collapsable sliders.

[jtval 0]

i know some of the effects of a collapsable slider. but how does it effect the canopy ride? i believe it makes the ride more maneuverable. but what about speed,flare, landing?
have fun, live free, SKYDIVE
JT

[RemiAndKaren 0]

Hi JT,
I think it ONLY affect the canopy ride (as long as you dont forget to un-collapse it when u pack...)
There's 3 things I can think of that this does:
1- reduces drag (so more horizontal speed hence more lift)(wow.. I used hence!)
2- reduces canopy "flutter": next time you see a canopy land with an slidder not collapsed, look at the stab of the canopy, they'll be flapping about, and that has to increase drag
3- if you lower the slider to behind your head, it will let the risers open widder, giving the canopy a flatter shape making it fly more efficiently; if on top of that you put some slack in your chest strap, you'll really let your canopy fly its best
the end result is reducing drag, alot, which will give you more horizontal speed and more lift

[jtval 0]

hey R&K
that was more then i thought thanks for the knowledge.
"more input, need more input"--johnny 5
have fun, live free, SKYDIVE
JT

[DBTECH 0]

The reduction in parasitic drag with a collapsed/stowed slider is a very-very small percentage of the total drag, both parasitic and inducted.
Show me the "measured difference" in forward airspeed with the slider left alone, vrs it being totality collapsed/stowed.
Dave Brownell

[alan 1]

"Show me the "measured difference" in forward airspeed with the slider left alone, vrs it being totality collapsed/stowed."
Depends on the class of canopy you are flying. On a 7 cell loaded at 1.1, the only real effect stowing the slider has, other than reducing wear on the slider itself and suspension lines inside the grommets is aestetic, ie. better view and less noise from it flapping.
On a VX loaded at 2.4, stowing the slider improves the speed and performance of the canopy and it is recommended by the manufacturer.
Most jumpers fall somewhere in between where performance is not a major factor but every little bit is nice and the quieter ride is appreciated. Parasitic and induced drag are concepts that have little meaning to most recreational pilots. If you want to get an idea of how much drag the slider can cause, find one that is laying around the DZ, tie a 4' piece of rope accross each pair of the outside grommets. Hold the pieces of rope in the middle and stand in back of a truck as it accellerates to canopy flight speed. See how difficult it is to hang onto at 15, 20, 25, 30, 35, and 40 mph. Those are typical sport canopy speeds. IF you want to see the effect it can have on a VX class canopy, try it at 60 or 70 mph. Next, try it with the slider collapsed (draw string(s) or velcro). Be prepared to let it it go during all of these very un-scientific tests. A safety harness would also be a good idea.
The change in airspeed on most recreational canopies may only be 2-3 mph or less, depending on if you are in normal flight or executing a high speed diving turn. As you move up the spectrum in canopy performance and speed, the difference is greater. You won't see any blade swoopers leaving the slider unstowed.
A collapsible pc will probably do more to improve performance, but combine the pc and the slider, most recreational pilots will benefit from the improvement on all but the biggest and slowest of canopies.
alan

[DBTECH 0]

Alan said>
>The change in airspeed on most recreational canopies MAY ONLY BE 2-3 mph or less,---
DB> As asked before--"Show me the "MEASURED DIFFERENCE" in forward airspeed with the slider left alone, vrs it being totality collapsed/stowed."
"Beware of the "PLACEBO EFFECT" in all claims of better performance."
Dave Brownell

[alan 1]

"DB> As asked before--"Show me the "MEASURED DIFFERENCE" in forward airspeed with the slider left alone, vrs it being totality collapsed/stowed.""
So far on my 89 VX at 2.4+ it has been about 6mph slower with the slider unstowed based on radar gun readings during my landing approach. That is nearly 10% slower.
alan

[weid14 0]

check it out - a measured difference. Now if you could only do something about slider rebound

• Quote

[DBTECH 0]

Alan said--
So far on my 89 VX at 2.4+ it has been about 6mph slower with the slider un stowed based on radar gun readings during my landing approach. That is nearly 10% slower.
DB> I could maybe buy into a number "approaching" an 8% loss in airspeed with a VX with the slider not collapsed/stowed, but radar gun readings are not IAS or true airspeed, but are in fact ground based readings subject to errors brought about from wind/wind shear conditions, which are different on every jump.
Let's see numbers with an actual "air speed indicator" that has good "confirmed resolution" in one MPH increments. Model/conditions--- Toggles up--stabilized flight-- slider not collapsed, then with slider
collapsed/stowed. (comparisons done with no change in the body shape/position--drag coefficient of the jumper)
Dave Brownell

[mikefarmer 0]

Quote

Let's see numbers with an actual "air speed indicator" that has good "confirmed resolution" in one MPH increments.

Bored much? Go jump.
Mike

[jtval 0]

i collapsed my slider this weekend. it was cool. not much of a change(i am on a big,low loaded main) but enough to know that there was a change in flight.
Have Fun, live free, SKYDIVE!!!
JT

[DBTECH 0]

Jtval said--
I collapsed my slider this weekend. it was cool. not much of a change (i am on a big,low loaded main)
but enough to know that there was a change in flight.
DB> Sounds like a classic case of the "placebo effect" in action.
Dave Brownell

[jfields 0]

It might be a "placebo effect". I don't know or care, as long as it stops the stupid flapping noise behind my head. Justin
"If it can't kill you, it isn't worth doing."

[DBTECH 0]

Justin said
It might be a "placebo effect". I don't know or care, as long as it stops the stupid flapping noise behind my head. DB> I'll second that big time, with two thumbs up ^^ Dave Brownell

[SkymonkeyONE 4]

In response to: "I don't know or care, as long as it stops the stupid flapping noise behind my head."
Ahem.. Slida-Flappida is a disease only YOU can cure.
Dave, enough with the negative vibes, Moriarty! LOL! I don't need an airspeed indicator to "prove" to you that collapsing my slider, pulling it down, and having a kill-line pilot chute do wonders to increase my performance. It just DOES. All that stuff adds TONS of parasitic drag if not properly stowed. Those of us who fly heavilly loaded elipticals right up to the posted maximum exit weight must use every trick in the book to get the cleanest landing possible.
Chuck

[jfields 0]

Quote

In response to: "I don't know or care, as long as it stops the stupid flapping noise behind my head."
Ahem.. Slida-Flappida is a disease only YOU can cure.

I suppose I wasn't clear. When I said that, what I meant by "it stops" was really "my collapsing my slider stops", which I do.
Now that I've cured my case of Slida-Flappida, I just need to work on my Slida-OnMyAssa when I land.Justin
"If it can't kill you, it isn't worth doing."

[DBTECH 0]

I will agree with your "highly loaded scenario," as the "ratio" of induced drag to parasitic drag is much higher, as apposed to lower airspeeds with much less parasitic drag with similar or higher induced drag.
Let's face it, the drag on a 28" PC could easily be 30 lbs at 60 MPH. A non collapsed slider on the other hand--hard call??
BTW: The parasitic drag of your body under canopy at 60 MPH forward speed is about 25% of your body weight!
BTW-again--not negative vibes, but I'm always in this mode--
"Always Question the Validity of the Obvious"
Skies,
Dave Brownell
DB Tech

[DZBone 0]

Here's another take: when I was demoing gear this weekend, the guy in the shop asked me to make sure to collapse the slider, as it reduced the wear on it.
I guess that if you are spending too much on worn-out sliders, you should be more cognizant of collapsing it.
Carl