Skymonkey13 0 #1 November 24, 2004 Why do some of the old rounds have holes at the top? What is that for? Quote Share this post Link to post Share on other sites
YahooLV 0 #2 November 24, 2004 ...so you can see who dropping in! Seriously, the hole in the top gives the round stability.http://www.curtisglennphotography.com Quote Share this post Link to post Share on other sites
Jib 0 #3 November 24, 2004 to let the air out. Think of a cup overflowing with water. It spills out one side. In a round, as the air spills over, it causes the canopy to swing. The idea of the hole was to let some of the air out to prevent the pendulum effect. -------------------------------------------------- the depth of his depravity sickens me. -- Jerry Falwell, People v. Larry Flynt Quote Share this post Link to post Share on other sites
AggieDave 6 #4 November 24, 2004 Quote Why do some of the old rounds have holes at the top That's a spent casing not a round, a round has a bullet in one end of the casing and they have a primer in the other, no holes.--"When I die, may I be surrounded by scattered chrome and burning gasoline." Quote Share this post Link to post Share on other sites
Zep 0 #5 November 24, 2004 Quote...so you can see who dropping in! Nice one Gone fishing Quote Share this post Link to post Share on other sites
bozo 0 #6 November 24, 2004 QuoteWhy do some of the old rounds have holes at the top? What is that for? On the PC they helped to give it drive. On others.....a hole at the apex kept oscillation to a minimum. bozo Pain is fleeting. Glory lasts forever. Chicks dig scars. Quote Share this post Link to post Share on other sites
Skymonkey13 0 #7 November 24, 2004 Thanks, Jib, and Bozo.And i got a kick out of the other answers too... Quote Share this post Link to post Share on other sites
coconutmonkey 0 #8 November 24, 2004 No, no, no.... he's talking about the good ol' reliable hollowpoints. Better energy transfer by faster expansion. Hearts & Minds 2 to the Heart- 1 to the Mind- Home of the Coconut Lounge, Spa, & Artillery Range Quote Share this post Link to post Share on other sites
AggieDave 6 #9 November 24, 2004 Quote No, no, no.... he's talking about the good ol' reliable hollowpoints. Better energy transfer by faster expansion. Ohhhhhhhhh...ok. My bad.--"When I die, may I be surrounded by scattered chrome and burning gasoline." Quote Share this post Link to post Share on other sites
ernguru 0 #10 November 24, 2004 When I did a round jump (first jump) We were told it was to give forward movement. Quote Share this post Link to post Share on other sites
larsrulz 0 #11 November 24, 2004 I am assuming you are talking about the mesh segments (as opposed to the hole at the appex)...they do give a small amount of forward drive, ~3 mph on the round I jumped. Like others have said, the hole at the appex is because a round without a hole would be terribly unstable (it would constantly vary where it dumps the air from). I got a strong urge to fly, but I got no where to fly to. -PF Quote Share this post Link to post Share on other sites
smiles 0 #12 November 24, 2004 My round reserve (for 10 years) was a four line release design, when I pulled on my handles the lines released and this allowed the back of the canopy to balloon up- giving more forward penetration. The symmetrical canopy without holes opened more reliably......... The first time I was under the army green 26 footer, I had no idea what 4 line release was- I was so impressed with the high speed opening, and was admiring the brand new baby cobra when I yanked on the handles- I though my lines were breaking?? Talk about freaked looking up uncertain if more lines would break................ meanwhile there was enough steer in her to miss landing in a tree... SMiles Quote Share this post Link to post Share on other sites
markd_nscr986 0 #13 November 24, 2004 To make it more aerodynamic......my 28' main also had slots cut out of the back(double L mod) to improve the handling and forward speed....after 200 some odd jumps under it,it's a wonder my knees work at all!Marc SCR 6046 SCS 3004 Quote Share this post Link to post Share on other sites
IanHarrop 42 #14 November 24, 2004 Baby Cobra --- sounds like Niagara Paracutes, Eddie Grimm stuff!"Where troubles melt like lemon drops, away above the chimney tops, that's where you'll find me" Dorothy Quote Share this post Link to post Share on other sites
smiles 0 #15 November 24, 2004 ...exactlypurchased new from Niagara in 1988- may have been one of Eddie Grimm's last. My prized possession saved my ass 2x in 10 yrs. Still on my shelf waiting to be jumped on a hop & pop day SMiles Quote Share this post Link to post Share on other sites
IanHarrop 42 #16 November 24, 2004 Cool I never owned any of Eddie's gear but knew many that did. Had him change out my Capwells for R3s and change the pack opening bands from hooks to dome-snaps on my first rig back in 1976. Those R3s worked like a charm the day I needed them."Where troubles melt like lemon drops, away above the chimney tops, that's where you'll find me" Dorothy Quote Share this post Link to post Share on other sites
matthewcline 0 #17 November 30, 2004 Yes it is to avoid oscilations wich whe nyou land in one hurts like hell! MattAn Instructors first concern is student safety. So, start being safe, first!!! Quote Share this post Link to post Share on other sites
mjosparky 4 #18 November 30, 2004 QuoteWhy do some of the old rounds have holes at the top? What is that for? The hole in the the top is the apex opening. It's size and design help control the opening characteristics of the canopy and can increase the drag coefficient of the canopy. (ie, cats eye apex) It vents high pressure during deployment to prevent damage to the canopy and the load. It has nothing to do with controlling oscillation. This is done by vents in the lower sections of the canopy or by a four line release. A by-product of this a slight forward speed.My idea of a fair fight is clubbing baby seals Quote Share this post Link to post Share on other sites
matthewcline 0 #19 December 1, 2004 on T-10's there are no such lower vents nor 4 line releases. Not that that actually applies to the explanation. the maker said to me (during a few test jumps to work on replacing the current round design for the military) while i was an instructor for the airborne school in Ft. Benning, His explanation was that if the canopy had a solid design (no apex vent) the canpopy would act like a cup full of air, eventually the canopy would have to tilt to relase air as it would start to ride a "bubble" and begin to wobble which would lead to oscilations. It made sense to me at the time as i had 140 + round jumps and had made 5 during the test to that point. But maybe my experience that the maker's explanation only applied to that type of round. The MC-1 (stearable round) has an apex and the rear ports for control. But the apex design is a bit different as it has a skirt that helps to make it smaller. just my experience is all. I am not a maker nor master rigger who has actually studied it in design nor aplication, just a joe who has jumped a few. Blue ones! MattAn Instructors first concern is student safety. So, start being safe, first!!! Quote Share this post Link to post Share on other sites
mjosparky 4 #20 December 1, 2004 You are right that oscillation is caused by a build up of pressure in the canopy. It will tilt to one side, spill air and then the load will swing back the other way and the canopy will spill air on the other side. Unless the apex opening was big enough to allow the same amount of air out through the top as is coming in the bottom you will have a pressure build up. This will vent under the skirt through oscillation. Also the amount of pressure build up will vary with the amount of load so apex opening would have to be changed for each change in load. A round canopy get forward seed by this pressure escaping through steering mod. to the back of the canopy. By closing off the mod. on one side of the canopy more air will escape from the other side, causing the canopy to turn. I hope this helps. SparkyMy idea of a fair fight is clubbing baby seals Quote Share this post Link to post Share on other sites
