• Content

  • Joined

  • Last visited

  • Feedback


Everything posted by billbooth

  1. Jeanice Dolan of Skydive Ocean City (MD), reports 5 years and 15,000 jumps with no malfunctions on their Tandem Sigmas. This involved several Tandem Instructors and a half a dozen rigs.
  2. I put the center line tapes, what you called "limiter tapes", in the original hand deployed pilot chute for two reasons: 1. To make the pilot chute open faster. (Without the initial "holding open effect" of a spring, the shapeless hand deployed pilot chute tended to streamer for a second or so.) 2. A pilot chute (or any round) with a pulled down apex creates 11% more drag, and could therefore be make a bit smaller and less bulky. But, opening speed was the main reason.
  3. "Who's on first" will never be surpassed, but the Johnny Carson/Jack Webb "Copper Clapper Caper" routine is right up there with it.
  4. When I started jumping, 53 years ago, one of the first things that struck me was how primitive and simplistic stowing lines in rubber bands seemed to be. There just had to be a more modern, technologically better way to do it. I tried everything, but kept coming back to the good old rubber band. It seems that, as usual, the simplest way turned out to be the best way. The "modern" semi-stowless bag is just a re-hash of the original Para-Flite reserve bag, except that we use tuck tabs or magnets instead of Velcro to stow most of the lines in a pouch. But the good old rubber band remains the best way to lock the bag shut. To quote the Bible: "As it was in the beginning, is now and ever shall be...Magnets make for great riser covers, but in this particular game of rock-paper-scissors, it's obvious that rubber bands trounce magnets. Trying to reinvent the wheel is not always a good idea.
  5. Gary; Perhaps you're right. I used the term "Line Dump" (it is a rare beast, but something more easily understood by most jumpers) rather loosely to cover the litany of problems that come from high separation velocity at line stretch, such as high snatch force and the general disorganization of the pack job it produces. I just know from conversations with legendary canopy designer Theo Knacke and decades of observation, that nothing good comes from separation velocities over 50 fps, which equates to line stretch times of about 0.5 seconds for average sized sport canopies deployed at terminal. As I have written here before, it is rather easy for a jumper to determine line stretch time by simply having someone video one of their deployments. Just count frames from container opening to line stretch.
  6. Pilot chute drag is very important. Depending on design and materials, the drag to two identically sized pilot chutes can be very different. This is one reason why buying any component after-market can be risky. You must communicate to the seller exactly what you will be using the component for, so that you get a truly comparable part. A correctly sized pilot chute should get you canopy to line stretch 0.5 to 0.7 seconds at terminal. (A bit slower on a hop and pop, of course.) Too big can cause line dump, and too small can cause a bag lock from lines blowing over the bag. What size rubber bands or tube stows you use, and whether you use a full-stow or semi-stowless bag can also alter your deployment time. But when you put all those considerations together, 0.5 to 0.7 seconds is what you should aim for. A pull out probably would not have made any difference in your situation, because I suspect your pilot chute, even though too small, pulled the curved pin (which should only take around 5 lbs. of force) opening the container. Your PC just didn't have enough oomph to pull the bag out of the container because of your low airspeed. Pilot chute hesitations, reserve pulls, and fatalities because of pull outs were numerous in the 70's when a lot of people first tried them. That's why hand deploys became the dominant system. When all is said and done, hand deployed systems simply have far fewer problems in actual usage.
  7. Great Job. A trip down memory lane. I'd love to get reprints of the articles introducing the hand deployed pilot chute (Sept '76 and Nov '77) and the 3-ring release (Aug '77). Does anyone have these issues?
  8. A while ago, I got back the first rig I ever made. It contained a PC which had been packed for over 25 years. What the hell I figured, let's put a jump on it and see if it still works. In two words, IT DID! One caveat: We DID replace the rubber bands, which had long since rotted, but we did not touch the packed canopy in the bag.
  9. I've said it before, but I'll say it again. After watching hundreds of videos of people cutting away from spinning malfunctions with Skyhooks, I firmly believe that the chance of reserve line twists is lessened with a Skyhook because of the speed of the reserve deployment. Line twists happen all the time on mains, and they (of course) are deployed without MARDS. "Getting stable" after a cutaway from a badly spinning main can take many hundreds of feet. While it is very unlikely that line twists on a reserve after a Skyhook deployment will kill you. It IS highly likely that hitting the ground without a fully opened reserve will.
  10. I'm missing more than I can remember...and it's been 52 years since my first jump, which by some miracle, I remember well. It's the 70's I'm a little foggy about. After all, it was the era of free love and even cheaper drugs.
  11. Damn you guys are getting soft! "In the old days", we really did have to contend with "Capewell Welts" from those 1 pound hunks of metal pounding us on the front of the shoulders on opening. You could actually see the bruises after a hard weekend jumping. However, this is the first time I've heard someone complain about a little bitty 3-ring biting them. Seriously, most rigs today have spacer foam under the 3-rings to help make openings as easy on you as possible. But proper harness fit, canopy and line choice, and packing technique can have an even greater effect on comfort.
  12. I did a solar eclipse jump back in March of 1970. There was a low broken layer under us, so I could see easily the moons shadow coming at us at 1,000 mph. We exited just before the shadow "hit" us. It was an amazing feeling physically as well a mentally; going from day to night and back to day, all in one jump. It was far better than just looking up at the sun. It was one of those "once in a lifetime" experiences that I now have a chance to do again, and I'm not going to miss it.
  13. Leave as little unstowed suspension line as possible. Never loop unstowed line in your pick tray. Your side flips "dive" right back into your pack tray as soon as the bag leaves. You don't want to leave any loose line for them to entangle with. This has killed people. You may be lucky for a long time, but eventually it will get you into trouble.
  14. Please let me toss in a few statistics in favor of one of my children...The Skyhook: It has been in the field for 17 years now. UPT, Sunpath, Aerodyne, and Avocet have filmed more than 300 Skyhook test jumps. Our demo program has allowed over 700 "average" jumpers to try a Skyhook breakaway. It has been installed on over 30,000 rigs. IF we assume an average of 500 jumps on each of these rigs, we get 15,000,000 (Yes, 15 million!) live jumps on Skyhook equipped rigs. (Assume more or less if you wish, but I bet I'm close.) IF we use the USPA statistic that a reserve is used every 607 jumps, we get about 25,000 actual reserve deployments on Skyhook equipped rigs in emergency situations. (I would like to take this moment to thank my loyal customers for providing all those test jumps for me, free of charge. I knew I could depend on you.) By comparison, TSO testing requires less than 100 jumps. In responce to some people's assertions that Skyhooks can cause line twists, or that Skyhooks were never tested on today's super hot mains, let me say this: I believe that with so many uses, we can safety assume every conceivable malfunction, on every conceivable canopy combination has happened , and I can't remember many (if any) occasions where a jumper has been injured of killed by reserve line twists, whereas MANY MANY jumpers have been killed by low reserve pulls. Besides, Skyhooks don't cause line twists. By getting your reserve directly over your head in half a second, I believe they actually lessens your chance of line twists. (What did you just breakaway from after all? Probably a main with line twists. And those line twists happened just fine without a Skyhook, didn't they.) AAD's and Skyhooks are not designed to help you when you do everything right. They are designed to give you a better chance of survival when you really screw up. So saying, "I always pull high", just doesn't hold water. That said: Nothing I have ever designed is perfect. Every device has malfunction modes. Every "safety device", from AAD's to airbags has "killed" people. However, the Skyhook has had far fewer problems than either my Hand Deployed Pilot Chute or my 3 Ring release. It has truly stood the test of time.
  15. Looks like we are going to need yet another warning label! Damn!
  16. As in most other cases, the speed at which the force is applied can make a big difference. When the force is applied rather quickly, like with an inflating pilot chute, the force required to break the thread is more like 4 lbs. When measured with our dynamic tester with a sampling rate of 50 htz. I agree the force reads higher when applied very slowly with a fish scale. The same relationship exists when measuring ripcord pull forces. As I've said before, a MARD must have some "hold together" force or it will release prematurely during spinning malfunctions.
  17. I really hope meshless pilot chutes work. I have built over 80 thousand of them.
  18. Of course I know, and have written about, measuring pull forces applied at different velocities for years. My reply was a purposefully simplistic reply to a simplistic remark. In real life things are much more complex. Everything I have designed in my life was the result of seeing a problem I thought needed solving...and a lot of these problems resulted from jumpers "pushing the envelope", just as wingsuiters are now doing. It is very possible that wingsuiters need gear that is specially designed for them. Problem is, I'm not a wingsuiter, and therefore do not experience these problems personally. All I know is what I see in videos, so I do need input from them about what they perceive their problems to be, just as I am getting here. I will schedule some tests to see if your assumptions have merit.
  19. Back in '08 I did some testing with two turns of red rigger's thread and the results were: High: 26 lbs Low: 23 lbs Average: 24 lbs It was not the most scientific test that I have ever completed but it gave the info that I wanted. Jerry; If that were true, it means that the same red seal thread would add an average of 24 lbs. to every reserve pull and all ripcords would fail the required 22 lb. test. Bill Jerry Baumchen
  20. The force required to break the red rigger seal thread is closer to 5 lbs. This amount is necessary for any MARD system, because without it, the system would prematurely release all the time, especially in the large burble behind a wing suit. I tried pin and loop MARDs first (over 30 years ago), but abandoned them because of the premature release problem. Also remember that during a breakaway, the MARD pulls on the plot chute as well as the bag. The unique 5-1 lever action of the Skyhook keeps the system together when the pilot chute is below the bag (after a breakaway), with a force equal to five times the weight of the free bag and canopy. Pin and loop systems have no such provision. Also, all other MARDs lack the Collins' lanyard, which in my opinion, makes them unsafe to use. Remember, the Skyhook has be installed on over 30,000 rigs over the last 17 years. To say that any other MARD works better might be a bit premature, don't ya' think?
  21. I designed the original Vector with a left hand deployed reserve. However, testing showed it awkward to use. Plus, a reserve activation system needs to be able to be used by either hand. And as I said above, precludes the use of an AAD.
  22. This is a very complicated subject. I been studying it my whole adult life. I would take an hour, with the help of videos, to fully explain it. But here are a couple of paragraphs: The Vector spring takes 40 -50 lbs. to compress it. It is as strong or stronger than any other pilot chute out there. However, even the force generated by our spring will not launch the pilot chute much more than 5 feet vertically.. a lot less in actual use, because the burble is exerting a downward force on the pilot chute as it leaves the container. The effect you see when you launch the pilot chute horizontally in the loft, has nothing to do with what happens in free fall. (Throw your hand deploy pilot chute on the ground, and your container totals every time.) These systems are dynamic and designed to function in freefall. A stable burble of a "normal" jumper falling straight down, consists of two counterrotating vortices with the relative wind "blowing" straight down toward the center of the body, and then curving outward. I don't know exactly what it looks like behind a modern wingsuiter. I just know it is larger in all dimensions. In other words the relative wind, not the spring, is what takes the pilot chute most of the way to "bridle stretch". Most reserve pilot chutes are designed like a parachute and don't develop much drag until they reach the end of the bridle, turn upright, and inflate.The Vector pilot chute is designed like a balloon to develop drag immediately, so that it reaches the end of the bridle faster, and is already inflated when it gets there. In other words, it is designed to "flow" with the burble instead of fight it. Although we have done very little testing with wing suits, we have extensive testing with tandem, which also has a gigantic burble, and we heave found no noticeable effect of the red break thread on pilot chute deployment. In videos, it is exactly like it thread does't exist. In answer to another question. I have tried spring loaded pilot chutes that deploy to the side, but it turned out to be a bad idea. You never know what body position a jumper will be in when the reserve container opens, so to lessen the chance of entanglement, the pilot chute needs to spring out directly away from the body and a far from the arms as possible. Spring loaded pilot chutes chutes hesitate...That's why I designed the hand deploy system. The bigger the burble, the greater the chance. Wing suits and spring loaded pilot chutes don't mix well. It's a problem.
  23. The burble behind a fully inflated wing suit is gigantic. I'm sure you've seen the video of an entire deploying main canopy, at line stretch, literally sucked back all the way to the jumper. Wingsuits were tried in the 30's and 50's, but almost everyone died. The reason was everyone was jumping spring loaded pilot chutes. It wasn't until the introduction of the hand deployed pilot chute, that modern wing suiting became possible. So, in answer to your question: Deploying a spring loaded pilot chute of any description, behind a wing suit, in certain flight modes, is very likely to produce a terrible pilot chute hesitation. If you're depending on an AAD set at normal settings (below 1,000 ft.), you're probably going to die if you ever need it. The Skyhook has nothing to do with it. PS. I've often thought that what wingsuiters really need is a rig with a hand deploy reserve. You couldn't have an AAD, but for the above stated reason, even if an AAD fires at its set altitude, you do not have a not very good chance of an "in-time" deployment anyway.
  24. Thank you Edgar. It's hard to believe, but the Skyhook is now 16 years old, and had been put on over 30,000 rigs. It has been used 10"s of thousands of times, and has had far fewer problems than any of my other inventions, including the hand deployed pilot chute and three ring release.