mjosparky 4 #76 June 13, 2004 QuotePractically all the skydiving advice I've received and overheard didn't come with premises anyway, or begged the question. Can you give a specific piece of advise that you are reffering to? And he is right, women should not fight bulls. SparkyMy idea of a fair fight is clubbing baby seals Quote Share this post Link to post Share on other sites
nathaniel 0 #77 June 13, 2004 Quote Can you give a specific piece of advise that you are reffering to? Examples are everywhere, about the only notable exception I can think of is Dr. Kallend's doctrine of exit separation. An easy example is the 45-degree rule. I overheard a DZO suggesting to a student to use the 45-degree rule. He didn't explain how it would work, and it's obvious to any reader of this board nobody can explain why it would work because it doesn't work. There's a dozen or more examples in all the little tweaks people do when they pack their canopies to improve the opening characteristics. As far as I can tell the business of which tweaks work and which don't is entirely subjective. The advice ebbs and flows and it seems everybody has their own method. And, as far as I know, there's little formal knowledge about the nitty-gritty details of parachute opening. There's no premises, only shaky advice. nathanielMy advice is to do what your parents did; get a job, sir. The bums will always lose. Do you hear me, Lebowski? Quote Share this post Link to post Share on other sites
billvon 3,078 #78 June 13, 2004 >Tell me then, when was the last time you felt the Pythagorean >theorem? About two months back, when I tried to build an aluminum frame for a solar mount and swag'ed the dimensions. Didn't work. >Do you really suppose astronomers have experienced the conditions >on the inside of stars? No, but there's a bit of a difference between coming up with theories about what's inside stars and figuring out if you will get a sunburn from one. >Right around the dawn of recorded history mankind started building > knowledge with logic and reason. This is what's missing from a lot of > skydiving advice. Quite true, but there are some things we just don't know. A canopy's opening is a chaotic event; there is no way to know exactly what will happen during opening. However, some tricks (like quartering the slider) work, and some (like stuffing both sides of the canopy in the center) don't. Often there's no way to deduce that stuff; it's stuff that we figure is sort of obvious in retrospect, but isn't that clear until you try building and packing a few hundred parachutes. I agree that there is some silly advice in skydiving, but there is also a lot of advice that works even if it has no basis in theory. Quote Share this post Link to post Share on other sites
mjosparky 4 #79 June 13, 2004 Having been involved in parachute design and testing for over 20 years, I can assure you there is a vast amount of "formal knowledge" on the details of parachute opening. If you feel this statement "begs the question" you can refer to "Decelerator Systems Technology" the Short course by Helmut G. Heinrich, The Parachute Manual, Vol. I & II by Dan Poynter, "The Aerodynamics and Piloting of High Performance Ram-Air Parachutes" by Jerry Sobieski or go to PD's web site and read some of the Tech. papers there. Just because you are not aware of something does not mean it does not exist. It seems that your conclusions "Beg the question". As you said yourself, "as far as I know". How can you say a statement/advise lacks logic or reason when your experience and knowledge can not determine if the statement/advise is factual. By the way, how do you know Kallend was right and the DZO was wrong? With Kallend's education in physics there is a good chance he is right. But then aren't you using the premises as the conclusion? The knowledge is out there, both formal and antidotal, it just takes the effort to find it. SparkyMy idea of a fair fight is clubbing baby seals Quote Share this post Link to post Share on other sites
nathaniel 0 #80 June 13, 2004 Quote Having been involved in parachute design and testing for over 20 years, I can assure you there is a vast amount of "formal knowledge" on the details of parachute opening. Why does nobody refer to it when suggesting to roll the nose or do this that or the other to the canopy immediately prior to bagging it? That is, all those little tweaks that aren't part of the standardized PRO pack. Where is the part that justifies all this weirdness? I'm not asking for page references, I'm asking why people don't bring the subject of this work up when offering advice. I don't mean to criticize the reference you provided, but you see, we're not exchanging skydiving advice here. It's more important to cite that book or its results in support of a deduction than it is to simply declare its existence here. Quote By the way, how do you know Kallend was right and the DZO was wrong? I believe Dr. Kallend's premises--3 second reaction time, ordinary physics, etc--and his deductions are sound. The DZO presented no premises, and he did not proclaim any deduction. There is no reason to believe the DZO at all. His statements are demonstrably false, tho it didn't take billvon's mounted camera to convince me of their falsity. Had I received his advice before learning of Dr Kallend's work or billvon's video, I may have entertained DZO at the door instead of immediately challenging him and delaying our exit, but I would have noted the question for further investigation. nathaniel edited for grammar...My advice is to do what your parents did; get a job, sir. The bums will always lose. Do you hear me, Lebowski? Quote Share this post Link to post Share on other sites
nathaniel 0 #81 June 13, 2004 Quote there is also a lot of advice that works even if it has no basis in theory. I contend that we don't truly know whether it works or not without the theory to back it up. Doesn't mean we shouldn't heed it, just that we need to hold it in question; recognize it as such and present it as such. So would you oppose deriving theory in an attempt to validate such practical advice? nathanielMy advice is to do what your parents did; get a job, sir. The bums will always lose. Do you hear me, Lebowski? Quote Share this post Link to post Share on other sites
skycat 0 #82 June 13, 2004 Then there is the day you know to much about the sport and the industry as a whole and the thought of going to the local DZ makes you want to vomit. Fly it like you stole it! Quote Share this post Link to post Share on other sites
TomAiello 26 #83 June 13, 2004 QuoteIf you feel this statement "begs the question" you can refer to "Decelerator Systems Technology" the Short course by Helmut G. Heinrich, The Parachute Manual, Vol. I & II by Dan Poynter, "The Aerodynamics and Piloting of High Performance Ram-Air Parachutes" by Jerry Sobieski or go to PD's web site and read some of the Tech. papers there. Off topic, but I've also found Knacke's Parachute Recovery Systems Design Manual very useful, mostly in understanding pilot chutes (and rounds).-- Tom Aiello Tom@SnakeRiverBASE.com SnakeRiverBASE.com Quote Share this post Link to post Share on other sites
TomAiello 26 #84 June 13, 2004 QuoteWhy does nobody refer to it when suggesting to roll the nose or do this that or the other to the canopy immediately prior to bagging it? Probably because the number of people who have actually looked for the research is vastly smaller than the number of people who just picked up a tip at the DZ.-- Tom Aiello Tom@SnakeRiverBASE.com SnakeRiverBASE.com Quote Share this post Link to post Share on other sites
billvon 3,078 #85 June 13, 2004 >I contend that we don't truly know whether it works or not without the >theory to back it up. Effects can be demonstrated as well as proven theoretically. Ideally you have both, of course. But I would have far more confidence in a rig that was designed by someone with experience in rig design, and then drop-tested to TSO C23d standards, than one that had never been tested but worked in FEA computer simulations. >So would you oppose deriving theory in an attempt to validate such >practical advice? Not at all. But it has been my experience that, unless you apply the usual scientific rigor to those theories and verify them independently of the one effect, these theories can be blatantly wrong. The 45 degree separation theory is a great example; I've heard some very long winded theoretical explanations as to why it works, and yet I'm going to go with my video (and my assumptions on how it works) when it comes to deciding if it's a good idea or not. Saw another one last weekend - a cessna pilot would level out, build up speed, then pull up hard, and repeat that cycle over and over. He had a theory on how you had less drag in level flight and so you could go faster which would translate to more lift etc. Again, nice theory, but I'd much rather just take a stopwatch and an altimeter to prove whether or not it works (which of course it doesn't.) Quote Share this post Link to post Share on other sites
piisfish 140 #86 June 13, 2004 QuoteThe only thing I know is that I don't know shit. but Ivan, that's normal, you only have 51 jumps... Listen to me, when you will have MY experience, you'll know much more scissors beat paper, paper beat rock, rock beat wingsuit - KarlM Quote Share this post Link to post Share on other sites
skybytch 273 #87 June 13, 2004 Quotebut Ivan, that's normal, you only have 51 jumps... Listen to me, when you will have MY experience, you'll know much more Yup. And when he has MY experience, he'll once again know that he don't know shit. Quote Share this post Link to post Share on other sites
piisfish 140 #88 June 13, 2004 sh*t, is that how it goes ?? at what number of jumps do you realise that ?? I thought as I was over 300 I knew everything... Do you get to know everything again at some point ??scissors beat paper, paper beat rock, rock beat wingsuit - KarlM Quote Share this post Link to post Share on other sites
skybytch 273 #89 June 13, 2004 QuoteDo you get to know everything again at some point ?? I don't know. I think you can know everything about one thing. But you can't know everything about everything. There's too much to know. Y'know? Quote Share this post Link to post Share on other sites
Damion 0 #90 June 13, 2004 i know everything, just PM me ill tell ya. ;) my exit weight is 210 and im jumping a Sabre2 190, i was about to downsize to a 170 on a gusty day and the rental shop stopped me. good thing cause i got my first taste of a unattempted wing over trying to compensate for gusting winds from one direction when i dropped below 20 feet and got them from the other direction. (whew) ill take the lil scrape i got.... just imagine if i had more speed, can you say incidents report. :) Quote Share this post Link to post Share on other sites
damion75 0 #91 June 13, 2004 QuoteQuote What is it with jumpers with 100-300 jumps that makes some of them think they know it all? Dunno, I'll let you know in 9 jump. I bet you won't, because then you'll know it all and you won't have any time for the rest of us! You'll be too busy on your new VX 78! *************** Not one shred of evidence supports the theory that life is serious - look at the platypus. Quote Share this post Link to post Share on other sites
MarkM 0 #92 June 14, 2004 Quote I bet you won't, because then you'll know it all and you won't have any time for the rest of us! You'll be too busy on your new VX 78! The 78 is so last year, the in thing these days is the VX 39. But back to the subject. I don't see how this is unique to skydiving. Get in the Jap motorcycle scene(rice burners) and you have the same thing going on there. People buying a 750 or a 1000 bike when they should be starting out on a 500 or something like my SV650. Bad accidents don't usually happen to newbies, it's the people with 3-5k miles under their belt that get cocky and do stupid things. I just think it's natural to have this stage where you get over the scary newbie period and begin to get confident in your abilities. The problem is though is that it's very very hard to really know what your abilities are. So you get cocky, get in over your head and get owned by your own arrogance. Quote Share this post Link to post Share on other sites
Ron 10 #93 June 14, 2004 QuoteHi Ron, Y'right (for some people) ... but also, what is it with people with big jump numbers that seem to forgotten what it was like to learn? Are you claiming I forgot what it is like to learn? Gee, I just made 17 jumps this weekend, and 30 min of tunnel, I plan on making another 40 jumps and fly another 2 hours of tunnel this week...Why? SO I can learn new stuff... Also I am post whoring on here right now instead of doing my damn school work... I learn new stuff everyday.. I TRY to learn new stuff everyday. I KNOW I don't know enough."No free man shall ever be debarred the use of arms." -- Thomas Jefferson, Thomas Jefferson Papers, 334 Quote Share this post Link to post Share on other sites
Ron 10 #94 June 14, 2004 QuoteWe're using the words know and knowledge for what the rest of the world terms experience. Proper knowledge is scarce in this sport; what there is seems to have been derived from anecdote and personal experience. This kind of "knowledge" is not portable, like we see here pretty much the only way people have been learning is through their own experience. The reason that people don't have experience is that they don't have experience. There's no mystery here Just remember....People used to teach the world was flat. So your "Knowledge" is suspect. Now if Dave the high school dropout walks up and tells me that if I hit the ground in a turn I will break my leg just like he did and he shows me his scar....Well I just learned."No free man shall ever be debarred the use of arms." -- Thomas Jefferson, Thomas Jefferson Papers, 334 Quote Share this post Link to post Share on other sites
mjosparky 4 #95 June 14, 2004 QuoteWhy does nobody refer to it when suggesting to roll the nose or do this that or the other to the canopy immediately prior to bagging it? When you were learning to drive and someone told you to turn right, did they give a detailed explanation on how rack & pinion steering works? If the information on the different "tweaks" is important to you, make an effort to research the "formal knowledge" on the subject. By discarding advise because you feel it does not have "logic or reason" could lead to you ignoring a small jewel that just might save your ass one day. Tom, That is not off subject. It has a wealth of information in it. And pilot chutes are rounds, just real little ones. SparkyMy idea of a fair fight is clubbing baby seals Quote Share this post Link to post Share on other sites
nathaniel 0 #96 June 14, 2004 Quote By discarding advise because you feel it does not have "logic or reason" could lead to you ignoring a small jewel that just might save your ass one day. It's a Faustian bargain. That same advice that does not have reason may also kill you one day. Whereas advice that carries the seal of reason will probably not. nathanielMy advice is to do what your parents did; get a job, sir. The bums will always lose. Do you hear me, Lebowski? Quote Share this post Link to post Share on other sites
nathaniel 0 #97 June 14, 2004 Quote The 45 degree separation theory is a great example; I've heard some very long winded theoretical explanations as to why it works But you have not heard any valid explanation of why it works, because it doesn't. Any proof that it works either has invalid premises or bad logic. A well-formed statement cannot be simultaneously true and not true, this is intrinsic. Quote He had a theory on how you had less drag in level flight and so you could go faster which would translate to more lift etc. Again, nice theory, but I'd much rather just take a stopwatch and an altimeter to prove whether or not it works Aha, but you knew another theory according to which your altimeter and stopwatch could be used to validate this pilot's hypothesis! If only the ordinary theory of kinematics could be used to solve problems like riser stowage, nose rolling, bagging, &c. nathanielMy advice is to do what your parents did; get a job, sir. The bums will always lose. Do you hear me, Lebowski? Quote Share this post Link to post Share on other sites
Ron 10 #98 June 14, 2004 This guy is an example of what I am talking about.... He has around 100 jumps, but thinks he knows more than people with many more years, and much more experience. And his whole reason is cause you have not written it down with some cool graphs and called it "research"....Instead you call it advice and share it over a beer."No free man shall ever be debarred the use of arms." -- Thomas Jefferson, Thomas Jefferson Papers, 334 Quote Share this post Link to post Share on other sites
nathaniel 0 #99 June 14, 2004 Quote And he is right, women should not fight bulls. Of all things, an article on female bullfighters. nathanielMy advice is to do what your parents did; get a job, sir. The bums will always lose. Do you hear me, Lebowski? Quote Share this post Link to post Share on other sites
mjosparky 4 #100 June 14, 2004 QuoteThis guy is an example of what I am talking about.... He has around 100 jumps, but thinks he knows more than people with many more years, and much more experience. And his whole reason is cause you have not written it down with some cool graphs and called it "research"....Instead you call it advice and share it over a beer. But Ron, Most of it is written down and has cool graphs. Not many people want to take the time to look through it or go through the test programs where some of the things are validated. Things will change when he goes out in the real world. Ah, to be cloistered in the velvet blanket of academia. SparkyMy idea of a fair fight is clubbing baby seals Quote Share this post Link to post Share on other sites
