speed calculation

[tosca 0]

I´m would like to calculate what forward speed my canopy has with different weights. Anyone who can help me with this?

[SkydiveMonkey 0]

Got a GPS? I imagine if you measure speed in one direction, turn 180 and measure in that direction then average it, that's your speed.

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[kevin922 0]

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I´m would like to calculate what forward speed my canopy has with different weights. Anyone who can help me with this?

I just stumbled upon this I am very tempted to get one.. it'll tell you your speed.

Kevin

[SkydiveMonkey 0]

It'll tell you your groundspeed anyway. Airpseed would be harder to find. Was it Quade made a post about this a while ago?

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[quade 4]

Yeah, I was looking at my wind meter and thought I might try some experiments with it.

I haven't gotten around to actually doing it yet though. In -theory- if you know the full flight speed at one weight you should be able to calculate other weights with a fair degree of accuracy. It's more than simply knowing the forward speed though, you'd also need to know the decent rate to come up with a glide angle. Again, in -theory- this angle doesn't change with an increase in weight, only the speed at which you are on the angle does.

BTW, I'll be using a Kestral 4000 for my experiments, so I'll get both vertical and horizontal data as well as temp and baro. The 4000 has a recording function that will make things a bit easier too.

quade -
The World's Most Boring Skydiver

[councilman24 37]

I use a smaller version anemometer similar to this.
http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&langId=-1&catalogId=10001&classNum=1&subdeptNum=&storeNum=&productId=49922

I measured the air speed of both a 190 Sabre and 190 Triathlon. Both were 30 mph with about 230 lbs suspended.

Any calculation would only be available based on fitting an equation to emperical data. In other words, measure speed at two or three weights (the more the better) and fit an equation to the points. And do you really want air speed or glide ratio? Or only the horizontal vector of the canopy speed, which includes a vertical vector.

I'm old for my age.
Terry Urban
D-8631
FAA DPRE

[Hooknswoop 19]

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It'll tell you your groundspeed anyway. Airpseed would be harder to find. Was it Quade made a post about this a while ago?

Right, if you are travelling exactly crosswind then turn 180 degrees, again travelling exactly crosswind, your groundspeed would be higher than your airspeed and exactly the same in both directions.

Quade was working with a Kesrtal 4000, I believe, and getting some accurate measurements.

Hook

[SkydiveMonkey 0]

although you could see this on the GPS screen I suppose if you keep hold of it. Could use it to point into / downwind

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[quade 4]

Yes, I did make a few jumps just to see if the dang thing would work after a freefall. I was taking it one step at a time and just focusing on decent rate for that.

quade -
The World's Most Boring Skydiver

[tosca 0]

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Any calculation would only be available based on fitting an equation to emperical data.

I think it could be pretty many things to consider though.. It would take a LOT of tests and good knowlegde of aerodynamics to find out the equation, wouldn´t it?

I thought that maybe someone else already had done that, somewhere in the world. I´m a bit lazy My idea was to try to guess the airspeed by calculation and see how accurate such a guess could be, maybe by using some kind of GPS.

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And do you really want air speed or glide ratio?

I was thinking about the air speed. But why not test both

[JYorkster 0]

I used a Kestrel 1000 which resulted in an airspeed about 23-24 mph on a Sabre 170 loaded about 1.1. As has already been noted though, this is total speed which includes the downward movement. Without knowing the exact glide angle, the true horizontal speed would be hard to calculate.

Rock

[cobaltdan 0]

a good 3d gps will give you your 'vector velocity'.
this is a speed measurement from the delta of two 3 dimensional points in space.

this is how we calculate foward speeds.

sincerely,

dan<><>

Daniel Preston <><>
atairaerodynamics.com (sport)
atairaerospace.com (military)

[riddler 0]

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Quade was working with a Kesrtal 4000, I believe, and getting some accurate measurements.

Someone in Longmont did this with a wind speed indicator - looked like a tiny fan with a digital read-out. I think it was a Kestral. I don't like to drop real names on public forums, so you can PM me if you want to know who. He might even let you borrow it - I'm sure we would all like to know your speed under that handkerchief you call a parachute.

Trapped on the surface of a sphere. XKCD