Tornolf

warning: math below Well, if they're both the same length then I wouldn't call the 2nd one "secondary" as both are acting in tandem. Obviously it's much better to have them varying in length in case something causes the first to break when loaded. The main advantage to different lengths is that if something such as a sharp railing cut the break cord prematurely, there's a chance it won't happen to the second one. If they're both the same length, you're trading off for a very small gain in overall breaking strength for no real benefits. I think there might be some confusion of the physics of multiple break cords though. It would be nearly impossible for 2 pieces of break cord acting in tandem to do something like that. Also, when using redundant breakcord (different lengths), the jumper's momentum will be very similar, although a tiny bit more, after both pieces break when compared to 2 equal pieces. Note that a bridle made from 1" squareweave has a tensile strength of 1000lbs, 1.5" squareweave is 1500lbs. I'm not sure how much the larkshead and stitching at the pc attachment point (which matters since the larkshead on that end is not loaded during a static line) will weaken the tensile strength, but I doubt it's anywhere over 60%. So my guestimate for the breaking strength of a bridle (which is low imo) is 400lbs. Canopies, as mentioned earlier, have a strength of more than 550lbs. It would take way more than 4 breakcords tied in tandem to cause something else to fail before the breakcord. This should clear some things up: Force (F) = ma Momentum (p) = mv a = dv/dt Force = dp/dt (change in momentum with respect to time) To get some concrete numbers to hopefully make this easier to understand, we'll assume that the jumper's center of mass falls 25 feet before reaching linestretch and beginning to load the static line in a significant manner. He weighs 160 lb (~5lbm - 5 pounds mass) This means his velocity is 40 feet /sec. His momentum is 200 ft * lbm / s WIth 2 breakcords in tandem and in good working order, the breaking strength will be 192 lbf (pounds force, btw 32.2 lbf = 1 lbm). For this to *not* break, dp/dt < 192 lbf: F = 192 lbf = dp/dt dp/dt = d (200 ft * lbm / s) / dt = 192lbf with some simple integration it shows that it would take nearly an entire second of constant momentum change before the static line would not break. So if the cord is loaded for less than 1 second if dp/dt is linear, it will break. I doubt there is any way the loading will be constant, so any spike over 192 lbf will break the cord. When you consider the speeds and distances involved, the breakcord is loaded for a very small amount of time. When discussing "shock force or load", people are mainly talking about the change in momentum with respect to time rather than static force. In the case of 2 different length break cords, the overall change in momentum will be nearly equal to the previous example. The only reason it's different is due to the small, negligible extra inch or 2 of freefall the jumper gets between the two break cords. In other words, if 2 break cords of equal lengths would cause someone a hangup, 2 different length of break cords should do the same thing, but the first cord will break and the second will hold the person. Using 2 different lengths of breakcord to try avoid a hangup is ineffective. (math below) F1 = 96lbf F2=96lbf dp/dt = d (200 ft * lbm / s) / dt after breaking the 1st breakcord, dp/dt = d (200 ft * lbm / s) / dt - 96lbf when loading the second cord, if dp/dt < 96lbf, the second cord won't break. d (200 ft * lbm / s) / dt - 96lbf = 96lbf d (200 ft * lbm / s) / dt = 192lbf it's the same equation as for 2 pieces of static line the same length. A waddling elephant seal is the cutest thing in the entire world. -TJ

think about comparing the speed of rotation between front tucks and inward front tucks. with proper technique, it's totally doable, but I've seen very very few base jumpers use proper technique with aerials. if you don't use the right technique doing it ronald's way, it's not going to work. but yeah, slider fronts are much harder than backs or gainers if you don't twist into reverse flips prior to opening. this reminds me of when I was training with a guy who had trained some earlier base jumpers. his kids were 10 and 12 and had dove all their life. we were sitting in his living room watching some old video of previous base jumper students and his kids would burst out laughing when these guys would attempt aerials. that really put things in perspective, especially when a 12 year old can do sicker aerials than the best base jumpers I've ever seen. A waddling elephant seal is the cutest thing in the entire world. -TJ

See attached pic. Since the loading on the break cord is at a single point, which pulls the break cord taught, the load is spread evenly on both sides of the static line. In this case, T2 and T3 are equal, and breakcord breaks when T2=80lbs. Thereforce, since T1=2T2, the load will break the cord at 2*80= 160lbs. This is the theoretical maximum breaking force on the break cord. Since things such at tie off points and knots weaken it, it will never break this high if rigged properly. In the dozens of static lines I've done and seen, when tieing off to a fabric tie-off, the break cord always breaks at the knot. If it breaks elsewhere, then it means that something caused the cord to break at less than 96lbs of tension (approx). A waddling elephant seal is the cutest thing in the entire world. -TJ

easily doable if you use proper technique A waddling elephant seal is the cutest thing in the entire world. -TJ

4. I was putting together most of the mechanical parts of the system we were going to use. Actually it was what I was going to use, since somehow I became the test jumper... With 4 there's almost no force on your mouth at all. I was using some really old suspension cord and I'm thinking it would be better to use something like dacron, then fingertrap a 6" piece over the loop that goes in your mouth. So you'd basically pull the loop through the 6" piece so the 6" piece can be a protective sheath. It seems like using a rubber tube or tape to protect the line from your teeth causes major hangups when you release. Then again, since the force is so low on the last line (approx 1/16 the total force), you should be able to tell when the line needs to be replaced long before it fails. Other than that it seems like the safest system you can tow with. With an active and passive cutaway system, it's really easy to bail if shit goes wrong. We ended up planning to use a grigri to pay out line, which was attached to a riser, which was attached to a biner attached to a rope spanning the back of a truck. If you have a cutaway handle with 2 ends (looks like a Y) then either the person on the grigri or a person beside them, designated to cutaway if shit goes down, can chop the rope. Basically you end up with 3 people (jumper, grigri payout, cutaway person next to grigri) that can chop at any time, completely bailing from the tow. I give myself like a 75% chance of not dying. A waddling elephant seal is the cutest thing in the entire world. -TJ

hey I just made one of those! didn't use it though, going to try another day. A waddling elephant seal is the cutest thing in the entire world. -TJ

It would double, however it would not be 160lbs. 80lb breakcord looped once will break at 160lbs, best case scenario (no uneven loading on the sides, etc - which is hard to do with the way we tie static lines). Since knots weaken the strength, it's lower. A surgeon's knot weakens it around 40%, which is pretty good. So you end up with 96lb breaking force max with a standard piece of 80lb breakcord tied with a surgeons knot. (80*2)(1-0.40)=96. So the force in that situation would be 192lb, not 160. A waddling elephant seal is the cutest thing in the entire world. -TJ

I have no problems wearing Acuvue2 contacts with a pair of sunglasses. Most of my jumps are wingsuit jumps with total speed around 100mph. (low 40s vertical, low 90s horizontal). I've never had a problem with the wind blowing behind/around the glasses and bothering my eyes. A waddling elephant seal is the cutest thing in the entire world. -TJ

as a geek, that's one of the coolest tattoos I've heard of in a long time A waddling elephant seal is the cutest thing in the entire world. -TJ

Well you are exceptionally muscular. btw come visit, we did 6 jumps last weekend and none of that scary slider up crap surrounded by guy wires A waddling elephant seal is the cutest thing in the entire world. -TJ

baby steps! A waddling elephant seal is the cutest thing in the entire world. -TJ

Give me some time Current goal for my V2 is 35mph vertical and 85+ horizontal. A waddling elephant seal is the cutest thing in the entire world. -TJ

Freepacking allows you to more easily distribute the volume during closing. I found that packing my F111 245 into a container made for a 160ZP was impossible if it was in a bag, but possible, and ugly, if it was freepacked. Granted, I got tired of it so I bought a 24 year old Racer with a 22' round reserve and a 680 cu in main tray for $125

I'm not a rigger, but I very much prefer to pack my own reserve. I do so under the supervision of a rigger obviously, as forging a seal would be a pain in the ass, not to mention an asshole thing to do. Only costs me $15 to get watched and it gives me peace of mind. I've even saved myself once. I only do it because I guess it's the kind of person I am. I also do all of my own rigging work on my non-TSO'd gear. A waddling elephant seal is the cutest thing in the entire world. -TJ

and they usually jump at bardstown until sunset on weds. cessna 180 and beaver. about 40min from downtown louisville www.skydiveky.com A waddling elephant seal is the cutest thing in the entire world. -TJ

bars downtown or on bardstown road, phoenix hill is cool A waddling elephant seal is the cutest thing in the entire world. -TJ

It's a really fun suit. Different, but really fun. Now if I could only get mine back from the guy who's been borrowing it for a year... A waddling elephant seal is the cutest thing in the entire world. -TJ

That would be boring as hell. A waddling elephant seal is the cutest thing in the entire world. -TJ

That's what I'm thinking. The most likely time perfectly working breakcord will break prematurely is when the shock load occurs just as it starts pulling the canopy and lines out of the container - when it has to overcome the downward momentum of the canopy/lines and completely stop the canopy. Past this point, all the breakcord is doing is holding the canopy/remaining lines in a suspended manner, thus the force on the breakcord is equal to the weight of the canopy and remaining lines. During this time, the chance of premature breakage of perfectly working breakcord is 0. When you add in the fact that nothing is ever perfectly working, this scares me a bit more. In this situation, premature breakage just as the static line is loaded will kill the jumper, as the container is open but there is basically no canopy out. With no backup PC to pull it out, or enough canopy exposed to the airstream to drag the rest out/prematurely inflate, not much is going to happen. A waddling elephant seal is the cutest thing in the entire world. -TJ

So, if for some reason the breakcord broke before pulling the canopy to linestretch, like during the shock load when overcoming the canopy and line's inertia in the container, the only thing that would continue bringing the canopy to linestretch would be the drag it creates on its own? A waddling elephant seal is the cutest thing in the entire world. -TJ

I can easily do 80's in a track in an RW suit. I can do lower in a tracking suit. Granted I am 6' and 130lbs, but it's very far from impossible. And see my previous post. There's more ways to create lift than a traditional aircraft's airfoil. A waddling elephant seal is the cutest thing in the entire world. -TJ

Wingsuits are terrible airfoils with respect to creating lift as aircraft do. Don't think about aircraft wings, think vortex lift. http://www.dropzone.com/cgi-bin/forum/gforum.cgi?do=post_view_flat;post=2683420;page=1;sb=post_latest_reply;so=ASC;mh=20; From the guy who's been designing wingsuits for nearly 10 years: A waddling elephant seal is the cutest thing in the entire world. -TJ

The only person I've jumped with who went through Tom's course was one of the most heads up and knowledgeable inexperienced jumpers I've met. I think he only had like 20 or 30 jumps when he hooked up with us, all from Perrine. This could very well be more a result of the person than the course though. And who I'm talking about, don't get a big head cause you're still not allowed to fuck up and die - it's against the rules. A waddling elephant seal is the cutest thing in the entire world. -TJ

For 1st year mechanical engineers in my area, it was about right. It's even a little bit lower than the average pay for graduates in their first year after getting a Bachelor's in ME from my university. This average pay is from our ME co-op advising office, updated each semester. From talking to my friends who have already graduated and been hired, I'm fairly confident the numbers from my uni are accurate. A waddling elephant seal is the cutest thing in the entire world. -TJ

Prodigy, V2, Classic (S.U.I.T.!!), GTi, or Skyflyer 1. Depends if I'm loaning any of my suits out or not. If I want to "work" then I jump the V2, otherwise I like jumping the Prodigy and Skyflyer 1. edit: and the Classic still kicks ass. It flies forEVER A waddling elephant seal is the cutest thing in the entire world. -TJ