johnny1488 1 #76 November 24, 2003 QuoteThe same holds true for landing. I know this from landing my canopy. I don't have to give it as much input/flare to get the lift on high wind days This is what I have told a few jumpers I was helping out. When you are coming down in say a wind that gives you zero groundspeed (or close to it), They dont have to contend with the foward speed of the canopy, only the altitude loss. Its much easier to get the flare perfect when you dont have to focus on both. Johnny --"This ain't no book club, we're all gonna die!" Mike Rome Quote Share this post Link to post Share on other sites
marks 0 #77 November 24, 2003 well ive been following this thread and i agree 100% with hooknswoop. i can understand it but in no way could i explain it.... geese hooknswoop i got mad respect for you now. just sitting here reading the way your explaining it.. then well... you lost me here..... QuoteFor the 0 mph current, 200 foot wide river, swimming at a 45-degree angle: 2 mph=2.93 FPS A right triangle w/ 200 foot sides has a Hypotenuse of 282.84 feet. (a^2+b^2=c^2) At 2.93 FPS it takes 96.53 seconds to travel 282.84 feet. For the 20 mph current and swimming upstream at a 45-degree angle: Swimming upstream at 2.93 fps breaks down to a 2.07 fps vector directly across the stream. {Sine 45= opposite/2.93}= 2.07 This means the resulting vector is 27.937 fps with an angle downstream of 4.25 degrees. {29.33-2.07=27.86}{(27.86^2 + 2.07^2 = RV^2)= 27.937}{Inverse sine x = 2.07/27.937} = 4.25 degrees. So the swimmer’s actual direction over the ground is 4.25 degrees from the shoreline. His resultant speed over the ground is 27.937 fps. The distance he will actually travel is 2638.75 feet. {(sin 4.25 = 200 / TD) = 2698.75} The distance downstream he will travel is 2691.33 feet. {(DS^2 + 200^2 = 2698.75^2) = 2691.33) It will take the swimmer 96.60 seconds to travel 2838.77 feet at 29.40 fps. {(2838.77 feet/29.40 fps) = 96.56 seconds} The difference of 96.53 seconds and 96.60 (0.07 seconds) seconds is because I only took it out 2 places and rounding. Derek Think Quote Share this post Link to post Share on other sites
kallend 2,129 #78 November 24, 2003 Quote It only plays a role in ground speed. It appears to float with zero airspeed, but that is only because it’s airspeed matches the wind speed. The role wind plays is to reduce it’s ground speed. You are actually landing at a higher airspeed than in no wind. If you suddenly took the wind away, you would suddenly begin moving over the ground again. Derek If the groundspeed is zero and you instantaneously took the wind away it would fall like a rock and rotate nose down until the combination of thrust and gravity accelerated it to flying airspeed. Most of the arguments about the effects of wind ignore wind shear and turbulence, and also ignore pilots' control inputs being changed because they usually fly by ground reference, not airmass reference, unless in IMC or under the hood.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
Hooknswoop 19 #79 November 24, 2003 QuoteIf the groundspeed is zero and you instantaneously took the wind away it would fall like a rock and rotate nose down until the combination of thrust and gravity accelerated it to flying airspeed I meant if you ‘magically’ take away the wind. Just trying to illustrate a point Quote Most of the arguments about the effects of wind ignore wind shear and turbulence, and also ignore pilots' control inputs being changed because they usually fly by ground reference, not airmass reference, unless in IMC or under the hood. Right, but wind shear and turbulence is different than just wind. All bets are off when it comes to wind shear and turbulence. Derek Quote Share this post Link to post Share on other sites
kallend 2,129 #80 November 24, 2003 QuoteQuoteIf the groundspeed is zero and you instantaneously took the wind away it would fall like a rock and rotate nose down until the combination of thrust and gravity accelerated it to flying airspeed I meant if you ‘magically’ take away the wind. Just trying to illustrate a point Quote Most of the arguments about the effects of wind ignore wind shear and turbulence, and also ignore pilots' control inputs being changed because they usually fly by ground reference, not airmass reference, unless in IMC or under the hood. Right, but wind shear and turbulence is different than just wind. All bets are off when it comes to wind shear and turbulence. Derek But that's my point. Someone says they lose more altitude or something like that when turning from base to final in a wind, and all these folks jump up and down saying no, the plane/canopy doesn't know about the wind and there's no such effect. But planes and canopies do know about windshears and about control inputs. And in the real world windshears DO exist and people DO fly by ground reference and their control inputs ARE different as a consequence.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
Hooknswoop 19 #81 November 24, 2003 QuoteAnd in the real world windshears DO exist and people DO fly by ground reference and their control inputs ARE different as a consequence. If the question had been, "Can windshear or turbulence cause a canopy to dive more?", then the answer would be yes, it can, and it can also cause it to dive less. But that wasn't the question. We do fly by ground refernce, but a canopy doesn't dive any more because there is wind and I don't change my inputs into the canopy if there is wind. Derek Quote Share this post Link to post Share on other sites
davelepka 4 #82 November 24, 2003 Just popping in on this thread. I can't believe it's still alive... ***And in the real world windshears DO exist and people DO fly by ground reference and their control inputs ARE different as a consequence Windshear does exist AT TIMES, and people do fly via a ground reference, but the fact is that anyone participating in swooping activities needs to know the facts of whats really going on. The trouble spot I see with people equating higher winds with increased dive, is the inverse of that theory, and the newer swooper on a sunset load w/ no wind thinking they can take it down to the basement before starting their turn. For this reason it's important that people know and understand the cause/effect relationship between windspeed and swooping. Quote Share this post Link to post Share on other sites
kallend 2,129 #83 November 24, 2003 QuoteQuoteAnd in the real world windshears DO exist and people DO fly by ground reference and their control inputs ARE different as a consequence. If the question had been, "Can windshear or turbulence cause a canopy to dive more?", then the answer would be yes, it can, and it can also cause it to dive less. But that wasn't the question. We do fly by ground refernce, but a canopy doesn't dive any more because there is wind and I don't change my inputs into the canopy if there is wind. Derek Does that mean that if you wished to fly a rectangular pattern, you'd actually fly a trapezoid over the ground when there's a strong wind, because relative to the airmass it's still rectangular? Or do you make it rectangular relative to the ground, in which case your control inputs have changed? I'll bet most people fly by ground reference. You don't get windshears when there's no wind. Windshears are a consequence of wind. There's always a windshear close to the ground on a windy day. A canopy may well dive more on account of windshear.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
Hooknswoop 19 #84 November 24, 2003 QuoteDoes that mean that if you wished to fly a rectangular pattern, you'd actually fly a trapezoid over the ground when there's a strong wind, because relative to the airmass it's still rectangular? Or do you make it rectangular relative to the ground, in which case your control inputs have changed? I'll bet most people fly by ground reference. It means that if I start my landing hook turn at 500 on a calm day, I start it at 500 feet on a windy day. I deal with turbulence, wind shear, etc as I find it. QuoteYou don't get windshears when there's no wind. Windshears are a consequence of wind. There's always a windshear close to the ground on a windy day. A canopy may well dive more on account of windshear. It may and it may not. The atmosphere is a very dynamic meduim. A hot air balloon can be landed by a form of thermal ground effect. But as a rule, again, wind does not cause a canopy to dive more. Derek Quote Share this post Link to post Share on other sites
kallend 2,129 #85 November 24, 2003 QuoteQuoteDoes that mean that if you wished to fly a rectangular pattern, you'd actually fly a trapezoid over the ground when there's a strong wind, because relative to the airmass it's still rectangular? Or do you make it rectangular relative to the ground, in which case your control inputs have changed? I'll bet most people fly by ground reference. It means that if I start my landing hook turn at 500 on a calm day, I start it at 500 feet on a windy day. I deal with turbulence, wind shear, etc as I find it. QuoteYou don't get windshears when there's no wind. Windshears are a consequence of wind. There's always a windshear close to the ground on a windy day. A canopy may well dive more on account of windshear. It may and it may not. The atmosphere is a very dynamic meduim. A hot air balloon can be landed by a form of thermal ground effect. But as a rule, again, wind does not cause a canopy to dive more. Derek Windshears are real consequences of wind that affect real pilots and real skydivers. Telling someone that they are wrong when they say their canopy flies differently in a wind is misleading at best.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
kallend 2,129 #86 November 24, 2003 QuoteQuoteIf the groundspeed is zero and you instantaneously took the wind away it would fall like a rock and rotate nose down until the combination of thrust and gravity accelerated it to flying airspeed I meant if you ‘magically’ take away the wind. Just trying to illustrate a point Also 'magically' revoking Newton's 1st and 2nd laws.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
Hooknswoop 19 #87 November 24, 2003 Do you believe wind (and only wind) cause a canopy to dive more than zero wind? Derek Quote Share this post Link to post Share on other sites
kallend 2,129 #88 November 25, 2003 QuoteDo you believe wind (and only wind) cause a canopy to dive more than zero wind? Derek Lots of things besides wind can make a canopy dive. Like hanging on the front risers. The issue I have in this thread is that someone made an observation and then everyone jumped on him telling him he imagined it. That is a simplistic response because, as you said previously, the atmosphere is a dynamic system and situations exist in a wind that can cause a canopy to descend faster than it would on a calm day. .... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
marks 0 #89 November 25, 2003 QuoteThe issue I have in this thread is that someone made an observation and then everyone jumped on him telling him he imagined it acually somone posted on observation and others including hooknswoop has just tried to explain the missconception and also did it in a very proffessional manner. and that said.... let me try .. im horrible at this but here it goes... well say your flying you canopy above a solid layer of clouds and the air mass was moving at 100 mph... the same air mass you canopy is in is the same air mass the cloud is in you just "above the cloud".... now imagine if you could paint an x in one spot of that cloud but you could not see the ground in any direction.........ok now.. say the canopy has 20 mph forward speed..... say you got right over the top of the x and preformed a hook turn..... downwind or upwind ... you tell me...... how could you tell if you turned down wind or up wind or even crosswind for that matter..... you cant.... because the wind has no effect on the canopy... if you turn facing north with the x to your back.. you would move 20 mph away from the x in a norther direction... say you faced south.. with the x to you back... you would move 20 mph away from that x.....if you faced east or west or any other direction for that matter you would move at a rate of 20 mph from that x... if you did a hookturn or any other turn with your canopy in relation to that x... you would not tell a difference in wich way you went.... because it doesnt matter...... but the airmass is moveing at 100mph... i hope this makes sense........ mark edit to add..... the solid cloud layer would be your pretend ground.... and since it is.. it takes away the ground sheer theory..... also this is only to talk about wind..... im not talking about updrafts wind sheer turbulance or anything else but wind.... Quote Share this post Link to post Share on other sites
kallend 2,129 #90 November 25, 2003 QuoteQuoteThe issue I have in this thread is that someone made an observation and then everyone jumped on him telling him he imagined it acually somone posted on observation and others including hooknswoop has just tried to explain the missconception and also did it in a very proffessional manner. and that said.... let me try .. im horrible at this but here it goes... well say your flying you canopy above a solid layer of clouds and the air mass was moving at 100 mph... the same air mass you canopy is in is the same air mass the cloud is in you just "above the cloud".... now imagine if you could paint an x in one spot of that cloud but you could not see the ground in any direction.........ok now.. say the canopy has 20 mph forward speed..... say you got right over the top of the x and preformed a hook turn..... downwind or upwind ... you tell me...... how could you tell if you turned down wind or up wind or even crosswind for that matter..... you cant.... because the wind has no effect on the canopy... if you turn facing north with the x to your back.. you would move 20 mph away from the x in a norther direction... say you faced south.. with the x to you back... you would move 20 mph away from that x.....if you faced east or west or any other direction for that matter you would move at a rate of 20 mph from that x... if you did a hookturn or any other turn with your canopy in relation to that x... you would not tell a difference in wich way you went.... because it doesnt matter...... but the airmass is moveing at 100mph... i hope this makes sense........ mark edit to add..... the solid cloud layer would be your pretend ground.... and since it is.. it takes away the ground sheer theory..... also this is only to talk about wind..... im not talking about updrafts wind sheer turbulance or anything else but wind.... Thank you. I'm quite familiar with Galilean relativity, what with being a professor of physics and all. Lets repeat your experiment but over hard ground, and you intend to perform a 90degree carving turn to land into the wind. Let's also have a more realistic wind, say 25kt from 270. You are on a heading of 360 before the carve. What is your course? What will be your response to what you see? Will you adjust your heading so your course is 360? What will be your heading if your course is 360? What does that do to your carve to landing? Next: Why exclude atmospheric phenomena that are associated with wind? When you skydive, can you turn off windshear close to the ground? I can't. Let's assume you are on final, flying directly into the wind. Your airspeed is 30kt and your groundspeed is 5kt. As you descend through 20ft agl the windspeed drops by 10kt. Can you tell? What happens to your airspeed? What does your canopy do? Now make it more difficult: the same wind and shear, but you are halfway through a carving turn when you encounter the shear. What does the canopy do? The question that started this thread is about real skydiver in a real atmosphere, yet you wish to simplify it to an idealized atmosphere where difficult-to-analyze phenomena are excluded. A strong wind will always have an associated shear close to the ground, and skydivers swoop over the ground, not over clouds in 100mph winds per your example.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
marks 0 #91 November 25, 2003 QuoteQuoteQuoteThe issue I have in this thread is that someone made an observation and then everyone jumped on him telling him he imagined it acually somone posted on observation and others including hooknswoop has just tried to explain the missconception and also did it in a very proffessional manner. and that said.... let me try .. im horrible at this but here it goes... well say your flying you canopy above a solid layer of clouds and the air mass was moving at 100 mph... the same air mass you canopy is in is the same air mass the cloud is in you just "above the cloud".... now imagine if you could paint an x in one spot of that cloud but you could not see the ground in any direction.........ok now.. say the canopy has 20 mph forward speed..... say you got right over the top of the x and preformed a hook turn..... downwind or upwind ... you tell me...... how could you tell if you turned down wind or up wind or even crosswind for that matter..... you cant.... because the wind has no effect on the canopy... if you turn facing north with the x to your back.. you would move 20 mph away from the x in a norther direction... say you faced south.. with the x to you back... you would move 20 mph away from that x.....if you faced east or west or any other direction for that matter you would move at a rate of 20 mph from that x... if you did a hookturn or any other turn with your canopy in relation to that x... you would not tell a difference in wich way you went.... because it doesnt matter...... but the airmass is moveing at 100mph... i hope this makes sense........ mark edit to add..... the solid cloud layer would be your pretend ground.... and since it is.. it takes away the ground sheer theory..... also this is only to talk about wind..... im not talking about updrafts wind sheer turbulance or anything else but wind.... Thank you. I'm quite familiar with Galilean relativity, what with being a professor of physics and all. Lets repeat your experiment but over hard ground, and you intend to perform a 90degree carving turn to land into the wind. Let's also have a more realistic wind, say 25kt from 270. You are on a heading of 360 before the carve. What is your course? What will be your response to what you see? Will you adjust your heading so your course is 360? What will be your heading if your course is 360? What does that do to your carve to landing? Next: Why exclude atmospheric phenomena that are associated with wind? When you skydive, can you turn off windshear close to the ground? I can't. Let's assume you are on final, flying directly into the wind. Your airspeed is 30kt and your groundspeed is 5kt. As you descend through 20ft agl the windspeed drops by 10kt. Can you tell? What happens to your airspeed? What does your canopy do? Now make it more difficult: the same wind and shear, but you are halfway through a carving turn when you encounter the shear. What does the canopy do? The question that started this thread is about real skydiver in a real atmosphere, yet you wish to simplify it to an idealized atmosphere where difficult-to-analyze phenomena are excluded. A strong wind will always have an associated shear close to the ground, and skydivers swoop over the ground, not over clouds in 100mph winds per your example. QuoteGalilean relativityis that what thats called..?....i feel smart already... no but seriously... you are correct..... i think you missing the point of what peaple were trying to explain...... it is dificult for some to grasp.... not because of mathmatics or anything else... it is just hard to picture all this in some peaples head... so it was simplified to try and make sense to peaple... everyone learns in a different way and not every explanation is going to get through to everyone..... i do not dissagree with you at all..... your just getting into all the other aspecst that you have to deal with in the real world..... this isnt the real world is it.... no..... it is the internet... same as trying to explain somthing to somone without ever seeing them or makeing hand jestures... or useing models..... it was simplified to just discus the efect of solid wind effect on how you turn..... of course there is 5 million other things that effect the way you fly your canopy.......... QuoteLets repeat your experiment but over hard ground, and you intend to perform a 90degree carving turn to land into the wind. Let's also have a more realistic wind, say 25kt from 270. You are on a heading of 360 before the carve. What is your course? What will be your response to what you see? Will you adjust your heading so your course is 360? What will be your heading if your course is 360? What does that do to your carve to landing? and ... see well .. i dont really quite understand this..... maybee because it is in writing...... if you could show me by pointing and maybee models... then maybee i would understand it... but i think... maybee im wrong... but i would definatly start my turn.. in a different spot relitive to the ground.... but at the same altitude..... as i would inrelation to there being no wind.... i dont know.. maybee im not getting this annalogy..... Quote Share this post Link to post Share on other sites
Hooknswoop 19 #92 November 25, 2003 QuoteDo you believe wind (and only wind) cause a canopy to dive more than zero wind? QuoteLots of things besides wind can make a canopy dive. Like hanging on the front risers. Was that a yes or no? QuoteLet's assume you are on final, flying directly into the wind. Your airspeed is 30kt and your groundspeed is 5kt. As you descend through 20ft agl the windspeed drops by 10kt. Can you tell? What happens to your airspeed? What does your canopy do? By 20 feet agl you had better be almost completely out of the dive of weather or not a canopy dives more in wind isn’t going to matter. The question that was; “Here's a question which has bugged me for a while. It appears that when I jump in some fairly strong (yet constant) winds and I am performing a carving front riser turn, I tend to lose more altitude that if I was jumping in low to no winds. Is this something to be aware of, or am I just out to lunch as the canopy will lose the same amount of altitude no matter what the winds are doing.” The answer is no, it doesn’t. There were (are) some skydivers that feel that wind hits the top skin of the canopy, causing it to dive more and that was the theory I was/am attempting to disprove. When the wind speed changes at different altitude, it does have a small effect on the recovery arc of a canopy. When there is turbulence present, it affects the recovery arc of a canopy. When there are thermals present, they can affect the recovery arc of a canopy. When there are updrafts or downdrafts present, they can affect the recovery arc of a canopy. Wind, in and of itself, does not affect the recovery arc of a canopy. Derek Quote Share this post Link to post Share on other sites
kallend 2,129 #93 November 25, 2003 QuoteQuoteDo you believe wind (and only wind) cause a canopy to dive more than zero wind? QuoteLots of things besides wind can make a canopy dive. Like hanging on the front risers. Was that a yes or no? It was a "your question is worded ambiguously, so I'm giving an answer I can live with regardless of what your question actually meant" answer. QuoteLet's assume you are on final, flying directly into the wind. Your airspeed is 30kt and your groundspeed is 5kt. As you descend through 20ft agl the windspeed drops by 10kt. Can you tell? What happens to your airspeed? What does your canopy do? By 20 feet agl you had better be almost completely out of the dive of weather or not a canopy dives more in wind isn’t going to matter. [ Agreed. Just an example (like yours). Wind shears are found higher too The question that was; “Here's a question which has bugged me for a while. It appears that when I jump in some fairly strong (yet constant) winds and I am performing a carving front riser turn, I tend to lose more altitude that if I was jumping in low to no winds. Is this something to be aware of, or am I just out to lunch as the canopy will lose the same amount of altitude no matter what the winds are doing.” The answer is no, it doesn’t. There were (are) some skydivers that feel that wind hits the top skin of the canopy, causing it to dive more and that was the theory I was/am attempting to disprove. When the wind speed changes at different altitude, it does have a small effect on the recovery arc of a canopy. When there is turbulence present, it affects the recovery arc of a canopy. When there are thermals present, they can affect the recovery arc of a canopy. When there are updrafts or downdrafts present, they can affect the recovery arc of a canopy. Wind, in and of itself, does not affect the recovery arc of a canopy. Derek So this skydiver observes an effect that can be due to windshears and can be due to natural changes in control inputs as his sight picture changes, and you tell him he's imagining it because in a uniformly moving airmass with unchanged control inputs it can't happen. Well, in that idealized situation you are absolutely right. It's like freshman physics: Step 1, assume the horse is a sphere. Well, the horse ain't a sphere. And the problem with your answer is that near the ground, uniformly moving airmasses don't exist, and people do adjust their control inputs according to what they see, which is the ground, not the airmass. Think harder! ... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
twnsnd 1 #94 November 25, 2003 Yeah, no shit. Just let it go already. -We are the Swoophaters. We have travelled back in time to hate on your swoops.- Quote Share this post Link to post Share on other sites
Hooknswoop 19 #95 November 25, 2003 I think we've beat this horse to death. Derek Quote Share this post Link to post Share on other sites
