collapsing canopies

[rgoper 0]

marcin:
trust me, that was a bad joke, well, it's not a joke, because it's not funny. i can't believe somone suggested that to you, even in jest. i've had one come unstowed on deployment on a sabre, trust me, it's not at all pleaseant.
Richard
"Gravity Is My Friend"

[DBTECH 0]

I must agree with Dan on this one, as in turbulence/wind shear, the highest airspeed is desired, not only for higher cell pressurization, but for the unknown 'horizontal component' of wind shear, which can cause a stall. A full stall/dive at very low altitude-due to horizontal wind shear, can ruin your day also.
Dave Brownell

[Geoff 0]

Quote

do non cascaded lines make a difference?
yea, double the line drag making the lines the highest source of drag on your canopy.

I was jumping a Cobalt at the weekend, and I couldn't help but notice that some of the lines were not cascaded (I think it was just the centre two A/B lines). Presumably that increases the drag, but it has some other advantage?
Just curious,
Geoff

[Geoff 0]

For what it's worth, PD seem to believe that full-flight is the best approach to turbulence.
They've added an interesting FAQ including this issue to their web site since i last looked.
Geoff

[GroundZero 0]

Now Dan,
Look at a Ground Zero canopy before you make an uninformed comment like you do so often... The HMA line on all Ground Zero canopies is about 35% smaller than spectra or vectran. Less drag = more speed.
No malice intended!
Chris

[mnischalke 0]

Do you have anything to do with the GZ canopies??
If so, when's the RavenMax coming out?
thanks
mike
Black and white are all I see, in my infancy...

[PhreeZone 20]

My question is if the lines are 35% smaller, but there are twice as many of them due to them being non cascaded, is there a real speed increse or is it just marketing?
I want to touch the sky, I want to fly so high ~ Sonique

[mnischalke 0]

Phree,
If you think about it, there wouldn't be twice as many lines on a non-cascaded canopy. Cascaded canopies have just as many lines attached, it's just that some of them are cut off by about 70% (just estimating for that figure). (I am also not doing the trig to figure out how much longer the lines are to form the legs of the triangle at the cascade.) So if 50% of the lines are 70% longer on a non-cascaded canopy, there's actually 35% more lines on the non-cascaded canopy than the cascaded. So, if you reduce the surface area of the non-cascaded lines by 35%, you would be about even.
But wait, I neglected to add in brake lines. If the brake lines are also 35% thinner and my original 70% line ratio factoring was correct, then the non-cascaded canopy would have slightly less total area and therefore be less wind resistant.
mike
Black and white are all I see, in my infancy...

[markbaur 0]

Quote

. . . making the lines the highest source of drag on your canopy.

Under canopy, would your jumpsuit (say, slick freestyle suit vs. baggy freefly suit) make much difference in how fast you could fly?
Mark

[PhreeZone 20]

I can't imagine the barakes are made from the same material size. I know on BigAir Sportz canopys with Vectran brake lines, they use the 1000 lb lines to minimize the possiblilty of breaking on opening. So if they use larger HMA lines on the brakes, it should be the same drag right?
Once again.... is this a real advantage or is it just marketing ticks?
I want to touch the sky, I want to fly so high ~ Sonique

[mnischalke 0]

Well, when you run the well of aerodynamic canopy designs dry, it's always nice to find some other way to make people feel they need to spend more money.
I can't wait until retro is in vogue. I have a great Maverick that needs a little attention. "Dude, I love the chocolate cell."
mike
Black and white are all I see, in my infancy...

[Watcher 0]

I have a Nitron with the HMA lines, and besides the fact that the lines only start to go significantly out of trim enough to need a reline are there and about 800 jumps, my line bulk with double the lines, is still about half of what Spectra lines are, its insane how tiny the lines are.
Jonathan

[Iflyme 0]

Quote

I only have about a 100 jumps on a square canopy so I still have lots to learn... I was using a bigger canopy for a demo type jump.

I'm still curious about doing demo type jumps when you have only 100 jumps under a square... At my DZ you need minimum 500 jumps ...

[freeflir29 0]

"At my DZ you need minimum 500 jumps"
The USPA says a C license for certain types of demos. I think this guy gets a few brownie points for having many round jumps. It's not like he started from scratch. Trust me....if you can put a P/C on a disk you can land a square on a football field.
"I got some beers....Let's Drink em!!!"
Clay

[cobaltdan 0]

on a small canopy, yes your suit will make a difference...
you can see this by flying side by side with someone of similar loading, then experiment, ie. tuck your arms and legs in and watch what happens.
many top swoopers wear skin tight shirts and shorts to get a edge.... additionally many swoop competitors are meticulous about stowing their slider, some rolling them into a pencil like roll, a few even removing them entirely once in full flight.
sincerely,
dan
www.extremefly.com

[apoil 0]

Quote

Look at a Ground Zero canopy before you make an uninformed comment like you do so often... The HMA line on all Ground Zero canopies is about 35% smaller than spectra or vectran. Less drag = more speed.

The Ground Zero canopies also have non-cascading lines.
More lines=more drag=less speed.
The original Nitro compensated for this by making the lines shorter.
The net effect is dependent on a lot of different factors. Some of them may be based on theory at the time of canopy design, but the designs are surely tweaked based on practical experience during the development process.

[weid14 0]

you do know you were responding to Chris Martin.... right?

[freeflir29 0]

"you do know you were responding to Chris Martin.... right"
Who is............
"I got some beers....Let's Drink em!!!"
Clay

[weid14 0]

I believe one of the designers at Precision. I think he knows a little about their canopies

[mnischalke 0]

look up his profile then go to www.aerodynamics.com. compare the addresses.
mike
Black then white are all I see, in my infancy...

[freeflir29 0]

"I believe one of the designers at Precision. I think he knows a little about their canopies"
Well...damn I hope so!!! If he doesn't know about them I'm not buyin one...LOL "I got some beers....Let's Drink em!!!"
Clay

[GroundZero 0]

Let me clarify... line bulk/line surface area/line drag....
The HMA lines used on the Ground Zero canopies have a combined total of approximately 35% less surface area when compared to the next smallest line(set) available (Dynema- the smallest weave spectra available). During prototype testing and during a crucial time (competition), we found ourselves without enough HMA in house to outfit all of our team canopies with the HMA. For cosmetic reasons, after all, we want our guys to look good, we chose to use the next smallest line available (other than HMA). Because of the advantages of the continuous lines and the additional total length required, we had to minimize the diameter (surface area/drag). We chose the next smallest available line ...Dynema... great results, but we knew our final design was better. The total surface area of the HMA lineset, with continuous lines is roughly 35% less than a cascaded lineset built of Dynema. While Dynema is not prolific in sport canopies, it is the next smallest line available.
To get an idea of the drag reduction through the use of HMA, grab any Ground Zero canopy with HMA lines, shove it in the d-bag and start stowing the lines... you'll notice that you'll need smaller rubber bands and need to double wrap to hold that tiny bite. 35% smaller than the NEXT smallest lineset. Even smaller than other linesets!
Yehaa, it's fast!
If you haven't seen HMA, you must search it out... Fast and FUN!
Chris

[mnischalke 0]

Well, you are the master. I was expecting the lines to be slightly less bulk but not the full 35%. Wow!
Now I am starting to think of all the cool applications of HMA.
Hmm, if you put HMA lines on a reserve, might one be able to put a larger reserve in a smaller container? Hmmmm.......
Speaking of reserves, any word on the release of the RavenMax? My 16-year-old raven wants to retire. PM me if you want to keep it a secret. I'd really love to know, and I swear, even under extreme torture, I won't tell a soul.
peace,
mike
Black then white are all I see, in my infancy...

[rainman 0]

I think I need to start with my disclaimer here: I'm a newbie jumper (50 jumps) with no particular knowledge of parachute design.
Most modern kites use dynema lines as well, and I have noticed some properties of dynema that would seem to make it less usable for skydiving:
- Dynema lines have significant stretch (about 3%) when new.
- Dynema lines that are subject to high loadings, tend to go 'stiff'. I don't really know how to explain this, but after flying a kite in high winds for some time, the lines will remain 'stiff' even when they are not loaded.
Out of interest: Do you notice these problems with dynema lines and if yes how do you deal with them?
Ramon

• Quote