JohnSherman

Oh, BTW: The Racer Tandem does not require wide rubber bands. We only need the 3/8 wide standard because of the speed bag and the balanced stows. John

Yes, they did. I had developed the "Speed Bag" about 5 years earlier which was a spin off of the "Balanced line stow bag". All an evolution which began about the time of the introduction of the Safety stow. I didn't like the safety stow and I began testing. I had to ride the tide until I had proven my case. I told my people in 2003 that I thought 5 years of constant use of the "Speed Bag" on mains without any malfunctions meant we should consider it for our reserves. They had all ready done it. The USAFA reduced their malfunction rate from 14 per year to 1in 3 years using home made speed bag copies.

Not true! We don't use the Safety Stow on our Free bag and haven't since 2003. Our Free Bag is also a "Speed Bag" see http://www.jumpshack.com/default.asp?CategoryID=TECH&PageID=Reserve_Speedbag&SortBy=DATE_D I have a copy of that pic on my bulliten board. It shows the power of "Bag Extraction" and the forces encountered. If some of the guys messing around with stowless lines would digest that pic they would move on to something else. It clearly demonstrates the need for the "Speed Bag" BTW; that is on a Vector Tandem with a collapsed drogue. (lower lift forces) The problem was line dump or line strip or bag dump or ILS or whatever. They were using tube stows with very small bights. Stows located on the edge of the bag. They were getting openings in the 2500 pound range.

I will speak for the Racer = Fabric in. Did you ever stand on the end of your necktie and try to stand up straight? I have seen pilot chute springs fail to extend because the canopy fabric was tightly tucked under the spring base. I have seen it both in Free fall and on the table. John

Reading "Rubber Bands Break For A Reason" @ http://www.jumpshack.com/default.asp?CategoryID=TECH&PageID=Rubberbands&SortBy=DATE_D might shed some light on the subject. There is no way you are going to cause a bag lock with a Mil Spec Stow band. The breaking strength of this band is 40 pounds. They seem to maintain that level of strength until they all of a sudden break. If the stows are divided into equal parts, by the bands, so as to balance the mass of the line bights, there is no need to double wrap. A designer knows that the breaking strength of a rubber band is directly linked to the drag ability of the pilot chute

Back before square parachutes, in the day of the PC. There was a jumper from Madison Wisconsin who was a Gold Winger, Master Rigger, USPA I/E and a hell of a competitor in style and accuracy. Jack broke his leg on a bad landing and had a cast from his knee down. It wasn’t a walking cast so he continued to practice his profession as a hair dresser jumping around on the good leg. That good leg got so strong that Jack decided he could jump and land on the good leg. He figured the knee down cast would be manageable in free fall. It was, and Jack made a bunch of jumps like this. Then they got winded and Jack landed in a tree. While climbing down from the tree with a cast on his broken leg he fell and broke his good leg on landing. Think about the conversation he told me he had with his orthopod: “How did you break your other leg?” pause “I fell out of a tree” pause... “How did you get into a tree?” long pause... “I landed there in my parachute!”

Rob, Xxx Xxxxxxx (name withheld 'cause they probably don't want to discuss the Q or A with anyone) has been working with the FAA updating the Rigger Written for years. It has a bunch of questions about squares. Some of which the answer is debatable based on different experiences. I believe the total field of questions is some 4 or 5 complete exams. You can access this field of questions (with some research). Most of the study guides have all of them. However, that is no guarantee that you won't get a question not covered in the study guide as the Rigger Written might be more up to date than the study guide. I have seen it happen! I actually had it happen when I had to take the Rigger Written for the DPRE Appointment. I got a question wrong about frequency of skin damage between bottom and top. My 15 years of, canopy design and manufacturing, experience was different from the test answer John

No science here, just my observations over the years. White seems to be the lowest followed by yellow (not gold) and lite blue and pink. Reds, black and dark blue seem to be the most bulky. Feel the "Hand" of the cloth, you can tell if you compare them side by side. George Galloway at Percission tried to identify and correlate this issue but it gets elusive in the middle ranges and defies consistancy.

Ok, seeing that I am a manufacturer who makes both canopies and containers perhaps I can shed some light on this novice problem. Canopies are sized (for the purpose of container selection) by cubic inches. They are volume measured in a cylinder. Containers can be measured for volume but they are not all square and the exact numbers don't always work. Therefore some container makers might apply a coefficient or size adjustment to the calculated numbers. So if the container maker says 350 cubic inches that number should be honored. Now to canopies. To tell you how difficult it is let’s start with the bulk of the fabric. It varies from vendor to vendor and even from die lot to die lot. Color will change the volume. Want low volume, jump white, I do. The next group of variables deals with shape of the canopy. Aspect Ratio (Cord vs. Span), air foil thickness, keels or flairs, stabilizers, etc. Now comes construction method. Not all canopies are built the same. Some methods might increase bulk and some might reduce it. Now lets introduce environmental variables. Humidity: When I jump in Arizona I take a squirt gun with me to moisten the fabric while packing so it will lay more quietly. In my native Florida the moisture content from the green grass performs this task just fine. I have seen canopies pack well in a moist environment and not be closeable in Arizona. So you see it is not an exact science and there are many variables. We provide the guidance found at: http://www.jumpshack.com/default.asp?CategoryID=TECH&PageID=CANOPYVOL&SortBy=DATE_D However, it is just a guide. The only guarantee is to buy a mated system, mated by the manufacturer and guaranteed as such. This way if something doesn’t fit (and sometimes it doesn’t) it is not your problem but on the manufacturer to make it right. If you buy used components it may take several tries before you get it right and you find yourself in the equipment business. It has happened! [url]

Seeing as I was part of the original discussions back in the day I might be able to shed some light on the thinking back then. What most people miss is; what is the function of the rigger? The rigger is an inspector, primarily. His job is to inspect the equipment, make repairs as necessary and certify it for use. It is not a repack cycle it is an inspection cycle. All parachutes with which I have become familure, orient the same way for packing. This seems to be world wide though there is no formal standard. All packing instructions are written with the same orientation. By following the packing instructions to completion, what difference does it make where it hangs or what shape canopy is in it? Seat, Back Chest & Lap are unnecessary. When a rigger is trained they are trained to read manuals and to follow instructions. They are taught about materials and construction and how to test if necessary. They are field techs. They have limitations based on the possible effect on airworthiness. Rigging is a documented process and as such requires the use of manuals, and the completion of forms. It provides a paper trail. It has requirements for currency. If you haven’t packed a square lately, or never, it is your duty to get current. There is more difference between a Soviet D5 (mass tact military rig) (which incidentally has a triangle reserve) and a T-10, both round, than there is between a round and a square. Therefore in consideration of codifying characteristics for parachutes we should write regulations which are procedural in nature and which can accommodate all current and future designs. All we need is “Senior” and “Master”. Master handles airworthy stuff and Senior handles non-airworthy stuff.

What's the difference between a "Tandem" canopy and another kind. Is that bad? 298 Square foot Tandem canopy?

In the beginning all running ends had rolled ends which could not be pulled through the friction adaptor or other hardware without unstitching. When we started designing sport equipment and wanted to make it lighter we eliminated the mating hardware where we could. The original chest strat had a hook on one end and a "V" Ring on the other. We eliminated both and replaced them with a single thread through adaptor. Under certain conditionas and orientations it can be pulled open very easly unless it has a fold back of some type.. It's your judgement from now on as the legal requirements say its OK if it was drop tested and certified that way. I say its dumb!

If you think that a dynamic pressure of 33 ponunds per square foot (Q @ 120MPH) is going to equate to more than the forces I measuresd on the ground over the miniminual surface area (3.5 sq. inches, .017 Sq. Ft.)) of a metal handle, which you will need to pull the handle, is going to happen you had better recalculate. Don't forget to calculate in the Drag coefficient of the .3125" diameter "High Drag

Ok: That was fun 75/25, disappointing. But we are talking about it. The poll isn’t growing anymore so I will add my 2 cents. Thanks to everyone for their comments. I would like to rebut some and make my own. Remember the purpose of talking is learning! Ok, so I'll try it. I took a rig with a low profile metal handle, Teflon coated cable and a non-compressible housing. I pulled the metal handle out of the pocket, it just hung there. I jumped up and down, it just hung there. I put a pull scale on it and had to sustain a 5 pound pull in addition to the weight of the handle to move the cable in the housing. If I stopped pulling the cable stopped moving. The weight of the handle alone would not pull the release. The purpose of the metal core is to make the reserve ripcord extendable to allow for loads on the housing which might stretch it as the cable and ball float in a slot in the tube. It doesn't prevent "Tuck Unders" or make them less likely. If it did we would be putting metal tubes in the cutaway side. Housing exit location controls the propensity to tuck under. With a pud I must keep the housing exits outside the pocket, exposing them to snag. With a metal handle the concern is gone and the housing end can be built into the pocket. The only way to prevent "Tuck Unders" is with a metal handle (ridged across the width). The metal handle offers two methods of griping, the pud one. We have been protecting open ring handles for years. As to the cloth loop with a cable inside it. Way too snag gable. The trend toward the pud reserve handle is mostly with the newer jumpers 'cause "it is cool" it disturbs me and I won't build one. I do make the base for other gear makers but I don't put puds on them. I guess it is down to your personal thinking. Is it more important to be able to pull the handle and save your life than to have a partially exposed snag gable ring which must be protected? Or, to have handles which are difficult to grip and pull but require less protection so you can “Skydive “with abandon?

I must take this opporitunity to comment on what I believe to be a toung & cheek post. Those "modern" methods might look good but they have a hidden defect. They are too heavy. Hold the spring arm high whith the orientation horizontal. Release the PC and watch the top of the spring, where all that beautiful construction is, head for the ground. I want my spring to at least stay horizontal. When Booth was testing the teardrop, during his deliberations to buy it. He commented to me that it was the only system he had ever tested where the pilot chute went toward the ground faster than the jumper after cutaway. I keep the top of my pilot chute as light as possible so it will launch. It is one of many considerations in designing a deployment system. There is more to rig design than looks! Function over Form!

Mark, If you are going to re-post Helmuts letter then you should re-post my reply. I'll answer it here so it is unnecessary. Helmuts statement that it, the floating loop, was rejected for additional packing effort its dead wrong. I rejected it because of a failure of a simular situation. I still feel the floating loop is a bad idea and prohibit it's use in Racers anywhere. I haven't changed my mine. John

As the manufacturer of the ripcord and probably the rig. It's OK to use it as most everyone says. However, As a purest rigger I would change it. It's just the way we riggers are. Send me the ripcord and I will replace the cable and pin for shipping cost and return it to you. E-mail me your info so I can make it happen. John

It was a TSO'd part then and it is now. And you can still make one. However, It must be made from traceable certified material and made to the original drawing. Also an entry on the card would be nice. I don't think the one Peter ran into had all that. And yes you are a very "OLD Dude"

Recently there was a fatality where there was no cutaway and there should have been. This probably was not the first time. The Cutaway “Pud” was of matching color to the jump suit. It was apparently not removed from its Velcro retainer. The video shows the jumper looking to the chest area 2 times. After the second time he pulled the reserve handle. Did he decide after the second look that he was too low, therefore electing to pull the reserve? He wasn’t! Or did he have a problem pulling the Pud? We will never know. This all brings to question a category I call “Handle Talk”. What is the best handle design for activating the cutaway or for that matter the reserve or main?. As the main is not generally for emergency use and the pulling of which is well practiced we will leave it out of the discussion. Generally in the sport we have a choice of two types of handles. A soft “Pud” or pillow type or a metal loop handle such as generally used on the reserve. There are those who think the reserve handle should be like a Pud. They believe it reduces the chance of accidental pull. Some manufacturers have recently been supplying, to some of their customers, on request, Red Power Coated Stainless Steel Reserve Handle drilled to accept the cutaway cables. They simply add a mating piece of Velcro to the already existing pud Velcro, on the harness, creating a pocket for the new metal handle. So we have two schools of thought. Soft pud types and ridge metal handles, which is best?. In its pocket, the grip edge of the metal handle has a tendency to stick out away from the body a small amount because of the curve of the body at that point. The Pud doesn’t do that, it contours. The metal handles can be “thumb hooked” as well as being grab able like the pud. OK, personal preference. We were all taught from the beginning to protect all handles. This hasn’t changed. The handles today are easier to protect but even the Pud must be protected. So, I bring this question to you! I bring it to stimulate discussion and awareness. I not only want your vote on which handle is best, but your comment on the advisability of the choice you rejected.

The problem with the LOR is the same as any single sidded system. One side can release without the other. Consentrating the release forces to the unreleased side. The cross connector keeps thes forces more even when only one side releases. As to Chucks suggestion about a new approach. I wish!! The problem comes back to flexiable components and the housing compression. Every system needs housings and we are doing the state of the art in housings. The 2 inches slop I have now is all in the long side housing. John

Try as I may we just can't get them to release evenly every time. The best we can do is guarantee release within 2 inches every time, which we do! To do that it requires housings which have minimum compression. No such thing as Zero. We control our housing length by dimension and cut our cable length also to dimension, never relative, as the amount of compression is unknown. Like trying to even the table legs. I think the reason we want this is: "if one side goes both sides should go, if one side stays both sides should stay". It is easier to release two sides than one side under the total load. Therefore we must have a slick release cable cause it is always the loop load which hangs them up. There I’ve said it, have fun with it.

It wouldn't matter if that was all there was. But there is more within the compression of the long housing. That housing can compress as much as 6 to 8 inches if the cable is unlubed and the loop is tight holding the cable at the riser. I have had it happen to me in the air. This means that even with the cutting differential quoted, the difference would be inadiquet to prevent the right side from releasing if the left side locks up. Reserve out Main in tow.

The Racer RSL will not pull the reserve until BOTH risers are Released. One more point, that no one has realized, is the compression of the housing during the pull. Most 3 ring housings are "Relaxed" which means they may be more than 10% compressible. If the left riser retainer loop is tight then the right side could release with as much as 6-8 inches differential causing a right side release with no left side release, this fires the Reserve on a single sided system with right side activation. Thus the reason for the extra cable on some single sided or side sensitive systems. Read:http://www.jumpshack.com/default.asp?CategoryID=TECH&PageID=RSL&SortBy=DATE_D and follow the links for further discussion about this subject. We use non-compressible housings, at a considerable higher price, which provide for no more than 2 inches differential for release. No other manufacturer does this. It would be cheaper for us if they did. To the original point that 5 pounds could cause a release failure of a 3 ring riser. True, but this is unlikely considering the dynamics of the cutaway. I have seen both risers fail to separate during a high speed with an experimental pilot chute of 19 inches diameter. This demonstrates the need for sufficient drag separate it and pull it all out.

To AAD or not to AAD: Automatic Activation Devices are designed to activate your parachute when you can’t or don’t. Most of the common AAD’s used today go on the reserve. They really should be on the main but we don’t want to give up our hand deploy PC’s. It seems foolish to me to become conscious under a malfunctioned reserve and have a perfectly good main packed up that you can’t get to. These common AAD’s used on reserves mostly have loop cutters which may trap the loop preventing normal deployment. While this potential violates the doctrine of “Must not interfere with the normal function of the parachute” AAD’s are beneficial to saving your life and should be given serious consideration. I believe in AAD’s, I believe they save lives. However, we should be asking the question “Will the rig in which I put the AAD deploy the reserve within the required 300 feet or at least from the 750 foot firing altitude”? All TSO’ed reserves are required to be able to do this. However, recently some have failed to accomplish this basic requirement of law. Therefore, you should spend more time choosing the container you are going to put the AAD into, than choosing the AAD itself. All an AAD will do in a defective rig is “Fink” on it. The AAD data will prove the activation occurred at 750 feet and you will see the deployment time, maybe not completely. Most of this problem is a compatibility problem and caused by overstuffed containers. Your rigger should be “Short lining you” if you try to put too big a canopy into a container causing excessive extraction effort. You should ask your dealer what the maximum allowable extraction force is and what the drag capability of the pilot chute is. If they can’t give you a definitive answer move on. Drag Capability may be given in Drag Coefficient or “Effective Size” or what it will drag at a given speed and altitude. Yes! You should have an AAD but you should only put it into a system which has consistently performed and never failed. The info is out there! If you want to test it your self: Tape up the loose ends of the harness and throw the rig out of an airplane, with a fully packed main & reserve, from high enough to activate the AAD. You don’t need a dummy. If the rig works then you have a winner. If it doesn’t then you have a very dirty mess to send back to the manufacturer for a refund. It would be worth the price of a cutter to know.

As to Riser length: Riser length can only be determined by the canopy designer. Because of equal line length a ramair canopy transcribes an arc through its span. This arc has a confluence point where all of the lines, which are radial to the arc would theoretically meet. The designer then cuts the lines off at some point in order to fit the jumper with his harness and risers into the assembly. At this point a decision is made as to the delineation of the riser and lines. There are a number of obvious considerations for selection of a good length for the riser, but it must be matched to its line length. Therefore if your riser is too long the canopy spreads and the top skin wrinkles or if they are too short the canopy is pinched and the bottom skin is not tensioned to its optimum. Certainly this is more critical on a smaller canopy. The big canopy accuracy folks can get away with anything ‘cause they don’t need lift anyway. The bottom line is we aren’t building jet fighters, these are after all “Ragwings” but this is the theory for perfection. There is incidentally, an industry standard for the distance from the end of the riser to the brake ring. As to being able to reach your toggles or slider, this is more of an issue as to where the risers attach to your harness. If they are attached at the top of you shoulders you will hang like a monkey and find them to far away. If they are attached at your upper chest your harness will lift up on your legs putting you into a sitting position with the end of the risers reachable. Also if you can look under your harness suspension point, when sitting in it, the harness is either too big or the risers are attaching to high. This suggests trying a harness in suspension before you buy it.