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Hey guys, Is there a way I can calculate the different air speeds I would have under different canopies with different wingloadings?

Buy a windmeter, they're fairly cheap, use it to find your airspeed (both vertical and horizontal components). Then time your vertical descent over, say, 1000' to calculate the vertical component. Subtract the vertical from the combined and voila, you have the horizontal airspeed. Add weights to find numbers for different wingloadings. Then post your data along with canopy type, size and wingloading so we can all know the answer. Calculating things like this won't likely give you reliable figures, the variables are complex.

won't an anemometer give true airspeed? why do you need vert components?

If measuring is fine by you, then an anemometer is obviously the way to go.

if you're looking to calculate it without doing it, and without (for example) extrapolating from sizes that you *are* jumping, then I suggest contacting the manufacturer for the panel shapes, line lengths, and materials for the canopy and size in question, building a finite element model, and pulling your results from that.

Which is to say... Unless you have a lot more data than "245 square feet" and "rectangular" and "7-cell", you'll be better off just measuring it or guessing from similar canopies. Worse, if you find somebody who's got the data you'd need to do the calculations, the odds are good that you've also found somebody who's got the airspeed of the canopy under the wingloading you want, or has data you can use to interpolate/extrapolate.

Caveat: While I've got a Ph.D. in Physics, I'm not an aeronautical specialist

What Martini said. This method will give you true horizontal and vertical airspeeds. Just make sure you mount anemometer far enough from the body - from my experiments, even 2ft from the body is not enough, the boundary layer slows down the air and anemometer will show lower airspeeds.

However, you don't need to repeat this with different weights - you can easily and rather accurately prorate the speed measured with known weight, to a different weight (under the same canopy). If jumper 1 weighs W1 (including all gear) and jumper 2 weighs W2, the ratio of their speeds will be

V2/V1 = (W2/W1)^0.5

This is because aerodynamic forces are proportional to the square of airspeed - and vice versa, airspeed is proportional to the square root of wingloading.

For example, jumper 1 is 180lbs with gear and his rate of descent under Trango 225 is 8ft/s. Then, for jumper 2 who's 250lbs with gear, the rate of descent under the same canopy will be 8*(250/180)^0.5 = 9.5ft/s.

For the same weight but different canopy size (S1 and S2),

V2/V1 = (S1/S2)^0.5.

For example, if a jumper under Flik 240 has rate of descent 8ft/s, then the same jumper under Flik 300 will have rate of descent 8*(240/300)^0.5 = 7.2ft/s.

Knowing rate of descent is oftentimes useful to estimate your opening height. For example, my Flik 322 descends at 10ft/s, so 30s canopy flight pretty consistently equates to 300ft of fully open canopy.

I like the math/physics Yuri but your algorithm doesn't take into account the increased drag (increasing as the square of speed), canopy distortion, jumper drag etc. My perception is that actual speed is somewhat less than calculated speed for increasing wingloading. I won't even guess at the amount and it's probably fairly small. My problem with measurement has been inconsistency in the windmeter measurement, the measurements I've done have been in somewhat windy conditions and aren't reliable. Beside that, when you mention V-1 and V-2 my train of thought derails to the wingsuit track.

Thanks guys! some pretty in depth ideas floating around there! I guess with my level of understanding of physics I'd do better to jump a few different size canopies off the same object in the same conditions and observe the difference in penetration first hand, and just deal with rough estimates!

Sorry, that not exactly right
The horizontal speed of a canopy is the square ruts of :
Total speed measured a the square, less vertical speed a the square.
Take air
Christophe

I was speaking loosely. The horizontal speed can be derived using the measured airspeed as the Hypotenuse, the measured/calculated descent speed as the Adjacent and the calculated resultant horizontal speed as the Opposite. H squared minus A squared = O squared. Or O= the square root of (H squared minus A squared). All those numbers being applied as vectors in a right triangle.

Just like you said

Those are tangibles, relatively easy to work with. Inferring horizontal speeds using those vectors when changing canopy loading doesn't take into account a bunch of drag factors that change when you alter the wingload. I don't think you can successfully predict the horizontal speed when you delta the wingload but it would be interesting to compare predicted speed with calculated speed to see what the error looks like.

It's not very very important, but it's just an easy way to know the exact horizontale speed from a mesurement done while flying.
In case somebody need it for something precise
take air
Christophe

That's how I got interested, the need to know speed and flyable distance for a ground launch. I decided that the margin for error was too small to make the flight safe. I have a standing offer to help launch anyone willing to try it though and I'll even call 911 immediately after launch.