JaapSuter

I wonder if Dexterbase, KMonster or anybody else that has ever been busted or hurt there agrees with you. Besides, even if it's legal one month a year, that doesn't stop you making illegal jumps the rest of the year. Just try not to ruin it for the rest of the people. Considering you were my partner in crime for a week, you should know that we're not 180 degrees at all.

Yeah, me too! On many occasions.

That's exactly why I didn't state it as fact and said it was open for debate. I do believe the exercise is productive though, if only because it is the question asked by the very people who will try to stop us from base jumping. Surely you have thought about how dangerous base really is? Maybe not in comparison to other sports, but certainly in relation to some sort of safety point that you consider your absolute zero. Maybe lying in bed all day? It's a risk-reward thing. Do you think mandatory seatbelt and helmet laws are a good thing or not? Any answer to this question will be strongly related to your opinions on base regulation.

That's an interesting but very ironic point you bring up. Climbing the Everest requires a government permit that can cost up to 70.000 US dollars (albeit up to seven people can share one permit). So don't think that base jumping is the only thing being regulated. Climbers, mountaineers, skydivers, stockcar racers, and even your neighbour's hiking trips; they're all regulated in some way or another. The fact is that we're living on a small planet with six billion people. We need ways to coexist in peace and sometimes regulation helps us and sometimes it works against us. Never stop trying to fix the deficiencies! I'm just not sure if a continued underground and clandestine movement is the best way to do it. It sucks the cave is closed. It's because of the hard work that people like Basehoundsam and the Stavanger Base club put in that other sites in Mexico and Norway aren't closed yet. Thanks guys! I'll take one month of legal jumping over year round illegal jumping. I take legal jumps between six and nine AM over year round illegal jumping. Your mileage may vary! The argument that limiting legal dates or times will make some people jump in sub optimal conditions is moot. It is each jumpers responsibility to jump in perfect conditions and those not only include the weather but also the politics, the legalities, the bust-factor, the nesting periods of local birds and what the hell not. The trade-offs are yours and yours only.

Fact: for any activity our society has an acceptable risk threshold. If the scope of accidents increases beyond this threshold, society stops perceiving it as a sport and starts considering it suicide. Fact: the perceived risk of base jumping puts us in the suicide camp. Fact: whenever an accident happens, somebody has to clean up the mess, tax-money is spend, and people are saddened. Ergo: Society would rather prohibit us from jumping. Not-a-fact and open for debate: the actual risk of base jumping is not determined, but undeniably higher than that of most other outdoor sports. What I used to think: the fastest way to convince society that the actual risk is not as high as the perceived risk is through legal jumping and full exposure. This will certainly be faster than remaining clandestine and underground. The latter will just put us on a ticking time-bomb given the explosive growth of the sport. My current opinion: the actual risk is not quite as far from the perceived risk as I originally hoped for. If climbing were as dangerous as base jumping, maybe the NPS would ban them too. Here's a question to everybody; do you think society should protect people from themselves to a certain extend, by for example mandating seatbelts and wearing helmets on motorcycles? I don't know what my answer to this question is, but I'm hoping somebody has thought about this and has good arguments either way.

The problem is that the more precise you try to make the simulation, the less trustworthy it gets. The increase in complexity, resolution and dimensions when you add just the simplest extra variable is exponential in computational fluid dynamics (CFD). I'd say that Jason's 2D simulation of a single object is about as far as we can go while still being able to let skeptical laymen like us trust the results. And even then the results are still nothing more than an interesting thought experiment. Interesting for sure. But not super useful for BASE. If anything, wind simulations like this and the Gallery of Fluid Motion book just scare the crap out of me and make me realize I should only jump buildings and cliffs in zero wind conditions. Then again, I'm a pussy that way. Nothing like a good ol' crosswinder to ruin your day.

And that brings up an idea that might just be crazy enough to work. What if minor differences (up to an inch) can have a profound enough effect on the size of the street in relation to its speed? Sort of like wave theory where tiny differences can cancel each other out resulting in a flat signal. Maybe we should have been jumping 43 and 47 inch PCs all along. I suppose there are still too many variables (speed, weight and shape of body, weight of parachute, density of air) to do anything useful with this information, but it's fun to ramble about anyway.

Thanks! I managed to find one prebuild Lapack library but when I tried it, I still got linker errors, meaning the two functions that Jason used were either not in there, or their names were decorated differently. I think I'll try and get a copy of Visual Fortran and compile my own Lapack to link in. Stay tuned, I'll hack something together tonight.

Sorry Mac, what I actually meant was Lapack. Win32 binaries for LibTiff are easily obtainable. Thanks though! If any geeks on here want the compilable Visual Studio project (I had to make some minor changes to Jason's code) except for Lapack, let me know. I'll take another look and see if I can find Lapack tonight. Jason, can you send me the latest version of your code? The one I have is a few weeks old. You're telling me you're using a dense-matrix? Nice! Nothing like a good ol' float[100][100] eh? Check out the Boost implementation of UBLAS. It's pretty neat.

I have it compiling and linking on Windows except for a Windows version of LibTiff. If somebody can find me a Win32 LibTiff binary or the sources and a Fortran compiler that is easy to set up, I'll make you an executable. Edit to mention that it's not LibTiff that's the problem but Lapack. I could only find one prebuilt win32 Lapack library but it didn't have the two required functions. I'll spend some more time looking tonight. Great work Jason! The images look a lot like what we expected, don't they? I'm getting the semi-circle versus arc as well now. I'm wondering if you can increase the resolution by an order of magnitude and change the single vent to a buch of smaller vents. Thanks for writing this, very interesting. Cheers, Jaap

I'm assuming you did, but I'll ask anyway; did you tune the position of your toggles? Have you done any rear riser landings in zero winds? Oddly enough I have found rear riser landings to be softer than some of my flared landings, until I properly tuned my toggle setting. I'm not sure what that means, but it surprised me.

Just give any of the base manufacturers a call and they'll send you some. It's about 75 cents per yard. Alternatively, I can give you a couple of yards if you're in Twin Falls this weekend. Or, in case you're not coming, tell any of the other Texas locals to come grab it from me and they'll bring it back for ya.

The latter. The difference being that you're trying to make sense and I am full of shit. I just visited that Wolfram website and couldn't help but laugh after reading about the nondimensionalization of the Navier-Stokes equations. So I took a few complicated words and slapped them together in a sentence. The dimensionalized Navier-Stokes are tricky enough for me already, and sometimes with math I just have to step back, respect the complexity of it all, and admire that somewhere in the world there are people that actually have a clue about this kind of thing. I think I just lost the last little piece of credibility I had on these forums. Sweet!

That's precisely my point, but expressed much more succinct. I have heard several people state that the drag created by a vented pilotchute is the same as the drag from a nonvented pilotchute. Their argument was that the same amount of air would spill either though the vents or from underneath the skirt. I believe the statement is correct (drag is the same for all practical purposes) but the argumentation is flawed. If one were to compare the airflow between the two types of pilotchuts we would see very complicated differences resulting in definite measurable differences in drag. Sufficiently neglectible to argue the two types are interchangable, but real enough to warrant research. It's too bad that manufacturers can't devote the resources to such R&D. Especially during the inflation stage (in which everybody agrees there are noticable differences) there's plenty of interesting stuff to be found. But again, it seems another one of those cases where the science is too complicated and we just have to leave it up to practical experience to prove our hypothesis.

Dude, the Reynolds Number only applies after nondimensionalizing the Navier-Stokes equations. Given an average Ro of < 30, we find an experimental Poiseuille (laminar) flow that isn't turbulent enough to exhibit viscosity. Okay, taking it to the extreme was a bad example. How about this scenario. Take a 42 inch non-vented PC. Measure the drag at a certain speed. Not cut a hole the size of a penny in the top. Measure the drag again at the same speed. I'm pretty sure it'll have less drag. Probably neglectible, but measurable with sufficiently precise instruments. Now enlarge the pilotchute all around (at the skirt) by the same area as what you cut out from the top. Then measure the drag again. Will it be less or the same as what it was before it was vented? And what scenario do PC manufacturers use? Do they take a 42 inch PC and cut something out, or do they offset the area they cut out for vents by increasing the diameter by a miniscule amount. I'm probably splitting hairs here, like I did in an older thread about breakcord strength. The bottomline is that it works in practice and that vented PCs are interchangable with non-vented PCs. Blah...

Obviously that was meant in a figure-of-speech kind of reply to the 4999 comment. I realize that in any chaotic process there are going to be runs of occurences that are only explicable by randomness.

The counter got reset twice the last few weeks.

I have heard several experienced jumpers say this, but I am at a loss for the physics of this. The argument I have heard is that the pilotchute is going to spill air regardless, it's just that with an unvented PC the air spills out from underneath (encouraging oscillation). Taking that argument to the extreme, wouldn't this mean that if I were to completely open up the apex (have a big hole where normally the cap is), while making sure the total surface area of my pilotchute is still the same (by increasing the diameter), the pull force would remain consistent? I find this hard to believe. That doesn't mean you can't use vented PCs where you use unvented ones (except maybe in ultra-low freefall), but it does mean I believe there is a neglectible difference. Don't hesitate to prove me wrong.

Obviously. But what about my question; are we just fooling ourselves? Are we as much in control as we'd like to believe? Dude, if you ever start a cult, let me know. I'll join it.

If I understand your post correctly, the reason you do base jump and you don't play Russian roulette is because you believe that in base you are more in control of things? I guess that is what most base jumpers think. Because we prepare, pack, check our gear, do the jump ourselves, etcetera, we think we can cheat the odds (if there are any) and stick around long enough. I wonder if maybe we're all just fooling ourselves though. Surely some base jumpers are safer than others, but the game is pretty deadly and on a long enough timeline everybody's survival rate drops to zero.

The more I jump, the scarier it gets. Funny how that works. Anyway, Nick's recent post about the amount of jumps being made every year got me thinking about this one. Disregarding the many different approaches people take in base and grosly generalizing a sport for which there aren't enough statistics to even create useful conclusions, I'll try this anyway. Have you ever thought about the odds that you can survive in this sport? It matters a lot if you're mostly a potato bridge jumper or you prefer doing double gainers off of 200ft underhung cliffs, but have you ever tried to come up with a number for yourself? Having put about 10 minutes of guestimating into it, I think there are about 30.000 base jumps being made every year. The past five or so years, the average fatality rate has been around six per year. 30.000 over 6 means that for every 5000 jumps, one person dies. To stress again; it's a statistic that involves a number we don't really know and every base jumper has different comfort zones which puts them at different amounts of risk. Let's for now wipe all that aside and disregard that base jumping involves a lot of skill. Imagine, hypothetically, that base jumping is like Russian roulette and that on every jump you are just rolling the dice. Given the above; one in every five thousand jumps somebody dies, would you still base jump? Or do you consider yourself that one special base jumper that is better than the average jumper? Are you a base jumper that is safer than the rest and will manage to stay ahead of the pack? Do you have the special ingredient? What do you believe your odds are? With my limited amount of experience and extremely short amount of time in the sport I am in no position to comment on this. But holy crap is this shit dangerous. Let's be careful people. Know what you're getting into!

What a beautiful song to hear right after my qualifying jump! 39 jumps from 2 bridges, 2 cliffs, 1 building, 4 cranes and two nights ago; an antenna. A big thanks to Tom Aiello, Jimmy Pouchert and Niko for doing two incredible first jump courses in which I learned tons! Many thanks to Cornishe, LifeWithoutANet, Rick, Tom Alex., Tom D., SabreDave, ScottW, Chris (RIP), Grasshopper, Rob, Seth, Kevin, Kris, Chad&Katie, Russel, NickDG, The Coopers, Faber, BASE813 and all the other great people I've met along the way. I've learned something from everybody, and I'm looking forward to learning a great deal more and sharing many more laughs along the way. Cheers, Jaap Suter

For those that recall the plans for my LA trip, we just completed the Seven Q's Bongo part. Quoting a hysterically laughing Los Angeles police officer at 2:35 am, just after I jumped from the back of our get-away car and ran into the hotel... I am so not over that James Bond shit... Tomorrow we'll be traveling to Xanadu, do a flipmode squash, and then the mission will be complete.

Hi Maxim, that's a great question since object-strike (this applies to buildings and other things too) is still the number one cause of fatalities in our sport. If you do a search on these forums for "wall strike", "rear riser turns" or related items, you'll find a ton of great information. For example, this post by Tom quoting a post by Dwain. This one and this one ain't bad either. Don't hesitate to ask more specific questions in this thread though. Searching the archives is a great tool, but sometimes new threads about old topics can bring out new information or experiences. Regards, Jaap Suter

Starting threads with such a title makes my heart skip a beat. Next time, try something more upbeat.