How fast can a chute open (static line)

[cesslon 0]

HI,
if you do a static line off say a antenna whats the fastest it can open and gain full flight.

like can it do that in under 100feet ? and if so how many feet exactly, and by full flight I mean, fully inflated and flying forward at 4:1 forward to down etc

[nicknitro71 0]

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4:1 forward to down etc

No BASE canopy can give you 4:1 glide ratio. It's more like 2:1. Now even the most efficent skydiving canopy gives you 4:1, maybe 3:1, at most.

As for your question there is no simple answer. There are many other variables to plug in but I bet under 100' you'd better off not releasing the brakes and land on rears otherwise you might risk a forward surge. Just my .2. Someone with sub 100' jumps can comment better, I don't jump that low, I'm chicken

Memento Audere Semper

903

[gus 1]

There are a couple of videos floating around of some pretty low jumps, the one I'm thinking of was from something like 64 feet (on to a beach?). That canopy was nowhere near full flight when the jumper landed.
I haven't done any jumps even approaching that kind of altitude but I have recently done a couple of static lines from 160 (Troll 265 MDV). I had time to pop the brakes, let it fly for a few seconds and get a proper flare. So in answer to your question, I think under 100 ft is unlikely. 120? 130? There are a lot of variables.

Gus

OutpatientsOnline.com

[sabre210 0]

Still a lot of factors to narrow down. Headwind , crosswind, tailwind or no wind??? Vented or non vented canopy, size of canopy, jumpers weight??? wing loading????Static line attachment point: if you remove the pilot chute and 9ft bridle and attach directly to a shorter bridle of say 2feet that's a 7ft gain straight away. 7ft difference would be huge if you're jumping from 120ft

Then there's a fully pressurised flying stable canopy and a landable inflated but not fully pressurised canopy. Which one are you after??? How hard a landing do you want???

ian

[TomAiello 26]

It depends on too many factors to provide a clear answer.

I did get a video emailed to me recently that shows a static line from 113 feet, where the canopy is fully flying by landing.

-- Tom Aiello

Tom@SnakeRiverBASE.com
SnakeRiverBASE.com

[Treejumps 0]

You should be fine from the roof of your mom's house.

[skreamer 1]

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if you remove the pilot chute and 9ft bridle and attach directly to a shorter bridle of say 2feet that's a 7ft gain straight away.

I know we were recently discussing ways of tying off on the bridle itself but your suggestion/idea above intrigues me. Maybe tying off onto a regular bridle 2' from the pin would still be better because you could then still have the PC as a backup?

[DexterBase 1]

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Maybe tying off onto a regular bridle 2' from the pin would still be better because you could then still have the PC as a backup?

I agree with this setup because you are effectively shortening the distance you need to drop to get to linestretch but you're not shortening the bridle.

While there's not much burble at all on a SL jump, I don't like the idea of having a 2 foot bridle. There is an exception I'm aware of where a shorter bridle is desirable, but I'm unsure of the relation to SL type jumps.

[sabre210 0]

Will and Dexter (that was a short retirement!!!)

I totally agree and in fact that kind of is what i do (we do) anyway. I usually larkshead a loop in the bridle about 3ft away from the pilot chute and tie off to that.

The benefit of using a specifically made shortened bridle is that it would be inherently simpler (K.I.S.S.). If you tied off to a loop 2ft from the shrivel flap or pins using a standard BASE bridle then you would have 7ft of bridle and then a big PC dangling down from the object. The more stuff flapping around down there, the more chance of a snag or hang up. You can only stow the excess bridle (using a tailgate bungee or tape) between the pins/flap and the anchor point, and not between the anchor point and the pc as this will never get popped apart and effectively renders the pc pretty useless from the altitudes we're talking about here.

So what it boils down to is losing the backup (PC)and gaining simplicity and manageability on the exit point (but losing any second chance in the event of a premature breakage) or retaining the backup (which might be more of a psychological than physical advantage) but complicating the rigging and enhancing the chance of snagging the object.

It's a tough call, but all said and done i have yet to static line without a PC attached so i guess we agree.

laters

ian

[Faber 0]

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While there's not much burble at all on a SL jump, I don't like the idea of having a 2 foot bridle. There is an exception I'm aware of where a shorter bridle is desirable, but I'm unsure of the relation to SL type jumps.

Huh? i made you a 1 ft bridel,thourght we should flik some low shit in the summer

Stay safe
Stefan Faber

[vid666 0]

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Will and Dexter (that was a short retirement!!!)

I totally agree and in fact that kind of is what i do (we do) anyway. I usually larkshead a loop in the bridle about 3ft away from the pilot chute and tie off to that.

The benefit of using a specifically made shortened bridle is that it would be inherently simpler (K.I.S.S.). If you tied off to a loop 2ft from the shrivel flap or pins using a standard BASE bridle then you would have 7ft of bridle and then a big PC dangling down from the object. The more stuff flapping around down there, the more chance of a snag or hang up. You can only stow the excess bridle (using a tailgate bungee or tape) between the pins/flap and the anchor point, and not between the anchor point and the pc as this will never get popped apart and effectively renders the pc pretty useless from the altitudes we're talking about here.

So what it boils down to is losing the backup (PC)and gaining simplicity and manageability on the exit point (but losing any second chance in the event of a premature breakage) or retaining the backup (which might be more of a psychological than physical advantage) but complicating the rigging and enhancing the chance of snagging the object.

It's a tough call, but all said and done i have yet to static line without a PC attached so i guess we agree.

laters

ian

Unless I missed it :

a 2 ft bridle ??? That would mean your canopy is 2ft MAX from the object - is the fact that you can be 4-5 or even more feet away with a good push, thus having less chance of a snag ( think underhung 3 legged freestander or a balcony jump with more balconies underneath ) not important enough ?

sorry for the run-on sentence... What am I missing here ?

[sabre210 0]

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What am I missing here ?

not much but....we're talking ultra low static line here, around the 110ft mark (maybe even lower).2 feet of bridle, whether a regular bridle attached 2 feet from the pins/flap or a specifically constructed one i alluded to earlier will indeed put your canopy closer to the object. What you have to weigh up is if that is a greater risk than losing say 7ft of your 110ft in altitude. On the one hand a potential snag with the object, on the other a very real appointment with the hard ground.

These are the kind of dilemmas and decisions which really get the blood pumping don't you think?

ian

[pilotdave 0]

Videos:
102 feet
88 feet
63 feet

Dave

[vid666 0]

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Videos:
102 feet
88 feet
63 feet

Dave

102ft - TARD from a span - minimal canopy snag factor ( roaddeck) ?
88 ft - DBAG from what looks like severely overhung cliff over wet sand
63 ft - I am not sure what the deploymenth method was, perhaps Jason can fill us in.

All in all, I am still interested in rehashing my original question of SL hooked to the very beginning of the bridle and the effect it may have on the canopy pressurizing pretty much next to the object.

In one post NickDG said something to the effect of "jumping an underhung tower has one good thing : if you have a 180 you don't build enough forward speed to smack it hard" - perhaps that is also true of a SL attached to the beginning of the bridle ( provided bottom skin inlets are present )

Sorry I am i am rambling. I definitely don't have much experience, but this thread caught my attention.

[vid666 0]

Quote

Quote

What am I missing here ?

not much but....we're talking ultra low static line here, around the 110ft mark (maybe even lower).2 feet of bridle, whether a regular bridle attached 2 feet from the pins/flap or a specifically constructed one i alluded to earlier will indeed put your canopy closer to the object. What you have to weigh up is if that is a greater risk than losing say 7ft of your 110ft in altitude. On the one hand a potential snag with the object, on the other a very real appointment with the hard ground.

These are the kind of dilemmas and decisions which really get the blood pumping don't you think?

ian

Ok,

I see what you are saying.

But why not :

install some kind of trap on the bridle very close to where it comes out of the container ( a knot is what i was thinking but i am guessing it can move a bit down ) - hook your SL into it, stretch the rest of the bridle so instead of hanging down, it's above you ( if possible ) or behind you, stretched out ( again if possible ). Rubberbanding it or masking taping parts of it in the appropriate locations would make it more snag proof as well as make the PC "engage" above or level with exit point vs. below it

now what am i missing ?

[sabre210 0]

I couldn't really visualise what you described if i am completely honest but it sounded complex. Regardless ,unless i am missing something i'm not sure how it would help. To my mind (and it is a simple one) we're dealing with a relationship which is inversely proportionate. The faster you aim to open the canopy after stepping off the object, by that very nature the closer you will be to the object. The longer you take to open the canopy after exiting, the further you will be from the object (tracking being the extreme of this). On a very low static line jump you need a canopy fast and so by shortening the bridle by X feet, you will begin the deployment sequence X feet sooner, just as surely as by using a 100ft bridle on a 110ft jump you will bounce.

Now if the object in question had a lot of filthy shit hanging off it just below the exit point (small localised antenna for example) then I'd consider walking away and just daydreaming about it.....after all, there's no shortage of 100ish feet objects in the world is there.

That's just me.....i'm queer like that.

ian

[crwper 7]

In that altitude range, your time to full flight also depends very strongly on a) your launch technique and b) how you unstow the toggles. In my humble opinion, it's one of these cases where, "If you have to ask, it's too low." By the time you're jumping something like that, you should already have significant experience from an object, say, 10 feet higher which will answer your questions.

Michael

[cesslon 0]

Hi,

thanx for the replys.

I think my answer was missunderstood (or not asked correctly)
what I meant by "can it open in under 100 feet" I didn't mean jump off somthing under 100 feet I asked this question with no object heigh in mind, it could be 2000 feet, I was just curious as to how soon on average a base chute would be fully inflated and flying

[sabre210 0]

In answer to your question then, yes if you static lined a 2000 ft antenna you should expect to be under a flying canopy above 1900ft. Just the right height to watch a skydiver scream by at terminal under a pilot chute hesitation.

Crwper: could you describe your toggle unstowing technique for low static line jumps??? I am curious as to how you limit the forward surge.

ian

[TomAiello 26]

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...ould you describe your toggle unstowing technique for low static line jumps??? I am curious as to how you limit the forward surge.

I'm not sure of crwper's technique. But what I do is bring the toggles all the way down to the level of the brake setting immediately, then slowly ease them up. Generally, I flare before they get all the way up. The idea is to build speed gradually into the flare, without letting the canopy dive forward (potentially into the ground). This way, you can flare effectively at any point (i.e. whenever you reach the ground).

-- Tom Aiello

Tom@SnakeRiverBASE.com
SnakeRiverBASE.com

[crwper 7]

Hey,

Tom's described it perfectly. You want to release the brakes from the set as quickly as possible with a fast downward motion. Then let them up in a very controlled manner. You'll need to feel that out a bit, but the idea is that if you let the toggles up too quickly, you'll actually put energy into the canopy's natural forward surge. If you let them up too slowly, well, you won't get forward speed as quickly as you could. Somewhere in between is the optimum.

What comes to mind for me is "critical damping" in suspension systems, for example. If your shocks weren't stiff enough, every time you hit a bump you'd bounce down the road for a while afterward. If they are too stiff, the springs never really get a chance to do their job, since all the force is translated straight into the car. Somewhere in there is "critical damping". Basically the idea is that when you compress the spring, the shock will let the spring unload at the fastest possible rate without "overshooting".

Let me know if this is helpful, or possibly I have just bungled the explanation. :)

Michael

[sabre210 0]

Tom and Mike

Thanks. This is what i effectively try and do....however in the heat of the moment, i suspect i probably let the toggles up too quickly and get the surge. I'll keep this in mind on my next jump. Cheers

ian