Basejumper.com - archive

Dead air exit, of course.

Approximately 652 feet....

http://offheading.com/tabels.html


Or about halfway to the ground...in your recent case!

haha

Don't you think you should have known this before making the jump.

No.

hey..give the man a little credibility...he have 345 base jumps with a skydive rig..i bet that`s more than NickDG have in the 80`s.....oldschool jumping rocks

I'm not sure if my input is valid in this case however to the freefall chart quoted I then add another 2 seconds of unimpeded (accelerating) freefall to account for deciding to pull, the actual pull, pilot chute inflation, bridal & line stretch and canopy bottom skin inflation. This in scientific terms is not at all accurate as various rates of decelleration are taking place and a multitude of sub deployment elements occuring but it does give me a usable method and not least of all a safety margin.

Kindly note I have less than 100 base jumps.


John

He only had about 600 skydives and was making his first base jump from a 1300' A on borrowed gear. I was just saying that if you are planning on taking a 6 or 7 sec delay for the first time on your first jump you should know how far you are going to fall and where you are going to be.

Kynan I am not trying to rag on you. It just seems like you are more interested on making your videos for ytube then thinking about the jump.

Since someone mentioned my name I'll jump in . . .

On lower jumps a rule of thumb that works for me is knowing no matter how I launch (stable, unstable, or aerials) I'll cover 150-feet in three seconds.

If the altitude allows a longer delay then three seconds I would just eyeball it on the way down. And luckily, because we can feel speed it's kind of easy to know how close to the deck you want to get.

And all you guys with your lasers and sideways math leave me alone, 'cause I'm still here . . .

NickD
BASE 194

only 600skyhumps is probably more than i can managed in my whole life..

i made it to the 145 marker and just burnt out. i cant afford that damned sport.

636 feet 7 inches if you're falling in stable belly-to-earth position and your terminal velocity in this position is 120mph.

If you weigh 200lbs and drank a 6-pack (4.5lbs of beer), your terminal speed will be increased to 120*sqrt(1.0225) = 121.3mph due to 2.25% increase in weight and you'll fall 28 inches more in 7 seconds. Your groundrush will be more intense by 0.7%.

If you went headdown on exit, you'll fall 708 feet (assuming terminal velocity of 180mph) - an equivalent of drinking 333 beers!


P.S. Curiously enough, 28 inches is approximately the height of a stack of 6 12oz. beer cans. Another fact: the amount of energy generated by a terminal impact (120mph) of a 200lbs jumper is enough to lift a 6-pack of beer to 13,500ft. The mystical connection between beer and freefall is now 100% scientifically proven.

That's awesome. What's the formula for the acceleration with wind resistance?

How does your average rock compare to a jumper when doing rock drops?

Terminal velocity for BASE and skydive

Good question. You need to know rock's terminal velocity, which will obviously depend on it's weight, size, and shape. No hard data here, but a gut feeling is that an 8-inch rounded heavy rock will have terminal speed of more than 120mph, while a porous flat slab of lightweight rock might have speed less than 120mph. Heavy rocks will create an impression of a bit lower height to impact - which is good - while light rocks can create an illusion of more altitude than there actually is.

What's there to think about? Jump, track, pull, winds. I know the longest you can delay is about 10 seconds. I couldn't tell you exactly how many feet you drop in 5 seconds or 8 seconds. Plus, the ground is a pretty good indication of where you are.
I've seen a good amount of footage of this antenna, before jumping it.
Do you think it would be better to have 1500 skydives, before this jump? haha Come on man.
630 jumps in 18 months, seems pretty frequent to me.
On borrowed gear, if the pilot chute is in the right place, what more do you need? Using new gear for the first time would worry me more.
This is base jumping bro, not bowling. There are risks involved, I'm ok with that. I knew I'd delay between 5-10 seconds. To overthink, what most would say is a pretty irrational act to begin with, is foolish. If you don't feel comfortable jumping something, don't. I felt fine jumping an antenna on my first jump.
I know just a little on base jumping, but considering someone with over 500 base jumps was mentoring me, I felt confident in the advice given.
You seem more concerned with "making a point" than actually contributing something.

Point made.

uh, why?
idle curiousity?
must-clear obstacle?

you must already know your terminal velocity to apply Yuri's calculations. do you?

how will you time it?
being off by 1/2 sec will be a significant distance. few count seconds in their head well. the best timing device is a video camera. if conditions permit, simply set it up on the ground and then you can analyze solid evidence of both time and distance.

personally, eyes work fantastic on antennas. remember to stop and look around as you climb. pause near your intended opening altitude. find some visual cue and use it.

The speed tables are just plain wrong. For the first few seconds, it's 20 mph per second or 32 kph per second. So at 1 second, the speed is ~20 mph. At 3 seconds, the speed is ~60 mph. At 4 seconds, the speed is somewhat less that ~80 mph, maybe 75 mph, due to drag. Mark Hewitt (BASE 46) got these tables from an unknown source and published them from circa 1985 onward without authenticating them. Everyone has used them without questioning their validity. If you want to prove it to yourself, plot speed versus time. It's not consistent with distance versus time. Everything so far does indicate the distance versus time is somewhat accurate.

True. But they are also very approximately plain correct.
Most people begin counting the delay when the last foot leaves the ground. But at this very moment, you usually have a positive vertical component. Just like when you're running, your jumping up to the next step, and the gravity pushes you back to the ground level. So there's a delay between the "0 second" instant and the moment the speed goes back to 0mph. So in this case, speed versus time might be correct.

Anyway i guess the consensus is that you will fly all the way down until something stops you suddenly whatever you do

Just stop. Please. Go back to a drop zone. Ground crew more. I don't even want to respond to every point in your post because it would take too long and boil down to something simple like: I don't see an open casket in your future unless you wise up.

The table I was referring to was on the website http://offheading.com/tabels.html. That info has been recycled by many people including some of the BASE manufacturers. A cursory inspection of what yuri_base put together looks correct.

Yesterday I fell down the stairs and after 7 seconds had still only covered 14 feet.

I'm on a diet so the discrepancy is easily explained.