Sign Task

[Flavorflav]

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?

Cooling the balloon would be counterproductive. Cooling the air around the balloon would be beneficial, but probably not very practical.

[Primate]

Um, I think you can just fill the balloon with a vacuum. And then throw in a helium atom or two to fulfill the rules.

[Flavorflav]

Um, I think you can just fill the balloon with a vacuum. And then throw in a helium atom or two to fulfill the rules.

Sure, just fill it with a vacuum. Easy as pie.

[paronomasia]

I guess you could consider the shape of the balloon. Spheres have the best volume/SA ratio, but so far I've only been able to find foil balloons that are cylindrical. For latex balloons, I hear soaking it in boiling water helps loosen it up + increase diameter, and reduce weight by cutting the bit that's left after you tie it.

Also: A helium balloon with a 50-ft radius has the ability to lift 33,000 pounds.... if only.

[epo173]

where are we supposed to get inflated balloons? since they lose helium pretty quickly, it seems like the only way to inflate them the right amount is to buy a helium tank. this seems really inefficient, considering that we only need a few balloons.

[Paradox21]

where are we supposed to get inflated balloons? since they lose helium pretty quickly, it seems like the only way to inflate them the right amount is to buy a helium tank. this seems really inefficient, considering that we only need a few balloons.

If you buy foil balloons the evening before a competition, they will stay inflated overnight. Of course they will lose some lift during that time period. If you want to be able to fill up right before your run, you will probably need a tank, unless you want to try a system of buying 2 balloons and partially re-filling one with the other. But I couldn't tell you how much lift is actually lost overnight...

[Flavorflav]

But I couldn't tell you how much lift is actually lost overnight...

Barely any, for a mylar balloon. I didn't have a decent scale at home, but I made one neutrally buoyant with paperclips, ribbon etc, and it was still neutrally buoyant two days later.

[aubrey048]

The simple advice I can give is tie it tightly and make sure it doesn't get popped by any of the sharp objects in your Rube Goldberg device. Last year we had issues with air-filled balloons, and this is really what worked above all else. Be careful! Balloons just love breaking at *convenient* times (as my team discovered last year on our test run)!

[NikitaB]

Where is everyone getting there balloons from? I have looked at bargainballoons.com, at their 18" balloons (the max. size that will fit in a 50x50x80cm box), but their shipping is close to ten dollars, while each balloon is only 69 cents!

[Flavorflav]

Where is everyone getting there balloons from? I have looked at bargainballoons.com, at their 18" balloons (the max. size that will fit in a 50x50x80cm box), but their shipping is close to ten dollars, while each balloon is only 69 cents!

Party stores are best, but some drug and grocery stores have some.