|
|
|
|
ozjunkie
Jun 11, 2012, 11:46 PM
Post #1 of 8
(2453 views)
Shortcut
Registered: Jun 11, 2012
Posts: 3
|
|
Drag vs Opening Height?
|
Can't Post
|
|
the situation i'm talking about is a 2000ft hill with a 350ft cliff at the top and a long flight to the landing area. I have jumped it with a 48 to get my 277 out fast and maximize altitude for the long flight to the LZ. or...? i know a 42 will get the canopy out no worries but sacrificing a little more height and gaining distance with less drag. At what point does drag and altitude cross and one becomes more beneficial than the other? I hope this question makes sense to someone, i'm finding it difficult to put into words. there would be an exact equation for what i'm trying to work out, but has anyone figured it out? assume wind is zero and not a variable.
|
|
|
|
|
possibility
Jun 12, 2012, 1:18 AM
Post #2 of 8
(2415 views)
Shortcut
Registered: Sep 6, 2011
Posts: 3
|
|
Re: [ozjunkie] Drag vs Opening Height?
[In reply to]
|
Can't Post
|
|
As I understand, the equation has 1 variable (pilot chute), which influences 2 factors: Opening height and glide ratio of your chute.
For this, you have to find out how much faster (in ft) your 48 will open your canopy and what GRs your canopy will have with the chutes. (you have to find this out for your own canopy)
Then you can calculate your possible horizontal distance after opening at canopy:
opening altitude with 48" (e.g. 1900) - 1/GR (e.g. 1/3x) = 0
x= 1900/1*3 = 5700ft possible horizontal distance
open altitude with 42" (e.g. 1850) - 1/GR (e.g. 3,2x)=0
x=1850/1*3,2 = 5920ft possible horizontal distance
|
|
|
|
|
ozjunkie
Jun 12, 2012, 4:23 AM
Post #3 of 8
(2368 views)
Shortcut
Registered: Jun 11, 2012
Posts: 3
|
|
Re: [possibility] Drag vs Opening Height?
[In reply to]
|
Can't Post
|
|
hey possibility, i really like your answer and i'll try to calculate. but getting accurate glide distance and opening height measurements will be very difficult. but again great answer and thanks. does anyone have a rough answer based on personal experience? i think because the LZ is small i might have to measure height i reach over the LZ? usually with a 48 i have about 400ft to spare at the LZ. and record opening height. i guess it's time to run a 42 and see what height i have at opening and at LZ... I'll try and do the calculations as accurately as possible and and post them up. horizontal distance can be calculated on a map. any more thoughts? Thanks.
|
|
|
|
|
RiggerLee
Jun 12, 2012, 7:33 AM
Post #4 of 8
(2291 views)
Shortcut
Registered: Dec 12, 2005
Posts: 521
|
|
Re: [ozjunkie] Drag vs Opening Height?
[In reply to]
|
Can't Post
|
|
Have you ever thought about useing a "choaker flap" or some equivelent?
Setting that aside I think you have more then enough altitude that the glide will make up for the small loss of opening distance and make sure you remove your slider rather then just tieing it down.
Lee
|
|
|
|
|
GreenMachine
Jun 13, 2012, 6:04 AM
Post #6 of 8
(2124 views)
Shortcut
Registered: Jan 24, 2003
Posts: 3466
|
Disclaimer:
I have never done these two togther,
as in type of jump and type of flying,
but have done each seperately many,
many times and would like to share
my thoughts so someone with more
experience can bless or correct them
of course douche bags/bored buddies
are welcome to throw one liners for fun.
Use a 42" vented PC, newer the better,
definitely take slider off, once open
loosen the chest strap, then unstow
the brakes, sit with legs closed in the
harness, wear slick clothing, try to be
light, as in piss and shit before but do
not eat or drink a bunch before jump.
The best route from opening point to the
landing area is not always a straight line.
For example:
In ITW you exit a bowl and have a long
haul to the LZ, one day there was wind
coming down the valley so I aimed into
the wind slightly and crabbed to the LZ
with much more altitude than most of
the tracksuiters on that load.
Well I guess the line of flight in space
was straight just not the vector that a
novice might naturally choose...
|
|
|
|
|
GreenMachine
Jun 14, 2012, 6:49 AM
Post #8 of 8
(1978 views)
Shortcut
Registered: Jan 24, 2003
Posts: 3466
|
Prime the pins, open pin cover, open riser covers,
if possible route the bridle to the bottom pin then
the top pin IF a. you are deploying handheld and
b. this practice is compatible on your rig.
Please Note: most of this does little good but in
my opinion it does zero bad for getting a quick
go & throw to open and fly straight.
|
|
|
|
|
