Spaceball Speeds?

[321seeya 0]

Just curious if there is a chart out there to determine how fast a spaceball will fall with a given amout of weight added to it. For example: how much weight to add to achieve 120 vs how much weight to add to achieve 180. Thanks for your help in advance.

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BASE 3:16 - Even if you are about to land on a cop - DONT FORGET TO FLARE!
Free the soul -- DJ

[lowie 0]

The equation for terminal velocity is

v(terminal) = ((2*m*g)/(Cd*roe*A))^(1/2) using SI units ie

v(terminal) = velocity in metres/sec
m = mass in kilograms
g = gravitational acceleration (10m/s/s)
Cd = drag cooeficient (which needs to be for SI units)
roe = air density in kg/m3 (cubed)
A = area in metres squared

So saying all that, for a given skyball, if you know its speed for a certain weight, you can calculate the approx speed for any weight by multiplying that speed by the square root of the ratio of new wieght divided by the test weight and this weight can be in pounds, ounces, kilos etc.

eg. if the ball falls at 120 mph if it's weight is 10oz then to calculate the velocity for a weight of 20oz

V(new weight) = v(10oz) * (new weight/10oz)^(1/2)
= 120mph * (20oz/10oz)^(1/2)
= 169mph

[kallend 2,113]

Quote

The equation for terminal velocity is

v(terminal) = ((2*m*g)/(Cd*roe*A))^(1/2) using SI units ie

v(terminal) = velocity in metres/sec
m = mass in kilograms
g = gravitational acceleration (10m/s/s)
Cd = drag cooeficient (which needs to be for SI units)

Cd is DIMENSIONLESS, so it doesn't matter what units you are using as long as they are internally consistent.

The density is RHO, not ROE (Greek letter)

Quote

roe = air density in kg/m3 (cubed)
A = area in metres squared

So saying all that, for a given skyball, if you know its speed for a certain weight, you can calulate the approx speed for any weight by multiplying that speed by the square root of the ratio of new wieght divided by the test weight and this weight can be in pounds, ounces, kilos etc.

eg.

V(new weight) = v(50oz) * (new weight/50oz)^(1/2)

Cd for smooth spheres is around 0.4. A furry tennis ball is probably a bit higher than 0.4.

Air density (rho) at sea level is 1.23kg/m^3

this should enable you to make a first approximation to the weight needed, then you can adjust as necessary.

Be safe with the spaceball, they can do a lot of damage.

...

The only sure way to survive a canopy collision is not to have one.

[PhreeZone 20]

Tail length has a huge factor in speeds also. If you make too long of a tail the ball is very slow. You need to figure the Coeffecent of drag with the tail also.

Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

[Levin 0]

I know this isn't what you asked but I'm throin' at ya anyway. You're goal on every ball jump is to catch the ball before you deploy. Otherwise you are endangering any people and/or animals on the ground that may be under the balls path. If the ball impacts concrete then you are endandering anyone or anything with a 50 yard radius of the point of impact. If you have a ball that falls 120mph and you have sunk out or floated above the ball at the retrieving ailtitude then you will have to arch or de-arch like hell to be able to catch it in time before you have to deploy. If you have a ball that falls 180mph you have even less time to retrieve it. If you sink out (not likely) then you will have to float a little to get it. If you float above it (likely) then you are going to have to dive to catch it. To catch a 180mph ball you may have to increase your speed to 200mph to quickly catch it. When travelling at that speed it is very difficult to get your arms out in front of you to grab it. 180 - 200mph is a very sensitive speed for minor movements. You may actually float above it by simply just trying to grab it. Consider this before making a ball jump. If you fail to retrieve a ball and it kills somebody on the ground 1. you are eligible for manslaughter charges 2. the dz will be sued 3. the pilot will lose his license 4. the FAA will specifically ban spaceballs and 5. lots of freeflyers will be pissed. Perhaps you should consider narrowing your search to information on how much weight to make a spaceball that falls between 145 - 165mph. When making your ball the brand of ball, the number on the outside and the size of your lead shot will determine how much weight you can put in it. Depending on where you jump and if your DZO allows spaceballs, I will PM you the correct instructions on how to make one so that you will not have to experiment. My ball falls 154mph. Good luck and be safe.

[davedlg 0]

I'm just a newbie, but when I saw this thread title I was thinking:
Light Speed
Ridiculous Speed
Ludicrous Speed

[RyanofOZ 0]

I did to haha!

Oz

[davelepka 4]

For an experienced freeflyer in Fla, I say go find a DZ which allows Spaceballs, and ask the guy with the ball (s).

If you're trying to build your own ball, don't. You have to be a skilled flyer at any speed to experiement with ball weights and speeds. If you are a skilled flyer like that, see paragraph one, and after you meet the guy with the ball (s), go jump with him.

[Levin 0]

Quote

For an experienced freeflyer in Fla, I say go find a DZ which allows Spaceballs, and ask the guy with the ball (s).

If you're trying to build your own ball, don't. You have to be a skilled flyer at any speed to experiement with ball weights and speeds. If you are a skilled flyer like that, see paragraph one, and after you meet the guy with the ball (s), go jump with him.

yah, what dave said.

if you're in texas you can come see me at skydive houston for a ball jump. i'll take ya on one after a 2-way to prove your skilled enough to do it. as for ballmastering yourself i have adeal with dzo that only myself and moffet can ballmaster. this way i don't ever have to worry about one being dropped, especially behind my back. and the pilot doesn't have to worry about losing his license. maybe sounds a little unfair but it's in the best interest of everyone.

[packerboy 3]

What everyone needs is a place where they can drop cars, couches, bikes, tires etc. Ever heard of such a place?

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In matters of style, swim with the current; in matters of principle, stand like a rock. ~ Thomas Jefferson

[Levin 0]

eloy, az