airdog07
April 22nd, 2014, 04:38 AM
as the pc becomes bigger, parachute inversion problem starts
"An "inversion" occurs when one skirt of the canopy blows between the suspension lines on the opposite side of the parachute and then catches air. That portion then forms a secondary lobe with the canopy inverted. The secondary lobe grows until the canopy turns completely inside out."
so not too may people use 52" and over pc any more, also for throw and go it is not practical because it take too long to open, bigger the pc you need more speed (fall rate) to properly open with out causing hesitation. if you going to use 52,58, have vent at the apex.
"Parachute stability and venting
Usually parachutes will swing wildly because of the air spilling from alternating sides of thecanopy. This swinging can be reduced by cutting a hole at the parachute's apex, or altogethereliminated by cutting a large number of holes all over the canopy. But remember that addingvents will increase the descent speed. In the case of apex venting, the area of the apex hole shouldbe about 1 to 10 percent of the parachute's flat surface area, depending of the desired trade-offbetween a slower descent speed and improved stability. Remember, the larger the hole, the fasterthe descent speed, since the value of the drag coefficient CD will decrease in the process."
normaly you only need PC of 36",38",42" and 46". now vent or not to vent for another discussion.
I like 42" vented zp. there nice.
there is no reason to have 32",34". to slow down the opening just a couple inch is not going to make difference, instead use modified slider, roll the nose tight as you can use clamps to keep it that way.
the OSP is for slider down because of short line set. that's why it open fast, and slam you for terminal opening. you only need to have few hard opening for your body to cause pain, in long run (five,ten, twenty years)bad back,neck. you well never be same again.
2061
https://www.youtube.com/watch?v=nciajWdFd9c
I have use 36" for eiger, 36" for 3-4 sec. jump, should you do it no.
I jump in wind the you should never jump in,
we do some stupid things you can get away with it so many time's, but it well catch up with you. you well pay in the end.
http://www.wpi.edu/Pubs/E-project/Available/E-project-042407-112440/unrestricted/Brighenti_Duffen_Head_Vented_Parachutes_MQP.pdf
Aerodynamic Decelerator Systems (http://www.aerodecelerator.org/DOC_ARCHIVE.htm)
"An "inversion" occurs when one skirt of the canopy blows between the suspension lines on the opposite side of the parachute and then catches air. That portion then forms a secondary lobe with the canopy inverted. The secondary lobe grows until the canopy turns completely inside out."
so not too may people use 52" and over pc any more, also for throw and go it is not practical because it take too long to open, bigger the pc you need more speed (fall rate) to properly open with out causing hesitation. if you going to use 52,58, have vent at the apex.
"Parachute stability and venting
Usually parachutes will swing wildly because of the air spilling from alternating sides of thecanopy. This swinging can be reduced by cutting a hole at the parachute's apex, or altogethereliminated by cutting a large number of holes all over the canopy. But remember that addingvents will increase the descent speed. In the case of apex venting, the area of the apex hole shouldbe about 1 to 10 percent of the parachute's flat surface area, depending of the desired trade-offbetween a slower descent speed and improved stability. Remember, the larger the hole, the fasterthe descent speed, since the value of the drag coefficient CD will decrease in the process."
normaly you only need PC of 36",38",42" and 46". now vent or not to vent for another discussion.
I like 42" vented zp. there nice.
there is no reason to have 32",34". to slow down the opening just a couple inch is not going to make difference, instead use modified slider, roll the nose tight as you can use clamps to keep it that way.
the OSP is for slider down because of short line set. that's why it open fast, and slam you for terminal opening. you only need to have few hard opening for your body to cause pain, in long run (five,ten, twenty years)bad back,neck. you well never be same again.
2061
https://www.youtube.com/watch?v=nciajWdFd9c
I have use 36" for eiger, 36" for 3-4 sec. jump, should you do it no.
I jump in wind the you should never jump in,
we do some stupid things you can get away with it so many time's, but it well catch up with you. you well pay in the end.
http://www.wpi.edu/Pubs/E-project/Available/E-project-042407-112440/unrestricted/Brighenti_Duffen_Head_Vented_Parachutes_MQP.pdf
Aerodynamic Decelerator Systems (http://www.aerodecelerator.org/DOC_ARCHIVE.htm)