beavdog 0 #1 July 14, 2004 I read in a thread in the incidents forum that switching from a single front riser turn to double fronts can cause the nose of a canopy to fold under. This doesn't seem right to me and I have done it with no indication from my canopy of any way the nose could do this. Could someone please clear this up fo me. Thanks Here's to the Breezes that blows through the Trezzez..... Quote Share this post Link to post Share on other sites
ccowden 0 #2 July 15, 2004 No- using double fronts will not cause the nose to fold over. If someone said that, it is just speculation with no real evidence to back it up. Quote Share this post Link to post Share on other sites
towerrat 0 #3 July 15, 2004 never heard that one. can you post a link to the thread?Play stupid games, win stupid prizes! Quote Share this post Link to post Share on other sites
Cacophony 0 #4 July 15, 2004 Using your front risers pulls down both the A and B lines on your canopy. The post was probably brought upon by the fact that pulling down your front riser creates a stair step effect in your canopy. I have heard that it isn't recommended to do front riser turns in high winds because the stair stepping effect can potentially (I don't know the odds of it happeneing though) cause the relative wind to fold the nose under. This might be the idea that the person was trying to convey. I'll try to find where I read that at. I'm sure the likely hood of such an incident is more likely to occur with a canopy that has less cell pressurization. For example a Sabre might be more suceptable to this than a Vengeance because a Vengeance is designed to keep the cells pressurized better. Quote Share this post Link to post Share on other sites
masher 1 #5 July 15, 2004 I thought it would depend on how smoothly you pulled the risers down. As with all things, what you get is dependent on how you do it. To my way of thinking, pulling smoothly on the fronts will allow the canopy to transition from normal flight to front riser flight. If you jab down on the risers, then the canopy will respond how it will. Sound reasonable? (This from a person who has just started double front riser approaches)-- Arching is overrated - Marlies Quote Share this post Link to post Share on other sites
ianmdrennan 2 #6 July 15, 2004 Quote I read in a thread in the incidents forum that switching from a single front riser turn to double fronts can cause the nose of a canopy to fold under. I read it too. They are incorrect. What they could have meant though was to avoid front risers in GENERAL in turbulent conditions (note high wind speed does not necessarily mean turbulent). If it's really bumpy under canopy or there are rotors in the area it's advisable to stay off them. Blues, IanPerformance Designs Factory Team Quote Share this post Link to post Share on other sites
Zenister 0 #7 July 15, 2004 i think my post might be the one your refering to... Quotethe way it was explained to me is that as long as you never take pressure off the riser you used to turn and can straighten out with your opposite riser, you were ok...the issue is when front riser pressure is high enough that you have to let up your 'turning' riser as you pull down the other to straighten out the turn.. causing distortion of the canopy that (i'm told) can result in the nose rolling under at an altitude to low to recover... obviously i am not a canopy control expert so........ can any more experienced pilots confirm?? essentially i was told that by letting up one riser coming out of the turn and pulling down the other you were distorting your canopy which could lead to the nose rolling (?) as long as you could pull the opposite riser (from the one you were turning with) down evenly without letting up pressure on the other it wasnt an issue, but that with many canopies the pressure would be to great at that point to even them out?? certainly not giving advice here, this is just what was relayed to me...____________________________________ Those who fail to learn from the past are simply Doomed. Quote Share this post Link to post Share on other sites
beavdog 0 #8 July 15, 2004 that was the post that i was referring to. it sounded funny to me so i thougth i would check it out. thanks everyone for clearing that up Here's to the Breezes that blows through the Trezzez..... Quote Share this post Link to post Share on other sites
cybervagrant 0 #9 July 15, 2004 PD's ram air parachute manual states that using frount risers for a turn or dive in turblent air can lead to a canopy colapse. Cheers, Cyber Whoops, is my ignorance showing again? Quote Share this post Link to post Share on other sites
goose491 0 #10 July 15, 2004 So what gives then? I'm on double fronts each and everytime I land. Usually 180 at this point but I've got pressure on both fronts during the entire carve... should I be thinking about doing something else? Quote Share this post Link to post Share on other sites
ianmdrennan 2 #11 July 15, 2004 If it's turbulent you should reconsider your approach and avoid the fronts. If it isn't turbulent then it's not an factor from a stability standpoint. Blues, IanPerformance Designs Factory Team Quote Share this post Link to post Share on other sites
ccowden 0 #12 July 15, 2004 I think by "turbulent conditions", PD is referring to situations beyond the average. Winds and turbulence that are quite high and unusual. In these conditions your best bet is to keep the canopy in full flight and not to alter the wing by any aggressive manuevers like front risers. In normal conditions and even in steady high winds, using front risers will not pose a problem. Quote Share this post Link to post Share on other sites
Cacophony 0 #13 July 16, 2004 QuoteI'm on double fronts each and everytime I land. Usually 180 at this point but I've got pressure on both fronts during the entire carve... should I be thinking about doing something else? Are your jump numbers mis-typed? If not, then you should definately not be doing the kind of turns you are describing. Think about the angle that your canopy takes as it is diving towards the ground. The steeper the dive, the more the top skin is exposed to the relative wind (possibly the wrong term here). The stronger the wind gust, the more it is going to push on the top of your canopy. If you have one or both front risers pulled down is creates a stair step in your canopy. Think about it, the front risers are only attached to the A and B lines right? Well, that is half of your canopy from nose to tail. Between the B & C lines is where the biggest cell distortion is. That area can also serve as a pivot point for the front half of the canopy to be forced under the rear. Excuse my rough explanation. Anyone care to re-inforce or shoot it down? Quote Share this post Link to post Share on other sites
RaulDuke 0 #14 July 16, 2004 I'll reinforce it. If you are flying your canopy straight towards the ground during your hook (w/ sufficient altitude of course) then the top of your canopy is fully exposed, and being pushed on, by the winds parallel to the ground. (Assuming you are not hook turning downwind) The windier it is on the ground the more push on the canopy, hence the concern of the nose folding under since you're pulling on those risers too. I've felt my canopy hiccup a couple times hooking aggresively into high winds and didn't care for it one bit. So dont bother. If it's windier then hell you ain't getting a good turf surf anyway. **You want a toe? I can get you a toe, dude.** Quote Share this post Link to post Share on other sites
headoverheels 291 #15 July 16, 2004 The amount of wind has absolutely nothing to do with it; gusts and/or turbulence may. I can't believe that people don't realize that they are just being carried along relative to the ground, and that the parachute doesn't "know" that the wind is blowing 20 knots rather than zero. The difference in ground speed changes the sight picture, and often causes the pilot to make different control inputs. Quote Share this post Link to post Share on other sites
kaerock 1 #16 July 16, 2004 Firstly, the jump-number comment is a crock of shit, please don't include un-informed subjective judgments in technical discussions. Secondly, your explanation requires a retort. The 'stair-step' effect and canopy distortion from a riser is so minimal, I don't think it matters. What does matter is that you are travelling at a higher speed and have less time between a de-stabilizing wind-gust and hitting the ground. A gust hitting the top-skin of the canopy while you are in a vertical dive I believe is also minimal as your canopy is travelling quite fast at that point, generating a LOT of lift in the opposite direction of this wind-gust, I think it's negligible. If you are getting significant uneven pressure on one side due to something like a rotor, or a cross-wind gust you might experience a partial collapse. If you've ever watched people single or double front-riser a landing, you will not see a major distortion of the canopy. Riser movement is very subtle and most of the time you can't even tell what someone is doing if you're watching it from the ground. The problem isn't the distortion of the canopy when hitting turbulence, it's what your angle, speed, altitude and direction are when the gust hits you. -Rory QuoteQuoteI'm on double fronts each and everytime I land. Usually 180 at this point but I've got pressure on both fronts during the entire carve... should I be thinking about doing something else? Are your jump numbers mis-typed? If not, then you should definately not be doing the kind of turns you are describing. Think about the angle that your canopy takes as it is diving towards the ground. The steeper the dive, the more the top skin is exposed to the relative wind (possibly the wrong term here). The stronger the wind gust, the more it is going to push on the top of your canopy. If you have one or both front risers pulled down is creates a stair step in your canopy. Think about it, the front risers are only attached to the A and B lines right? Well, that is half of your canopy from nose to tail. Between the B & C lines is where the biggest cell distortion is. That area can also serve as a pivot point for the front half of the canopy to be forced under the rear. Excuse my rough explanation. Anyone care to re-inforce or shoot it down? You be the king and I'll overthrow your government. --KRS-ONE Quote Share this post Link to post Share on other sites
DanG 1 #17 July 16, 2004 QuoteFirstly, the jump-number comment is a crock of shit, please don't include un-informed subjective judgments in technical discussions. I don't see it as a 'crock of shit'. Perhaps his assessment is wrong, but to call in a 'crock of shit' seems a bit extreme. I, for one, agree with his 'crock of shit' analysis that someone with 141 jumps should not be doing 180 degree front riser approaches, but that is my opinion. In any case, to get back on the subject, I think hard diving canopies are more subject to turbulence because most wind gusts near the ground will be horizontal, therefore striking the top or bottom of the canopy instead of the front, rear or side, as in normal flight. - Dan G Quote Share this post Link to post Share on other sites
ManBird 0 #18 July 16, 2004 The best philosophy on dealing with turbulence came from Harry Waller: "When the ground's there, pull the thingies." It seems to work with just about any condition and/or approach."¯"`-._.-¯) ManBird (¯-._.-´"¯" Click Quote Share this post Link to post Share on other sites
raymod2 1 #19 July 16, 2004 To keep your canopy inflated you need to maintain a positive angle of attack. Angle of attack is defined as the angle of the airfoil with respect to the relative wind. Relative wind is generally dictated by the flight path. For example, if you are diving your canopy straight at the ground the relative wind is coming straight up at you. Wind gusts and turbulence (NOT steady winds) can suddenly change the direction of the relative wind and cause the angle of attack to reach zero (or go negative). That can cause a canopy collapse. Front riser inputs exacerbate this problem because they lower your angle of attack so it takes a smaller gust to cause trouble. Quote Share this post Link to post Share on other sites
DanG 1 #20 July 16, 2004 QuoteTo keep your canopy inflated you need to maintain a positive angle of attack. Angle of attack is defined as the angle of the airfoil with respect to the relative wind. Relative wind is generally dictated by the flight path. For example, if you are diving your canopy straight at the ground the relative wind is coming straight up at you. Wind gusts and turbulence (NOT steady winds) can suddenly change the direction of the relative wind and cause the angle of attack to reach zero (or go negative). That can cause a canopy collapse. Front riser inputs exacerbate this problem because they lower your angle of attack so it takes a smaller gust to cause trouble. If I understand you correctly, you are saying that changing the orientation of the canopy relative the the earth causes wind gusts and turbulence to affect the canopy differently, since the wind gusts are now coming from a different angle (relative to the canopy), than they do in full flight. If that is what you mean, then I agree. If, however, you mean that pulling down on the front risers lowers the angle (relative to the jumper) of the chordline, thereby reducing the angle of attack, I'm not sure if that is the root cause of the problem. Yes, the angle of the chord changes relative to the jumper, but so does the freestream direction. I suspect that they will generally not change an equal amount, but I'm not sure if the change in chord (relative to the jumper) necessarily makes the steady state angle of attack lower. Sorry for any unnecessary technicality. - Dan G Quote Share this post Link to post Share on other sites
RaulDuke 0 #21 July 16, 2004 OK, I see where you're coming from, and for the most part you're correct. A spiralling (or diving) canopy will be carried along relative to the ground with the wind. But how about initiating that condition? Suppose you're under a canopy wing loaded around 2.0 or more, which happens to have very light, responsive front riser input. Flying straight into a 25 knot wind, pull the right front riser down good and hard, and just as you've swung out level with the canopy pull the other front riser down, stopping the turn at a 180 and going into a dive. I'm talking agressive input. I betcha you could fold it up doing that. If you disagree you can prove me wrong. I'll watch from the ground. Course if it did crumple you'ld blame it on a gust. haw haw! **You want a toe? I can get you a toe, dude.** Quote Share this post Link to post Share on other sites
headoverheels 291 #22 July 16, 2004 You could likely collapse the canopy that way, but the wind has nothing to do with it, as long as your control input is the same. There is a tendency to turn steeper in higher wind. e.g., as I start a 180, I seem not to be turning fast enough, since the higher-than-usual wind is taking me farther down wind. I compensate by turning faster to face into the wind, and by using more fronts to make my ground speed appear more normal. So, I am using more aggressive control. What I should do, is start the whole maneuver farther upwind, and realize that the sight picture will be different. Quote Share this post Link to post Share on other sites
hookitt 0 #23 July 16, 2004 If it's GUSTY, it matters. Other wise the canopy doesn't know what the air is doing. Quote Share this post Link to post Share on other sites
PhreeZone 15 #24 July 16, 2004 Ray, you are correct in your assumptions. The AOA decreases when you pull down on the front riser. It also moves the stagnation point on the canopy and AOI (I forget which direction). The canopy is completly blind to the effects of steady wind. Turbulence is something different though. Try this at altitude. Open up, take care of your canopy and then close your eyes. Do a sprial, are you facing into the wind? Downwind? Crosswind? Do a 90 degree turn. What direction are you facing now? How can you tell? (Your eyes are still closed right?) Guess what? You can't tell because the canopy is moving in a moving airmass that it has no refrence to. Only when you involve things like the ground that is a stationary refrence point can you develop things like "Downwind", "Crosswind" or "upwind". Only when turbulence/updrafts/downdrafts and microclimates are taken into consideration does the canopy see the outside wind.Yesterday is history And tomorrow is a mystery Parachutemanuals.com Quote Share this post Link to post Share on other sites
cybervagrant 0 #25 July 16, 2004 As I understand it: Pulling on the front risers decreases the angle of attack. A lower angle of attack means less pressure at the nose of the canopy, which means less pressure in the cells. In turblent conditions the canopy might experience a gust of wind from behind. That is, the relative wind might momentarily strike the trailing edge of the canopy first tending to push the air out of the cells and thereby cause a collapse. By using the front risers you make the canopy more vunerable to this case by lowering the pressure in the cells. It makes a good case for airlocks, aye? Cheers, Cyber Whoops, is my ignorance showing again? Quote Share this post Link to post Share on other sites
