crwper

Another thought on skydiving reserve times... The time between repacks is based on a couple of factors, IIRC. One is historical: silk has a tendency to deteriorate easily, so it was important to inspect the reserve often. With newer materials, for example, Canada moved to a 180-day repack cycle. Another factor is wear and tear. If someone spills a Coke on their reserve, but is dense enough not to realize this might be a problem, it's best that a rigger see it within a reasonably short period of time. Opening times are not really an issue. So, if my rig was stored in a cool, dry place I wouldn't have a problem jumping it a year later. The only questions left on my mind would be, did I pack it slider up or slider down? Brakes deep or shallow? When I'm standing at the exit point, I like to be able to remember specific points of the last packjob. With a year between, I'm not sure I would remember what I want. Michael

It depends. A direct bag will get you open higher, but there are a couple of things I really like about s/l: First, it is consistent. There's no chance of the bag being held a bit cockeyed. If something does go wrong, it's very likely a mechanical failure of some sort. Certainly, I won't leave behind a bag holder who will always wonder if he did something wrong. Second, it's quick. If I tie the break cord onto a karabiner which is attached to a short leash beforehand, I can quickly get out of the vehicle, throw the leash around the railing, climb and jump. If I was going sub-100, I would consider a direct bag, but obviously I'd need to have done a lot of practice with the bag holder beforehand. Michael

Dave: As 980 pointed out, there are two sides to the loop, so it breaks at about 160 lb. My understanding is thus: If you put 80 lb of tension on the cord, that's 80 lb per side, which means the total force between the anchor and the bridle is 160 lb. For the knot, use a surgeon's knot. Back it up with as many overhand knots as you like. Vincent: The bridle attachment point is much stronger than a loop of break cord. It's a good idea to check the attachment point regularly regardless of what kind of jumping you do, but unless something unusual is happening, there should be no problems. I have done one static line jump with no pilot chute. We were jumping a 111-foot span and the canopy barely had time to fly. I thought if I removed the PC, it might help, and also thought it couldn't really be much of a backup from that height. There was no measurable difference in canopy flight between jumps with/without the pilot chute. DW later pointed out that the most likely time to get a premature break is actually fairly late in the deployment sequence, and there is a good chance that a 48" pilot chute would help even on very low jumps. So I don't think there's any reason to jump without one. Michael

Hey all, There were a couple of climbers on Tombstone (I think they were working on a free ascent of Epitaph) on Friday, November 24. I chatted with them a couple of days earlier but didn't get their names. One of them said, I think, that he is from Denver. Anyway, I took an interesting series of photos from which I've produced the attached composite, and thought they might be interested in it. If anyone knows who they are, please let me know. Michael

This reminds me that if I'm jumping with a group and someone is doing something I think is really dumb, I need to be quite vocal about it. Who knows, I might save a life. Michael

Now that's a disturbing photo. Here's something I've never thought of before: Suppose the crosswind is from the left. You jump, you pitch. The PC moves to the right slowly as it pulls your canopy out. By the time your canopy is nearing line stretch, the line from you, through your canopy, and to the PC is angled to the right. Now, take that line, and imagine how your canopy sits on it. Looking from the front, you see the exposed nose of the canopy, and the whole packjob is kind of cockeyed, tilted to the side the PC is pulling from. The natural tendency of the packjob will be to slump toward the bottom side of the line. From the jumper's point of view, that means it's going to swing so that the nose faces left. The risers aren't even loaded, and already your packjob is 90-left. I suspect this effect is independent of whether or not you have a Multi. At this point, the Multi is still closed. Another interesting thing is that this won't happen every time. It's possible you will get lucky and your packjob will be relatively well-balanced on the line. In that case, it may not rotate at all before it begins to inflate (at which point it becomes much more stable in regards to this kind of thing). But it means that crosswinds are a bit of a crap shoot, which I think we all know from experience. Michael

When I was first taught how to stow a PC for BASE, I used a clamp. The critical part is keeping the top of the mesh/bridle folds tight against the cap. When you reach back, this is what you want to grab, so that you're applying force to as much of the PC as possible. If you grab just cap, you're likely to leave some of the "guts" behind, which is bad news. A clamp helps ensure that those folds stay in place while you stuff the PC. Over time, I've learned to pack a PC without the clamp, but I can see why some might prefer to use a tool. The preferred tool definitely should be a clamp, and not a pull-up or rubber band. Michael

I consider the list mandatory reading for anyone who's thinking about getting into BASE. With so many videos out there which make BASE look really cool, I think it's important to provide some balance by showing what can (and frequently does) go wrong. For more experienced jumpers, I think the list is equally valuable as a reminder of how easily we can get into a situation from which we cannot recover. Almost certainly, most of the jumpers on the list thought things were going to go just great prior to their fatal jump. Michael

Are you suggesting just sticking the nose of the toggle through the brake setting rather than using the white loop? Does this offer anything other than the obvious (but, I would argue, marginal) increase in security and savings in wear-and-tear from not involving the white loop where it's not necessary? I believe the problem is that the extra bulk passing through the small metal ring (brake line plus white loop) can cause things to lock up, either before you release the toggle or after. Michael

Once the canopy is fully inflated and turning a bit, it seems clear that the right side of the canopy is in full flight, and the left side is partially braked (looking at the tail). What also seems clear is that the jumper is using a lot of right rear riser to counter the turn. If the brakes were set very deep to start with, and just the left brake was left stowed, then countering with the right rear riser will likely stall the canopy, which is consistent with what we see. So I'd say the proximal cause of the problem is that the jumper is stalling the canopy by countering the turn with the right rear riser while the left toggle is still set in deep brakes. I don't see a toggle trailing behind the canopy, so I assume the right toggle is in the jumper's hand. In that case I see two options: Either the left toggle was never released (possibly the jumper responded to the left off-heading by popping the right toggle, but then switched to the riser), or else the left toggle was released, but (as others have suggested) the white loop never cleared the line. I suppose it could also be a tension knot on the left side of the canopy which is preventing the brake lines on that side from extending. Michael Edited to add: Yuri has a point. When the right rear riser is applied, it should pull the brakes down a bit, too, right? Although I can't see anything trailing behind the canopy, perhaps the jumper blew the right toggle on opening. Realizing the canopy was turning left, the jumper countered with right rear riser. However, that could easily stall the canopy, since the left side is still set in deep brakes. There really isn't a lot of time for the jumper to realize the left brake is still set.

I've been looking into building a "cheap" inertial unit out of this. The unit is small and light, and sampling rate would be more than 100 Hz. I'm not completely certain about the integration accuracy yet. It could be combined with a GPS, but what I'd like to do is keep it simple and just use the inertial data. This isn't really useful for skydiving (with a long plane right before the jump), but for BASE jumping (where you can guarantee that you're standing still just before exit, the jump is a couple of minutes at most, and you can additionally guarantee that you're standing still at the end), it might be enough. Michael

I don't actually know enough about the dynamics of water impacts to say. I've heard a lot of people say that hitting water at that speed is like hitting concrete, but I have a feeling those people are exaggerating the point somewhat. You may well be right. One other thing that comes to mind regarding helmets is unusual, but perhaps worth metioning. When I got to Jason about 15 seconds after he had hit, he was lying face-up in about a foot of water. He had never lost consciousness, but was in very rough shape. His head was being kept afloat by the foam in his helmet. Had this not been the case, I really don't think he would have been able to keep his own head above water. It's not the sort of thing you plan for, but I would say it's at least as important as the increase in projected area. Although there are a lot better reasons to get a helmet with proper crush material (as opposed to a shell with a thin padded lining), I've added this one to my own mental list. Michael

Following my brother's accident at the bridge earlier this year, in which he landed on his back in the water, one of the things that surprised us was that there was absolutely no damage to his helmet. I'm not sure if we would have recognized the symptoms of whiplash, but there was no damage whatsoever to his head and neck, either. Several years ago, 587 and I were jumping a low span. In the search for better head protection, he tried a motorcycle helmet. On that object we were hitting the ground pretty hard, and on impact his head kept moving because of the momentum of the helmet. His neck was quite sore for a few days. Still, I think that's a good reason to jump fairly lightweight helmets, rather than jump without. Michael

Poynter Volume 1, section 9.3.1.8.18: Michael

Here is the latest version of the vario program. As before, I've attached archives with installation files and a bit of documentation ("bin1.zip and bin2.zip") and source code ("src.zip"). I have not yet had a chance to update the documentation, so I'll describe the new features briefly here. First, I've opened up the display a bit. The "status" area at the top is reduced to a single line. On the right is GPS status and on the left (if you're connected to the GPS) is some piece of information from the GPS. If you tap on the status area, this will switch between time, altitude, climb rate, and horizontal/vertical position error. Second, you can view more than just glide angle (although the beeps are still glide angle only). To change the plot, use the drop-down list in the top-right corner. You can switch between altitude, horizontal distance, glide ratio, vertical speed, horizontal speed, and bearing. The glide ratio plot goes between the minimum and maximum defined in the preferences. All the other plots go between min and max for the current data set. Third, these plots aren't quite as simple as they seem. Under Options, I've added a "Wind" menu. Here, you can define the winds at altitude. The wind speed and direction (actual direction of the wind, i.e. where it's going to) are subtracted from the data for (a) calculating glide angle, and (b) displaying the various plots. That is, the data is relative to the moving air mass. If you don't like this, just set the wind to zero speed. Otherwise, it can be used to correct for wind so you still get meaningful data. That's it for the big changes. For those looking at the source code, I apologize that I have not yet had a chance to clean it up very much. I also have not had a chance to test the latest changes (except testing on the ground). If you download this version, please save the old one just in case. If you try out the new version, let me know how it works! On the way... I will be changing things so the jump data is stored in the Palm database, and so you can flip between many past jumps to compare. I'll also be adding options for the beeps, so you can have the program beep depending on your horizontal speed, for example. Have fun! Michael

If you look at static line as one option in your arsenal, then in some situations you might choose to use it. Examples which come to mind: You need the altitude to make an acceptable landing area. There's just not enough altitude for freefall, but you fancy the idea of sneaking onto the object and hucking yourself off. Your options for off-heading openings are bleak, and the improved heading performance of static line sounds like a good idea. I think it's silly to eliminate such a useful option on principle alone. It would be a bit like saying, "If you can't jump it with a skydiving rig, maybe you shouldn't be jumping it. If you only feel safe using a BASE-specific rig, should you even be jumping it?" I mean, that's BASE jumping, right? Michael

This is something I've considered. Basically the effect is that the beeps would indicate change in glide ratio, rather than the glide ratio itself. I think this might actually be more confusing in the air. Since it is not possible, really, that you would constantly be improving your glide ratio, you would always wind up chasing small improvements, without any real indication of how they stack up over time. If I understand correctly, I think this could also be confusing. Having tried this thing out a couple of times, it's certainly fairly obvious when you're doing well and when you're not, but if you try to include more information in the beeps (for example, indicating the window position), I think it would become considerably less intuitive. Again, I think this may add more complexity than is necessary. My feeling is that the device should be as simple as possible. If it turns out you have very complex wind conditions, for instance, it might just not be the right day to play with this particular toy. What I have in mind at the moment is just to subtract an assumed wind vector from the horizontal velocity before doing calculations. Data would be stored without the correction made, so that when you get down to the ground you could make adjustments to your assumption and re-interpret the results. Basically, you would use the results from one jump to adjust the wind assumptions for the next. The wind vector could be entered manually, or possibly calculated from an existing jump if certain things are known about the jump itself (for example, if you can select a period of time where you performed a constant-rate turn). Michael

I was walking to work this morning, and passed an independent theatre which is currently hosting the Calgary International Film Festival. This caught my eye, but it looks like I missed the show date. Has anyone else seen it? Michael

I've looked a little more into this. As it turns out, my GPS was set to "automatic" velocity averaging. I've set it to "none", but it will be a couple of weeks before I can try it out. Hopefully this resolves the problems with vertical velocity. Michael

I've heard that consumer "noise-cancelling" earphones are not as good as "isolating" earphones like the ER's or the Sony MDR-EX line. Have you tried them? Michael

You can. The cable shouldn't be too hard to get. Google gives a few hits for eTrex to Palm Universal cables. The problem with this kind of set-up is that the Palm Universal connector isn't really meant to be used in mobile applications where stress is applied to the connector, so it has a tendency to come undone. For the Palm, or the eTrex? Again, Google turns up a few hits on Bluetooth adaptors for the eTrex, but they all seem to be something that plugs into a cigarette lighter. The eTrex doesn't supply power through its connector, so you'd need to find something that has its own power. There are many Bluetooth adaptors available for the Palm itself. If you can do it, wireless is the way to go. I built my first prototype using a hacked-together Palm-Garmin cable and a Geko 301. I actually never got it to work, because every time I headed for the door, the Universal connector would come undone. I currently use the Garmin GPS 10 and a Palm Tungsten T (has Bluetooth). The difference is incredible. Instead of fussing with a cable, I only have to manage the Palm and earphones on the way up. On jump run, I tuck the GPS into a pocket on my ankle and I'm off. I use Etymotic Research ER-6i earphones. These provide excellent noise reduction. They are always available on eBay. I have been wearing just one when I jump, so that I can hear other jumpers just before exit. There is no problem at all hearing the audio in freefall. Michael

The minimum and maximum glide ratio can be set to anything between 0.0 and 25.5. The tighter the range, the better you will be able to distinguish small differences in glide angle. On the other hand, if the range is too tight then a bit of wind will push you right out of it, so it's a bit tricky. There is no direct export to Paralog at this point. However, it is possible to export data to a comma-separated file in Memo Pad. This is usually synchronized to the PC on each HotSync, and can be accessed in Palm Desktop. A sample of the data output is found in "GPS Data.txt" in my previous post. If Paralog can read that, you'd be set. Michael

In that case I would be tempted to leave the Velcro alone. It seems like the danger of having the rig come open while climbing is greater than the danger of it staying closed a pull time. Are the side flaps on your rig stiffened? As Jaap mentioned, non-stiffened side flaps seriously reduce the effectiveness of the shrivel flap. I'm curious why you've decided to freefall this one. At your experience level, I certainly would have chosen static line. Heck, I'd probably s/l the first time just to get a feel for it. Static line gives excellent heading performance, and also leaves your hands free. It can be awkward moving around with a pc in hand on the side of an antenna. Simpler, yes. Less force, not necessarily. Velcro should provide a more consistent pull force with a variety of pack jobs, but a pin rig with Spectra closing loops can have very low pull force. Michael

The Odyssey is a good rig but has very strong Velcro, if I remember correctly. If you're taking a short delay, I would prime the Velcro first. Michael

Well, the program uses an ARM callback to generate the sound stream just-in-time, so I suppose the PALM will have to use an ARM processor. Anything newer than my old Tungsten T should do it. I think any Palm running OS 5 has to be ARM. Other than that, the connection is either through the cradle connector (which goes way back) or through Bluetooth. If you go through the cradle, there could be a bit of tinkering to come up with a cable. I made my own using an old Garmin serial cable, Palm serial HotSync cable, and a null modem adapter and gender bender between. If you find a Palm with a connection other than these two which you would like to see supported, please let me know. It would take about 2 minutes to add another port to the list. I doubt it, but would love to know the results if you give it a shot. More than the port stuff, I think the ARM callback might throw it for a loop. Michael