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Airman1270

Why Downsize?

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I don't hear you really disagreeing with me on the technical side, and on the safety issue we are in full agreement.

Jacques

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>>1. A smaller canopy is more stable in turbulent/gusty conditions

Stable how? As for being 'blown around', no they are not. You feel turbulence much more under a smaller canopy and if you're not 'on top of it' in your corrections the situation can deteriorate in a hurry.

>>2. A smaller canopy gives better wind penetration

But we should be getting out upwind anyway....right?

>>3. A smaller canopy is easier to pack

I'll bet there is a new jumper out there struggling with their first ZP that would disagree. (I don't don't think this outweighs the safety aspects.)

>>4. A smaller canopy allows a smaller container which makes you more aerodynamic in freefall

Again, I don't know if this really outweighs the safety considerations.

>>5. A smaller canopy gives more speed and thus potentially better landings

Something I hear quite often but I will not promote it. The trick to landing is achieving that descent rate of zero and then placing your feet down to start the weight transfer from your harness to your feet. With a low WL this zero descent rate lasts only a short time. I will agree, it is a little harder to judge because it may only last a half-second. With the extra speed on a highly loaded parachute, this zero descent rate lasts a little longer, giving us more time to adjust and put our feet down. Less of a chance of us placing our feet before or after that 'window' of zero descent.

I have to give this boring explanation because this same comment is made to justify low turns. "I have to make a low turn, it makes the landings better." Bull...all that tells me is I'm looking at someone who doesn't have a full understanding of what's happening.

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>>1. A smaller canopy is more stable in turbulent/gusty conditions

Stable how? As for being 'blown around', no they are not. You feel turbulence much more under a smaller canopy and if you're not 'on top of it' in your corrections the situation can deteriorate in a hurry.



At least my old Sabre-170 was terrible in the slightest bit of turbulence. It was jumping all over the place where others almost hadn't noticed any turbulence at all and I choose to stay on ground a lot more with it than I feel I have to do with my Safire2-139. With the safire, it takes a lot more turbulence to affect the canopy to the same degree. I believe it is due to its higher speed, thus both penetrating the turbulent areas faster and keeping a higher pressure in the canopy.

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>>1. A smaller canopy is more stable in turbulent/gusty conditions

Stable how? As for being 'blown around', no they are not. You feel turbulence much more under a smaller canopy and if you're not 'on top of it' in your corrections the situation can deteriorate in a hurry.



At least my old Sabre-170 was terrible in the slightest bit of turbulence. It was jumping all over the place where others almost hadn't noticed any turbulence at all and I choose to stay on ground a lot more with it than I feel I have to do with my Safire2-139. With the safire, it takes a lot more turbulence to affect the canopy to the same degree. I believe it is due to its higher speed, thus both penetrating the turbulent areas faster and keeping a higher pressure in the canopy.



We have had much different experiences and there are any number of reasons for that.

I flew a Raven III (249 sq ft 7-cell) as a main for my first 300 jumps. It was a 0.8:1 wing loading and I never had any any problems with turbulence that couldn't be traced to my own mistakes. Never did I sit out a load as long as we were jumping. In fact as I started downsizing, I spent more time sitting out loads because I didn't care for the 'twitchy' feeling from turbulence.

Higher internal pressure can possibly make the canopy less pron to 'collapse', but it does not make the canopy more stable in regards to being pushed around. Smaller canopies react more radically to input. That input can be induced by the pilot or turbulence. Hence, as wing-loading increases, the same amount of turbulence would have a more pronounced affect on the canopy. Requiring that much more skill on the pilot's part.

There is also the idea that what once used to feel like 'radical' turbulence now does not feel all that radical. It becomes a matter of what you're used to. The most dramatic example I've felt of this is when I used to stall my canopies to the point of a 'horseshoe'. It used to feel insane and scary. Of course as I've downsized I haven't been able to do that as much. But after flying a Jedi and Velocity for so long stalling a larger canopy to that level doesn't feel bad at all. And that's experiencing a total collapse!

I guess my point in this is that there really is no good reason for downsizing if you're looking at it from a safety perspective. History backs this up. We go on and on about canopy collapses, backing up, and why we 'need' higher wing loadings. If this were true, why were their virtually no landing fatalities during the eighties?
"Any language where the unassuming word fly signifies an annoying insect, a means of travel, and a critical part of a gentleman's apparel is clearly asking to be mangled."

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I fly a 240 navigator. My exit weight is about 235lbs. I have 89 jumps. I'm happy with it and since I began the sport at 40, I am very conservative. As far as ribbing, it is constant I am called the "Sky Barge". I just take it in stride. I even had a hat made up with the nickname that I wear to the DZ. I'll downsize when I'm ready to do so safely.

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I'd like to ask a question here, being a noob, it might sound dumb. In the course of this thread, I've seen references to wind penetration, flight (air) speed and ease of control.

I'm conteplating that first rig and I want to stay conservative for quite a while (old bones heal slowly). I was thinking the PD Sabre2 (230) aspect ratio 2.58:1, PD Spectre (same size) ar 2.14:1, and PD Navigator (220) ar 2.52:1. I weigh in at 185 sans rig. All of these should put my wl at under 1:1.

The questions-
1) How does aspect ratio affect the handling?
2) How much of an effect does line material choice make? Dacron v others

Sorry for the thread drift, I couldn't find out quite what I wanted to know through Search.

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1) How does aspect ratio affect the handling?

In sport parachutes, we're talking fairly small differences in AR. The number of cells, and shape (elliptical/rectangle) all help determine the AR of a ram-air wing.
Basically the higher aspect ratio (AR) a wing has, the more lift it will produce for a given angle of attack. But the high AR wing will stall at a lower AoA. Of course, the greater the difference in in AR the more noticable the effects become.
A high AR parachute will tend to have a flatter glide than a low AR parachute because of the reduced 'induced' drag. Turns tend to 'dive' a bit more with a high AR wing also.
The low AR wing is good for 'sinking' into a tight area because of it's ability to handle a high AoA without stalling. This is why a lightly loaded 7-cell is desirable when landing in a tight area. (Remember, 'stall speed' has much to do with wingloading also.) In flying low AR designs I've always thought they feel more like they 'pivot' through a turn rather than dive.

2) How much of an effect does line material choice make? Dacron v others

I think the main reason for moving from Dacron to spectra and vectran was mainly to reduce 'parasite' drag and pack volume. If you're talking purely canopy performance, spectra or vectran offers less drag. This type of drag increases with speed. 2Xairspeed = 4Xparasite drag. So you are only going to see the benefits on higher-loaded canopies. Or rather, the faster your canopy, the more effect it will have.
Spectra, or 'microline' was found to shrink over time and the canopy would become out of trim. This affected openings and flying characteristics. Again, becoming more important as wing-loading increases.
In short, spectra or vectran offer less drag. But be sure you replace them when needed......which would go for Dacron too.
"Any language where the unassuming word fly signifies an annoying insect, a means of travel, and a critical part of a gentleman's apparel is clearly asking to be mangled."

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well, I'm still kicking it with a pilot 210 @ 1,05 :)
While I know I'm up for a handkerchief 97 sqft stiletto @ 61 jumps and swooping mr. hookitlow senseless, I'll just stick with the 210 for a while.

When I see some of the long timers at my dz and the movies on skydivingmovies.com, I know that at thing point I know just enough to get down gracefully (most of the time).

So much skill left to learn, thats why I like the sport (and also finally some ppl around that also fell on their heads as babies) and intend to keep doing it for a long long time. So whats the rush?

Definitely NOT a sport where overconfidence is an asset. (so i hope hookit is either a troll or has never actually jumped but stumbled onto this forum by accident hehe)



I like hearign that

I wish I had taken the you have the rest of your life to skydive lesson to heart

Dave
http://www.skyjunky.com

CSpenceFLY - I can't believe the number of people willing to bet their life on someone else doing the right thing.

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What do the experienced jumpers think about those canopies I've listed for a novice/student that will be about 210 out the door?



Depends. What kind of canopy are you jumping as a student?
"Any language where the unassuming word fly signifies an annoying insect, a means of travel, and a critical part of a gentleman's apparel is clearly asking to be mangled."

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