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Everything posted by JohnSherman

  1. Can't find one with the proper characteristics. 1.1 isn't permeable enough.
  2. All FireBolts have always been made this way. Some 20 + Years. It is how Parachute Labs does all of their canopies, AngleFire Reserves, Blackhawk Mains and Reserves and Nighthawk mains and reserves. Racer Tandem Reserves and Mentor Student Canopies. It is done to reduce rib distortion.
  3. The participants were representatives from Strong, UPT, PLI, Mirage Sys. as well as 8 NASA Engineers and 4 NASA managers and some 6 or 8 photographers from the Skydiving world. There were 14 pilot chutes tested 2 each from 2 of the represented companies and one military surplus. One each from the other two companies present which leaves 7 unrepresented. Some manufacturers were invited but could not make the trip as it was on short notice. There were additionally; 3 drogues and one rocket recovery parachute tested. They will not be reported on.
  4. The military/government has no such test. They do require this test: When the pins are initially formed they have a blade length of about 3 inches. They are mounted to the cable then the end of the pin is bent 90 degrees. This bend makes attaching a holding fixture to the blade of the pin, for pull testing to 300 pounds, possible as a straight blade would have a propensity to pull out of a compression grip. Some other folks were testing by "hook gripping" at the junction of the pin shank and the cable. This doesn't stress the blade which is required. This was a principal reason for pin failures getting into the field some years ago. We have done loop load vs. pin pull force tests in the past and were convinced then of our current position.
  5. Ripcord pins are made from .188 dia 302SS Cond A (303 is also allowed but I don't use it) they are then rotary swaged to a diameter of .094 using the rotary Swag process of cold forming as you can't harden SS with Heat treat. The overall length of the blade is dictated by the end user but is usually 1.25 inches. Column strength of the blade is tested by inserting it into an .096 dia hole one half inch deep and applying an 8 pound weight to the end. The results is checked in a go-no go gage of .104 dia to the full depth and the pin must fall out without friction after insertion. This process and design was originally for a pin and metal cone thru a 9/16 and 7/16 grommet situation. The amount of allowable bend was critical as the thru hole in the cone was about a half inch deep/thick. Today we use 1/4 inch grommets with a cloth loop. A far less critical arrangement. Yes, the pin can bend in that configuration but it is usually from dropping or throwing the rig down or against something as the rig is compressed when it hits something and this causes the rest of the rig to want to expand causing a great load on the loop and subsequently on the pin causing a bent pin. The good news is that is can still be pulled even with a bend. The Military still uses this pin on their center pull chest reserve with cloth loops and even with the rough treatment they get have had no problem. Larger diameter pins would cause a harder pull with the same loop load. Additionally, the shank and cable would also have to be enlarged to obtain the necessary strength as the blade would still have to be cold formed to make it hard enough. The thicker pins used on some assemblies have no greater column strength as they are not cold formed from a larger diameter. Don't let size fool you.
  6. This is a great discussion. It's about time. I believe it is rig/canopy specific and that it has to do with bag extraction effort vs. pilot chute drag capability. There are videos which show it happening. There have been about 20 of these instances recorded. All have been with the main closed. There are some rigs on which this has never happened and there are rigs on which it has happened numerous times. The distribution is not aligned with rig sales distribution. The problem is easy to define with a simple test. During the FAA/Rigger Investigation with the same rig from an incident. Assemble the rig with a fresh AAD charge and pack job. Packed with both main and reserve. Add enough weight to the harness reach AAD firing speed. You could use bar bell weights in the leg straps. You will need enough weight to achieve about 7 pounds per square feet of rig surface area, which I would guess at 3 sq ft. or, 25 pounds which will give you the weight of the rig plus the 25 pounds enough to reach the necessary speed. Tape down all lose webs and stuff. Toss it out at an altitude high enough to satisfy the AAD firing requirements. We would expect it to fire at 750 and to deploy the reserve before it hits the ground, if it does it won't go far from less than 450 feet. If it doesn't leave it there and call the manufacturer. If it doesn't we will know the answer. If you can't get the involved rig from the incident get one just like it with the same canopies. The Deland test project seems to be stalled, however there are other testing activities occurring. We should have data by Symposium.
  7. We began supplying "Snap Toggles" standard on our reserve risers about 6 months ago. When it was confirmed by several drop zones that "brake fires" were the biggest cause of malfunctions, something we have believed for many years. There have been no known fires of a snap toggle in the 20 years in service, so we felt it was time to upgrade the reserves.
  8. Happy to, here you go. [inline Racer_Risers.jpg] [inline Snap_toggle.jpg]
  9. I doubt this is the answer but for grins I offer it. In the very early days of the sport I was taught to pack my 28' Single Blank Gore, C-9, 1.1 oz, round canopy with talcum powder. This was to condition the fabric to make it subtle and last longer or so we were told. We were only required to do this for the first 25 jumps or so. As a result we learned to mix baby power with dye to give the powder color for demos. When the canopy opened it gave off a puff of the powder whatever color it was. I did it for demos until I bought me first PC at 32 jumps. Yes, I was doing demos with less than 10 jumps.
  10. Drop them side by side from any reasonable height and you will be able to see for yourself. When they are new, both perform exactly the same in the wind tunnel or from a free drop. Old ones of either type will not do as well as new ones but not by much. FYI: The Power Racer Pilot Chute (SRP) is the one with the 4 inch diameter top and the 32 inch diameter canopy. The MA-1 has a 36 inch canopy and a 6 inch top. The MA-1 has a publisher Cd of .65. The SRP has a published Cd of .83. Calculate the Cd*So (effective size) of both and you will understand the similarity. Remember Pilot chute terminal occurs at about .6 seconds after inflation/release as opposed to humans who take about 12 seconds to reach terminal after launch.
  11. That's what we called it when we first looked at development of the MARD idea Eric Fradet brought to us some 20+/- years ago. Jarrett named it the "Air Snare" when we developed and rejected it several years ago. We just don't need it. It is slower than a conventional deployment at high speeds and the same at low speeds. I believe it is better to depend on a good pilot chute with a good launch and high drag which is consistent, rather than a malfunctioned main which has infinite variable drag capabilities. The first thing we don't need is complexity. The second thing we don't need is inconsistency. "KISS"
  12. Good job Peter. Here is a riddle for you: When don't you have to worry about the velcro on your reserve toggles damaging your container?
  13. The problem with the horizontal wind tunnel and the stream of water analogy is that neither have the gravitational component which is the weight of the object. If we go to a vertical wind tunnel or could run the water up vertically then the gravitational component would come into play and would resist the flow. Without gravity or something to resist the flow you have no Drag. To keep the analogy horizontal and in water we could say the air we skydive in is like a still water lake and we are plowing through it in a gravity strength powered submerged body. Put a pilot chute out thru the turbulence into the still water and that will give you a look at the same thing that happens in the air.
  14. If I throw a stick into a moving stream of water and it floats away with the flow of the stream is that drag? Maybe it is "going with the flow". In order to have drag you must have a Force and a Resistance.
  15. We all know that a pilot chute doesn’t drag, after launch, until it reaches the end of the bridle. It can’t drag if it has nothing to drag against. It has to travel from the container some 16 total feet (13 feet of bridle and 3 feet to the top of the PC) to a point where it applies tension to the bridle. That’s the beginning of drag. This causes orientation if required, and provides lift/drag to the deployment bag through the bridle thus extracting the bag. The question is: What are the forces which transport the reserve pilot chute from the container to the end of the bridle, some 16 feet? 1. The Free Stream Air flow? 2. The force of the spring? 3. Acceleration due to gravity?
  16. This study might help. We used a Pasco system for both altitude vs. Time (ROD) and an anemometer input. The Pasco company has an excellent data logger system for all phases of parachute testing. We have been using this system for over 10 years. I am attaching a URL for a brochure for the system, modified and accessorized for parachute testing. We mounted the anemometer to a stand off at about 12 inches in front of the chest of the wearer. Directly in front of the logger in the mounting vest. Using this system we have a common time line. This is much easier when it comes to selecting data points for speed and ROD. The Data Studio software (also from Pasco) is excellent for analysing and viewing data. We used it for extracting the data point for constructing the Polar Curve. See attachment.
  17. Maybe it didn't inflate. The spring doesn't matter if it doesn't drag when it get into the air stream. Not only that but the launch part of the study shows no improvement over the MA-1 spring, the most common spring in service. I disagree about the Cd. The Formula is F=Cd*So*Q. THe So is the Square feet area not the diameter. The Area of a 36 inch PC is 7.06 Sq. Ft. I believe the Drag levels to be slightly low as compared to other studies. I think this is due to the ground speed being used instead of air speed. This would have a greater effect at the high end. I am attaching the other half of the study with the suffix "Data Half" added to the end. Just merge the 2 documents for a complete study. This data half is too large to attach to a PM reply.
  18. That is what I thought. However, the Australian Parachute Federation has apparently done just that. They did it in about the early 80's. My staff found this study in our archives in hard copy. It was missing its cover page. However, that doesn't effect the data enclosed. I have made attempts to get a complete copy but haven't heard back yet. The study is over 100 MB in PDF form (too big to upload) as it is some 43 pages long without the cover page. I am uploading the last 2 chapters of the document which covers the conclusions. I will make the entire document available to anyone who want's it, just PM a request to me. It was originally done to investigate pilot chutes for use on AFF students mains. However, The same performance requirements are germain for both mains and reserves. If a pilot chute is not good enough for AFF mains then how can it be acceptable for reserves? They investigated both the launch and the drag in separate chapters then combined the data for each tested subject and made an evaluation. There were 10 pilot chutes tested most of which are in use today. They were: 1. 357 Magnum 2. MA-1 (Lite-Flite) 3. MA-1 (1.5 OZ) 4. Talon 5. Hotdog 6. Skyhook 7. Vector MK I 8. Vector MK I1 9. MA-1 (Pioneer) 10. The Woomera (Hand Deploy) was also tested but only for drag. I believe this to be an excellent study which shows the relative performance of the tested subjects and is comparable to other investigations. The only difficulty I have with the study is the apparent use of Ground Speed as opposed to Air Speed. This might offset the values when compared to other studies but doesn't affect the relative performance. This is a must read for Riggers and interested parties.
  19. All of those ideas are worth trying. One thing we agree upon is that the Free Bag and Safety Stow needs improvement. The SPEED bag has done just that and it has proven it over the last 20 years. What have the other manufacturers done to address the problem of line/bag dump/strip? For those of you who still doubt that it is a better idea. I offer an opportunity to judge for yourself. Send a request for a SPEED bag to demo as a main to PLI. Include the dimensions of your current main bag. Jump it as a main and judge for yourself. That is how we did it except we jumped it for years before we put it on the reserve. The opening are smoother and more consistent and it has proven to reduce malfunctions yet some riggers continue to bad mouth it for difficult in packing and table problems. You can't judge it on the table, drop it from a ladder or take it into the air. Remember you need acceleration due to gravity.
  20. That is true today on a number of pilot chutes and drogues.
  21. The line stow system of the SPEED bag has been in service for over 20 years. We used it on mains for 10 years before we put it on reserves. It has been proven to reduce malfunctions and provide more consistent softer openings. There has never been a reported problem of improper performance in the air in all that time and usage. We estimate over 5 million jumps. The USFAA demonstrated a malfunction rate of 1 in 3000 over a period of 3 years after modifying their main d-bags to a SPEED bag configuration. If you really want to test it, climb a latter and hold the bridle as you release the container, do it with the main full. That way you test the bag extraction at the same time as the line stow release. Of course all that is not as important and germain as how it performs horizontally on a packing table.
  22. Ok, Here is how it works: TSO C23(b) has 2 categories of certification. "Low Speed" tested to 3000 pound shock load and placarded "Limited to use in aircraft under 150 MPH" and "Standard Category" tested to 5000 pound and not placarded because it is "Unlimited" as to weight and speed. Some might ask. "Why is weight not specified in the "Low Speed" category placard? Weight is not significant in the differential loading of the human body in a parachute deployment scenario. That is to say that if you double the weight you will only increase the opening forces by 10%. OK now put you eye ball back into your head and look at the "Decreasing Load Factor" (The X1 factor) in the design guide. The chart produces a factor of one tenth of one percent of the pounds per square foot loading. In the context of the model doubling the weight will only increase the force by one tenth. Mike Furry once said "Harnesses should be so strong that we start shedding body parts before they come apart." He is correct and "Standard Category" harnesses are that strong. Based upon what little research I can find and looking at anecdotal information from the past 50 years it appears that a human body can't take much more than 3000 pounds and survive. Line dump on a square can and has produced more than 3000 pounds. Harnesses have failed under these conditions. However, it is difficult to deploy a parachute at over 150 MPH which is the limit for the "Low Speed" category. This type of approach provides compatibility between components and avoids the unanswerable question about weight and speed posed in the earlier portion of this thread.
  23. Jump Shack (Parachute Labs) uses Standard Type 13 (black traced edge) Mil Spec. webbing on all of it's harnesses. This Type 13 webbing was originally designed to replace the old cotton webbing harnesses were made of before Nylon. The Hardware we use today is the same. It was designed for cotton webbing. The Nylon Type 13 was designed to specifically replace the cotton and to be used with that hardware. Tp 7 (Yellow Traced edge) was designed for use on cargo harnesses where they don't come in contact with friction adaptors. I remember my first piggy back, an old Security system, I would tighten up the leg straps before I got into the plane, tighten them again on the way up and again before exit only to find it was loose after opening. I learned about the difference in the design purpose of the webbing and selected Type 13 for use on all of my gear. It is more comfortable as it doesn't roll as much and it is stronger and hardware compatible and Oh Yeah it is more expensive. The military only allows Type 13 on their harnesses.