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Say i had a standard 4 vent canopy,i dont know, maybe in the 240-260-280 sizes, and just for simplicity lets use a BlackJack. Yeah, say i had a blackjack 260 stock canopy. And i wanted to modify it and install a 5th, center cell valve. Logic says I should probably use the same type of valve as the other 4, so we would want to install a 5th PAC on the center cell.

3 Questions:

1. Would it make a drastic difference where the vent was located on the center cell?

2. Would it make a drastic difference if the vent was larger/smaller or size size as the other 4?

3. Would the 5th vent even make a noticable difference in my opening pressurization time/controlability/flying time? Would i be able to (in theory) jump something that i could not with only 4 vents?

 

Not sure on this one. I'd put it in the same place just to keep symmetry.


I'd say "technically yes but not really" to making a difference in regard to opening time, but a "likely no" to influencing heading performance. If it were a difference in size between left and right of center then it would be an issue.

Also the "technically yes but not really" is for low stuff. I would be wary of putting on a 5th AND larger vent and then taking it terminal.



I'm very curious to what others have to say about this. My friend jumps a troll with 5 vents and I jump a flik with 4 vents at about the same wingloading. I've never had much comparison, but just recently we did a ~200' cliff static line and in the video it seems as though there was a mild but noticeable difference in opening heights, but TBH it's probably not much difference since I think the vents on a flik are larger which would compensate some for having one less. I'll PM you the video links.

Zebu typed:
I'd put it in the same place just to keep symmetry.

Since there are 7 cells and Chris is considering
modifying the center cell... your concern about
keeping the wing symmetrical is unfounded.

Imagine a hot chick with nice D cup tits, now she
can get both nipples pierced or just her navel, but
either way see will remain symmetrical along her
center line or vertical axis & remain asymmetrical
along her horizon axis or waistline. See photo.


Hey Chris

Vents: 4 vs. 5, FWIW in 2008 I was about to order
custom gear and debating over Troll vs. BlackJack.
Rob (RIP) of Morpheus recommended/sold me on
the Troll because of the extra vent, which he said
definitely helps with inflation and is much more of
a benefit on bigger canopies, like my 285.

I meant its alignment from nose to tail being the same as the other vents. I doubt it'd make a difference though.

I would say not to go any closer to the tail than where the other vents are already located. The ideal opeining would have the leading edge of the center cell inflating first (say 1/3 of the center cell). As the canopy fans out the rest of the center cell begins to inflate.

The way I see it, the trailing edge of the center cell is the last part of the canopy to inflate, so as close to the leading edge as the rest of the vents or a little closer would be preferable, IMO.

And yes, any spot up and down the center cell would still be symetrical.

Yes.

Technically, yes. In reality, probably not. Within reason of course.

Yes

No.

I can't see the point of a center cell vent. During inflation it's already inflating through the nose before any vent is exposed, during a strike, all pressure is being forced to the center anyway, I kinda think a center vent is useless. Correct me if I'm wrong. Not to mention the fact the dudes building the canopies probably would have made them that way in the first place if there was any gain from it.

The first canopy on the market with bottom skin inlets was the FOX vtec.

It is important to note that this was a 2 way vent--not a one way valve.

The vent location on that canopy was selected for a variety of reasons, but one of them was to reduce the negative effects of outflow from the 2 way vent system. An uncovered center cell vent could have some substantial negatives that would not apply to a (one way) center cell valve inlet.

The considerations that led the initial vented canopy designers to leave off a center cell inlet may no longer be valid with one way valve systems.

I'd also look at it from a different perspective... cost.

what is the current value of your parachute?
how much will it cost to modify?
will the mod add to the value of the parachute (done poorly, it obviously will detract from the value)?

compare that to the cost of just ordering a new one originally made with the center vent.
it will be easier to resell down the road...

which is better? it depends.

Hmmm....OK, you have my attention, care to explain a little deeper or maybe a link to something? I understand the points, pro's, and con's between vents and valves and placement, but the center cell thing makes no sense regardless of vent or valve with center placement. Just wondering the reasoning....Would a center vent/valve improve vertical/backward flight and inflation timing and stabilization if added to a standard set up and not compromise flare strength, glide, and forward speed enough to make it worth doing? What about reaction time s far as maneuverability goes? I can't see the positive to a vent or valve on a center cell...

I don't know if I'm showing my naivety here but is the thread starter implying this could help with on heading openings? - Centre cell first inflation being aided by a central valve?

The original (FOX vtec) vent location was chosen by BR, working with a wing engineer they hired to consult. They were very concerned with outflow through the (uncovered) vent, especially during hard toggle turns and flare.

I still own an original FOX that I had retrofitted with (uncovered) vtec valves when they first hit the market. In my opinion, the canopy has a tendency to "accordion" in hard toggle turns, with the vented cells narrowing as they compress. The hard toggle inputs feel "squishy" when compared to hard toggle inputs on a similar FOX vtec (covered valves) in the same size that I also owned for several years.

I theorize that when hard toggle inputs are applied, they create higher pressure which leads to outflow from the uncovered bottom skin inlets. With a one way valve, this issue disappears.

I think that adding an uncovered center cell vent (or moving the vents forward--my uncovered vents are immediately forward of the B lines, where the Consolidated Rigging and Atair vented canopies I own have the vents placed midway between the A's and B's) would exacerbate this problem.

I think this is likely why there was no center cell vent on the original BR vtec canopies, and that the other manufacturers originally adopted this same vent placement.

Note that in the era of one way valves on the inlets, most manufacturers (Atair and Apex, but not Consolidated Rigging) have moved to center cell inlets.

In fact, one manufacturer (Atair) has actually enlarged the center cell inlet, which I personally think is a good decision.



I think that a one way inlet has no negative effect on riser toggle response or on flare strength. I also don't think that the one way inlets change the glide angle or available forward speed of the canopy in flight.



I've recently been reviewing a lot of footage (and some stills, which are really interesting) of the inflation of canopies with different vent arrangements.

While I haven't reached any really hard and fast conclusions, I do think that the center cell vent is helping with pressurization substantially--almost to the point that a single vent on the center cell gives almost as much pressurization inflow as all four outside vents.

I have heard the argument that the center cell vent helps the heading rate of the canopy, and I'm not sure I buy that at this point, but I'm still looking around at this stuff and trying to come to my own conclusion.

Gotcha, thanx for the response.