Basejumper.com - archive

for a 200m base jump from a tower should we use slider up or slider down?
and should the brake line goes through the lope on the risers ?

Slider down

Outside the slider grommets and the guide ring.

Download this manual. Look on page 31.

Packing Manual

I realize that you must not have anyone to help guide you so take extra care to think things through.

Good luck.

Awesome! Anyone other than an Iranian would have been set on fire publicly, but because of where he lives and the assumption of his ability to access the information, it is handed to him to hopefully save his life.

Some things just don't need to be said. I don't flame people D. No matter where they live. This is text on a website, there's no real fire here.

I'd like to see more of this, in a non-tree-hugger fashion of course...

once you use sail slider at 200m you never go back....the ground rush is awesome!

I didn't think about the different ways people could see my post before I posted it. wwarped sent me a pm saying I didn't need to be so harsh. I didn't mean to seem harsh. This was my reply to him.

I guess I should go clarify in my post that I have no prejudice, I didn't mean to seem harsh, it was just something I noticed and wanted to point out. Not just Iranian obviously, but any country with similar circumstances, that us citizens and many other countries can not freely travel in and out of, don't really have the access to people with knowledge that the rest of the world does, and therefore people don't have a problem with the fact that this guy is going to make a base jump based solely off of information from the internet.

go slider down. tie the slider to your links on the front risers - not the back risers. use appropriate toggles that won't jam in case of a line over. use the line mod. use the tailgate. use a 2.5 to 3 m long bridle. use a large pilot chute - a 42 inch ( 1 inch = 2.54 cm) pilot chute in this case. if you use a pin rig, make sure the pin is not too tight. use deep brake settings. make sure the wind is at your back bisecting the wires in the section you plan on jumping. read as much here in the articles section as you can. don't repeat mistakes that the BASE community has learned from for the past 30 years.

This article does not include information about the tailgate. The tail gate is essential now for safe slider down jumping.

From Walt Appel, circa 1995:

This is the fifth in a series of articles that I am posting about BASE jumping. It gives general tips on how to set up a parachute for BASE jumps. In this article the focus, of course, is on skydiving parachutes, since canopies designed and manufactured specifically for BASE jumping should need no significant modification. I will be devoting the next several articles to canopies. Future articles will include more discussion on equipment, techniques, and general info. I will also discuss sources for gear and information.

Feel free to e-mail me, but don't ask me to recommend specific sites. I will not recommend specific sites, nor do I recommend BASE jumping. BASE, even though it has evolved a great deal over the past few years, is still somewhat experimental and I consider it to be an extremely dangerous activity. I am posting these articles because the lessons that have been learned about BASE have cost us dearly. I do not want to see anyone hurt or killed because they were unknowingly re-inventing the sport.

In case, you're wondering about my background in BASE, I have made 55 BASE jumps, mostly freefalls from under 500 ft, from a variety of sites. I make and sell BASE accessories, e.g., pilot chutes, bridles, mesh sliders, etc., and I have been on the Bridge Day staff for the past few years.

Disclaimer: I am not now, nor will I ever be, the final word on BASE jumping. Nobody is the ultimate authority.

BASE is an extremely dangerous activity. In my opinion, the best way to reduce your chances of injury or death is to talk with as many experienced BASE jumpers as you can, learn as much as possible, *think* about it, and jump in a way that makes sense to you. This article is written from one person's point of view (mine) and you'd be nuts to consider it the best or only point of view. There is a lot more to BASE than any series of articles can present. Use the information only as a starting point.

Attitude
Before I get to the subject at hand, I'd like to discuss attitude. BASE jumping is very psychological. Making your mind function properly in the presence of extreme adrenaline is not an easy thing. Because of this, you need to make the most of your preparation, including gear setup. Build in as much safety margin as you can. Humans are fallible, and you need to acknowledge to yourself that you are capable of making mistakes. Try to choose gear that will make up for your mistakes. Use the gear that gives you the highest probability of a safe outcome; it will give you a comfort level that you desperately need at the exit point.

Setting Up a Canopy for BASE Jumping
In previous articles, I've emphasized that BASE jumping gear needs to be configured for the site and the type of jump that it will be used on. In this article, I'll explain how to setup a ram-air canopy so it can easily be used for a variety of jumps and sites.

Note: I'm not going to discuss round canopies in this article because the rounds that are suited as special-purpose BASE canopies need very few, if any, changes. I'll point out a few things in a future article when I discuss packing round canopies.

Let's start by summarizing the features that a good ram-air BASE canopy will generally have, as discussed in the previous article.

# It will be a low aspect ratio seven cell, made of non-zero- porosity fabric;
# It will have dacron or nylon (not Spectra) suspension lines;
# It will have a very strong reinforcement scheme at the bridle attachment point(s) and all suspension line attachment points;
# It will have a very durable construction;
# It will have a surface area that is large enough to give soft landings even in deep-brakes approaches.
What more could you want? Here's a list. Bear in mind that I'm talking about setting up a canopy that will be used for BASE jumping at a variety of sites. You may not want or need all of these items:

# At least one BASE pilot chute and one BASE bridle,
# A mesh slider,
# A tailpocket,
# A riser/toggle combination that is secure but will release very easily, even under high loading on the steering lines,
# Multiple (2 or 3) brake settings, including deep brakes.
BASE Pilot Chutes and Bridles
You may have noticed that BASE jumpers put a great deal of emphasis on their pilot chutes. There is plenty of good reason for this. BASE jumping without a pilot chute that will provide quick deployment at low airspeeds is can quickly lead to a sudden, violent death. Don't do it. Most BASE jumpers have at least two BASE pilot chutes--one for very short delays, e.g., 0-2 seconds, and one for longer delays, e.g., 2-5 seconds.

My choices for BASE pilot chutes are:

# A 42 inch diameter zero porosity PC for delays of 2 to 4 secs.
# A 46 inch diameter zero porosity PC for delays of less than 2 secs.
These choices are reasonably conservative in nature and I consider them to be a good starting point. You wouldn't want to go much larger on the pilot chutes unless you are using F-111 pilot chutes. In that case, I recommend a 45 or 46 inch F-111 pilot chute for 2 to 4 second delays and a 48 to 50 inch F-111 pilot chute for the shorter delays.

I could easily write an entire article on BASE pilot chutes, but that seems a little too detailed for the series right now. If you'd like more detail on PCs, e-mail me and I'll write an article.

A BASE bridle is about 9 feet long from the closure, i.e., closing pin or velcro shrivel flap, to the base of the pilot chute. Don't deviate from this length by more than 1 foot.

A BASE pilot chute costs from 50 to 70 dollars U.S., depending on size, F-111 or ZP, and the manufacturer. A BASE bridle cost about 10 to 15 dollars.

Mesh Sliders
Slider up or slider down? Depends; for short delays at low altitudes, I prefer slider removed. For 2 to 4 second delays, a mesh slider is an excellent choice--it will not give an explosive opening, like a slider down 4 second delay, but it will give a significantly faster opening than a normal skydiving (sail) slider. It also gives a more reliable opening, i.e., not as much chance of a malfunction, than slider down or slider removed. Every BASE jumper I know has one of these in their bag of tricks. If you plan on jumping at Bridge Day, this is a good thing to have. The setup part is pretty simple--just replace the regular sail slider on a canopy with a BASE mesh slider. I'll tell you where to get one when I discuss gear sources in a future article. By the way, this item costs about 35-40 dollars U.S.

The Tailpocket
As explained in Article 2 , the tailpocket is a pouch sewn to a ram-air canopy's center cell along the trailing edge. It provides a place to stow the suspension lines. The reason for having a tailpocket is to avoid "bag spin" or "bag lock", and to give a faster deployment than a normal skydiving deployment bag. Tailpockets also seem have better performance than bags as far as giving on-heading openings. Depending on the specific tailpocket, it may have rubber bands for stowing the lines, or may be designed for free-stowing the lines.

By the way, I'm not trying to give the impression that you absolutely need a tailpocket for BASE jumping--you don't--but if you start getting into the low stuff, it will give you a better chance at getting a fast straight opening than using a deployment bag. Don't get one of these just for Bridge Day, but if you have a canopy that you will be using regularly for low BASE jumps, I'd highly recommend this piece of gear.

Setting up a canopy with a tailpocket is not nearly as simple or quick as installing a BASE pilot chute and bridle, or a mesh slider. It needs to be sewn on. You can install one with a home sewing machine, but I wouldn't recommend it unless you have the right thread and the skills to do it properly. Your best bet is to have a rigger either do it or at least supervise it.

By the way, you can still use a deployment bag on a canopy equipped with a tailpocket. Just pack it as you normally do--it won't interfere with deployment.

The cost of a tailpocket is about 30 to 40 dollars U.S. Installation costs extra, roughly 10 to 25 dollars, depending on how it is installed.

The "Line Mod" and Steering Toggles
The steering line modification, referred to as the "line mod" by most BASE jumpers, was developed by Mark Hewitt. As simple as the line mod is, it ranks among the most important and controversial gear innovations ever in modern BASE jumping. It refers to routing a ram-air canopy's steering lines outside the slider grommets and the keeper rings on the risers and is used to clear a lineover malfunction.

If you get a lineover malfunction on a skydive, the procedure is to cutaway because, short of cutting the steering line causing the problem, there is nothing you can do to clear it. On many BASE jumps, there is not sufficient altitude to get a reserve out. Mark Hewitt's solution was to route the steering lines outside of the slider grommets and keeper rings so that simply releasing the brakes and letting go of the toggles would clear the lineover. It was (and still is) a clever, effective solution to a very dangerous problem, and no doubt has saved a number of lives and prevented serious injury. It does have its limitations and quirks, however:

1. You can only use it for slider down (or slider removed) jumps because it may hinder the slider from descending on a slider up jump.
2. Your canopy may handle differently when flying with the line mod. Personally, I prefer the way a canopy with the line mod flies.
3. You may need to shorten the distance between the brake settings and the steering toggles because the line mod changes a canopy's flare point--the steering line goes straight from the tail to your hand instead of going around a corner because of the keeper rings.
4. If you release the toggles to clear a malfunction, you must steer and flare with rear risers. This can be tricky on some canopies.
5. A toggle can accidentally release during deployment, forcing you to release the other toggle and steer/flare with rear risers.

Also related to the possibility of a premature toggle release is the need for a toggle that will release under very high loading, which occurs on a lineover malfunction. The most common solution is to use "Zoo toggles", which have been adapted to BASE jumping. A Zoo toggle has a loop made of suspension line (looks somewhat like a container closing loop), a straight stainless steel pin, a grommet near the top of the toggle, and a fold that is held in place by velcro (similar to what a lot of skydiving bridles have). The loop on the toggle is passed through the steering line's brake setting, then through the keeper ring on the riser, then through the grommet on the toggle. The brake is set by inserting the pin on the toggle through the loop. It's a good system that releases very easily, yet is fairly secure. The drawback is that if you pull on the toggles incorrectly, they will not release. They are not completely secure, either. Premature releases do happen, although not very often.

Zoo toggles will work with nearly any set of skydiving risers, but there are some BASE-specific risers made that have toggles designed to mimic the function of a Zoo toggle. They generally work well, and I'll be discussing them in upcoming articles.

Remember, the need for these toggles goes along with using the line mod. I recommend the line mod be used on all slider down (or slider removed) jumps. In the case a a jump with a single canopy system, the line mod *is* the reserve.

No need to buy this item just for Bridge Day, but if you will be doing any slider down jumps, get either a pair of Zoo toggles or a BASE riser/toggle system, and use the line mod.

Deep Brake Settings
Many BASE jumpers have multiple brake settings on their canopy. They come into play when jumping walls, e.g., cliffs or buildings. A canopy with deep brake settings has less initial forward surge during opening and lower forward speed after inflation. Jumping off a wall with a ram-air canopy and having a 180 degree off-heading opening is a worst-case scenario in BASE jumping. If it happens on a canopy with deep brake settings, the decreased surge during inflation and the lower forward speed after inflation give the jumper a chance of avoiding an object strike. If there is no line twist, simply flaring with the rear risers will stall the canopy and make it fly backwards. This is a very effective remedy and has certainly saved lives and prevented serious injury.

I personally don't have deep brake setting on any of my BASE canopies because I rarely jump walls, but I will be putting some on soon. To add deep brake settings to a canopy, take it on a skydive and experiment with deep brakes. Find a point where the forward speed of the canopy is *very slow*, but still above the stall point. Mark the steering lines (at the keeper rings) and recheck the setting. Have your rigger finger trap brake settings at that point. Two cautions: do not risk opening in a stall--always test new brake settings on a short-delay, slider-up skydive before using them on a BASE jump; also be aware that jumper weight makes a difference--a lighter jumper using the same brake settings could open in a stall.

More On Deep Brake Settings by Adam Filipino
There are a lot of details that I haven't covered in this article, but it does give a good overview of the common tricks that most BASE jumpers are using on their canopies. I'll include more details in future articles. Meanwhile, feel free to e-mail me with specific questions or comments-- especially suggestions for future articles.

All of Walts original posts on Rec.Skydiving can be found on BLiNC.... http://blincmagazine.com/....php?searchid=273296

Didn't seem that bad to me. I assumed you meant because of the remote locale and lack of training for the guy.

therefore it should be quite ok to jump slider-up from a 200 m span, wouldn't it?

 

sorry, my fault!

200 meters = 656 feet

7.1 seconds to impact

Sure, if you're jumping a span with available area to fly the canopy and a good landing area.
----------------------

Right now with limited base experience, the tower would be best suited for slider down. This also gives the option to jump from lower.

If a slider was used, the suggested delay would put the jumper in the region that statistically has the most off headings with a slider.

While it's certainly possible to jump it with a slider, it's recommended that the jumper works up some experience dealing with exit, delays, flying, rigging etc...

A certain height does not necessarily mean slider up or down. I jump an object that's almost exactly the same height as the perrine. I'll jump all day at the perrine with a slider but won't do it on the local object I have frequented.

You can't say that it is 7.1 seconds to impact. Wind resistance instantly plays a roll on freefall speed, which effects time and distance.

It is negligible at first, but after a few seconds you can see how exponentially wind resistance effects freefall speed. Not to mention body position (and jumper density I think?) effecting wind resistance.

I'm assuming your taking wind resistance into account, but without knowing how much wind resistance will be involved and how much it will effect the speed, there's no way to tell how many seconds, let alone how many 10ths of seconds.

Here's a sweet webpage you can use to help estimate freefall times though.

Can't remember how to clicky:
http://hyperphysics.phy-astr.gsu.edu/Hbase/traj.html

NOTE: This is with no wind resistance. You'll have to estimate that on your own.
Here's speeds in MPH, ft/s and M/s
1s - 21.92181818 MPH, 32.152ft/s, 9.8M/s
2s - 43.84363637 MPH, 64.304ft/s, 19.6M/s
3s - 65.76545456 MPH, 96.456ft/s, 29.4M/s
4s - 87.68727275 MPH, 128.608ft/s, 39.2M/s
5s - 109.60909093 MPH, 160.76ft/s, 49M/s
6s - 131.53090912 MPH, 192.912ft/s, 58.8M/s

We all know your not doing 131MPH at 6 seconds.

Here are the distances with no wind resistance
1s - 16.076ft, 4.9M
2s - 64.304ft, 19.6M
3s - 144.684ft, 44.1M
4s - 257.216ft, 78.4M
5s - 401.9ft, 122.5M
6s - 578.736ft, 176.4M
7s - 787.724ft, 240.1

And to make things even more interesting, don't forget about hang time.

just put a F - ing mesh slider on and end this post.

Hi Dave

You can't say that it is 7.1 seconds to impact.

Um, well I CAN type it, cause I did, but of
course everyone else who read it understood
it was just an ESTIMATE based on math and
not the gospel truth.

In all of your, "well what about this..." you
did not mention air density, more or less the
phases of the moon and whether or not the
jumper had just gotten laid.

Oh, and also, what are you calling "hang time"?

air density, the phases of the moon, and whether you're a load short or not, are all covered in wind resistance and jumper density

And by hang time I mean, some people start the free fall count the second your feet leave the object, but most people jump up and/or out, which creates a time delay before you begin your acceleration down.

Give the guy some time to sort out his jumping techniques, then put the slider on. Line twists and guy wires are a bitch.

Yeah, dude, slider down. I still wouldn't jump solid objects that are less than 700'. Openings are much too inconsistant, and especially for someone with limited experience.

do you have enough significant digits there? Ha!

What would YOU know about jumping towers anyway? I thought you were in to moving objects now...

No, it doesn't. You begin accelerating at 9.8 m/s^2 the moment your feet leave the object, no matter which way you're travelling when you do so.

oh yeah? what if you did a hand stand for, say, a minute, then 'jumped'?

Same thing, of course. The rules are the rules.

Maybe there is some sort of physics concept I'm unaware that you're referencing, but it seems pretty obvious to me that if you propel yourself upward, you don't begin downward until the acceleration of gravity has met and overcome the original upward force.

What you're saying is like saying that a plane taking off or the space shuttle going to space is accelerating at 9.8 m/s^2

Edit to add: Plane and shuttle aren't good examples because they have a driving force even after launch. An NFL punt though is a good example. Longest NFL punt hang time 8 seconds. They call hang time from kick to when it touches ground though. For the purpose of our discussion the hang time would be from kick to the instant it began moving back toward the ground. Which was probably 4 or 5 seconds.

physics 101.

F=Ma
Force = Mass * acceleration

Gravity creates a force by constantly applying an acceleration to your Mass of 9.8 m/s^2. When something prevents this acceleration, you feel weight in your feet (if you are standing upright).

when you launch upward, you apply a momentary for force that results in the upward movement. that force stops when your feet have left the structure.

the acceleration due to gravity acts continuously. it slows your upward progress and then continues to pull you towards the earth.

gravity is always attempting to accelerate everything at 9.8 m/s^2 (yes, gravity varies, but not of any practical significance). we have not yet discovered a way to make gravity stop.

Since F=MA and you're still accelerating until gravity brings you to a halt, the force still exists even after your feet leave the ground. Furthermore, since you have to jump out as well as up to leave the object, and some force is in an outward direction (which gravity has no effect on) the force still exists until you reach some equilibrium due to the air or the parachute.

I'm looking forward to Jason's reply.

Edit to add: If I remember right, he's a physics guru.

nope.

once the feet leave the structure, the only force acting on the jumper is gravity. (neglecting the affects of air).

forces in general do not act at distances. exceptions include gravity and magnetism.

the force in general does not act at distances

Nope, it sure don't, because if it did then I would
have already choked several people from a far.

It's like this... As wwarped says, as long as you're actually launching up, feet on the ground, you're accelerating up (like the plane or rocket in your example). The instant your feet leave the ground, though, you're not pushing anymore. You were, but you're not now.

F=ma tells us that since you're not pushing anymore (ie, no force from your legs), that's not causing an acceleration anymore either. Gravity, on the other hand, is still very much in effect, so you get a=9.81 m/s^2 as soon as your feet leave the ground.

That you're still going up (ie, velocity is up) isn't a problem, since acceleration is the change in your velocity (that's a really key bit there). You'll move a little faster downward, or a little slower upward, every second, until eventually your velocity is downward, but you're acceleration won't have changed the whole time -- not even when you were at rest momentarily.

... It's a question we like to catch first year physics students on, and catch them we do. Far more than we don't.

Edit to add: I should say, going back to the original point, that launching upward does, of course, mean that it'll take you longer to pick up the same downward speed (so the original point was valid enough). But that's because you started with some upward speed, and not because your acceleration was ever any different. Same way that if you start the race 10m back, you'll take longer to cross the finish line even if you run at the same speed.

So gravivity is not going to be thwarted in the least if you launch up really hard, unless you can jump at a velocity of 6.96 miles per second.
This is ground breaking stuff, changes everything.

One other thing, regarding how far a person falls with and without air resistance. Those with Microsoft Excel or a scientific calculator and with a sufficiently geeky inclination might be interested to know that (provided I haven't made an error in the calculations i just finished) the distance fallen in a time t by a person whose terminal velocity is vTerm is given by:

x = (vTerm^2)/g * ln(cosh(g*t/vTerm)) - v0*t

where g=9.81 m/s^2, or 32 ft/s^2. Notice that that's ln, the natural logarithm, and cosh, the hyperbolic cosine. Make sure your vTerm is in m/s or ft/s to match your choice of g. v0 is the initial speed of the jumper upward (again, same units). For a jumper with no initial vertical speed (which is a pretty good approximation), it looks like this for the first 15 seconds (taking vTerm=50m/s=180km/h=112mph):

Code

... After that, it's pretty near 50 m/s the whole way down.

damn , I'm really old school. I just climb up and fall off. Seems the same every time...carbon sucks...

so if i dropped a feather off the tower of pisa. wait, someone did that calc already.

Wow. I'm not familiar with cosh (spherical trig I think), but it gives me some stuff to look up on wikipedia...hehe Thanks.

If you jump backwards with your eyes closed it helps you maintain the gravitational electromagnetic rotational upward spiral syndrome which may cause you to briefly maintain a tradgectorial extraterrestrial vagina position

unholy SHITBALLS i hate it when that happens!

i love jetpacks!

Yeah, you're totally right! If someone from almost anywhere had asked the same question, the response would have been, "If you have to ask that than you have no business basejumping." Never have I seen such an outpouring of support for someone thinking about doing a jump in which they clearly have no relevant training for. I'll keep an eye out for the first North Korean to come here and say, " I reary wanna rearn how to base jump! Shourd I just buy an ord F1 ereven canopy?"

Not really, but it's appropriate.

Yep, I didn't think D_Goldsmith was out of line at all. What he said was the first thing I thought. It is an interesting observation, that's all. IMO

I kinda view it a bit differently...

most of the time, jumpers get abused when the ask questions here, and they have access to better sources of information.

if he has a better option than the internet, he should take it! unfortunately, I've seen posts from jumpers from fairly remote areas. (John from Kenya for example). this might be their only option.

Stop pretending you're some ignorant redneck...we know you've got more years of formal education than anyone else posting in this thread--including the university professors.

i have over 13 years of formal education.

I have a feeling 386 might still have you beat. That is awesome though. I'm coming up on 3 and just now finishing my associates

Lots of people go to school for 9 years.

Um yeah, we usually call them doctors.

I only stayed in school for the keggers !!!
386

Now you're in competition with 460, how many years you got?

Regardless of his years hes still a snapping turtle shooting redneck