Brakes and Openings

[guest]

I have heard different things from different people. Regardless of canopy control and object proximety issues after inflation, I am curious about how brake settings affect the speed of the opening for terminal and sub-term jumps.

Regarding slider off jumps (2 sec delay), does the canopy open faster or slower in deep brakes than shallow. What about not setting the brakes at all?

What about terminal and sub-term slider up jumps? Does anyone jump intentionaly without setting the brakes.

It would seem to me that not setting the brakes would result in a faster opening. Just curious, and don't want to learn anything the hard way.

thanks
BC

[imported_Tom Aiello]

Why on earth are you looking to improve opening speed at the possible expense of strike avoidance on a two second delay?

--Tom Aiello
tbaiello@ucdavis.edu

[d-dog]

Perhaps someone wants to hum a jump from a 250 foot bridge? There are logically conceivable configurations of jump variables in which heading performance is irrelevant but speed of deployment is essential. Perhaps unlikely configurations, but as a thought experiement they may aid our understanding of more common scenarios.

As to the effect of brake settings on opening speed sub-terminal, all I can say is that there is likely a difference between vented and non-vented canopies when it comes to answering this question. Which sort of leads me to my own rhetorical question:

Why would anyone consider freefalling low (sub 225 foot) objects under an un-vented canopy? I'm sure it is done, and I'm sure jumpers have their reasons - so fire away.

Peace,

D-d0g
ddog@wrinko.com
www.wrinko.com

[crwper]

I believe one of the big issues with not setting the brakes would be opening surge. Because there's nothing holding the canopy back after it's inflated, it would naturally dive forward very strongly to gather speed. On a low object, in spite of the possible benefits in opening time, this would be a major problem.

Where opening speed is critical, I've been jumping shallow brake setting on my v-tec Fox. My feeling is that this gets the canopy flying sooner, but not so quickly that it surges toward the ground.

My only 180 so far happened on a go-and-throw off a slightly overhung cliff, using a non-vented Fox in deep brakes. I had my hands on the risers well before the canopy was open, and was correcting before it started to more forward. As far as I can tell, there is no way I could have made my response any faster. Still, I missed the rock by only a few feet. Having barely escaped using deep brakes, I would hesitate to jump the same object using shallow brakes. Where my ability to correct and off-heading is critical, I still use deep brakes.

Michael

[guest]

>Regardless of canopy control and object proximety >issues after inflation,

The statement above is called a qualifier. It is meant to reduce the scope of the question to the actual inflation phase of the canopy and how this is affected by brake settings or lack thereof.

So, lets assume a non vented canopy and lets just discuss shallow vs. deep brakes (I guess the idea of no brakes is too difficult to fathom - odd considering our company).

How do brake settings affect inflation speed? Try not to think in terms of a "200 ft free fall", but just about inflation. Including slider up sub-term jumps.

Any theories are apprecieated.
thanks
BC

[guest]

To extend your statement about opening surge, I've heard it said that on a VTec Fox there's an initial push backward on the part of the canopy, due to airflow through the vents and out of the nose.

In my very limited experience and from watching others, that in combination with deep brakes has (I think) led to a surge forward (due to a pendulum effect, I suppose) which might drop you a few critical feet on a really low jump.

Shallow brakes doesn't seem to give the same oscillation. You have to ask yourself whether you're more afraid of the wall behind you (in which case deep brakes *might* be your friend) or the ground below you (in which case shallow brakes might be the way to go).

Your mileage may vary.

[Skypuppy]

I'd be very careful about 'not setting the brakes at all' - the problem with no brakes is that the surge forward on opening (bottom skin) tends to plaster the top skin down across the cell openings, leading to collapsed end cells, squirrelly non-symmetrical openings and fast rates of descent with little horizontal penetration.

Cross-porting helps this a bit, but can only do so much.

Maybe newer designed canopies don't have as much of a problem with this (especially vented canopies), but older ones certainly did.

Skypuppy

[obi]

I've asked myself the same question already, but haven't done any testing on it neither, so my knowledge about it is pretty much 0.

I remember reading about it in a tutorial book in my early skydiving days, and there it was said that setting the brakes would speed up the opening by not letting the air escape at the rear end. But looking back, I have to say that I read a lot of theoretical BS in that tutorial books.

I would guess a little forward speed helps a non-vented canopy to open.

Hasn't anyone done some testing on this?

Cya, Obi

[Skypuppy]

As I said, there's a problem because on most older canopies anyways, the top skin extends a bit forward of the bottom skin at the cell openings, and even has a bit of a scoop effect, catching air into the openings - on a no-brakes opening, the canopy surges forward as the bottom skin starts catching air, and this top skin extension can become plastered down across the cell openings until you can pull on brakes enough to relax the air pressure on the top skin, allowing the cells to open up. This is especially prevalent at either end of the canopy, which could lead to exacerbating turns or even spirals, and which, if not corrected with input, could even get worse.

Anyone who has crew experience has probably seen this sort of situation.

I would not play around with this on a BASE jump. Do it on a skydive if you want, but brakes weren't just invented for no reason.

There's a fine line between the angle of attack of a para-glider, meant to be inflated on the ground and glide (and which takes generally well over 1000' to inflate on a regular skydive, because the angle of attack is not conducive to filling the cells), and a parachute designed to inflate almost unaided.

There may be a place in the future to eliminate brake lines (and brake line hang-ups or line-overs) by designing a parachute with a low enough angle of attack to open without cell collapses on opening surge, and then maybe lengthening the rear risers to increase the angle of attack and forward speed by some sort of system similar to a 3-ring. Thus instead of setting the brakes for opening, you would effectively be setting the rear risers, and instead of using toggles to steer and flare, you would use the rear risers alone.

Anyone follow me on this? Does it seem feasible?

Skypuppy
BASE92:+