Jan 7, 2002, 9:04 AM
Post #1 of 14
I just purchased a Hornet 190. I jumped it 3 times (4000,7500,9500). On the terminal velocity dives, it took about 800' and around 1000' on the subterminal hop 'n pop. The openings are soft and pleasant. My question is if there is a problem with slow openings. On the higher jumps, I'm fine and appreciate the slow and comfortable inflation. On the hop 'n pop, I started getting nervous when it was taking so long knowing I was already low enough to pull when I left the plane. At what point should I consider changing the packing style to speed up the opening? I don't want to lose the soft opening, but I also want enough altitude to make a decision if I have to cut away.
I'm not doubting what your saying, but a bit curious: it took about 1000 foot on a hop and pop?
quick rule of thumbs maths: for freefall, you get to terminal velocity in about 12 sec and it takes about 1000 (more or less) feet (bare with me on the roughness of the estimates). Considering you will never reach term velocity on a hop and pop, 12 sec to 1000 is a worst case. Are you sure it took more then 12 seconds for the canopy to open?
I may be slightly off, but I'm talking about distance to a fully inflated canopy (ready to fly) from the time I threw out. The time was definitely longer and distance further for a full inflation on the hop n pop.
Personally.....I don't worry about it. I can tell long before I get full inflation that my canopy is good. As soon as it's out of the bag I can see the lines. Unless I have a cell blow out (fairly unlikely) It only takes about 1-2 secs from the time I let go of the P/C before I can make a determination. Also, be aware that on Hop N Pops you are not at terminal speeds so you can move your decision alti a little lower than usual. If I got out at 2,500 I have 1,000 ft to deploy before I cut it away. That should be enough for ANY canopy.
The longest I've ever had a hop and pop take even on my old Spectre was just under 500 from toss. My current Cobalt opens in about 400 on subterminal openings and 600 at terminal.
Canopies open a bit different subterminal then they do terminal, but I can't imagine any canopy taking more time subterminal then terminal. Did the canopy snivel in the subterminal opening, or did it go to a normal opening sequence? If you took a 2 second delay you have fallen about 75 feet, then a toss and bag extraction should put you at more then 150 feet. The opening should be fairly quick since your body has not accelerated to terminal yet.
It was pointed out to me earlier this year what most people percieve to be 800-1000 foot openings are more like 500-600. Your altimeter is constantly playing catchup in freefall and under canopy it is able to fully catch up. It might be showing 3500 when you are really at 3250 and if you use that (3500) as what you start the measurement at, then have a full canopy at 2500, you think that its a 1000 opening ,but its really only a 750. You also have reaction time to figure in to the opening of a canopy. If you release the PC when you hit say 3500, by the time you actually react, you are at 3400 and that coupled with the slower reaction time at the bottom end of the opening distort the jumpers perception of a opening. The best determinate is to use a portable airspeed calculator to figure the real distance.
I want to touch the sky, I want to fly so high ~ Sonique
Why do you think a canopy will not open slower at subterminal speeds. The canopy will open slower on a hop in pop if the plane is flying slowly as well. Remeber the air has to pull the canopy out and inflate it. If you have less air going by per second it will take longer for the canopy to inflate.
The freefall calculator and audible was going to be my next purchase. You must be psychic. I'm sure most of it is perception and reaction time. I was simply estimating from what I saw. It didn't appear to be a snivel, just a slower sequence (At least it felt that way).
If you're not having fun, what's the point
billvon (D 16479)
Jan 7, 2002, 10:33 AM
Post #8 of 14
>Canopies open a bit different subterminal then they do terminal, but I can't >imagine any canopy taking more time subterminal then terminal.
This is pretty common. Just about any canopy will take longer to open when subterminal. Note that since you're also going slower to begin with, that longer time may not equate to a longer distance - 10 seconds at an average speed of 50fps is still a shorter distance than 5 seconds at 200fps.
>The opening should be fairly quick since your body has not accelerated to terminal yet.
Canopy reefing and deployment systems are designed to operate at 120mph. At 40mph (speed after 2 second delay) the PC will launch more slowly, pull the bag out more slowly, and the canopy will inflate more slowly. It's been my experience that even the slider comes down more slowly.
So do you pack any differently for a hop 'n pop knowing that it will take longer and bring you closer to a decision altitude?
Sure. If you do not have much experience packing, ask some of the staff riggers or packers at the DZ to give you some pointers about how to speed up, or slow down openings. I am a firm believer that beer was invented so skydivers would hang around the DZ while not jumping and pick each others' brains. You'll also get plenty of advice on this forum, just be sure to check it all out!
>So do you pack any differently for a hop 'n pop knowing that it will take > longer and bring you closer to a decision altitude?
You can but you don't have to. Usually I don't, unless I'm jumping something strange (like a canopy that I just worked on, and I'm not sure how it will open.) Keep in mind that a 10 second opening from 3000 feet puts you at about 2200 feet, still enough time to recognize a problem. To most skydivers, a 10 second opening is forever.
OTOH it can be a great way to try different pack jobs, because it's almost impossible to really "slam" yourself when you're subterminal. Since everything happens a little slower you can actually see the stages of deployment if you look.