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[Primate]

There's actually a couple other factors, but they're hard to take into account. Use the ideal gas law, PV=nRT. (If you're not familiar, pressure x volume = number of moles x gas constant x temperature.) Balloons float for the same reason that people can swim; the weight of the balloon is less than the weight of the air it displaces. This buoyancy force is determined by ρVg, density of displaced fluid x volume x gravitational acceleration.

Manipulating the equations, you find that the weight you can lift is equal to ρgnRT/P - mg (of balloon). Disregard the gas constant, the gravitational force, and the weight of the latex for simplicity's sake, and you're left with ρnT/P. This is where you realize you're screwed. Air density itself varies based on pressure, humidity, and temperature, yet so does the volume of your balloon. If you could somehow regulate the number of moles so that nT/P was constant for your current location, you'd be all set. Show up with a calculator and lots of paper, bring your barometer, pressure gauge, and thermometer, and you'd know exactly how many moles of helium to add to provide the proper lifting force.

Or, on the day of competition, you could fill up a balloon all the way, and just add weight until it stops going up.

[Xenarian]

How much mass have you guys successfully raised with your balloon? I've got as much as 6.9 grams up. That's a lot of points. ^_^

[WinWizard]

I looked at the rules and I was thinking, "Where am I going to put this balloon???" That's going to take up so much space.....and i'm a little nervous about leaving an inflated balloon in the same vacinity of potentialy sharp objects for a long period of time. All that balloon has to do is get a breeze on it and blow into the way of my other tasks or the pointy end of a screw that I used to put it all together and then there's a hole. You could tie it down to prevent that problem but when you release it, on its way up it could still bump against something and pop.

Try inserting a divider in between the balloon and the rest of the moving parts and essentially create a box around the balloon.

[jarrred_1415]

How much mass have you guys successfully raised with your balloon? I've got as much as 6.9 grams up. That's a lot of points. ^_^

i got a balloon to raise 13 grams. but it was bigger than the normal size but still within the parameters

[questionguy]

Does anyone know of a way to get a lot of mass without really having to increase the helium amount, or is that the only way?

[Flavorflav]

Does anyone know of a way to get a lot of mass without really having to increase the helium amount, or is that the only way?

Magic?

[Paradox21]

Does anyone know of a way to get a lot of mass without really having to increase the helium amount, or is that the only way?

Magic?

Fill the room you are running it in with a much denser gas?

No, you pretty much just have to have more helium.

[questionguy]

Does anyone know of a way to get a lot of mass without really having to increase the helium amount, or is that the only way?

Magic?

Fill the room you are running it in with a much denser gas?

No, you pretty much just have to have more helium.

Thanks, I'll look more into both of your suggestions

[Flavorflav]

Does anyone know of a way to get a lot of mass without really having to increase the helium amount, or is that the only way?

Magic?

Fill the room you are running it in with a much denser gas?

No, you pretty much just have to have more helium.

I suppose if your box was enclosed and you used a lot of dry ice, you could decrease the temperature to the point where the balloon might have more lifting power. I'm not sure it would be worth it, though.

ETA: I just did some math, and theoretically you wouldn't actually need much dry ice if you could get it to sublimate quickly. You wouldn't get that much return, though - at most 25% more mass if you could drop the temp down to -50 F, which is pretty ambitious. I think you might have better luck with magic.

[ichaelm]

Correct me if I'm wrong, but the buoyant force on a balloon is equal to the weight of the displaced air. Assuming a constant density of air and constant gravity, this means the buoyant force is proportional to the volume taken up by the balloon. And of course, you want the balloon to have as little mass as possible. So cooling helium and making it denser would not help at all, right?