation than the Vector.
Mind you, this is largely an academic debate, because they all work well in practice.
The only time cutter location is likely to slow opening is if the loop is vastly too long and it gets pinched between the top of the pilotchute and the edge of grommet on the flap immediately above it. I have only seen this hesitation on a rare main configuration, that thankfully has been retired.