riggerrob

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Posts posted by riggerrob


  1. There is something to be said for keeping it simple.
    For example, tandem rigs have twice as many handles as sport rigs. Roughly 1/3 of the dead tandem masters pulled handles out of sequence or forgot to pull handles.
    More handles equal more chances to mess up.

  2. The easiest sport reserve to close is probably the Wings.
    Second place would be the Flexon/Talon 2/Voodoo series.
    The worst civilian pilot emergency parachute has got to be the GQ Security Safety Chute series. They didn't get the loops right until the third try and they incorporated that silly extra spring to compensate for wimpy pilotchute springs. Fortunately the youngest (American-made) Security parachutes are 18 years old, so they will retire soon.
    The worst pilot emergency parachute would have to be some sort of exotic ejection seat rig, like the one in the Folland Gnat. The few Russian military surplus PEPs that I have seen were antiquated and overly complex.

  3. This string reminds me of when I worked for Rigging Innovations.
    We frequently did free updates on customers' gear without bothering to call them.
    Time spent talking to their answering machine was better spent on a sewing machine.
    Most of the updates did not change packing procedures, they just made it slightly easier to pack their Talon.
    Other mods - like RSL or Cypres updates - were done to reduce long-term wear and tear problems.
    Some of the modifications - like reserve toggle hoods - were done for free because I thought the earlier design "sucked the big one" and it took me as long to do the update as it took me to hand tack a pair fo reserve toggles.
    None of our customers complained as loudly as the first poster on this string.
    Come to think of it, I never heard a Rigging Innovations customer complain about free updates.

  4. Sounds like you guys are trying to use elastics to compensate for shoddy friction adapters.
    A good friction adapter will hold the strap without any elastic.
    We encountered this problem a few times when I worked at Rigging Innovations. If a customer send back a harness with complaints of slipping leg straps, it was usually caused by friction adapters that were too smooth. This happens when the hardware manufacturers don't clean their dies often enough. The short term/field solution is to sew some pile Velcro on the leg straps so it will catch in the teeth of the friction adapter. As soon as the rig got to the factory, we replaced slippery friction adapters for free.

  5. Another possible problem with a double-sided RSL is that it might catch under the back of a helmet. Then the poor skydiver is suspended from his malfunctioning main. There have been a few cases of this happening on Racers or rigs that copied the Racer style of RSL.
    If this scenario bothers you, then go with Parachutes de France's double-sided LOR system with two separate lanyards and two pins.

  6. Line dump occurrs when your rubber bands are too loose.
    When the pilotchute lifts the d-bag and canopy out of the container, the lines dump into the container in a horrible "spaghetti mess."
    This might lead to line knots, but far worse are the hard openings that occur because the canopy is already partially inflated before it reaches line stretch.
    Finally, your slider will be somewhere between the slider stops and the risers, but no-one can predict accurately whether the slider will contribute any reefing force.
    The simplest way to prevent line dump is to keep your rubber bands tight around youir lines and leave a bight of line - about the same length as your little finger - hanging outboard of the rubber bands.

  7. I use WD 40 sprayed on a paper towel.
    I spread WD 40 on the cables and continue rubbing until the grime loosens up.
    Then I wipe the cables dry.
    Cleanliness is more important than lubrication.
    Too much lubrication will just trap grit and lead to a hard pull.

  8. Yes,
    The slippery fabric makes Raven MZ reserves more difficult to pack.
    Forget about pro-packing them over your shoulder.
    If you use all the straps and clamps called for in the Talon 2 manual, you can pack a Raven MZ neatly. It will take longer because you will have to clamp it and lay weights on top of it and step back for a few minutes several times during the pack job.
    Take your time if you want to pack a Raven MZ neatly.
    As for the notion that ZP fabric tears worse than F-111, I rarely see huge tears in ZP fabric.

  9. Start by reading both Volumes written by Poynter.
    One limitation of Poynter's manuals is that Volume Two was written just as Zero-porosity fabric was being introduced and Parachutes de France was the only company building tapered parachutes. We have learned a lot about parachute design and handling since then.
    Then read various posts and lectures by canopy manufacturers like Performance Designs and Icarus. Manufacturers readily share information at the user level, and frankly that is more than the average skydiver has the patience to listen to.
    For a more detailed explanation, go to the Australian Parachute Federation's website and download their 14 or 16 page pamphlet on High Performance Parachutes.
    This is compressed from a 40-some-odd-page thesis written by Jon Sobiesky about parachute design.
    A few years ago Bryan Burke wrote a similar paper explaining parachute aerodynamics. Burke's paper was available on-line.
    Manufacturers are reluctant to share trade secrets because a little knowledge can be dangerous.
    To design a canopy, you need a huge background of knowledge and have to understand how all the variables interelate. Much of that knowledge is written in blood.

  10. Good point Anyman,
    About a month ago, I thought about tying the slider to the bottom skin and using a Cypres cutter to release it. But I also thought that it might be a patentable idea, so I kept my mouth shut. The only disadvantage with that is that the slider reefed canopy would expose more bottom skin to the wind than a rope-reefed canopy.
    Something else for the engineers to figure out would be figuring out where to tie the slider to the canopy. One tie in the center would be simplest and most reliable, however, that would not control the position of the slider grommets relative to the bottom skin. You might need to tie each slider grommet to the bottom skin to get consistent openings.
    Manley Butler, are you listening?

  11. Private pilot, single engine land
    used to fly jumpers
    currently doing commercial pilot ground school so I can resume flying jumpers

  12. bbarnhouse,
    Not quite sure what you are driving at, but my interpretation is that the same accidents keep getting repeated. The only thing that changes is the date and the location.
    For about 20 years, I read accident reports in Parachutist magazine religiously. Reading those accident reports cured me of several bad habits.
    Recently I quit reading accident reports because they all started to blur together. It got to the point where I could be reading an accident report from 1982 or 1992 or 2002 and it all seemed the same.

  13. Cars should be reliable enough to get you to the DZ.
    Cars should be cheap enough that you have money left over for jump tickets.
    If they are big enough to sleep in, that is gravy.
    Hint, I have been driving a beat up old VW Westfalia since the early 1990s.

  14. The only stupid question is one that you don't ask.
    You actually crammed several questions into one post.
    First of all, your choice of canopy has little affect on how you freefly. If a canopy packs up any way except huge, it will work for any type of freefall.
    The key to chosing a main canopy is picking one forgiving enough that you will survive your first 100 jumps. That is another whole thread.
    Even if the canopies pack up huge, that is less important than how well the harness fits. Harness fit is separate from container design. A properly fitted harness will not restrict movement in freefall. Best to ask a rigger to watch while you try on a harness. He/she can quickly tell whether that harness is a decent fit.
    As for the question of which container to buy ... Each new generation of container addresses a few more safety issues. For example. Containers built in the 1970s were mainly designed for solo jumping. During the 1980s, speed star and canopy formation skydivers made some major improvements in container safety. During the 1990s, all the earlier improvements were retained, plus some new factors that related to high speed, head down freefall. Generally, the newer the rig, the safer it is.
    Keep in mind that any rig is only as good as its maintenance. Just like automobiles, after 3 years, you have to start paying for new mufflers, new tires, new shock absorbers, etc.

  15. As an addition to Bill Booth's post, back in the early 1980s, Manley Butler did a series of test drops at NAWS China Lake to prove that square canopies could be safely deployed from ejection seats. To limit opening shock during these high speed deployments, they installed two or three reefing ropes, in addition to the regular sail slider. They used a complex series of cutters (similar to Cypres cutters) to cut the reefing ropes at various times.
    To make reefing ropes work in a skydiving scenario, you would need airspeed sensors and a computer to tell the cutters when to cut.
    It is possible to build a reserve - using existing technology - that will satisfy both the high speed and low speed edges of the envelope. The problem is that it would be very expensive and very bulky. The other problem is that complexity might drive it beyond the abilities of amateur riggers. It would certainly have the full-time riggers scratching their heads and staring at the manual!

  16. Most modern mains are built of zero porosity fabric.
    Most modern reserves are built of 0-3 cubic feet per minute fabric that is a close copy of the old F-111 standard.
    Both fabrics start the same way on the loom. After weaving, 0-3 cfm fabric is "calendarized" by passing it between hot rollers. The hot rollers partially melt the round threads, making them half-round, partially filling in the gaps between threads. Then manufacturers add a variety of lustrants, UV inhibitors and other secret coatings to prolong the life of the fabric. F-111 fabric lasts 300 to 1,000 jumps depending upon care and climate. The first cross-braced canopies (PD Excalibur, circa 1988) were built of F-111 fabric. Excaliburs flew great at heavy wing loadings for about 300 jumps. Then they started thumping on landings.
    Zero porosity fabric is woven the same way, but then manufacturers subject ZP to a variety of secret processes to seal the holes between threads. Some - like Gelvenor in South Africa - calendarize fabric before coating it with silicone. Others - like the American mills - seem to depend upon a heavy coating of silicone to seal the fabric.
    I find Gelvenor fabric easier to pack because it is less slippery.
    As for durability, climate probably makes a greater difference. Jumping in the desert wears out fabric at a rapid rate. All that salt and grit quickly takes the shine off fabric while those salt crystals work their way in to seams where they slowly grind.

  17. Pilotchute size is related to the weight of the canopy.
    For a 150 square foot main, expect to use a 26" or 28" pilotchute.
    Stick with Zero-Porosity fabric - for the pilotchute - because it gives more consistent openings.

  18. Sounds like a harness fit problem that is best solved at the factory.
    You did not specify whether it was uncomfortable on the front or tops of your shoulders.
    Extra padding is a poor substitute for a decent fitting harness. If the harness geometry is perfect, you can get by without padding.

  19. Bungee cord.
    The answer is bungee cord.
    Take two pieces of bungee cord.
    Route them through the holes in the corners of your Alti ll.
    Tie one cord so is snug around your wrist.
    Tie the second cord so that is snug around two or three fingers.
    If you can't tie knots, tie lots! Ha! Ha!
    One of our instructors has been doing this for years.