JohnSherman

Why not just buy a rig with pure Teflon (FEPT) Coating instrad of Nylon which is hydroscopic. No lubrication or maintaince req'd. They are out there and the cables are colored red or orange. Wonder which rig that is? Probabally the one which has not changed in 20 years, the one which doesn't inovate.The one which does't need a MARD.

Bill called it a Ballute I didn't. You don't have to believe me but the NASA results are irrefutable. It may be old news but you should still listen to both sides. There are 3 possible reason for the late inflation or lack there of. 1. Low drag pilot chute. 2. High bag extraction forces. 3. AAD firing late. Take you choice and follow it to a conclusion, then choose another and follow it until you know the reasons. You bet people know, and seriously, the root cause may vary slightly form rig to rig. Some have high extraction and a normal pilot chute. Some have low extraction and a low drag pilot chute and some have both and it varies from model to model with each product line. The real problem is that some of those manufacturers don’t know. How many manufacturers do you know who can tell you what their pilot chutes actually drag in any environment. The only answer is a standard with metrics for the rigger to check at each inspection cycle. The extraction force should never exceed 18 pounds is a tenant of the standard I would propose. Pilot chutes should be placarded with their “Effective Sq. Ft.” is another tenant I would suggest. If that “Effective Sq. Footage” is less than 6 then it won’t extract the 18 pound pull on a maxed out container. You will have to wait until the speed builds up a bit.

Now that's a good question. To my knowledge the answer is no. If you want to know more about Ballutes you can find information in the Parachute Design Recovery Manual. This is the manual used by military and government designers. It may be down loaded from here: www.jumpshack.com I don’t have the exact URL and their site is currently down. Navigate to Home page and to Downloads, you will find it there. A Ballute is defined as a Supersonic Stabilization Drogue. It provides enough drag, without noticeable oscillation, to stabilize the store at over 600MPH. A fancy word which was used to baffle people into thinking it was something special when it actually almost used correctly. The thing which is call a Ballute in our sport would have to go to supersonic speed to get enough drag to extract some of the tight fits I have seen.

Here is a photo of a wings lifted from their web site. [inline Wings_pilotchute.jpg] Notice that 80% of the canopy is canopy cloth. While the Vector 2 might not be of the same proportions it still has more than 50% canopy cloth as does the Infinity, or so I am told. Information which I have not personally verified. The point is that, on all 3, the canopy cloth which extends beyond the equator of the canopy is deflecting air not grabbing it. The BS about getting it into the air stream is just that, BS. Things don't go up when released in FF they continue to fall at the same rate at which they were released unless their mass density is different or they reach the end of the bridle and start dragging. If the mass density is less they will slow down, if more they will accelerate. This is the baine for heavy springs and tops. As Bill noted, when he tested the Tear Drop, the PC accelerated away from the free falling body when released because of the heave metal hat. The same is now true for the big disk on some rigs which are combined with heave springs. Pilot Chutes should be as lite as possible so they will allow you to fall away from them. But it is the canopy design which does the dragging and non traditional designs have proven not to be of adiquet drag capability. The data has been out there for 25 years and the marketing has overcome it to the detriment of the sport.

We have and we measured it with both force transducers and accelerometers. We did not depend on some subjective test jumper evaluation. We controlled the variables and used a Speed Bag which compensates for variations in line bulk. It was Booth who said you can't use Spectra on Tandem. I not only used it on the Firebolt but I used it on the original Tandem 400 which was by design a fast opener, now our tandem reserve. We pre-stretch all of our line, both Spectra and Dacron before marking and cutting. The only time I have ever seen the amount of stretch to which you refer is before pre-stretch. I wonder if the manufacturer of the product upon which you found this anomaly did.

You are correct in your analysis but the spring only gets the PC out if the container. Once it is out of the container and at the end of the bridle it is the Drag capability of the PC that matters as it must overcome the container retention of the bag. Evaluation of the PC must be in terms of "Effective Square Feet". This is necessary because the other parameter is Dynamic Pressure which varies with Speed and altitude. The Dynamic Pressure is in terms of Pounds per Square feet and the Effective Size is the Square feet with witch you multiply to find Pounds of Drag. The only way to properly test pilot chutes is in a wind tunnel. There are other ways but they are not yet proven. Now what is "Effective Square feet". This term is the combination of the actual measurable size of the PC canopy and it's "Coefficient of Drag". The Drag coefficient is sufficient to evaluate the device but not to calculate the drag. Some manufactures will not state the physical size of their PC's but that doesn't matter if we use the combined results. Back in 1988 I was the principal investigator in development of mid-air refueling drogues. In that project, which was conducted at NASA Ames by NASA personnel, we tested 3 pilot chutes in common use. The Vector 1 and the Vector 2 and the Racer 36". The Racer and the Vector 1 are conventional pilot chute with about half mesh and half canopy cloth. The Vector 2 was the one in common use to day and it similar to the Wings and Infinity pilot chutes. The results are in terms of “Effective Square footage" are: Vector 1 = 5.6 Sq Ft., Racer = 5.8 Sq. Ft., Vector 2 = 2.3 Sq. Ft. If the Dynamic Pressure is, say, 3 pounds per sq. Ft. which it is 1 second after a cutaway at 2000 Ft from a Mal which was descending at 20 FPS. The results in terms of drag are as follows. Vector 1 = 3PSF * 5.6 Sq. Ft = 16.8 pounds Racer = 3PSF * 5.8Sq. Ft. = 17.4 pounds Vector 2 = 3PSF * 2.3 Sq. Ft = 6.9 pounds The results found by NASA and broadcast over this form for the past several years predicted the performance by certain product being discussed here. Here is the proof: https://www.youtube.com/watch?v=Zva4gHVX_zI Some people will not believe Science when it is too complicated or not convenient.

That rigger was probably my age. Let me add more contex about the concern for ripcord stops. Yes, they have killed people but that was in the days of "Gutter Gear" (chest mounted reserves). The mains, in those days, had pilot chutes and ripcords. Student and others kept loosing their main ripcords on many jumps thus ripocrd stops. Simply a metal ball was attached somewhere on the cable to prevent it from coming all the way out of the housing. This stopped the loss of main ripcords. But then! Folks would cutaway and deploy the reserve off their chest into a flailing ripcord. They would wrap and you got to spend the rest of your life untangleing them. Ripcord stops on piggy back reserves don't have this problem. JS

There is actually quite a lot of history and experience with cloth ripcords. In the mid-to-late seventies, I built an elastic retractible suspension line ripcord and mounted it on the belly band of an SST. I sent it to Para-Flite/SSE with which I was in cahoots at the time. Johnny Higgins, of North American Aerodynamics, saw it on a visit to Pennsauken and adapted it for his Condor. It was a standard item on the rig until it was eventually replaced with hand deployed pilotchutes. Both Para Flite/SSE and I rejected it back then because of the wear potential. If broken strands of wire are found on a stainless steel ripcord cable, we replace the ripcord assembly. Within a TSO’d system any damage is cause for rejection. You simply can’t, as a rigger, take a chance. Because of my experience with textile ripcords I now make stainless steel ones. Full Disclosure!

40 years of running a loft and relining and retrimming canopies don't show any real difference in trim loss. Dacron will stretch the inside lines as they take the initial loading. Spectra will shrink the outside lines from the heat of the slider grommets. I find this to be an offset. I doubt that the coefficient of friction between the 2 is much different. We have found that Grommet material might be making difference as to the descent of the slider. SS is heaver than Brasss and the phototogs will tell you brass opens softer as the slider comes down slower. I have not personally examined this claim but it seems good on the first look. This would diminish the effect of the line friction theorie. It would not matter if the SPEED bag were used or not as long as it was used in both evaluations. I have made this evaluation both with and without the SPEED bag. SPEED bags don't open softer than regular bags they just do it consistantly, every time. They prevent the aborant opening. Sure Dacron has its place. Accuracy canopies come to mind as the increase drag helps slow the canopy down on approach. JS

A word about Spectra vs. Dacron: I see here in the form and have heard others repeatedly say that Spectra lined canopies open harder than Dacron lined canopies. I would like to take issue with this foible. I do not agree with this premise and see no proof other than subjective evaluation of the reported phenomenon. When Spectra first became available to the sport we only had one size rubber band and we knew little about line dump/strip or “out of sequence deployment”. The diameter of the line was too small for the rubber bands of the time and some of us doubled wrapped the bights to hold them in. None the less we were getting slammed with line dumps and the Spectra line was blamed. This was the beginning of the myth. I have designed canopies of all shapes and sizes over the last twenty years. When I designed the Firebolt Tandem Main I was told (by the competition) that you could not use Spectra line on a Tandem canopy. Time has proven this was wrong. I have never used anything other than Spectra and have no plans to do differently. The Firebolt is known to be a soft opening canopy. Read the reviews on this site. http://www.dropzone.com/cgi-bin/gear/review.cgi?ID=435 I have swapped line from one to the other and seen no difference. Spectra like Kevlar is know to transfer loads faster than Dacron. Folks say that is doesn’t stretch. This is more significant in solid structure than in woven structure. Parachute line is woven. The weave provides the necessary stretch. I have measure opening force loads, hundreds of times, on both Dacron and Spectra lined canopies and can see no difference in resultant force. When I design a canopy I specify Spectra because it holds its trim better and has a better life is lighter and stronger. There is more significance in the spread of your arms when you open than there is in the difference between these 2 options. John Sherman

Jerry, You are correct that C23b had no cutaway tests but it does require all normal function test to open within 3 seconds from release at 70MPH. Therefor while none was requires at that time, it is required today. Sure I grandfathered in as did others but I have certified my tandem in C23c as all of us did. This is tant-amount to certifying the original rig in C23c as they are the effectively the same. TSO C23b was superceeded by TSO C23c on Aug 25 1984 which does requuire a 3 second cutaway test as does all subsiquent standards. I also would like to think any rig could do this but the truth is they can't. With this requirement being in place since 1984 and the previous standard requiring 3 seconds from 70MPH there is no excuse for a bag extraction effort of greater than 18 pounds. "canuse if you have even the slightest hang up of the bag extraction you won't meet any of the above required tests. JS

I don't know of any pilot chutes, including the Racer, which will lift 18 pounds, 1 second after cutaway. The Racer will only lift 17.9 pounds at that point. Therefore anything over 18 pounds is Taboo. Remember we are lifting the weight of the reserve plus any additional container restriction. JS

Hi Jerry, I wrote this some time back http://www.jumpshack.com/default.asp?CategoryID=TECH&PageID=18pounds&SortBy=DATE_D but I am presenting it here as I think it is important to this discussion..

Test were conducted by NASA on 3 different pilot chutes. The Vector 1 and Vector 2 and Racer. Here,again are the results of those tests. Study the results and remember that a Cd of less than .40 is a drogue not a pilot chute. A pilot chute requires a CD of greater than .60. An MA-1, the standard for the industry, has a CD of .65. https://www.youtube.com/watch?v=Zva4gHVX_zI A Ballute is a Supersonic drag stablization device. A pilot chute is a extraction drag device. To get drag out of a ballute you gotta go fast, we don't! The pilot chutes refered to as Ballutes by their manufacturer do not have enough drag for sport use. It is a major reason they have trouble meeting the 3 second cutaway test. As to getting out of the burble faster: This is good retoric for those who actually believe that things go "UP" when released in FF. They don't, we fall away from them. John

The Racer didn't fail Larry. Per the AAD data Larry had 1.5 seconds between cutaway and impact. Racers take 2 second. ALL rigs should be checked for extraction effort and if it requires more than 18 pounds don't certify it.

The 143W2 was a single throw (304) until it recieved the Cametron conversion to a double throw (308). The Cametron asdds the cam on the back and the mis-colored parts. Cametron is apparently the successor to Gelman as the conversion was known as a Gelman Mod. I have 2 of these. Their lift is low but they are fast and reliable.

David, I have a cartridge manufacturer who will manufacturer catridges for Skydiving. They manufactured the cartridge for this test: https://www.youtube.com/watch?v=uyP7m-HkXQY Oh! that's not a cutter is it? Looks like a Racer ripcord. It will plug into an Argus with an adaptor. What kind of plug are you using on your opener? It will plug directly into a Vigil. It has a 3.5MM stereo phone jack. JS

Do not lubricate any Racer loops!

The drogue adds to the square footage available for drag. The Tandem pair has about "X" Sq. Ft. The drogue is responsible for some of it. Your question is how much. In order to know what a drogue drags you must know its effective square footage. The Effective Sq. footage is the plan form sq. ft. times the Drag Coefficient. In order to know the Drag coefficient of the device it must be tested. Drogues generally have a Cd of .20 or so. They are low drag so as to minimize oscillation. We have done several instrumented test where we don't deploy the drogue until half way through the FF. We can analyze the data and conclude the effect of the drogue by equalizing the "Q" and observing the difference on Effective Sq. Ft. That difference is the effect of the drogue. This results in about 90 pounds of drag with 2 guys weighing 170 pound each and a rig weight of 40 pounds.

It is the same reserve we use today in our tandems. We call it a 400. We also originally called them 425. However later consideration indicated it was smaller. FCI originally made them for us and made a few for themselves. They tested it and we tested it. It has been around for over 20 years. It was the first canopy I designed and it doesn't have a Notre Dame Airfoil. PM me for TSO data.

The correct engineering method is "inflated plan form". This entails drawing the canopy in its inflated form and measuring the sq. footage as viewed from above. This shortens the physical span because of the perspective from above foreshortening it. The cord is additionally foreshortened by the attack angle being involved. If the canopy was designed in CAD 3D it is easy to measure the perimeter. However, early canopies were not designed this way 'cause CAD wasn't readily available. Other methods require different approaches to measuring the cord. If the airfoil is not cambered then it is tip to tip. If it is cambered then it is the “X” or horizontal axis is used. We use this method (inflated plan form) as it is the way we were taught. It does put us at a slight disadvantage when being compared to canopies from other manufacturers as our canopies will look smaller.

It is standard procedure within the competition to refute anything developed by Jump Shack. There is no down side to the procedure. We have been requiring it, in our manual to use a rubber band on all canopies since the beginning of Ram-airs in the 70's. I believe most manufacturers do now endorse the concept. Having said that let me caution you to the fact that while the rubber band on the slider will keep the slider from "falling" or inertially being pulled down the lines during opening it will not hold/help if the canopy begins inflation (spreading) and forces the slider out of the rubber band and down the lines before you reach line stretch. This can only be prevented with a bag which will not allow line dump/strip.

I was heavily criticized when I developed and introduced “Trash” packing back in the early 70’s, later renamed “PRO” (Proper Ram-Air Orientation) packing by Mike Fury. The method is based upon packing a round except the 4 line check is the outside 4 lines (corners) as opposed to the inside 4 for a round and because of the short cord equivalent could be done standing up. The Beechnut 10 way team did extensive testing with this and variations of it, as did the “Exitus” team, during their existence. Mike Johnston took the “Trash” out of the pack job by figuring out how to make the folds look neat. I showed it to Hank Aschutto (Piglet Designer, RIP) at the Nationals in Richmond Indiana and he went home and published the first manual. This was before the How To pack video that was produced by a passer by in the sport and who gave credit to a former rigger who worked for me and claimed he developed the method, which was a lie. The French, a number of years ago, conducted a government study of Ram-Air parachute at Toulouse, France. Their studies showed that The PRO pack was superior in force reduction and load distribution as it loaded more symmetrically. It was also better for on heading openings if the correct body position was maintained. Their data was presented at a PIA symposium in Orlando. We introduced it for reserves when we certified the Racer for square reserves. The rest is history.

Present your data for peer review otherwise it can not be considered. You made a statement now back it up. To refuse to answer because you don't think I will believe you is preposterus. It's not for me to judge in any event but for everyone else to see the data and make up their own mind. That's how these forums work.