base736

I've done my best to hide it for years, but I'm finally ready to admit it... I have problems standing it up. I fly a Fox 245 VTec (no valves) loaded at very nearly 0.7:1. My landing areas tend to be at 3,000-4,000 feet MSL in dry air. I consider myself a good 7-cell canopy pilot -- I've been jumping this setup for better than 80 jumps (over four years), and competed in CRW for a couple of years before I started into BASE. In moderate (say, coming up on 5 mph) and better winds, I can stand up my landings without a problem, consistently. I can sink it in, I can come in out of a turn... It's all good. No wind, though, and I'm useless -- I either come skidding in on my hands and knees (three cheers for the guy who invented gloves and armour, by the way) or drop out of the sky unceremoniously to a nearly ankle-breaking stop. ... Which seems odd to me, since I should (in theory) be able to execute the same landing I do in higher winds, and walk it out. But anyway... I was hoping somebody here could offer a little advice on landing this sort of configuration in no winds. Failing that, perhaps you might enjoy a chuckle at my expense?

Ro? Rotation number? For a 35-inch pilot chute at 120 mph I get Re=3E6. Could it be we're not talking about the same thing? Anywho, theory is notoriously bad (beyond the sort of handwaving arguments I already gave) for turbulent flow, and it doesn't get much more turbulent than a pilot chute being dragged at terminal. The experiment would be interesting, but -- setting aside the fact that I'm too lazy to build dozens of test-PC's -- would, I expect, be complicated by the following: (1) Particularly for small apex vents, the pull force of a pilot chute probably oscillates by an amount which I expect would swamp the effect of small changes in vent size; and (2) Just the idea of trying to build a pilot chute with an apex vent more than maybe 20% of its outer diameter which still resembles a pilot chute when inflated makes my skin crawl. Still, um... If you want to build them, I'll shoot video.

Certainly not. Take a square one meter on a side. It has four meters of edge over which it can spill air. Cut it into centimeter-sized pieces, and spread them out a bunch, and you've got 400 meters of edge. If you keep them close together, though, the air won't "see" the spaces between them as well. The key idea here (I think) is the Reynold's number (http://scienceworld.wolfram.com/physics/ReynoldsNumber.html). For small holes, viscosity is very important. The optimal apex vent will let through enough air to stabilize the PC without letting through so much air that it significantly reduces drag. Somebody better-versed in aerodynamics will hopefully drop by to correct me on all of this.

To address Jaap's original question... I think that, at the end of the day, the statistics are irrelevant. Not because I've got such m4d sk1llz that statistics don't apply to me, but for this reason... Either I will die BASE jumping (in which case the odds were 100% all along), or I won't (in which case they were zero). It's small-number statistics at its finest. Anyway, how (and even when) I will die seems somehow small in relation to the fact that, sooner or later, I will die -- I try not to get too hung up on the details.

It's interesting that you should interpret the results this way, because I had exactly the opposite reaction when (some years ago) I ran the same numbers. I think the ages you calculate are working out fine -- that statistically, even an active jumper (100 jumps per year) has a half-life of thirty years or more jumping. Why does it seem like it should be so much shorter? Because most of us get squeamish at odds that are much lower than we would expect. I think Nick put it really well here http://www.dropzone.com/cgi-bin/forum/gforum.cgi?post=1551590;search_string=goober;#1551590: I think most of us know this, and instinctively keep things pretty safe even if we're telling ourselves that this one is 50/50.

This question comes up a lot. I'm just going to repeat myself here, so ignore me if you've heard it before. I have yet to meet a skydiving helmet that I like as a BASE helmet. I'm not saying they don't exist, and I'm not saying you'd be wrong to choose one anyway. My feeling is that the difference goes like this: In skydiving, your primary concerns are small bumps and scrapes (with the plane, or a botched landing maybe near a small rock in the field) and larger hits from stuff that is, relatively speaking, soft (somebody's foot, for instance). Given that one sometimes experiences hard openings, the ideal helmet is lightweight, with a hard shell to protect from sharp trauma and a little padding -- usually just a quarter inch or so of pillow lining -- for comfort and to help distribute other impacts. In BASE, your primary concerns are bigger bumps and scrapes (say, a large rock in the landing area) and large hits from hard stuff possibly at speed (like the object). These are the sort of impacts that will turn a skydiving helmet into a colourful spray of carbon fibre without dissipating much energy. What you need in BASE is a hard-shell helmet with an inch or so of crush material (foam), and optionally chin protection. There are some pretty light-weight helmets available that fit this description. My suggestion is a good skate/ski/mountain bike helmet. ProTec has served me well in one pretty bad situation. Want to fly camera? Rivet a camera mount to one of the above (I can help you out there, as I'm sure a number of people can).

Nice!

Pulled this frame from some video I took this weekend. I've seen similar stuff in video from other jumpers (this means you 587). Does it occur to anybody else that this might be an odd thing to do for fun? Edit to add: Jaap, who apparently is a forum whore, has pointed out to me within seconds of my posting this that the picture might be unclear. I'm referring, of course, to the clear pain in the jumper's face...

SabreDave would be your man on this one, if he hasn't responded already by the time I hit "Post".

It's been pointed out to me that I have, in fact, chickened out (in the above sense) on an 'E', and I've managed to recall what is indisputably a chicken 'A'. That's chicken BASE for me!

Chicken BASE, anybody? Must have been geared up, at the exit point, in what appeared to be near-optimal conditions, then backed down anyway. In my short BASE career I've managed 'B', 'S', and 'A' I believe. Though that last might better have been called an 'O'.

That would help explain some of my unstable exits...

I only jumped once with Chris -- a night jump from an 'A'. The guy was a natural. He was one of the few people I would broadly characterize as a "high performance individual" in that I have 100% confidence that he would perform well in any sport one might call high-performance. That said, he suggested on a number of occasions, when I invited him out on a cliff jump, that he'd like to do something from an 'A' first, with a tailwind, to get current (no good spans around here). Crazy, but not stupid. Probably more importantly, he had this awesome attitude toward other people that you'll see mentioned wherever people are talking about Chris. The guy practically glowed with positive energy every time I saw him. It was truly a pleasure to have Chris in our little community for as long as we did.

This is an interesting statement, and I'm curious how many people feel this way. Certainly I feel that a BASE mentor ought to be a very experienced jumper. Where I differ from the above is that, since I've never met somebody in BASE who wasn't an adult, my feeling is that what you do is, at the end of the day, your choice. i.e., your BASE mentor is not responsible for your actions. Your life is not "in their hands". This came to feel particularly relevant when there was (recently) an accident out here. There was this long list of people here lining up to tar and feather the mentors / instructors involved and all I can think is, "For God's sake, the guy is 41!" I feel it is important to own all of my decisions -- both the good ones and the bad ones. Consider this your warning... If I should die BASE jumping, I will personally haunt those who try to steal them posthumously. Boo!

Well, I know for a fact that it's at least one.

I'm curious whether anybody can share some video done without a wide angle, or with something higher than a 0.3... I've always used a 0.3 myself, and while my experience has been that that gives an image which I would say is nearly "what I saw", I've toyed with the idea of just zooming out, no adapter lens -- particularly if I were planning to shoot something specific (another canopy, stuff on the ground, whatever...). Anyway, if anybody's got video to share...

Most skydivers find their hands near the risers eventually on a jump -- sometimes even before they're ready to grab the toggles . If you're truly on your shit as soon as that PC has you sitting up, then that's commendable. But it's not typical. I've taught CRW to skydivers who figured they were on things pretty quick if they were steering five seconds after the canopy opened. ... Which is part of why CRW is such amazing prep for BASE.

Nice! I competed in CRW before I took the BASE FJC. I hadn't mentioned it to them in advance, but I can remember coming up from my first bungee jump as part of that course and having the guy up top say, "So... CRW, eh?" Apparently I had reached to where the risers should have been as soon as the bungee started to take my weight.

Could it be a codec problem? The video requires 3ivx, which you can get from www.3ivx.com, if your player of choice doesn't have it by default. Brilliant. That makes complete sense, of course, since the same ridge lift that carries you up will eventually carry you back and then rapidly down. Even simpler with a BASE canopy, since I wouldn't anticipate getting much or any lift from thermals in that case. Thanks!

I was planning to talk to some local PG pilots about this. The back slopes away quite quickly -- say, 30-40 degrees. The winds along the back, this particular day, were of course calm. On the one hand, a buddy of mine once lost a pair of sunglasses over the front edge on a windy day, only to watch them get lifted 100 feet up and back, and thrown hard into the rocks... So clearly there's some wierd winds going on there. On the other hand, maybe if one were a couple hundred feet up, one could avoid that entirely and land in the calm winds a few hundred feet back from the edge? Not that I think I'd ever wrangle up the balls to try it when there's a sure thing the other way.

Thanks for sharing the exit point with me.

Yeah, that's my second tree encounter under canopy -- the first one didn't turn out so nicely. Because of the 10 mph into the face, things got shifty (as I expected them to) near the ground, and I wound up blade-running a couple of trees.

For almost a year, now, I've been shooting BASE video with a stereo pair of hi-fi external mic's mounted on my helmet above the ears. The results, I think, have been pretty awesome. Anyway, last weekend we headed out to the local E. There was a ~10 mph wind coming into (and therefore up) the face, but I've been getting more comfortable with these sorts of things so we went for it. What followed was some sweet lift -- we could have stayed up there indefinitely, or until the winds came down anyway. The visuals were amazing. I've uploaded the video to http://www.skydivingmovies.com under "lift.mov". My apologies for the size, which seems a bit much (despite the use of a good codec) for a few minutes of experimental video, but it is what it is. The first-person stuff is best enjoyed with a pair of headphones.

How are the Giro helmets for slosh back and forth at the chin? As I say, the full-face MTB helmets I've tried on are pretty loose up there.

I'm always skeptical about helmets put out by skydiving manufacturers, since the crush material tends to amount to a half-inch or less of something pillowy-soft. Your biggest problem (or certainly mine) will be finding a helmet with a chin cup (which brings you into full-face territory) which fits the remaining requirements. On a lot of the full-face MTB helmets I've tried, the fit is so loose that I think I'd just wind up breaking my chin on the helmet instead of the rock... Though you have mentioned that weight isn't a big issue, a lot of those with a better fit are really heavy. Any particular reason why you're not looking at a snug-fitting skate/snow helmet without chin cup? If future camera-mount isn't an issue, you might want to look in the direction of the Dainese Raptor series (which looks very promising), though I haven't managed to try one on myself.