Distance traveled

[base570]

OK I have been to an exit point and it lasered at 175ft straight down, the farthest I will be able to fly the canopy lasered at 258ft (from exit point). From my calculations having two sides of a right triangle the distance of the 3rd leg is approx. 190ft. This is the distance from directly under the exit point to the point I will crash into a "wall". My questions are these...
1. are my calculations correct?
2. will I have enough room to land safely?
3. how about if the exit point is 185ft.?
4. how much of a turn can I expect to get?
5. How about if brakes are stowed or unstowed?

from previous jumps I have done that are of similiar heights this doesn't seem to be a problem, but on those jumps I could have flown farther if I needed. This jump, I have to be on the ground before the "wall". This object can be jumped from different exits that have a clearer flight path, I'm just trying to figure out if I can put off more than one person at a time going in different directions.
Oh, the canopies being used are NOT vented so they will be flying slightly lower than those with vents.
Thanks for any input!
Stay tuned for a spectacular jump being planned by the NC crew!!

Jason, Naked NC BASE #1
:D :D :D :D :D :D :D :D :D

[base570]

Ah yes, once again I have tried to get some useable input from the BASE community and once again I get nothing.
Are the questions too hard?
Are they too easy to even garner a response?
Do I not have enough experience?
Is everyone on vacation?
Am I wearing the wrong color shirt?
What gives????

Jason 570

[crwper]

I had a whole bunch of info collected on static line jumps from 165/140 feet using a v-tec Fox. I seem to have deleted it from my computer, but will check my logbooks when I get home to see if I still have it there...

Michael

[crwper]

Okay... I have the numbers in my logbook.

Pre-amble... It should go without saying that no numbers (but especially not someone else's numbers) should be used without having personal experience as a "reality check". I say this not so much for you, Jason, because unless I'm mistaken you have more experience jumping than I do. I say it more for anyone who might be inspired by numbers alone to do something stupid. The numbers should serve only to confirm what you already knew.

All jumps were from a span with a frozen river below, so the landing area was wide open. We were trying to maximize our distance, so we dropped as vertically off the object as possible to minimize oscillation, and tweaked our toggle-unstowing technique (quick release, and smooth transition to full flight, again to avoid oscillation).

We were both jumping v-tec Fox 245's loaded about .65 to .7 lb/sq ft. Both using 48" f-111 pilot chutes and 80 lb break cord.

From 165 feet, temperature -1 Celsius, pressure 930 hPa:

tail wind < 5 mph - 55 yards distance
no wind - 49 yards distance

From 140 feet, again dropping straight off:

no wind - 21 yards for me, 40 yards for Spence
no wind - 29 yards for me, 40 yards for Spence

Your calculations of the distance are correct -- you're looking at about 190 ft (63 yards) distance from the 175 ft exit point.

I didn't record any numbers on it, but I jumped my non-vented Fox 245 a couple of times from the 165' exit point, and it felt qualitatively like jumping 140' with vents.

Hope this helps.

Michael

[flyin_ryan]

So here is a question for you. You said you felt the Vtec preasurized quciker. It also feels (I have no numbers to back this up, it just feels that way) that Vtec canopies have steep glide angles. Do you feel that this quicker preasurazation compensated for the steeper glide angle in situations like this? Do you feel that you would travel farther with a vtec canopy?

[imported_Tom Aiello]

Hi Jason,

What kind of object is it? In zero winds, this sounds ok, but if you start having to turn around to land, or have a tailwind pushing you toward the "wall", I'm not so sure.

>175ft straight down
>190ft forward

Is the area directly under the exit clear? Can you land there? What about off heading potential? My initial instinct would be to freefall from that exit point, get open around 80 feet, and fly straight into landing. Obviously this totally depends on the nature of the landing area. Also, I'd want a vented canopy for it. I think it would still be ok on an unvented Mojo or Ace, but I wouldn't want to try it on an unvented FOX or Troll.

A static line would make me nervous about striking that "wall." I don't have lots of experience with static lines at that altitude, though. If you want more data, I'd call Basic Research, as they have done a ton of static lines from that altitude, and ought to be able to give you a pretty good estimate of the maximum and minimum horizontal distance to landing.

Still, if you stall the canopy down, and there is no wind, you should be able to land within your 190 feet.

>1. are my calculations correct?

I'm sure that your math skills are stronger than mine, so I won't break out the calculator to check.

>2. will I have enough room to land safely?

It looks like it to me. I'd worry about a static line followed by full flight, but with a freefall, or just riding the brakes, I'd guess you will be ok. Without specifics (tailwind potential, off-heading obstacles, nature of landing area), I'm really just guessing, though.

>3. how about if the exit point is 185ft.?

I'd still guess that you will be ok. The other missing data considerations are way bigger, in my mind, than the extra 10 feet.

>4. how much of a turn can I expect to get?

Not much. With an unvented canopy and a static line, I would say that you will be able to safely make something around a 90 degree turn.

>5. How about if brakes are stowed or unstowed?

I would unstow the brakes as soon as possible, since the canopy in full flight will sink less during corective turns. Be careful not to just pop the toggles, though. If you are low, and do that, you could surge yourself into the ground. Plan on bringing the toggles all the way down, then easing them back up to flare.

There is just so much data missing here that I feel very nervous even hazarding a guess. The things we don't know are huge: is the object solid? will there be a tailwind? a headwind? what are the outs? is there an alternate landing for a 180? where are the other canopies on your multiway? will their burbles effect the flight of this canopy?

I think that as the guy who has actually seen the object, you are probably the one best qualified to plan the jump. There are just too many unknowns for any real valid comments from the BASE Board.

--Tom Aiello
tbaiello@mac.com

[base570]

Thanks Michael and Tom,
it seems you two always have quality information to add to the board.

Michael, your numbers fall pretty close in line with what I was thinking as maximums for my set-up (Fox 245 non-vented, .73 wing loading). I haven't had the opportunity to get as exact as you on these type of jumps because I had to "get out of Dodge" and couldn't get the numbers. I knew it would be close but do-able, I just wanted to get others opinions on it. Thanks a bunch! You are a wealth of information.
I do have one question for you though... How come Spence outflew you twice in a row by a considerable distance???

Tom,
Sorry but I can't divulge what type of object this is quite yet. I have been planning this jump for a few months now and have many hours invested and it would be stupid of me to let the cat out of the bag so close to the actual jump.
I can tell you that the LZ directly below IS open except for a few small things that shouldn't have any effect on the jump. The object is not solid. As far as off headings go, 90s would be the worst. 180s are OK with wide open LZ's. There will be no wind at all so getting a little push towards the "wall" won't happen. Freefalling this object is not a consideration (at least for me) I know what my limitations are right now with the gear I will be jumping (Fox 245 unvented, .73WL). The jump won't actually be a multi-way with everyone going off at the same time, there will be approx. 2-4 seconds between jumpers and also we will be going off in two opposite directions. Hence the question about distance traveled and a previous post on spacing of jumpers and the burble they leave behind. This configuration will help with the exit/escape plan that is in the works. It's going to be a really tough jump but well worth it. I don't know of too many people that have seen something that is similiar to this object let alone jump it. I'm really excited about it (as if you couldn't tell!!) I'll let you know how it goes after the Turkey day festivities.
Thanks again for the input.
Jason
Naked BASE #15
:*

[douggs]

>I'll let you know how it goes after the Turkey day festivities.

If your object is geographically close to the Turkey day boogie, you might want to give Muff Brother Number 1 a call. I've seen a bit of his video of multiple jumpers from an object very similar to what you are describing, and he might be able to give you some help on the planning.

Posted by Tom, using Douggs computer.

[base570]

What Turkey Day boogie are you reffering to?? And who is Muff Brother #1? Dennis?
Thanks for the help Tom.
570

[imported_Tom Aiello]

Vertigo's Turkey Day Boogie.

Yes, DM. Email me if you need more discusion. We're getting a little close to publicly discussing sites and jumpers by name, here.

--Tom Aiello
tbaiello@mac.com

[BASE 516]

Hey Jason,
I sure hope that the security force is not a bunch of jumpy,paranoid rookies who can't tell the difference between a cool base jump and a bunch of bleached haired terrorist.
good luck!
Tony Herring
BASE 516

[base570]

NO worries ;-)
The site I am reffering to is nowhere near Vertigo. It's many, many states away. And I'm sure DM won't know anything about this site, maybe something similiar but not this one.
peace, Jason
Naked BASE #15 :*

[crwper]

It's been my experience that, on jumps in the 150-200 foot range, the inflation time is the dominant factor and the v-tec will out-distance the unvented canopy. As I mentioned, I was able to do back-to-back jumps from a 165' span using the v-tec Fox and then the unvented Fox. The distance traveled with the unvented fox was qualitatively similar to a jump from 140' with the v-tec Fox.

Probably for a much higher object, say in the 500' range, differences in glide angle will start to become a factor.

Michael

[crwper]

>I do have one question for you though... How
>come Spence outflew you twice in a row by a
>considerable distance???

The difference seems almost entirely due to canopy oscillation. On video, it was clear on the first jump that my launch was harder than Spence's. Oscillation is clear on the video before I've unstowed my toggles. The best way to eliminate this is to drop off the object with as little forward momentum as possible. Below 150', "dead" launches start to make a big difference in canopy time/distance.

The other major factor in canopy oscillation, as Tom said, is toggle release. Spence was able to unstow his toggles more smoothly than I could, eliminating canopy oscillation. The key, as Tom said, is to pull the toggles down to release them, let them up gently, then flare. If you let them up too quickly, you'll induce an osciallation, and if you're unlucky, you'll be swinging forward when it's time to land.

A soft launch and proper technique releasing your toggles will add considerably to your canopy time.

Michael

[jason]

>A soft launch and proper technique releasing
>your toggles will add considerably to your
>canopy time.

Just a quick note here... I've been bitten twice by launching hard from a lowish object (165' the first time, 140' the second time). The first time ended in a bruised ego. Second time, not so lucky &-) . A soft launch is not just a good idea from the lowish stuff -- it is (in my humble opinion) a necessity.

As a rule of thumb... If the exit point is high enough that you can afford (even in the best case scenario) to *have* a 180, and even better to correct it, then launch hard. If it's low enough that you'd be more or less screwed from the moment you had the off-heading, launch soft.

I'd be interested in hearing others opinions on that...

[crwper]

I'd say if you're static lining the object, your best bet is to use a soft launch, since you're going to be open very close to the object no matter how big it is.

Generally, a hard launch is used to get clear of the object, right?. If you're using a static line, it seems like you're probably not going to gain much extra distance from the object (because you're tied to it). But you will definitely induce oscillations.

If I'm freefalling something, even in the 200' range, I'm expecting that my vertical speed will be much greater than my horizontal speed by the time my canopy extracts, no matter how hard I launch. I'm not too worried about getting a nice soft launch in that case, because even with a very short freefall, I can probably get enough distance from the object to correct a 180 (if I'm quick about it).

In addition, there's the fact that 180's (or any off-heading at all) seem much less likely with a static line configuration than with freefall jumps. When you weigh your options, this may decrease the importance of distance-from-object relative to minimizing oscillations...

Michael