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Does anyone use an OSP for terminal jumps? If so, what type of slider do you use (small mesh or slow slider I would guess) and how are your openings?

Also, what's your wingloading? I would think that all things being equal, you'd get a softer opening with a lighter wingloading. I have an OSP that I load pretty light (about 0.63) and I'm wondering if it would be okay for terminal openings with a small mesh or slow slider. Thanks.

yeah it's fine... people do it all the time. small mesh should be fine, but even large mesh should be doable. people have wingsuited OSPs... idk on the wingloading question... not so sure it's that simple. This all has been asked before though if you'd done any research in the forums.

Don't you think a lighter wingloading (a.k.a. less load) would be easier to stop than a heavy one? Therefore, stopping faster, a.k.a. firmer opening? I mean, I still don't think it is that simple... but it sounds reasonable.

I was thinking about it in terms of kinetic energy. When you're in freefall, you have a certain amount of kinetic energy and when you're under canopy, you have a much smaller amount. During opening, the difference has to go somewhere. It either goes into the elasticity of the material (lines, fabric, thread, etc) or into your body.

If you hold canopy design, slider type, packing technique, etc constant and decrease the weight, there is less kinetic energy to dissipate. If you hold the weight constant and increase the canopy size, there is more material to absorb the same amount of kinetic energy.

Yeah, that means it's not as hard on your CANOPY (evenly distributed load assumed spread more thinly over more material), not on YOU. There is ONE you to absorb whatever amount of shock. Your weight constant, if you increase the material overhead (a.k.a. drag... think like a bigger PC which when increasing in size has more snatch force) and keep the opening speed constant, the force of drag is greater and should slow you down more/faster. But this doesn't take lots of other small factors into play I'm sure.

Yes, if you decrease the weight there is less kinetic force, but we're not talking about decreasing your weight, but increasing the canopy size. The difference isn't whether you lose ten pounds, but whether .63 at the same weight is more force than say .70 at the same weight. Of course, if you decrease the weight there is less kinetic energy to stop, but we're assuming a constant kinetic energy to stop. If there is a stronger force pulling against it, don't you think it would decelerate more quickly? That is to say with a stronger negative acceleration? You might be putting it in the wrong terms by thinking "less weight."

Assume kinetic energy is constant if you wanna play this game.

Other factors you might have to consider include does a bigger canopy "snivel" more in either slider up or even somewhat in slider down opening mechanics since there is more canopy that has to inflate? And does wingloading affect pressurization in a way that influences that? 'Cause that could change the "softness" or "hardness" of the opening just as much.

I have no idea what the science predicting all of that with any certainty would entail. And it'd still probably be a guess.

Yeah, but a bigger canopy will take more time to fill with air, especially with a slider slowing it down. It will eventually apply more upward force on you, but not until it's full of air. That's why you hardly ever see people use 52" PCs even though they're on the market. 46s and 48s fill with air faster and still pull plenty hard enough.

I'm not sure either. I'm just thinking out loud.

I'm thinking more slider down physics than slider up physics I believe, but if we're talking only a 20 sq ft size difference, I doubt the opening speed will be very noticeably different... especially with vents.

I *think* I have heard someone say a REALLY lightly loaded canopy (like a 120 pound girl on a 305) can snivel into the ground slider up... and they tend to open in a stall slider down when lightly loaded. So there's that. It might be that there is a curve to it... hang on I'll draw what I mean and post the idea. But the basic principle is a bigger canopy by a little bit will give you more of a snivel pop and a properly loaded one would give you less snivel but a smoother overall opening progression?

Just a theory.

I have an osp that i am rocking a .71 wing loading and have taken it terminal a bunch of times. I actually like it more than my Troll for terminal. Small mesh slider and a double control stow on the slider is all you need. It almost acts like a round where it stands you up during the snivel and then pops open to a stop. Keep your head down until it completely opens or you'll get a sore neck ;)

So I'm thinking the "snivel-pop" feel COULD happen more with the bigger canopy which slows down faster once it has started inflating (in this theory, not necessarily in fact), versus the smaller canopy.

The general drag of my perfectly-sized rig would be represented by this initial jerk of speed-change when inflation begins (blue area in graph) followed by a smooth but fast slider slide (just made up "slider slide" as a term... that was weird) down the lines.

IF the bigger parachute makes more drag once it has started inflating a bit more fully (which took longer to get to), then it would open during the "slider slide" period a little firmer (with more resistant force) in this theory... so it comes down to whether or not the red circled area in these force vs. time graphs has a greater or lesser slope than the blue circled area. I don't actually know.

Also the initial speed change from just having more material overhead (uninflated of course at this stage) after opening and at line stretch could be greater with the bigger canopy and skew the numbers anyway...

It probably changes with WAY more factors than can be computed, and can vary even on the same rig from jump to jump, with packing method, and a billion other random reasons.

But here was my thinking anyway...

??? ideas??? I'm completely postulating beyond my expertise of course.

I am jumping an OSP 245 at 175lbs so its not a "big" base jumping canopy. I think it snivels like most canopies slider up, but then once the slider decides it wants to come down, it reacts like a slider down canopy and slams open. So far, the snivel has been quick but nice, and the pop is fine as long as you don't raise your head too quick. You can also just harden the fuck up as chopper read would say.

Firstly the wingloading differences in BASE are pretty negligible, but yes you are essentially correct. A heavier wingloading will cause faster inflation which in turn will feel like a harder opening. Atleast at higher airspeeds. All else being equal of course.

If you talk to the guys from Atair they're recommending the OSP Lite along with the Trango as the best wingsuit canopies they make.

You are looking at the wrong physical constant - you're not interested in force or energy, what you are interested in is impulse.

Parachutes have a two stage deployment. If you are after soft openings, regardless of size you want as much energy dissipated in slider up phase because whatever isn't released then is released nearly instantaneously once the slider lowers. It is my understanding that larger parachutes have more effective slider up braking phases, meaning softer openings.

Anecdotal, but my Blackjack 280 definitely opens harder than my Blackjack 260, slider up or slider down. Both canopies have the zero-P foreskin and approximately the same number of jumps. I pack both canopies exactly the same, they both have small mesh sliders.

according to a manufacturer, a smaller canopy may inflate faster, but a bigger one will fly faster - and that it is noticeable by a rather large margin.

OSP Light... IMO the best all-around canopy period. Notice I say 'all-around'. I think other canopies can do certain things better (meaning also other things worse) but the OSP Light can do everything SOLIDLY well.
I use my OSP Light as my sole canopy for low-and-dirty Moab as well as terminal Europe and wingsuiting.

The opening range on the OSP Light is phenomenal... it's all how you pack the nose and stow the slider with/without wraps.
Want smacker openings on low stuff?... keep the nose exposed and wide open, minimal rolls.
Want to snivel your wingsuit into the ground on a terminal pitch? Then roll the nose tight 8-9 times each side in toward the center cell, stuff the center cell as deep as you can, add 2-3 wraps of a slider-gate stowband around the slider. Just be prepped to pump the slider down with toggles!
Want something in between?... well, play with it! The perfect combo is most likely different for each person, but it's there.
OSP Light!!!

what do you mean by "fly"?