May 16, 2001, 5:51 PM
Post #1 of 10
Sabre Tip Correct
I had a very big problem with my sabre 190 with very hard openings. I was told by a jumper at my local DZ that rolling the slider into the tail roll will slow my openings. I have tried this and have not had a problem since. My question is......is this a common practise or is there any problem with this technique?
During the 2001 PIA Symposium, one of the guys from P.D. said that the main reason for rolling the tail is to ensure that the slider stays at the very top of the lines. The latest theory on hard openings says that slider rebound reduces the reefing effectiveness of the slider.
Hey, ah riggerrob, could up explain that last sentence please. Dont have a clue what you meant by that, but I am interested in finding out as I have a saber 170 that I want to learn how to get consistent smooth openings
Ongoing research/testing has been very educational, in so much as it has confirmed my theories/math on this phenomenon, which I claim is a major factor/source of those occasional, very fast/hard, brutal openings. We have also determined, that it's a factor, in most or all of, "so called" normal openings. I also believe that's it's a factor in line over malfunctions.
At this point in time, I will reveal the fact, that it's really "Slider Stop Line Rebound" which results in the slider prematurely moving down the lines slightly, thus allowing the canopy to be ahead of the slider in the opening sequence.
There are several factors that determine the amount/distance of slider rebound. The first is the amount of energy stored in the four slider stop lines at the point of maximum slider stop line tension/elongation. This energy is determined by the speed of the bag relative to the jumper at last locking line stow release, along with several other factors in the total parachute system, with deployment airspeed being a variable factor. This slider stop line rebound energy takes less than ten milliseconds to do it's evil deed! This event is over before the slider stops are hardly out of the bag! (10ms nom) The G forces on the slider during this time of slider stop line extension/rebound can be higher than two hundred G's!
Another factor is the factor of aerodynamic drag of the slider, which opposes this rebound energy during slider stop line rebound. Having a faster inflating slider to appose the slider stop line rebound energy is an obvious plus. But what if we could reduce the amount of energy stored in the slider stop lines at maximum slider stop line tension/elongation, by a huge amount? And what if we could also have a faster inflating slider to oppose this now much lesser rebound energy. I claim that my methods have done both. (Patent Pending)
I have reduced slider stop line rebound energy by 75%! I have also, theoretically, increased the inflation speed of the slider by a significant amount.
Both of these factors, when combined, produce an additive/positive "double whammy."
Yes, my big hope is for the reduction/elimination of those occasional very fast/hard, and sometimes brutal openings.
I have written an article that will be posted/published at a later date, that is entitled> Fast openings/Slow openings--The Real Physics of slider rebound; plus invention revealed. (Patent Pending) By David B. Brownell
When you talk about "slider stop lines", do you mean the lines on whose ends the grommets end up resting when stowed? And by rebound, do you mean that these lines reaching extension "boing" (forgive my misuse of technical terms) and force the slider part way down the lines before canopy inflation?
When you talk about "slider stop lines", do you mean the lines on whose ends the grommets end up resting when stowed?
DB: Yes indeed
And by rebound, do you mean that these lines reaching extension "boing" (forgive my misuse of technical terms) and force the slider part way down the lines before canopy inflation?
DB: Take a piece of suspension line twelve feet long and attach one end to a fixed point. Attach a solid; let's say, three ounce weight to the free end. With yourself standing at the fixed point throw the weight away from yourself at 35 MPH. When it comes to the end of this line, what happens?
35 MPH (51 FPS) is the nominal speed of a bagged canopy "relative to a jumper" at last locking stow release.
When will you be publishing this patent?
DB; The patent application itself will probably never be published on a news group, but my article probably will------
I have written an article that will be posted/published at a later date, that is entitled; Fast openings/Slow openings--The Real Physics of slider rebound; plus invention revealed. (Patent Pending) By David B. Brownell
<FONT SIZE=-1><EM>Edited by dbtech on 5/18/01 11:09 AM.</EM></FONT>