How much does slider size actually affect openings?

[JakeByTheOcean 0]

I recently started jumping a Safire 2 189, and it snivels for a long time. On my last jump, I pitched at 4500' and it wasn't fully open until 2900'. I have read that this kind of canopy can snivel for a bit, but I'm wondering if using a smaller slider would help with quicker openings. The current slider I'm using is pretty huge, and I have ordered a smaller one from Icarus in the hopes that my openings won't take so long and make me clutch the cutaway handle.

Will using a smaller slider help with quicker openings? How much of this depends on the slider, and how much depends on the canopy? I'd rather not have to change my packing technique, but I will if there are no more options left. Thanks in advance.

[Justincblount 4]

For me, that's too much altitude loss as well. Yes, a smaller slider affects opening speed, but if you are unclear on the equipment specs, I hope you relied on a rigger for ordering the slider. It's not always the slider. I jumped some student canopies in Z-hillls that a few of us complained about, they all went in for re-lines. But that depends how hard it has been jumped. There are definitely things you can do in packing... like, if people taught you to do anything to the nose when you wrap the tail around, that encourages sniveling. But talk to a good instructor, there are also things you can do under a sniveling canopy to encourage it to open.

[Cloggy 1]

Just ordering a smaller slider in the hope it will fix your problems, are you serious? 

I hope you did some more research than just 'reading' on the internet and did actually ask the people around you for advice?

-The packing could be the only thing you need to fix; review your packing technique with an experienced skydiver or have it packed by somebody else to compare openings.

-Did you discuss the slider size with a rigger or Icarus: how do you know this one is 'huge' or too large for your canopy? The manufacturer designs it to a particular size for a reason. And is the smaller slider appropriate for your canopy size and W/L? I bet a smaller slider opens faster, but you could be in for a painful surprise as well.

Edited May 3, 2019 by Cloggy

[betzilla 56]

It does make a difference - sometimes a significant one. First step would be to reach out to Icarus (j@icarusworld.net) and find out if you've got the factory-size slider or some other goofy thing (you never know what you're really getting when you buy used gear - people make all kinds of modifications and maybe the previous owner of your canopy wanted slower openings for whatever reason. who knows?), and go from there. J is quite responsive - you'll probably hear back from him right away.

Good luck!

[RiggerLee 61]

I don't really understand your post. If you want to alter the openings of the canopy your packing technique is by far the easiest thing to change. Is this a new canopy or used? The first thing I would check is the line specs, particularly the break lines. Could it have been built with the wrong break lines? Did some one replace them between relines? Altering the break set depth is the next easiest way to alter the openings. The slider is the third option. How big is it supposed to be? Was it assembled with the wrong slider? Did some one, perhaps of a different weight or tracking habits change it out to slow it down? Changing it's size or it's ratio can alter when the canopy becomes dominant over the slider on opening. Between the three you should be able to get nice openings out of a canopy.

 

Lee

[riggerrob 643]

Definitely start with an Icarus trim chart. Ask a local rigger to measure your line trim and compare it with the trim chart. As lines shrink out of trim, openings become more “interesting!”

Altering the distance between grommets changes more than just the amount of slider fabric exposed to the wind.

The old school solution was cutting progressively larger holes in sliders .... a job best done by a digger because it might need some reinforcing tapes sewn on.

Edited May 3, 2019 by riggerrob
Sentence

[RiggerLee 61]

I was going to suggest he cut a hole in the center of his slider with a coffee can but I figured people would give me too much shit in this day in age.

 

Lee

[timski 80]

Perhaps start with the cocooning and not wrapping it so much. For an example: https://squirrel.ws/public/manuals/Epicene_Pro_Manual_v201903rev2_WEB.pdf, perhaps not quite so loose, but you get the idea... Test jumping is fun/pull high!  

[20kN 93]

Slider size has a major effect on opening, but it's far from the only variable. Brake settings of both the LCL and UCL lines have a large effect as well. Even changing in the inboard brake lines by an inch can have a small effect. In fact, when I asked how to speed up the openings on one of my older canopies the manufacture did not tell me to change the slider, instead they told me to shorten the inboard UCL lines by 2".

[meat.missile 25]

To answer your question, drag is directly proportionate to the area of the footprint of the object. Assuming all other things equal. 

[Unstable 9]

The manufacturers I speak with have a formula for slider size which usually involves looking at the distances between the B-C lines on the center cell and the B-B lines across the center cell and building a slider where those dimensions matche up hole-to-hole on the slider. I have encountered this problem twice before, and in both cases two separate manufacturer recommended using the same size slider with a partial mesh center. 

Again, talk to the manufacturer about this, but that may be a more appropriate solution. 

[gowlerk 2,216]

19 minutes ago, Unstable said:

The manufacturers I speak with have a formula for slider size which usually involves looking at the distances between the B-C lines on the center cell and the B-B lines across the center cell and building a slider where those dimensions matche up hole-to-hole on the slider. I have encountered this problem twice before, and in both cases two separate manufacturer recommended using the same size slider with a partial mesh center. 

Again, talk to the manufacturer about this, but that may be a more appropriate solution. 

That would seem to be not really true when you consider that PD only has two sizes of slider all across the range of Sabre 2s from 97 to 260 sq ft. All of them have a 31" span, up to 170 have a 23" chord, large have a 26" chord.

[Unstable 9]

27 minutes ago, gowlerk said:

That would seem to be not really true when you consider that PD only has two sizes of slider all across the range of Sabre 2s from 97 to 260 sq ft. All of them have a 31" span, up to 170 have a 23" chord, large have a 26" chord.

Which is fine. PD is not one who I spoke with on the topic above. I'm sure they have their own designs. 

[gowlerk 2,216]

19 minutes ago, Unstable said:

Which is fine. PD is not one who I spoke with on the topic above. I'm sure they have their own designs. 

How many manufacturers have you spoken to? More than one?

[RiggerLee 61]

Interesting. Taking a wag at the cell width of a 97 I would guess that it was about 21 inches. Allowing about an inch on each side for the inset of the grommets. That still makes the slider about 8 inches wider then the cell. The depth of the stabilizers also factors in. Some canopies have a stabilizer attachment on the B line a good bit lower then the A attachment points. I doubt that it's 4 inches on a 97. So for a 97 the front of the slider is probable setting on the bottom skin but not by that much. The back half of the slider will not be supported on the bottom skin and is probable doing most of the work of holding the canopy closed during the initial part of the opening. Doing more math, by the time you get to a 135 I'm pretty sure that the whole slider is fully engaged. None of it would be sitting on the bottom skin. So I can kind of see where they getaway with a universal slider size and I guess they add just a bit for the larger sizes to help hold the slider up an decelerate the jumper. That also explanes why there is a market for after market slider for their canopies. It leaves a good bit of room increase the width on larger canopies or play with the aspect ratios. 

 

Lee