How much of an impact does wingloading affect snivel rate?

[regulator 0]

I have been pondering a question since I've gotten current and wanted a little clarification. I am 5'11 and weigh approximately 155 lbs. I jump a Sabre 2 190 wingloaded at approximately .97. I have been doing some simple tracking jumps recently to maintain my currency and the last 5 jumps I had, I have pulled at 4,000. Whenever I refer to my altitrack to log my jumps it shows me in the saddle at approximately 3,850. I asked another experienced jumper about this and he told me if that was accurate then the opening would have completely rocked my world. So its possible that since I wave off at 4,500 I could have pulled slightly higher than 4,000. But even if that did happen it seems that the snivel rate is still short OR my altitrack isn't accurate determining when I am in the saddle accurately. So it brings me to this question: Is your snivel rate shortened by your wingloading, or more of the characteristics purported by the canopy design, or possibly a combination of both of these attributes? And if I do encounter a 500 foot snivel why would my altitrack show it was at approximately 150 feet?

[AggieDave 6]

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And if I do encounter a 500 foot snivel why would my altitrack show it was at approximately 150 feet?

The instruments you're using to determine 150ft aren't exactly accurate and more importantly, they're not accurate to each other. A good example is back when speed skydiving was trendy, people figured out that they could fool a pro-track's speed to a higher speed by kicking their feet quickly (when it was attached to their ankle).

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[regulator 0]

Ok so the Altitrack aside...if two jumpers are jumping the same canopy and one is loaded at 1.0 and the other is at 1.5 the snivel for the person at the heavier wingloading should have a longer snivel correct?

[beowulf 1]

That isn't a good comparison, because the snival would depend on more then just wing loading. It also depends on how the canopy was packed and the design of the canopy also to a small degree the body position of the person. Pulling in a track would make a difference.

[davelepka 4]

No, that's not it. WL is not a determinate of opening speed. Canopy design, slider size, packing methods and airspeed at deployment will effect the opening speed.

[shropshire 0]

I'm not sure that 'wing loading' is the right factor (after all the wing isn't open so the air doesn't 'know' how big it's going to finally be once it's inflated.

(.)Y(.)
Chivalry is not dead; it only sleeps for want of work to do. - Jerome K Jerome

[beowulf 1]

I would think wingloading would be a minor factor in how long it takes for the parachute complete the opening process. The major factors would most likely be how the canopy was packed and the size of the slider (as a prevous poster pointed out.)

I don't know why this person really cares so much about the snivel? If it's too slow I could see that being a problem, but if it's fast and it's not hurting then I would consider that to be a good thing.

[chutem 0]

To make it a simple comparison how about if the op jumped his canopy at his .97 wingloading. Then packed it identically and jumped again with 75lbs of lead strapped to him and opened with the same body position. Taking randomness out of the equation do either of the jumps have a quicker opening/shorter snivel?

James

[regulator 0]

I'm not complaining trust me. But lets say your point is accurate and I'm deploying in a track. Could that lessen the altitude I burn from throwing the PC to being in the saddle enough to get a 150 foot snivel that doesn't hurt?

[riggerrob 643]

Usually, heavier wing-loadings mean harder openings, IF you are comparing identical, brand-new canopies with exactly the same pilot chutes, d-bags, etc.
... BUT .. there are so many other variables.

For example, I know that heavily-loaded tandems open much harder than lightly-loaded tandems, BUT that is mainly because heavy tandems start the opening sequence going 20 or 30 miles per hour faster. I can hear the speed difference with my eyes closed and no instruments.

[beowulf 1]

On wing suit jumps that I have done it appeared to me that I had less vertical altitude lost then on a non wing suit jump. It felt like I was thrown forward and the canopy was opening a little more horizontally then normal then I would swing back under the canopy. I never botherd to look for any data to back this up with, it wasn't something that I cared about.

[regulator 0]

I suppose the reason this question has been brought up is because I read that most Sabre 2's have 500-800 feet of snivel and was trying to figure out if the devices I am using to determine my snivel are inaccurate or if there is another factor that could be leading to such a short snivel. Thanks for any input you have provided.

[pchapman 279]

I have a theory of what was happening to you. While I've got some evidence, I'm not sure if it applies in your case.

I've got a Protrack & the Jumptrack software. It tends to sense that the jump is over when the last 6 seconds of averaged speed (which is what it uses) is dropping fast through 60-85 mph. It varies a lot, so I'm not sure what criteria it is looking at.

If I do a good track, I, being light & skinny and a decent tracker, can get down to 80-90 mph easily on a sustained track. So the Protrack doesn't see a lot of speed reduction before it "clocks out" . Therefore on the graphs it may show only a few hundred feet between the first deceleration and when it marks the opening -- despite me having a small crossbraced canopy that has a reasonable modern snivel.

So this might be part of the reason. I don't know whether the Altitrack really measures things differently, or whether your track is good enough at your jump numbers.

Also, if you do have a good long sustained track with a slower vertical speed, you'll lose less distance anyway. How much you've actually slowed down is another matter. On a simple mathematical basis, when decelerating, a given percentage reduction in initial speed will result in a greater percentage reduction in distance.

You can also start comparing the altitude you see on your alti immediately after opening to what the "opening" readout is later seen to be.

[darthur2000 0]

Wingloading, not so much, design, packing etc., yes. I think you'd have to work very hard to consistantly have your main open as fast or faster then your reserve would. (Your reserve is designed, tested and packed to consistently open in 300' or less.) And although I only have one terminal velocity opening on a reserve (took 200'), yeah somthing opening that fast will spank your ass hard and you will know it (but when you're blowing through 2k with a bag lock, you'll be happy for the spanking).

[regulator 0]

Well I'm sure that just about anybody with higher jump number could out track me anyday. But I have been using some advice my instructors gave me when I was first learning how to track... and that is to roll your shoulders forward which should flatten your body and help out with my tracking. I appreciate the assistance.

[virgin-burner 1]

all o' u guys just suck..

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