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jtval

descent

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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?
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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

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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

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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!
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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.

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Jim
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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 :S

- Citizen of the World -

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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

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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)

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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 :P
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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 :P



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...

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get 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!

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