SethInMI

IIRC, the horizontal car is moving when the vertical car is dropped. I don't know what terminal for a car is, and that is most important as the car would probably spend the majority of 4k fall at terminal. Didnt someone push a car out of a Skyvan at Eloy some time ago? Is there video? I thought the whole thing was odd. Near as I can tell the message suposed to be: "Lexus is run by nerds, so your car will be chock full of aerospace level technology" It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

Searching is your friend. This has been covered many times. Basically you start with a pro pack, but flip it over before laying it down, then roll it up and bag it. Here is a link from Icarus, who are proponents of the technique. Icarus Packing Pics IBhugeprosconsdebate It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

My manual Subaru STi could give your a run for your money. We both have three LSDs. I like them both. Until it died a few months ago, I had an old Ford wagon with auto, and I have the Subaru w/manual. With a 6spd, shifting can get to be annoying, so an auto is a nice change of pace. I like the ideas of the new "best of both" transmissions, DSGs and CVTs. Hopefully my next car will have one of those. Seth It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

I don't think the season has ended yet in MI. I just did two jumps last Sunday in Fremont, and I know Skydive Plainwell was going to have a plane up this Sunday. The weather tomorrow does look to be ugly, so I don't know if that will work out, but I would call around to see who is open. Seth It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

Thanks for the reply, beezy. I wish the name for this packing method was less bizzare; I look at as basically just a rolled-up pro-pack. I will try to pull the attachment point out some more, but I just think the distance from the attachment point to the dbag is a bit too short when the PC is fully cocked. Even when I put a knot in my bridle, the kill line mark has a habit of sliding out of the window. If I get ambitious, I will try to post a pic of how it looks right before I bag it. It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

for my psycho packed canopy. Will someone tell me who to get in touch with to find one? I have a 190 and it is hard to keep the PC fully cocked. Thanks, Seth Grammar/spelling nazi note: If I said I want a bridal extension, I would mean I want my wedding gown to be longer. It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

Cafepress is huge. 671 claimed skydiving designs, although some are in the category are not, and many others are variations on the same themes, but you still have alot of options. Here are two I liked after looking through about 1/2 the samples. Remember, you can't wear the 2nd design if you jump a pullout. It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

Way back in 2002, the DZ where I was a student had student gear with round reserves and FXC AADs, as did the larger rental gear. It was probably my 30th jump before I jumped a square reserve with a Cypres. I still remember the 1st jump class training: "If you have an AAD fire two out, the round will win. Wait till the main dives, then pull the silver handle (SOS gear) and don't flare the reserve on landing" I saw one round reserve ride under student gear when an FXC misfired on a backloop at 8-10k up. There are probably other small DZs with old gear out there, that one shutdown earlier this year, still with the same student gear. Seth It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

I will be near Perris for Christmas (palm springs), so I thought I would try to make a few jumps there at the time. I sent an email with some questions, but have not heard back. So before I hassle them somemore, I thought I would try out DZ.com. Don't fail me people!

I would be transferring the data from the GPS to my computer and saving the data there, so the amount of memory in the GPS is not a big concern. I know that there are excellent barometric loggers, but I would like to have something for logging XY and Z data, for Google Earth purposes, for tracking jumps, and just for the hell of being able to see my canopy flight in 3D. I have an Explorist 210. I guess the heart of my question goes to the track log difference between Magellan and Garmin, that is, Magellan only appears to support "automatic" tracking, while Garmin can log on an interval (1 per second, etc). Is this anything to worry about? How about mounting, I assume I would attach it to my chest strap or have a pocket sewn somewhere on my jumpsuit for it. I know people use the Etrex series, they look to be about the same size as the Explorist. Thanks, Seth It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

I got a Magellan Explorist as a gift. I would like to use it for general outdoor navigation and logging jump tracks. I haven't opened it yet, b/c I want to make sure it is suitable for skydive logging. I read the online manual, and found the logging feature is "automatic", it logs a point when a "significant" change in speed or position has occured. I am not too happy about this. A search of DZ.com does not reveal any references to the Explorist, so I wonder if I should just return it and buy a Garmin. Anyone with Explorist experience? Seth It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

My progression was static line; I am at a small Cessna DZ and that is all they offered. I will toss my 0.02 on several issues you are having: 1. Disposable income. You know that this is an expensive sport, in terms of training, gear and jumps, so if you can't handle giving the sport 2-4k over the next few years I would not pursue it. 2. Fear (incidents). I had alot of fear transitioning from SL to FF, I worried that I would get unstable and deploy unstable, end up with a horseshoe or a wrap and go in. My first terminal jump went fine, and it was the best jump I ever had. I ended up being pround of the fact that I did everything "myself", as my first few freefall jumps were solos, and my first jumps with instructors were not "Im here to help you save your life" but "Im here so you can get RW practice". 3. Progression issues: It took me a long time to get through training, 3 years and 35 jumps to A license. It was worth it to me. I told myself when I started what the completion cost would be and I commited to finishing the program (getting licensed) regardless of time or financial costs, and then I figured I would decide if the sport was right for me, before I took the plunge and bought gear. It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

Well, I carried the J3 on, and it was a little tight getting through the opening to the bin, but once inside it was fine. TSA hand-searched everyone's carryons at the gate for one of my flights. I was worried about having to argue about not opening the container, but one of the hand searchers was the same person who swabbed the container at the checkpoint, so it was not a problem, which would only happen at a smaller airport like GRR. The checkpoint staff was great: "Is that a parachute?" "I finally got to see one" "Get the supervisor". . . swab swab and done. Seth It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

Does a Javelin J3 fit in the overhead bins on a CRJ (Canadair Regional Jet)? The bins are pretty small, but I think it will fit. I would like confirmation though, cause if it does not, then it gets gate checked and chucked in the cargo hold... Thanks, Seth It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

That is hi-fricken-larious Eule!

You are now on the right track. However, the equation you have is the net force on the system, which determines how fast it will decelerate. If there is no deceleration, like under a fully open canopy, then m*g - C*v^2 = 0. But at that point there is still m*g force on the risers. The correct equation is: Riser Force = Drag Force on canopy (initially low, spikes up then settles on value = m*g) Think of it this way, the canopy weighs a lot less than a skydiver, so almost all the force exerted on the canopy as it opens travels down the risers and exerts itself on the suspended load. To be very precise, in the system equation m*g = Cv^2 , C is the sum of drag on the canopy and the skydiver. Initially all drag is skydiver, but very quickly canopy drag becomes dominant. Seth Regarding your comment for Figure 2, with the same suspended weight, a longer opening will have lower peak forces. I am talking about different weights. It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

980: you are correct, I see that article as further validation of the model I created, and what everyone is telling phoenix. phoenix: The spreadsheet I created matches well with the data measured in the article you posted. For example, the data in "Figure 2" shows shock loads of 4k-5k Newtons for a 200lb skydiver deploying at 110 mph. Using that data and a 3 sec opening time in my spreadsheet, you get 4.5k Newtons (1000 lbs) for peak loads. The article just shows that model I am using is valid. And the model shows that increasing suspended weight increases peak shock. There is a reason the model matches the measured data, and that is it is based on basic physics, Fd=Cv^2 and F=ma. Thanks for posting the link! Seth It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

Phoenix: I will try once more to convince you, by trying something that is commonly done in engineering when testing a formula: try the extreme case to see if that makes sense. Here I ran a 15k lb load from 160mph, simulating the cargo deployment blowup that was mentioned earlier. The kink in the load graph is where the chute finishes deploying. If you deploy a 15k lb skydiver shaped load at 160mph, it would start to accelerate, then slow as the chute opened. The new terminal velocity for such a load would be ~80 mph, which is one reason you would need more than one chute to stop the load. The other reason is the peak load forces for this opening are >50k lbs, even though peak g forces are only about 1 g. At 50k lbs the parachute will blow up. You can modify the opening time a bit, but the fact remains, higher suspended loads cause higher loading forces on the chute during opening. Other than getting a trusted parachute designer to personally explain things to you, I don't know what else to say. Seth It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

Phoenix: It is true I don't have a good way to model opening time, and that will affect the calculations. However, if increasing suspended weight makes the parachute open faster, as I think it would, then this would only increase the peak forces on the heavier jumper. I think you are only seeing what you want to see. Sparky: I did take way too much time to build that spreadsheet. I am glad I got something out of it that seemed to make sense, but I wish it didn't take me so long.

OK!! I feel even better about this spreadsheet. The only difference between this and previous one is how I ramped up C in Fd=Cv^2. In the previous spreadsheet, I increased C linearly. In this one, C increases at a quadratic rate. Since C is proportional to the area of the canopy, and area proportional to the square of the radius (for a round), I figured the radius of the canopy increases linearly during inflation (or close to it, and this would roughly apply to squares as well), so C increases quadratically. The interesting thing is with this spreadsheet, the values in the NAB test that Sparky posted make sense. I can plug in the combinations and see peak forces in the 5000 and 3000 lb range for the various tests with a 2 second opening time. This gives me some confidence that I am in the neighborhood of reality with the model that I have come up with. Now obviously this is just an approximation of the actual forces involved, but it further demonstrates the basic point I want to make: Heavier people cause higher forces on the canopy during opening. Seth It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

OK. I feel much better about this spreadsheet. I even attached a picture. The distortion I got was from assuming a constant C in Fd=Cv^2. I knew C varied as the parachute opened, but I did not think how dramatically that would affect the opening. This spreadsheet contains a crude means for ramping up C over time to simulate the opening. The difference is dramatic. There are two main mechanisms "fighting" eachother. As the parachute opens Drag increases, but that causes Speed to decrease which decreases Drag. Now it is easy to see that increased weight causes increased peak forces on the canopy lines. If you download the sheet, change the values in: J23 for exit weight L23 for opening speed Q20 for opening time in seconds Watching the results on the chart, it is very evident that larger masses cause higher peak loads. Try a very large mass like 20000 lbs. The force just keeps ramping up, enough to blowup the chute like that cargo parachute that opened early. Seth It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

I got the data from my own calculations. (Warning: Math!) As you know, Fd=Cv^2 (where C is area and drag coefficent and some other things). If a parachute is allowing a 220 lb person to descend at a constant rate of 10mph then 220 = C (10mph)^2. So C = 49 in SI units. Knowing C means that one can solve Fd=Cv^2 for any velocity (assuming the parachute has the same shape), and find the drag force for a given velocity (say 120mph). Then I used A = Fd/M for the 220lb weight and got deceleration A, which slows the parachute to a new velocity, which creates a lower drag force, which creates a smaller A, etc. (Someone better at math please provide a formula, I just iterated a spreadsheet). Now it takes time for the parachute to deploy, so C is changing during deployment, but I think the basic math is ok. My calculated deployment took less that 0.1 sec, and travelled a distance of about 8 feet, but that is fully open at terminal. If my math (excluding assumptions) is off, let me know. Seth It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

[SEE LATER POST FOR BETTER DATA] I did some more thinking about this, and ran some spread sheet numbers to try and make some sense of it. In my spreadsheet I assumed a parachute was completely open (a round) and checked to see how fast it would stop with different weights. I believe what happens is the heavier jumper does cause the parachute to open more slowly, but this subjects the lines and canopy to the high opening drag forces for a longer period of time which is what will cause the failure. Now a slower opening will change this, as has been pointed out, but the fact remains, a heavier load causes a longer deceleration which subjects the canopy to high drag forces for a longer period of time, which is tougher on the lines and fabric. Seth It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

Jerry, I think phoenix would agree (can't argue with Newton), but he is saying that F is basically constant, so a greater M results in a lower A. (Heavier people on a same size canopy just open more slowly). I think drag forces at high speeds are so great that the canopy is going to decelerate at about the same speed regardless of the weight below it. Then if A is constant a bigger M will result in a bigger F. Seth To put some numbers on my point: Fd=Cv^2 (Drag Force is proportional to square of the velocity) This means that for a canopy that can lower 220lb person at 10mph would require a force of 32000lb to move it at 120mph. It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".

You are mistaken. I will try to explain giving an extreme example: The drag force at a given speed and canopy size is fixed, but it is may also be very high. To deploy a canopy through the air at a continous terminal speed (behind a large plane for instance) would destroy the canopy as the drag force would be so high it would overstress the lines and fabric. In a normal deployment, this high drag force is quickly absorbed by slowing the jumper as the canopy deploys. A heavier jumper exposes the canopy lines to larger forces because the canopy cannot decelerate as fast. Since the drag force at terminal on a canopy is so high, I would think that the time it takes to slow from 120-10mph over a deployment would be almost the same whether the jumper is 100lbs or 200lbs. The difference is the forces on the lines. Seth I think I got that right! It's flare not flair, brakes not breaks, bridle not bridal, "could NOT care less" not "could care less".