Forums: Skydiving: Safety and Training:
1:1 glide/speed?

 


shah269  (A 59581)

Aug 5, 2012, 5:17 PM
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1:1 glide/speed? Can't Post

Does any manufacturer actually publish their 1:1 glide and or speed of full flight of a brand new wing with brand new lines?


SkyPiggie  (D License)

Aug 5, 2012, 7:45 PM
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Re: [shah269] 1:1 glide/speed? [In reply to] Can't Post

What the heck are you talking about? By "wing" do you mean wingsuit, or canopy? If canopy, then the glide ratio is much better than 1:1. They may advertise a "glide ratio". You're an engineer - you should understand that "1:1" is incorrect in the context in which you used it.


Quagmirian  (A 110392)

Aug 5, 2012, 7:56 PM
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Re: [shah269] 1:1 glide/speed? [In reply to] Can't Post

Hey Shah, has anyone really been far even as decided to use even go want to do look more like? Because if they have, I think they will have published the 1:1 glide ratio.


GLIDEANGLE  (D 30292)

Aug 5, 2012, 8:03 PM
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Re: [shah269] 1:1 glide/speed? [In reply to] Can't Post

By "1:1" do you mean a wing loading of 1 lb / sq ft?


shah269  (A 59581)

Aug 5, 2012, 8:04 PM
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Re: [SkyPiggie] 1:1 glide/speed? [In reply to] Can't Post

In reply to:
What the heck are you talking about? By "wing" do you mean wingsuit, or canopy? If canopy, then the glide ratio is much better than 1:1. They may advertise a "glide ratio". You're an engineer - you should understand that "1:1" is incorrect in the context in which you used it.
Sorry about that, 1:1 canopy(assume square 9 cell) ground speed in normal full flight.
Not swoop or any attitude changes. Simple full flight ground speed.

I had one of the students in one of my enrichment classes ask me and I did a quick google and didn't see anything on canopies.

Perhaps I was googling it incorrectly. Just wondering if such data was ever simulated or tested let alone determined?
Thank you


(This post was edited by shah269 on Aug 5, 2012, 8:06 PM)


Premier quade  (D 22635)
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Aug 5, 2012, 9:17 PM
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Re: [shah269] 1:1 glide/speed? [In reply to] Can't Post

In reply to:
Sorry about that, 1:1 canopy(assume square 9 cell) ground speed in normal full flight.
Not swoop or any attitude changes. Simple full flight ground speed.

Ground speed is not equal to airspeed unless in zero wind conditions.

What I believe you're asking for is airspeed, but in any case the answer is going to be no.

There are a couple of reasons for this, but the biggest one is that glide speed at a 1:1 wing loading would still vary by canopy size due to scaling factors and line trim. Not much, maybe a couple of mph, but it would be there none-the-less.

Rough rule of thumb, figure 25 mph.

Determining it more closely (though probably not exactly) would require nothing more than a GPS and a little math.


(This post was edited by quade on Aug 5, 2012, 9:24 PM)


format  (B 15348)

Aug 6, 2012, 12:29 AM
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Re: [shah269] 1:1 glide/speed? [In reply to] Can't Post

In reply to:
Does any manufacturer actually publish their 1:1 glide and or speed of full flight of a brand new wing with brand new lines?

On Rounds should be 0:1 on a no_wind day.. meaning weight/you going down 15ft/sec with zero ft anywhere else.

On 'glideable' canopies (say RamAir) 'Glide Ratio/Full Flight increases horizontal speed to 2.5 to 3+.. meaning your vertical speed counteracts with horizontal speed.

Now, I can't see reason to print a spreadsheet for ALL wind conditions you may jump in, in order for you to figure your relative forward speed.


sundevil777  (D License)

Aug 6, 2012, 4:39 AM
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Re: [quade] 1:1 glide/speed? [In reply to] Can't Post

In reply to:
Ground speed is not equal to airspeed unless in zero wind conditions.

No, airspeed includes a significant vertical component, unless you are flying level.


5.samadhi

Aug 6, 2012, 6:04 AM
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Re: [quade] 1:1 glide/speed? [In reply to] Can't Post

In reply to:
In reply to:
Sorry about that, 1:1 canopy(assume square 9 cell) ground speed in normal full flight.
Not swoop or any attitude changes. Simple full flight ground speed.

Ground speed is not equal to airspeed unless in zero wind conditions.

What I believe you're asking for is airspeed, but in any case the answer is going to be no.

There are a couple of reasons for this, but the biggest one is that glide speed at a 1:1 wing loading would still vary by canopy size due to scaling factors and line trim. Not much, maybe a couple of mph, but it would be there none-the-less.

Rough rule of thumb, figure 25 mph.

Determining it more closely (though probably not exactly) would require nothing more than a GPS and a little math.
glide ratio would also have to take into account drag of the canopy pilot which is not fixed obviously (we come in all shapes and sizes).


shah269  (A 59581)

Aug 6, 2012, 6:32 AM
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Re: [quade] 1:1 glide/speed? [In reply to] Can't Post

Quote:
Rough rule of thumb, figure 25 mph.
Quade,
Thank you that's what I was thinking but was not 100% sure.

One of the kids asked me how fast my 210 Tri traveled, ground speed. And I honestly did not know.
I guessed about 25mph but that was just a guess.


But manufactures don't measure this kind of thing?


5.samadhi

Aug 6, 2012, 6:35 AM
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Re: [shah269] 1:1 glide/speed? [In reply to] Can't Post

In reply to:
Quote:
Rough rule of thumb, figure 25 mph.
Quade,
Thank you that's what I was thinking but was not 100% sure.

One of the kids asked me how fast my 210 Tri traveled, ground speed. And I honestly did not know.
I guessed about 25mph but that was just a guess.


But manufactures don't measure this kind of thing?
thats like asking how long a piece of string is. It depends on the piece of string. Groundspeed depends on windspeed and airspeed.

In reply to:
But manufactures don't measure this kind of thing?
how can you quote his post and still ask this question? Did you read his post?


(This post was edited by 5.samadhi on Aug 6, 2012, 6:36 AM)


shah269  (A 59581)

Aug 6, 2012, 6:43 AM
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Re: [5.samadhi] 1:1 glide/speed? [In reply to] Can't Post

Quote:
Determining it more closely (though probably not exactly) would require nothing more than a GPS and a little math.
Again I'm going to ask, "Manufactures don't measure this kind of thing?"

Parameters, canopy loaded 1:1, factory trim, assuming 0 winds to determine ground speed? Or glide efficiency?

If the answer is no then well the answer is no. It was simply a question from me seeking insight to answer a question I was asked by a 12yo kid who himself just wanted to know more about the world he lives in.

If that offends you? Well I'm sorry. Maybe you should not be clicking reply unless you have some useful info to provide? maybe a math equation or even better a link to a graph demonstrating the speed of the cannopy Vs it's size.


(Sorry mate, having a bad day didn't mean to go off on you, it was wrong of me)

Well assume....point mass? As in if your drag were taken into account of the average person.

The kids wanted to know if they could jump from a plane and fly home and how if so how high they would need to jump from. Smile
You know kids being kids!

And i promiced them I would email them an answer.
I kind of like 25mph but I'm 100% sure they are going to ask me what about a bigger cannopy? Could they go further? You know how kids are.


(This post was edited by shah269 on Aug 6, 2012, 6:49 AM)


5.samadhi

Aug 6, 2012, 6:49 AM
Post #13 of 18 (1676 views)
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Re: [shah269] 1:1 glide/speed? [In reply to] Can't Post

In reply to:
Quote:
Determining it more closely (though probably not exactly) would require nothing more than a GPS and a little math.
Again I'm going to ask, "Manufactures don't measure this kind of thing?"

Parameters, canopy loaded 1:1, factory trim, assuming 0 winds to determine ground speed? Or glide efficiency?

If the answer is no then well the answer is no. It was simply a question from me seeking insight to answer a question I was asked by a 12yo kid who himself just wanted to know more about the world he lives in.

If that offends you? Well I'm sorry. Maybe you should not be clicking reply unless you have some useful info to provide? maybe a math equation or even better a link to a graph demonstrating the speed of the cannopy Vs it's size.


(Sorry mate, having a bad day didn't mean to go off on you, it was wrong of me)

Well assume....point mass? As in if your drag were taken into account of the average person.
No offense taken. I just didnt understand what was so complicated.

off the top of my head:
air density
drag of canopy pilot
drag of different type of lines
movement of canopy pilot in harness
spread of risers
windspeed

All these factors will change glide ratio of canopy. Thats just looking at one type of canopy at one size. Take into account different sizes of canopies and you have even more variables (line length, size of canopy, etc).

Too many variables for 'manufacturer' to give one answer. Only rough rule of thumb available.


davelepka  (D 21448)

Aug 6, 2012, 6:59 AM
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Re: [shah269] 1:1 glide/speed? [In reply to] Can't Post

Quote:
You know how kids are

Yeah, I feel like I'm reposnding to one right now. Use your brain and think about the questions you're asking. Show me the world where every canopy is loaded at 1 to 1, and there is zero windspeed, and then I'll give you some absolute answers.

That world doesn't exist, so consider the factors at play, and come with with your own answers. It's not hard to balance out the various factors and come up with a 'good' answer.

Case in point, what winds are too high to jump in? That's a personal question, for the most part, but ultimately what is the limiting factor? It's the ability of the canopy to penetrate the wind and achieve some forward speed. Eventually you reach wind speeds high enough that your canopy will come straight down, or even be backed up.

So we know that's the 'limit' and I'm sure you have an idea of what is considered 'higher' winds at the DZ, so add it all up and what do you come up with? The answer is the forward speed (or approx) of a canopy.

So if the student wind limit is 15/16, and most fun jumpers seem to stand down around 20-ish, you could then add in a couple mph for 'safety', and come up with a forward speed of (big surprise) the answer that was spoon fed to you, about 25mph.

If you want to be an engineer, fine, be one all the time. Don't be a know-it-all half the time, and a dumbass when you don't feel like thinking.


(This post was edited by davelepka on Aug 6, 2012, 6:59 AM)


theonlyski  (D License)

Aug 6, 2012, 6:59 AM
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Re: [shah269] 1:1 glide/speed? [In reply to] Can't Post

PD has a wind meter that they can deploy and drag to get an accurate wind speed. Why don't ya call/email them and ask them these questions? Betting they would have more info.


Dean358  (D 28881)

Aug 6, 2012, 10:26 AM
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Re: [shah269] 1:1 glide/speed? [In reply to] Can't Post

I'm not sure why this thread is in safety and training, but allow me to clarify a couple of things:

"Glide Ratio" is the ratio of lift divided by drag, symbol "L/D." Typically one talks about the L/D of the entire aircraft, not just the wing. In the case of unpowered aircraft, e.g. a canopy with a pilot hanging under it, the L/D is equal to the forward motion divided by the descent. For example, if you flew 3,000 feet horizontally and dropped 1,000 feet vertically then the effective glide ratio would be 3 to 1.

For any given aircraft there are a range of glide ratios that change with weight (related to wing loading in our case) and speed. Once you get a little faster than stall speed then as the airspeed increases the glide ratio decreases. There are two “optimum” speeds for L/D for every aircraft at any given weight: one will keep you in the air the longest (“minimum sink”) and the other will have you cover the most amount of horizontal distance (“maximum glide”). The engineering behind this is described by something called “flight polar characteristics” an explanation of which can be found here:

http://www.gliderbooks.com/downloads/H_Ch4.pdf

A ram air parachute with a pilot hanging under it has a very compressed flight polar and will be so affected by wind that it’s not all that meaningful to publish a standard “forward speed” for it. What is useful is realizing that if you’re upwind of your landing spot and trying to get home you want to fly in minimum sink configuration: deep brakes or rear risers to give the wind the most time to push you home. If you’re downwind of your landing spot and trying to get home you want to increase your forward speed by using no brakes or front risers and minimize your drag by getting small. (And pick an alternate landing area well in advance, of course.)

So, some crude generalizations:
A sport ram air parachute with pilot typically has a glide ratio of between 2 to 1 and 3 to 1. A sport ram air parachute of the type you might be flying typically has a forward air speed of about 20 - 25 MPH (use Quade and Dave's 25 MPH estimate).

Conclusions:
This means the primary variable affecting how much ground you can cover under canopy is: wind speed.

But the most important ratio of all, for you Shah? Number of skydives divided by number of posts on DZ.com. I strongly recommend you work on getting that above 1.00


(This post was edited by Dean358 on Aug 6, 2012, 11:11 AM)


jcd11235  (D License)

Aug 6, 2012, 11:13 AM
Post #17 of 18 (1582 views)
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Re: [shah269] 1:1 glide/speed? [In reply to] Can't Post

In reply to:
maybe a math equation or even better a link to a graph demonstrating the speed of the cannopy Vs it's size.

Don't you claim to be an engineer? You should be able to identify enough independent variables on which canopy speed depends to quickly realize that there couldn't be a single number given by the manufacturer. That's Physics 101 stuff.


shah269  (A 59581)

Aug 6, 2012, 11:37 AM
Post #18 of 18 (1559 views)
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Re: [Dean358] 1:1 glide/speed? [In reply to] Can't Post

Quote:
So, some crude generalizations:
A sport ram air parachute with pilot typically has a glide ratio of between 2 to 1 and 3 to 1. A sport ram air parachute of the type you might be flying typically has a forward air speed of about 20 - 25 MPH (use Quade and Dave's 25 MPH estimate).
Dean thank you, that's what I told the kids.
I said 25mph if the air was still which it never is.

And in it self it doesn't seem like it is very fast but when you think about it....25mph...that's fast!



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