crwper

I watched a pilot chute in tow malfunction caused by this exact problem on a CRW jump. The problem there was that we were using floating pins, and it's easy to install the pin "the wrong way". I just wanted to add that this is a really subtle rigging error, but can have disasterous consequences. Make sure that when you pull up on the bridle, it lifts the end of the pin up into a "U" shape instead of forcing it down into the flap. Michael

Everything is flawed. Most theories today are fundamentally a description of a mathematical system whose dynamics happen to be analogous to the dynamics of the world around us. Mathematical theories will always live in the domain of mathematics. The dynamics of the real world will always live in the domain of the real. I think it's very important, and often overlooked, to understand the implications of this. When we say the world is "three-dimensional", for example, what we are really trying to say is, "The world as we see it is nearly analogous to some three-dimensional mathematical system." But by saying it the short way, we've inadvertantly implied that "the world" and "three dimensional" live in the same domain, which they do not. Okay, maybe this is getting a bit too philosophical for this thread, but to bring it back, I'll say that a BASE student should have as clear an idea as possible of the fact that they are not jumping into a theoretical system. They are jumping into the real world. If anything, I would say too much book learning distances us from this fact. While I think the basic delay and pilot chute charts are fabulous, I also think that when we try to refine them too far, we lose sight of the fact that they were only ever meant as guidelines, not as exact models. As Nick said, when you stand at the edge of a cliff you will know the difference between theory and reality. Michael

I'm one course away from having degrees in Physics and Pure Mathematics. This doesn't mean very much. Maybe what would tell you more is if I said I have a major fetish for information. As well as studying what others have written, I like to do quantitative experiments. But I'm also aware of the limitations to this way of thinking. If you're going to jump an ultra-low object, doing it because the math works out is a terrible way to go. Yeah, to me it's cool to do the math anyway because I dig that sort of thing. But you should also have jumped something slightly higher before, and that should be the major thing which informs your decision to jump. What am I trying to say? I'm trying to say that the simple freefall chart which is printed on the inside of almost every logbook, as well as the manufacturer's conservative pilot chute sizing chart, are probably the only quantitative information you will ever need. Okay, I'm probably over-simplifying the case here. But if you need a chart to tell you what size pilot chute to use for your 180-foot freefall, you probably shouldn't be doing it in the first place. A physics degree alone means very little. I've seen plenty of examples of graduate and post-graduate physics students who can do most of the math, but show very little adaptability to unkown problems. A staggering percentage of the student population actually believes they are learning the right answers. That's one of the big messages we get in school. There is a right answer and a wrong answer, and we're learning the right one. If we buy into this too much, it is at the cost of adaptability. To get to the point... I think what is more important in a student than book learning is having a certain volume of knowledge, and knowing the limitations of that knowledge. I would rather that someone knew the basic delay and pilot chute charts, but also knew that there was some margin for error in thos numbers, as opposed to "knowing" the exact values. To me, the latter kind of knowledge shows a basic belief that we can know the right answer. The former shows more capacity for growth, which will be one of your greatest allies in this sport. Michael

Calculus? Michael

So, I'm used to the visuals at pull-time on a regular terminal BASE jump. The way I got there, I suppose, was that I went to some big walls where someone told me, "It's x seconds to impact, but if you aren't tumbling like an idiot you should be able to take at least y seconds." On the first jump, I counted to y and had a good look at the ground coming up. Next time, I counted to y and then waited a couple seconds more before pitching. And so on. However, one thing I've heard fairly consistently about wingsuit BASE is, "Don't wait for the familiar feeling of groundrush, because if you usually pull at 300 feet, you'll be pulling around 100 feet with a wingsuit." I'm getting set to do my first wingsuit BASE jump from a 1200-foot wall with about 2000 feet of high-angle talus below that. I've done a couple of jumps from this one before, but I haven't got any reliable accounts of wingsuit flights from here. So I have no one who can tell me, "Try 30 seconds for starters, then work your way up from there." What I'm wondering is, how should I judge pull-time? If groundrush is out, then I'm thinking either (a) I could use a conservative count based on the altitude available to me or (b) I could use some kind of visual reference on the opposite side of the valley. I'd like to hear any pointers on how to judge altitude the first few jumps, and also maybe any first-hand accounts of first wingsuit BASE jumps which might give me an idea what to expect. Thanks! Michael

Still sounds good for slider-down testing. I was thinking about just using my shallow-brakes setting and tying some knots in the line above the brake setting. However, I suspect the amount of line taken up by a single knot is way too much for this kind of adjustment. Michael

Ah, I clearly don't understand the setup exactly, then. I had imagined that, by folding the line and passing it through the grommet, you were putting the knot on the up-line side of the toggle. I know this is getting way off-topic at this point, but perhaps you could describe your method again for the slow kids in the audience? Thanks! Michael

In skydiving, I've seen a similar problem with the method of tying a loop in the brake line and larks-heading that around the toggle. The problem there is that some people leave quite a lot of slack in the loop, so that the knot winds up being an inch or more from the toggle. In this case, with the canopy in full flight it is possible for the knot to be pulled through the guide ring, which can sometimes give an unexpectedly hard pull when it comes time to flare (and the knot has to be pulled back through the ring). With the method of tying a knot in the line and then larks-heading the folded line around the toggle (I think this is your method) it is conceivable that this could happen, if I'm not mistaken. With the knot on the bottom side of the toggle and the line passing through the guide ring, it's possible the knot could find its way through the guide ring and hang up. However, since the knot isn't on the tensioned side of the line, I think this is extremely unlikely. There is no force which will pull the knot through, as in the above method (the force in that case being the tension in the brake line). Michael

Working on it. Well, that is, it will be Crossbow'ed, but close enough. I have a very good feeling that this is the summer. Michael

For the physics-inclined... Imagine you're looking down on someone's head. They have just launched on their back and are now in freefall, but not yet with any appreciable windspeed. They are going to roll over onto their left side. First, they cross the right arm and right leg over the left, and possibly also the left arm and leg under the right, but keeping them close to the axis of the body. This generates a small amount of angular momentum in the counter-clockwise direction (mass of arms and legs, but with a very small radius of motion). The body will respond by moving very slightly in a clockwise direction. Thus, total angular momentum is zero. Next, the arms and legs are brought back to the starting position but around a wide arc. This means arms and legs as far as possible from the body. This is the same mass as the first motion, but over a much larger radius. Thus, more angular momentum in a clockwise direction. The body responds with a significant movement in the counter-clockwise direction. When you have completed the cycle, you have at no point created anguular momentum (the total was zero all the time), but the net effect is that your body has rotated in a clockwise direction. As I said in another post, part of the reason this seems wierd is because it's possible to carry out a rotational motion and wind up back where you started. The classic linear momentum experiment, where you throw a ball away from you in freefall, would look a little different if you could throw the ball away from you, then catch it again without ever actually reversing the momentum of the ball. Michael

I don't think so. You can actually generate a continuous rotation of your body if your swing your arms. Imagine that you are floating in the middle of space. Then begin windmilling your arms. This introduces angular momentum to your arms, which must be countered by an opposing momentum in your body, i.e. your body will rotate in the opposite direction. The reason this can work is because angular motions can eventually return to the starting point without changing the direction of motion, so you can do it indefinitely. With a linear motion, the only way to move forward would be to shoot something backward. But you can't get back to the "starting point" without reversing your hard work. Michael

The phrase, "Let's try something a little different," as well as the ensuing flail-fest is burned into my mind. This is one of the reasons I'm not so sure about the back-to-earth exit. I believe the key would be to launch into it, rather than rotate off the exit point. I haven't heard from Michel in forever, but I heard he's back in town, so perhaps that will change. Michael

My bad. I meant to say "slider-down" would result in less chance of extreme line twist. Michael

I'm heading to TF this weekend and one of the things on my "may do" list is what I've been calling the cat flip. I've seen this done many times before, and it seems like a good starting point for exits other than "flat and stable". The idea, in case it isn't perfectly obvious, would be to exit more or less on my back, then roll onto my front and pitch. I've been thinking about this for a year or so now, and I think I've got the mechanics worked out. But I want to take this opportunity to confer with the rest of you who may have tried this before... For the exit, I'm thinking it's important to launch into the back-to-earth position, rather than rotating into it. I've seen a friend try to rotate backward off the bridge, and naturally it turned into an aweful mess. I've never done this kind of exit before, but it doesn't really seem like the sort of thing one can try before doing a cat flip (otherwise, what are you going to do about pulling?). On my face-to-earth exits lately, I've been toying with exiting fairly flat--not by rotating there, but just by placing my body on the air that way. This seems to work fine, and I assume the theory would carry across to a backward exit. Once I'm in the air, as I understand it what I want to do is to cross my right arm over my chest with sort of a "pushing through" motion instead of swinging around a wide arc. Similarly, I want to cross my right leg over top of my left. To do the flip, I imagine using my crossed right arm and leg as kind of an inertial "anchor" while I bring the left half of my body underneath so that I am face-to-earth. There are a couple of safety points I've thought about. I'm thinking of doing this slider-down in order to minimize the risk of severe line twists on opening, but I am also aware that this puts time constraints on the manoeuvre. Also, I'm obviously thinking of rolling onto my left side, so that if the thing goes only partway I am at least chucking the pilot chute into clean air. What I'd like to hear is any advice on performing the flip. If you think this is a great/terrible idea as a first advanced exit, I'd like to hear that. If you have tried this and have some tips to share, I'd like to hear that. Also, I'd like to hear any recommendations on the gear configuration, things I should watch out for, etc. Of course, if you have something to share that doesn't fit neatly into the above categories, I am positively not interested in hearing it. I'm kidding. Any advice at all is welcome. Thanks, everyone! Michael P.S. Edited because I meant to say that slider-down should result in less chance of severe line twists.

I had something like 150 jumps when I did my first "big" wall. The highest thing I'd jumped up to that point was maybe 600 feet (we're obviously not including skydives here). One of the biggest issues for me, on that jump, was that as I looked down at the rocks below the exit point it looked very much like about 300 feet, and not so much like 1200-plus. We had triangulated the height a number of times, had looked on topo maps, had some idea of the length of the climbing route up the face. In my mind, I was as certain as one can be that it was more than 1200 feet. We had done a rock drop and heard what we thought must be the impact at 11 seconds. Take off a couple of seconds for the sound to get back to the exit point, and we thought conservatively that impact might be at 9 seconds. I decided to take a 6-second delay. My body still told me I was about to take a 6-second delay off a 300-foot cliff. I rapped over the edge to take a look. I've climbed a lot of one-or-two-pitch stuff before, but just rapping over the edge of a 1200-foot cliff was something else. We had arrived at the exit point about 8 am, in what can only be described as absolutely perfect wind conditions. There was a bit of mist rising slowly up the face. No wind to speak of. A beautiful sky. I had secretly hoped for even a 5 mph wind so I'd have something to be unsure about. Some of the wierdest jumps I've done have been when I show up at the exit point, and there is absolutely no reason not to do the jump. Except maybe one reason, and that one's part of the reason I do this. When there are no other reasons but this one, everything seems thrown into stark contrast. By the time I was ready to jump, it was noon. When I radioed down to my ground crew that I was going to "put on my gear and see how it feels," those who have been with me before knew what was going on. The jump went well, but to be honest sensory overload was definitely a factor. I took about a five second delay, but except for a few moments I don't remember very much of the jump. I landed in a high meadow with my ground crew running across the scree slopes to meet me. Last summer I went to Norway and Switzerland with a few friends. When we returned home, we went back to our 1200-foot cliff and did some beautiful 8-10 second delays. On this second round of jumps, I felt completely aware. On most of the jumps I've done, there isn't a lot of time to enjoy freefall, except in that basic reptile-brain way which leaves me remembering later that I had a really good time, but unclear about some of the details. Our trip to Europe has changed even my experience of the lower stuff. The uprushing ground looks a little different now, because it's actually giving me quantitative information about my movement. I think the biggest misconception that we have is that the ground will be one moment just floating there in front of us, and then very suddenly it will rise up and take us out. I think the best way to correct this is to make a few jumps at the terminal walls. At first, I counted, "One thousand one..." up to fifteen seconds. I think this is was a good way to calibrate my visuals. Then, after a couple of jumps, I'd count to fifteen and then just watch the ground a couple of seconds more. The thing is, it never really jumps up to get you. It's a fairly gradual kind of acceleration of groundrush. Yeah, the ground is coming up mighty fast in the last couple of seconds. But it's not impossibly fast. In fact, it's quite finite. I've heard some people say it almost looks survivable. Michael

It's been a while since I saw Dwain doing aerials. But watching, for example, Jeb's video, what I'm struck by is the athleticism of the sort of aerials you describe (e.g. front, front, back, back, front, pull, or whatever). I've never spent much time checking out diving competitions, but after watching a bunch of BASE aerials, I think I might have a new appreciation for them. Maybe BASE aerials are like a "gateway drug". Michael

My impression also has been that sail slliders offer less consistency than mesh sliders. This seems to be true in terms of heading performance, and also altitude required for an open canopy. A friend of mine has back problems, but managed to make it through a 3-week trip to the big walls in Europe with a mesh slider (large holes, I think) and careful rolling of the nose on his vented canopy. I really can't imagine a situation in which I would choose to use a sail slider. Michael

You can see the inner bridle folds up closer to the pc fabric in Jimmy's photo. He's then wrapped a bit of mesh around that before making the outer bridle folds. Michael

I was going to make the same suggestion. It's not quite the same, but I got whacked using a 38" at terminal last summer. Consistently good results with a 32", though. Michael

I was thinking of heading down that weekend. Nothing definite yet, but likely. Michael

Interesting. I've used the same method, for the same reason, for maybe 100 jumps without anything I could recognize as hesitation. I'll definitely do some testing, and probably update my pc packjob. Can you describe more the conditions in which you notice a snag when testing this on the ground? Thanks! Michael

Screw personal safety. Won't someone think of the video? Michael

Bingo. A 10 mph wind into the face meant that as soon as we flew away from the face, we were just flying into a headwind. Made the usual landing areas a bit harder to get to. Michael

Hey Jaap! I have a couple of questions about the Mace. First, how is the weight? Second, one of the things I look for in a motorcycle helmet is that I should be able to grab the chin bar, pull it upward, and it shouldn't get too much further than my chin. No point having a chin bar if it isn't going to stay where your chin is. With every full-face mtb helmet I've tried on, I could get the chin bar at least as far as my nose before I encountered resistance. So much for the bottom half of my face. Michael

Just curious... For those who have said they only jump in calm conditions, do you know this because you drop a WDI, or just because it's calm at the exit point? Michael