Just wondering why airlocks aren't used more in BASE. Seems like with the bottom skin vents/valves being so great, having a nose valve that would shut closed after initial inflation would lead to a rigid, flyable canopy quicker, and maybe even keep it inflated during certain object strikes... I guess it would suck stashing and running with the airlocks wanting to stay rigid, but might be worth it...
I think you hit on one issue... airlocks would definitely hinder a hasty getaway.
I flew a PD Vengeance 120 and a Jedei 136 for many, many jumps... so I am very familiar with airlocked canopies.
The advantages I see are, as you mentioned:
1. their ability to maintain pressurization in the event of an object strike; and
2. their stability in turbulence.
The obvious disadvantage is the quick getaway issue. Collecting an airlocked canopy in windy conditions SUCKS... though it usually has to be fairly windy before it becomes a severe problem.
One potential drawback that is unknown to me is the difference in cell pressurization speed between airlocked and non-airlocked canopies. I suppose it is possible that airlocks might slight slow pressurization... which would not be ideal in the BASE environment. Differential pressurization might also lead to performance issues. But again I'm just guessing.
probably the biggest reason why you don't see them is that the main advantage of airlocks... maintaining cell rigidity and pressurization in the event of an object strike... is essentially achieved through bottom skin inlets. So an airlock would pretty much be redundant.
When I was looking at getting a new canopy, the more I read and talked to people, the more I wanted bottom skin vents and valves. The more jumps I put on the Blackjack, the more I love vents and valves. It seems to make much more sense to have the secondary inlets pressurizing the canopy, espacially on lower stuff, with none of the disadvantages of unvalved vents...
I don't think that an airlocked nose would lead to slower openings. Instead, I would think that you would have a flyable canopy much sooner, since you would have the inflation surge, with little to no escape of air in that next outrush. Esentially eliminating jellyfishing. I could see how it could possibly lead to some cells closing shut asymettrically- some faster, some slower, and more off-heading, *maybe* (but not any more than bottom vents opening and closing asymetrically)... (And I haven't heard about the airlocked skydiving canopies out there having a similar problem-note disclaimer about BASE is not skydiving) Simply, they allow the air to come into the cell nose, and when the pressure is the same/higher in the cell than outside the canopy, the valves will close. Same idea, just bigger, with bottom skin vents...
I also think that the last paragraph might be one of the most misunderstood about venting and valving. I thought the same thing, and when I was talking to one of the bigger BASE canopy manufacturers, and told him that despite all the advantages in opening that a vented/valved canopy has, it still makes me feel better on top of a solid object, that if there is an object strike on opening, the canopy will stay semi-rigid from the air getting forced into the canopy through the secondary inlets, despite the pinched off nose. According to him, although the idea sounds good, he's never heard of it really working that way, and said that he couldn't imagine the design working as such that you would still have it rigid and flyable in that scenario... Don't know for sure, that was a while ago, and came up out of casual conversation... But this could be "ensured" with nose valves, at least long enough to back away after that suckyness...
Don't know, I'm not a BASE canopy designer either, but I am going to stay in a Holiday Inn at BridgeDay, so I'll know a lot more by late-October...
I'm not sure if I'm following you here. If I am...Originally Posted by baseninja
I have good video of a Vtec FOX staying inflated through the bottom skin inlets despite a pinched nose and zero forward speed (i.e. it ought to have been stalling and deflating) in Norway in 2000. The canopy goes through very evident stall-deflate-inflate cycles, even though it doesn't achieve any forward speed to reinflate throught the nose.
Last edited by Tom Aiello; July 26th, 2004 at 09:50 PM.
Why would you need the airlocks?
Why not just completely close the nose of the canopy, and allow inflation only through the bottom skin inlets?
Re: With vents/valves being great, why not airlocks?
...the "hybrid"...
hopefully soon...
Spence
Tom, I would love to see that video...
As far as closing off the nose, what do you see the advantages as? How would effective pressurization occur with a sealed nose, and only bottom skin vents/valves, or to what extent? Would the thin vents, parallel with the airflow, be able to keep a large canopy rigidly inflated?
As far as the original question- Why aren't these things being talked about on a daily basis, and researched more? Are they that futuristic?
Looking forward to seeing the video...
Let me see if I can dig it out and digitize it. It's on VHS, so it may take a bit. If you have a copy of "Lodi Daze" it's on there, in the carnage section.
I dunno. It was more a "if airlocks are good, would this be better?" kind of thought problem.As far as closing off the nose, what do you see the advantages as? How would effective pressurization occur with a sealed nose, and only bottom skin vents/valves, or to what extent? Would the thin vents, parallel with the airflow, be able to keep a large canopy rigidly inflated?
Let's see. Advantages would be a better performing airfoil--presumably much the same advantages of airlocks (or crossbracing, or ZP, or whatever).
Pressurization? I bet it would suck at first. But if you used one way valves covering the majority of the canopies bottom skin, I bet you could help that.
Would the vents keep it inflated? Perhaps if enough of the bottom skin was vented. Perhaps not, though. I'm not sure what the dynamics of doing it with an F-111 canopy would be. I bet it would work better with ZP (to prevent airloss and canopy collapse).
Here's an even wackier thought problem. Why not hire Space to build us a parachute that is completely airtight, and rockets out to line stretch, then uses a ballistic spreader and pressurized gas cannisters inside the canopy to inflate? Would that be a better BASE system? Hmmmm....
Inflated cells drastically outperform non-inflated cells on an airlocked canopy. If the canopy inflates unevenly, there'd be an off-heading opening. At least the canopy will stay pressurized through the object strike.
Now that you mention it, my Vengeance particularly had a tendency to "hunt" during opening. It rarely spun up, but I didn't have it loaded particularly high either.Inflated cells drastically outperform non-inflated cells on an airlocked canopy. If the canopy inflates unevenly, there'd be an off-heading opening. At least the canopy will stay pressurized through the object strike.
After talking to a couple canopy manufacturers, it seems like this isn't a bad idea. In fact, its been tested a couple times, sounds like the tests went well. But the only thing is that it costs money, just like vents/valves, and it is unclear if people would spend more for the nose vents.
I think the benefits would be incredible in BASE- for canopy object strike safety, for low stuff, for turbulence, etc....
Anyone, anyone?
When Brian Germain sold the license for the Jedei to Performance Designs, he agreed to stay out of the skydiving market for a certain period of time. He went on to start Big Air Sports Equipment (notice the acronym?), and in addition to doing R&D for the Lotus and Samurai, he built a handful of airlocked BASE canopies, which, as I have heard performed superbly. According to the tests, the prototypes inflated faster than the open nosed canopies since there was no breathing. I don't recall hearing anything unusual in heading performance, but I could be mistaken.
One story I heard was of a now-late jumper who grabbed a prototype (in a dual container, but didn't realize it was packed slider down) for a night skydive. He went terminal and opened. The opening split the topskin of the centercell from asshole to bellybutton, but said jumper managed to land it with little issue. According to the storyteller, the jumper didn't even know the canopy was damaged until he was on the ground.
I am still working on the storyteller to make me one of those canopies.
This has been discussed and looked into by Adam F. Quick getaways are a big problem. Quick inflation and stability during zero speed and object strike have been addressed by vents/valves on bottom skin. A closed nose is a bad idea, as it is the nose that causes "ram air" wings to inflate, With bottom skin vents only openings would take a long time. Basically, all of this has been looked into years ago, and no benefit was seen. Maybe new technology will emerge, but airlocks won't be coming to base anytime in the near future, with good reason.
"To the extreme I rock the mike like a vandal
light up the stage and wax a chump like a candle"
www.TandemBASE.com
Quick inflation and stability during zero speed
…………………………………….
That is a very good sentence.
All you need is a Canopy that inflates Fast and consistent
across the cell span. Plus gets a consistent good Heading.
If you are jumping that.?
You don’t need anything else.
You might want valves on the bottom skin vents to
Give a better glide ratio.
Give me quick inflation and I will slow it down to fit
The circumstances of the delay and object.
Bottom line is … Don’t complicate it.
Or if it’s not broke don’t fix it.
Posting Permissions
Reply With Quote
Bookmarks