Basejumper.com - archive

Nice ass save on toogles from 140 meter E
http://vimeo.com/69884781#

damn nice save-wish they would have put up the rest of the aerial footage of the 180

Nice save indeed, but the toggle-ninja reflexes might not have been necessary if the jumper had properly set custom deep brakes. Look at the angle of the surge on opening. That thing had quite a bit of forward speed. I have a fLik with the same vent configuration with proper DBS and it doesn't surge forward like that on opening, allowing precious extra tenths of a second to respond before striking the wall. Tune your DBS people!

One thing to remember, is even with properly set brakes, when you have a 180 and are still on the pendulum forwards, you are technically loading the front risers for a certain period of time. Until you swing back underneath the canopy, you will be loading the front risers... after that, a good custom deep brake setting will help you with your rear riser turns. I have custom set brakes that the canopy more or less falls backwards upon opening, but when i do packed 180 practices, there is a certain surge on opening from loading the fronts.

I've now seen a number of vids from this wall now and it seems like you guys always take it down and open beside that big ledge. Any reason why you don't open above it?

Also try to pop both brakes.

why?

I have often struggled to understand when people describe the position of the jumper (in absolute terms or with respect to the harness) as having an effect on the fore/aft loading of the risers. The front and rear riser meet at a single attachment point that is hinged. The distribution of force across the canopy (and therefore line attachment points) is what determines fore/aft riser loading. And this has a natural tendency to average out quickly. The position of the jumper can only affect lateral distribution of riser loading.

This is to say, we can make harness turns, but we cannot make harness dives (or flares for that matter).

I have also experienced the pendulum effect that try2live described.

I don't think it's about forces through the "hinge point," I think it's better visualized as where the jumper's center of mass is compared to the aerodynamic center of the wing. When you push off and do a short/no delay, and have an on-heading, you are in front of your canopy's direction of travel, and you swing backwards relative to the wing. It happens so fast you might not notice it. But open in a full track and you can't ignore it.

If you had a 180 on this same jump, you are now aft relative to the canopy's direction of travel, and you will still swing back under the canopy. Which is "backward" from your point of view, because you are facing the trailing edge of the canopy. But the canopy is facing the other direction, so it surges "forward" in that direction as you spin out of the 180-- hence the forward surge.

A more technical explanation:

Every wing has an inherent pitching moment, which is the difference between the center of pressure and the aerodynamic center of the wing. In an airplane, this moment is counterbalanced by the horizontal stabilizer and elevator inputs.

A parachute does not have an empennage, so the pitching moment is counteracted by where underneath the canopy the jumper is hanging, and it can be a very sensitive position (i.e. just put a tiny bit of pressure on your front or rear risers). In the first instant after opening, the moment caused by the hanging jumper is not yet in equilibrium with the pitching moment, hence a pendulum swing until equilibrium is established. It's an inherently stable system that is well-damped and quickly reaches equilibrium.

Furthermore, although it's perhaps more subtle:

If you have line twists, and not just a simple 180 half twist, the "hinge point" as you call it shifts upward. Additionally, and someone correct me if I'm wrong, but line twists will shorten different line groups unequally. I can remember line twists where one riser's lines were shortened subtly more than others, and the result is canopy warp, and an induced turn until the twists are cleared.

And even with just a simple 180, still think about what it is doing to the effective canopy trim. There is probably some effect and depending on how asymmetric the twist is, could be very noticeable.

Colm,

Thanks for the notes. This explanation makes much more sense than foreward/aft riser loading to me.

Cheers,

Chris

Any time!

The guys just like the longer delays.

Well, I see a couple of things which I would like to comment..
First: DBS wasn´t on that packjob (seen in the screenshot, DBS is at the connector link).
Next, for a slider down jump, I do not route the brakelines through the slider and the ring. With a tailgate, the chances for a lineover became very small, but you never know...
In addition, the routing on my brakesetting comes from the outer side of the risers, due to the expected force on the brakelines during SD or no slider jumps. I think, that routing the brakelines from inside might lead to friction on the LRT configuration. I don´t want to have that..

To the flying, this is the old discussion about riser or toggleturns.
He managed it, so ok. Congrats.
But for me its obvious, that with one steering line down and the other still attached (even not in deep brakes), the turn is with right hand half brake (more or less). so the outcome is what we see: slow turn to the left. if you fly with toggles, be sure that you release both and you know the technique to fly in very deep brakes.

For the pendulum thing, the explanation for me is: if falling flat you will swing to the direction you´ve jumped.. because you are attached at your shoulders. if you have a 180, then the game starts... no DBS? >canopy will dive "forward", supported by the drag on the tail (swing...). assymmetrical opening will support linetwists as well because with the swing, the crossing of risers or linegroups occur more easily. once the risers or linegroups are crossed, you have an ideal turningpoint with very low friction...
Everyone who tried as a child to twist the ropes/chains on a swing remembers that. first it is hard to twist it, once the ropes or chains came across each other, you easily spin with low input..

(sorry for my bad english..)

Was there a bit of a harness turn there to try and huck it around?

Q for everyone, now that Ive seen the screen shots with break lines routed through slider and ring (like a SU set-up), is this a common practice is todays BASE world? I was always told by my mentor and many, many experienced jumpers/riggers that this set-up on SD jumps was no good. I always felt like the lines being "free" once toggles unstowed gave much more "control" for sinking, flat-turns, etc on tight landing areas. I've been retired for a few years now so just curious if a majority of folks are rigging this way or just personal preference like most things in BASE? Thx

its not very common in fact I have not seen it from anyone else personally. Im a toggle guy and switch a lot from slider down to up and just started playing around with it slider down.

I've seen brakes routed through the rings and grommets a couple of times on SD. It was usually b/c the guy packing the rig got distracted during the pack job, had a beer too many , etc. and left them configured for SU accidentally. In the three or four times I've seen it (I did it myself; once)-it worked out. That being said, I wouldn't make a habit of it.

Homey did a nice job of sorting that 180. You can argue unstowing both toggles, etc. But it worked. And that's what matters.

-Harry

I dont rig lines outside the keeper rings when going slider down. This follows a discussion with a very experienced gear manufacturer who outlined the following as his rationale:

Correct tailgate eliminates line overs to a degree where you have much bigger things to worry about in base 1). If your brake lines are in good condition then the likelihood of them breaking is virtually nil 2). Re-rigging can potentially introduce errors 3). Canopy flies differently when re-rigged 4) and if you let go of a brake you've lost effective control having to rely on rear risers 5). I was convinced although i am in a minority. Disclaimer- i do very little SD jumping, virtually all SU.

1) Inspect your canopy, if they start to wear, replace them.
2/3) you are base jumping, know how to rig your shit up. stop being lazy. this is no excuse.
4) have you tried this personally? i know i have and i still made it to where i wanted to be.

Pro: more control over the canopy. you are flying it with less constrictions allowing more range. i do a bit of SD jumping, i recommend you see the difference with making turns outside of the ring at different lengths from your body. full arms out, half out, down your center. try seeing how deep you can get a turn by crossing your arm across your body.

Thanks for your reply to my post. In response to your points;

1. Yes, i do inspect my brake lines, usually before every trip where i do 25-35 jumps.
2-3. i think i "know my shit" to use your venacular. Reducing the level of complexity of a system generally reduces the number of areas for error or fault. Im human and dont think i am immune to inducing an error but more than competent at minimising.
4. Yes, i used to get stand up landings on rear risers under a phatomn 22, jumped both 7 and 9 cells and landed each on rear risers on one occasion each.
As an aside your canopy wont fly as well if you have lost one brake and are compensating with both a riser and opposing brake. If you can identify ONE person who you know or have met who has had a line over with a correctly installed tail gate, I am sure the base community would love to know.
Ps I am not lazy, just old.
Pps. I will leave it to any other expereinced jumpers to chime in, but i can think of 2 gear manufacturers who either do as I do (i took their lead) or another who couldnt fault my approach when i asked for them to find the flaws with the approach inwas thinking of taking.
Have a nice day.

Leaving the lines inside the rings may be a good idea if:

Most of your jumps are slider up (and you don't want to have the 1 jump re-learning curve on your 1 in 100 that is slider down)

You are a professional skydiver and occasional BASE jumper, so you are very familiar/comfortable with the feel of the lines through the rings, but not so much with the lines outside the rings.

You are a toggle grabber for offheading correction (because if you fumble and drop a toggle you can get it back).

Your landing areas are so tight/broken that a riser landing is either an impossibility or a very likely injury.



If you do route the lines inside the rings, I would definitely recommend using some sort of line release system.

Personally, my lines stay outside the rings, but I can't remember the last time I did a slider up jump, and I don't want to have to re-adjust to flying the canopy with the lines inside the rings.

I have it on video.

I'm not sure he wants me to share his name publicly, so I'll PM it to you.