jtval 0 #1 November 1, 2002 ok I have a question. this has been asked a ferw times but i never knew how to answer it, other then " I'm not sure exactly" How can you tell your rate of descent under canopy? i know my Main is rated at around 14mph with zero wind, but that is foward. what about downward? anyone know?My photos My Videos Quote Share this post Link to post Share on other sites
gus 1 #2 November 1, 2002 How about just starting a stopwatch at a given altitude, stopping it on the ground and working the decent rate out in the bar? GusOutpatientsOnline.com Quote Share this post Link to post Share on other sites
Staso 0 #3 November 1, 2002 Quote i know my Main is rated at around 14mph with zero wind, but that is foward. what about downward? anyone know? zero or not zero wind it shouldn't make any difference. your air speed should be the same. as for downward, i guess you can try to clock it. it's not gonna be very accurate, but it will give you the rough number. it's kinda hard thoug since any maneuvers will change your descent rate. stan -- it's not about defying gravity; it's how hard you can abuse it. speed skydiving it is ... Speed Skydiving Forum Quote Share this post Link to post Share on other sites
markbaur 0 #4 November 1, 2002 You can get a rough idea by using a glide ratio of 3:1. At 14 mph of forward speed, that's a little less than 5 mph down, or about 7 fps. You'll get a better number if you take a stopwatch and your Digitude that measures altitude in 10-foot increments. 14 mph seems really slow. At that speed and 3:1 glide ratio, you should be able to stand up easily in 14-mph winds without flaring! What do you mean by "rated at around 14 mph"? Mark Quote Share this post Link to post Share on other sites
jtval 0 #5 November 1, 2002 What do you mean by "rated at around 14 mph"? this is just what I have heard about the approximate size of my main. your air speed should be the same. unless we're talking abou two different things air speed will change with winds. If I am flying with the wind I will go the speed of the wind plus the speed of my canopy. If I fly against it it will fly at the speed of the wind Minus my canopy's speed!My photos My Videos Quote Share this post Link to post Share on other sites
Jimbo 0 #6 November 1, 2002 Actually JT your airspeed will remain the same. Your ground speed however will change. There is a difference and I'm sure that Quade and Kallend are better qualified than me to explain the differences. - Jim"Like" - The modern day comma Good bye, my friends. You are missed. Quote Share this post Link to post Share on other sites
Wavelength 0 #7 November 1, 2002 You are talking about different things. The speed of the wind combined with the speed of your canopy will give you your ground speed. Air speed is relative to the winds and will be the same as a function of the canopies flight characteristics. Quote Share this post Link to post Share on other sites
Plucky 0 #8 November 2, 2002 airspeed = speed relative to the air. groundspeed = speed relative to the earth. your airspeed is measured because any wing (canopy or otherwise) needs a certain amount of air passing over it to give lift ... your canopy cares not what the ground is doing underneath it. therefore in my humble opinion, all other things being constant, your rate of descent shouldn't change if the wind speed changes. hope it makes sense - Citizen of the World - Quote Share this post Link to post Share on other sites
decompresion 2 #9 March 1, 2012 Quote it's kinda hard thoug since any maneuvers will change your descent rate. stan If you flatten out the canopy (rear risers for example) and create as little drag as possible in your body...you could gain altitude for a short burst of time? Unless you are in a paraglider riding thermals...everyone reaches the ground at some point right?There are no dangerous dives Only dangerous divers Quote Share this post Link to post Share on other sites
DaVincisEnvy 0 #10 March 1, 2012 Unless I'm missing something major here: You can think of your ground speed as having both a horizontal and a vertical component. 1) Ground speed = canopy's airspeed + wind speed Therefore: 2) Horizontal ground speed = horizontal airspeed + horizontal wind speed 3) Vertical ground speed = vertical airspeed + vertical wind speed Since the canopy's airspeed is constant in full flight (e.g. when you don't deform the airfoil by pulling on risers or toggles), the factor that causes your ground speed to change is the wind speed. Wind has an obvious horizontal component, but, unless you're caught in an updraft, downdraft, or turbulence, the vertical component is fairly negligible. Assuming, then, that vertical wind speed = 0, that last equation becomes: 3b) Vertical ground speed = vertical airspeed + 0 Your vertical ground speed is therefore determined by your canopy's vertical airspeed (a function of its flight characteristics at your wing loading), not by wind conditions. So, yes, you should just be able to clock your descent time from a given altitude and figure: Decent rate (i.e. speed) = (altitude)/(time to descend from that altitude) Quote Share this post Link to post Share on other sites
faulk04 0 #11 March 1, 2012 get a neptune, it tells you your descent rate :) Quote Share this post Link to post Share on other sites
theonlyski 3 #12 March 1, 2012 Quote 1) Ground speed = canopy's airspeed + wind speed Therefore: That's only if flying directly with the wind, the opposite would be flying into the wind which would make your ground speed = canopy air speed - windspeed. Then there's the off angles, best break out an E6B and calculate those "I may be a dirty pirate hooker...but I'm not about to go stand on the corner." iluvtofly DPH -7, TDS 578, Muff 5153, SCR 14890 I'm an asshole, and I approve this message Quote Share this post Link to post Share on other sites
DaVincisEnvy 0 #13 March 1, 2012 Quote That's only if flying directly with the wind, the opposite would be flying into the wind which would make your ground speed = canopy air speed - windspeed. Then there's the off angles, best break out an E6B and calculate those Nah, just define your positive and negative directions of motion, then use trig to break your wind vector into downwind/upwind and crosswind components as applicable. If you define: 1) direction the canopy is flying = positive 2) then wind blowing in the direction the canopy is flying (flying with the wind) = also positive So ground speed = canopy airspeed + wind speed If you're flying into the wind, then the wind is blowing in the opposite direction that the canopy is flying, so: 1) direction the canopy is flying = positive 2) wind opposite the direction the canopy is flying = negative ground speed = canopy airspeed + (negative) wind speed Since adding a negative number is the same as subtracting that same number, the equation reduces to: ground speed = canopy airspeed - wind speed (for flying into the wind) The same equation works, you just have to define your positive and negative directions of motion. But you're right, when you start calculating ground speeds when flying crosswind, you'll have to do the vector math, and a calculator certainly helps with that... Quote Share this post Link to post Share on other sites
jtval 0 #14 March 2, 2012 Quoteget a neptune, it tells you your descent rate :) Lotta good that does me after TEN YEARS. LOL Back then Neptunes were on the market.I think they came out around 2000-ish actually.My photos My Videos Quote Share this post Link to post Share on other sites
faulk04 0 #15 March 2, 2012 QuoteQuoteget a neptune, it tells you your descent rate :) Lotta good that does me after TEN YEARS. LOL Back then Neptunes were on the market.I think they came out around 2000-ish actually. didnt realize this thread was started back then...fail by me! Quote Share this post Link to post Share on other sites