):
July 27th, 2003 My Fox (no Vtec or valves) seems to take a long time to fully inflate. The top skin “ripples” when seen from a top view on a go & throw. Rear riser input doesn’t seem to do much during this period, which concerns me. Consequently I’m about to get it vented. Any thoughts on this?
July 28th, 2003 You are not the first to experience this. My BAES bro jumps a un-vented Fox 245. I jump a vented Fox 245. I have several videos of both our canopies opening (slider up, slider down, static line, and short free falls.) The difference is incredible. The unvented Fox "ripples" from nose to tail several times before full pressurization, usualy three waves. He chooses not to use the deep break settings. However, it still ripples even slider up with four plus second delays. We found that grabing risers before releasing toggles only makes the problem worse. The best result we found was to go for the toggles, off heading or not! Furthermore, he will borrow a vented Fox for anything lower than 250. Pyro, if you have anything to add feel free to correct any of my inaccuracies.
My spealing SUCKS!
Crater Nate
July 28th, 2003 OH YEAH, Landing the Fox with V-tech takes some practice to get a decent flare. Once you get the hang of it, it lands pretty nice.
In the previus post I spelled BASE wrong. I am indeed a Choad Munch.
Peace,
July 28th, 2003 Bottomskin venting was specifically developed to increase the consistency and speed of slider-off openings, particularly in low airspeed situations. The "jellyfish" action you see on the topskin results from the lack of air pressure into the cells during pressurization, and yes it is dangerous. Not only does it eat altitude, it also can develop into an off-heading and is nearly impossible to steer until sufficient pressurization is achieved through the inlets.
Anyone who is jumping low and/or technical objects today owes it to themselves to be jumping a proven, vented canopy. If you jump enough with an unvented canopy from these types of objects, you WILL injure yourself in a way that could have been prevented had you had current (i.e. vented) technology. Injuries suck, fyi.
Just as few folks eschew the tailgate nowadays (it is safer with essentially no mitigating drawbacks), anyone jumping low and unvented is really taking unnecessary risk that will translate into unnecessary injury or death, eventually. Death, as they say, continues to suck.
Peace,
D-d0g
July 29th, 2003 >Landing the Fox with V-tech takes some practice to get a decent flare.
Yes, it's true, landing a Vtec Fox can yield hard landings.
For your own and everybody's information, from now on, BR does NOT do any more Vtec only on Fox's. If you ask BR to apply a Vtec to your Fox, they will do the "Vtec+covers" modification (for the cheap amount of 350$). I.e., either you keep your Fox as it is (=unvented) or you do the "valve" modification.
Valve modification means that on opening you get immediate pressurization (with all the associated benefits: immediately steerable, start flying soon without eating altitude, etc etc etc) and after few seconds of flight, once internal (to canopy) pressure becomes greater than external pressure, the "covers" go to close the vents, so from 3 s after opening to landing, you have above your head an "original" Fox with all its "untouched" characteristics: good flare and so on.
Unless you do a semi-vertical approach to landing, in which case covers open up again to allow air to flow into canopy through vents, keeping the airflow enflated enough to keep it flying, but that's another story...
Stay safe out there
Blue Skies and Soft Walls
BASE #689 :-)
e-mail: base_689@yahoo.com
July 29th, 2003 D-Dog,
One mans high is definitely another mans low. Being Irish I would consider 300' very high whereas a Norgie would probably consider this low. At which point do you think the vents become necessary (not desirable, as this will obviously be a lot higher than required) - sub 250', sub 200', sub 175'?
FYI - I jump an unvented Mojo 240 (very rarely I must say), not a Fox 245
C-Ya,
MT
July 29th, 2003 > At which point do you think the vents become necessary...
Sorry if I answer to your question!!! D-dog is obviously free to answer as well!!!
The main reason why Vtec (vents, holes, whatever...) has been created is because of "jellyfish" behaviour of Fox immediately after opening; this is due to shallow angle of attach on Fox's, yielding low forward speed, which is a desirable thing when you jump fixed objects, especially if you experience a 180° on opening. The main drawback for shallow angle of attack/low forward speed is that, just because low speed, Fox takes a while (few seconds) to pressurize and so it takes few seconds before responding to riser/toggle input to steer away from object.
With Vtec you eliminated this drawback: the vents/holes in the bottom skin allow pressurization milliseconds after primary canopy expansion, so, as soon as the canopy is open/spread, it is indeed pressurized/inflated and so it can immediately respond to any kind of input, risers or toggle that could be.
So, main purpose of Vtec: to have an immediately steerable canopy, making an object strike avoidable in case of a 180° (granted that you are fast in reacting...).
A side effect of Vtec is that, because it pressurizes immediately after opening, it start flying immediately after opening, much earlier (=higher) than an unmodified Fox canopy, which takes few seconds to fully pressurize and to start flying, eating up some spare altitude in the process.
Because of such a side effect of Vtec, now we are capable of freefalling objects whose heights were NOT considered "safe" to be freefallen with a standard canopy.
So my answer is: a Vtec is desirable any time you do a no slider jump off an object, no slider meaning you do from 0.5 s to 3 s of freefall, meaning also that you are quite close to the object (few meters - feet), meaning that in case of a 180° you want to avoid an object strike by any means. Vtec gives you this possibility.
How low can you go? It's very personal, the lowest freefall I did is off a 65 m - 213 ft S, having 7.5 s of open canopy flight. I would feel confident, provided a good landing area, to jump off a 60 m - 197 ft.
To jump in freefall lower than 60 m - 197 ft, it could be done (and it is done...!!!), but that would mean to shave off any residual "safety" margin. Freefall off objects whose height is 48÷50 m - 157÷164 ft are being done, but canopy flight means only: canopy open up, going for your risers and flare up and do your best PLF.
Just my 0.02 €.
Stay safe out there
Blue Skies and Soft Walls
BASE #689 :D
e-mail: base_689@yahoo.com
July 29th, 2003 Lowest I've freefallen without vtec was about 300 feet. Lower than that, I feel more comfortable jumping my vtec Fox. I'm sure others here have explored the 200-300 foot freefall range more completely with unvented canopies, and hope to read their responses.
I've done much more experimenting with low static-line jumps. The lowest I have jumped with my unvented canopy is 165 feet. The canopy was soft even at landing, although it had enough forward speed to get a decent flare. Up around 210 feet (static line), the unvented canopy performs just fine.
On some very low static-line jumps with vented canopies, the canopy doesn't have time to begin flying forward (so it is not producing lift as a wing does). In this range, the canopy still seems to act as an adequate decelerator, and it remains an open question in my mind whether an unvented canopy might be superior to a vented one for ultra-low static-line jumps.
However... The reality is, I still haven't explored this very much because I have a hard time convincing myself to do static-line jumps lower than about 165 feet without the vents.
Michael
July 29th, 2003 As Andrea says, it's not just about object height when choosing gear. There are two other factors, at least. First, whether there is a hard object behind you during deployment (i.e. cliff, building). If so, the venting unambiguously allows for better response to serious off-heading problems with less altitude loss during proper correction.
Second, there's the question of taking deep delays. 250 feet may not be very low, but take 2.5 seconds off it and I'd prefer a vented canopy. Yes, there are rational reasons sometimes to take deeper delays ( get past underhung section, landing area issues, wind issues), so it's not all simply enhancing the visuals.
Crwper brings up interesting questions regarding static lines versus freefalls. I don't have much sub-200 freefall experience compared to a number of other folks out there, but in my experience I pretty much won't do that sort of stuff without a vented canopy. Even at my "summer slim" weight of 205 pounds, I fall fast and decelerate slow and have a big heavy canopy on my back. Consequently, I want pressurization quickly as my poor ankles really aren't up for more damage. However, there's been several Mojo freefalls from 156 feet that resulted in no injuries so it is possible with proper technique and perhaps some good luck mixed in! I would simply not do sub-180 stuff without a crisp, vented, quality canopy over my head; that's just personal preference for risk/return for me.
Static line I've jumped probably a dozen objects lower than 180 feet with various canopies, again much less than some other folks out there. I'd agree that I notice relatively less vented/unvented difference on pressurization here, and at least in theory we're not worrying about off-heading correction so there's no need for vents for that. However for the truly dodgy static lines I have done (sub-155, bad landings, wind, etc.) I still have a "horse sense" that venting gets going perhaps not faster but more consistently than unvented rigs.
We have one 185 foot waterfall that due to landing area we don't freefall (unless someone drops a pilot chute, right?) and as a static line it's not exactly low. However it does require some setup for landing and when the water flow is high there are some turbulent vectors in the wind and a pretty consistent tail-push on landing. I've done this object probably 20+ times under various Mojos without injury or mishap. However, I started watching video of these pressurizations and I noticed that in many cases I had one or even two end cells that never pressurized, even during flarestroke! I still landed ok, but after one fast ride last year I swore off doing this object with unvented rigs, period. Eventually, it'd cost me a broken something-or-other due to the pressure wave issues and I'll simply stick to vented technology for this (and, actually, all) jumps since there's no real drawback but less objective risk.
I've got several dozens of jumps from a 156 foot S (static line) on vented and unvented rigs. I seem to feel from memory that the vented rigs do get flying a bit better, but not by much. Perhaps it's more the newness of the vented canopies I've jumped there, versus the sad-sack Mojos I was taking off it for many months quite regularly! After a while, those old Mojos are so porous that they deflate into a little puddle of tattered fabric on landing so quickly as to be laughable. That's not so much a question of venting as it is just an old canopy with not much life left in it after hundreds of jumps.
If I was playing in the sub-150 foot static line game quite alot, I'd worry more about the WEIGHT of the canopy perhaps than the vents, valves, or otherwise, plus the overall condition of the fabric (new or clapped-out). Actually, ditto for freefalling really low stuff (this advice came originally from Slim who was the fellow taking the Mojo freefall off the 156 footer a few times). However, I think there are currently very few folks worldwide who are playing either of these games seriously nowadays which may be for the best. If anyone does want to play this game, I suspect they already know the list of "usual suspects" to contact regarding advice and technology to minimize the risk.
So, anyway, vents rock! Valves rock also, but I find much more that they affect glide ratio versus landing/flare. I've never had problems with landing under vented and un-valved rigs myself, while others winge about them endlessly. The valves on the Fox, however, make a BIG difference in glide and that factor alone allowed me to do a jump recently and land without mishap. Without valves, I suspect I'd still be stuck in the middle of a forest of big, green, nasty-looking trees!
Peace,
D-d0g
July 30th, 2003 Thanks everyone who took the time to reply. From what has been said, it seems fair to summarise that if you had three Fox’s to choose from for the low stuff, you would be best off firstly with the one with vents + valves, secondly with the one with vents only, and lastly the un-vented canopy. Also, venting the canopy appears to provide a bigger safety factor increase than adding the valves. Please correct me if I’m wrong.
I will definitely be getting a vent mod now (everything around here is low!). Thanks again, I appreciate it.
July 30th, 2003 >Also, venting the canopy appears to provide a bigger
>safety factor increase than adding the valves.
>Please correct me if I’m wrong.
Not exactly. D-dog just said that adding valves, according to his opinion, affects MORE the glide ratio THAN the flare stroke.
Personally, I would say that valves affect BOTH aspects of Fox's flight!!!
So, my personal advice is to go for Vtec+covers=valves!!!
Also, I remind you that Basic Research, nowadays, does NOT do any more the "Vtec only" modification on Fox's, but instead they do the Vtec+covers modification (check their website).
Stay safe out there
Blue Skies and Soft Walls
BASE #689 :-)
e-mail: base_689@yahoo.com
July 30th, 2003 I'm curious what experiences everyone has had with valves and static-line jumps in the 120- to 140-foot range. I had heard (possibly just speculation), when CR started producing valved canopies, that they pressurized slightly slower than a vented but un-valved canopy.
Michael
July 30th, 2003 >>Also, venting the canopy appears to provide a bigger
>>safety factor increase than adding the valves.
>>Please correct me if I’m wrong.
>Not exactly. D-dog just said that adding valves, according to
>his opinion, affects MORE the glide ratio THAN the flare
>stroke.
>Personally, I would say that valves affect BOTH aspects of
>Fox's flight!!!
>So, my personal advice is to go for Vtec+covers=valves!!!
BASE #689,
D-dog’s valve-comments seem to relate to performance more than safety. I read it that priority-one for safety was to get vents; the valves were more for glide & flare. The valves, of course, may well increase landing safety, but this isn’t as important as avoiding object strike.
Yes I agree, given the choice I would go for the option of both vents + valves, & I’m sure BR are doing the right thing by always doing both. But here is my problem: our country’s currency is weak compared to the US$ & due to the large distance the postage costs are a large component. It is not cost effective to send to the manufacturer for the full mod. A local rigger can however competently do the vents (only –he doesn’t do valves) for a fraction of the cost.
I expect some people to be outraged by this statement (i.e. you should only deal with a manufacturer, don’t be so cheap etc) but this rigger’s work is good & it simply would not be worth sending it to the US on price. So practically my choice is to jump it unmodified, with vents, or buy a new canopy (and do what with the old one?)
July 30th, 2003 >I'm curious what experiences everyone has had with valves and
>static-line jumps in the 120- to 140-foot range. I had heard
>(possibly just speculation), when CR started producing valved
>canopies, that they pressurized slightly slower than a vented
>but un-valved canopy.
I've probably got about a dozen sub-160 jumps from 6 or so objects on a vented and valved Fox 285, and 20-30 similar jumps on it before I retrofitted it with valves but when it was vented only. I've not noticed any difference in opening speed at all, and particularly considering the mechanics of static line pressrization it doesn't seem to be too likely.
Perhaps in the sub-120 foot range a potential difference across a wide sample of jumps of a few feet in terms of pressurization height might matter and might be noticed, but for stuff taller than that I do not think there is a substantive difference caused by the valves.
This is just one Dog's opinion and I've been avoiding sub-140 foot stuff lately so there's likely other folks out there with a bigger data set than I.
Peace,
D-d0g
July 31st, 2003 >I read it that priority-one for safety was to get
>vents; the valves were more for glide & flare.
Yes, indeed, it is true.
>our country’s currency is weak compared to the US$...
I can understand (by the way, where are you from?).
So, yes, vents only is a HUGE improvement in safety, and, so, yes, go for vents only.
Just be sure that your rigger is a very very very good one and that he sews with the proper thread and very very accurately, because when you do the vents, you un-sew and then re-sew (with mesh/tapes/whatever) 6 (out of 8 in the "B" line of your parachute) critical sewings just in correspondence of same number (=6) of lines/load bering ribs.
> So practically my choice is to jump it unmodified,
> with vents, or buy a new canopy...
Your choice being: jump your canopy with vents (made by your local rigger)!!!! :)
Good luck and let us know, please, the results of modifications!!!!
Stay safe out there
Blue Skies and Soft Walls
BASE #689 :)
e-mail: base_689@yahoo.com
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