My daughter’s sweet sixteen party is tomorrow. Last weekend she went out shopping with her aunt and picked up decorations, including a “kit” for making a balloon arch. She’s been doing some research online about making balloon arches, and one site indicated that using helium can lead to the arch behaving “unpredictably” (not quite sure exactly what was meant by that).
Still, we’re kinda skeptical that the balloons will “arch” at all if they have no lift. Also, I’m not particularly eager to use my own personal lungs to blow up the 150 balloons she picked up. So we’re leaning toward biting the bullet and adding a bottle of helium to the tables, chairs and drink cooler that will be rented and delivered tomorrow morning.
Thing is, I just found out that the rental place wants $85.00 for a bottle of helium that will fill 200 ballons. $55.00 for 110, $50.00 for 75, $40.00 for 35. That’s getting a little pricey, and right now I’m considering getting the small one, and making about one balloon in five be a helium balloon.
Anybody know if this is doable? And if so, should we put the helium balloons in the center of the arch, or space them evenly along the length of the arch?
Thanks for any input, especially if it’s based on experience.
In general, you don’t need lift to make an arch. There are plenty of arches made of brick out there. I’ve never built a balloon arch, so take this with a grain of salt:
If your total arch has negative buoyancy (all balloons are helium and the strings don’t weigh too much), it will stay upright as long as it’s anchored at its ends. The irregular behavior some sites might be alluding to is the fact that the arch wants to go up, so if it gets untied or unmoored, spontaneous fun will erupt.
If you mix some air-filled balloons in with your helium, you are reducing the buoyancy of the arch in air, and at some point the arch will need some sort of supports to stay upright. Depending on what’s in your kit, and where you want to put the arch, you might be able to get away with using all air balloons. For example, if it is indoors, you could tie the balloons to an arch made of florist wire to maintain the arch shape and attach the top to the ceiling to keep it upright.
I would check with the kit instructions, since a lot of this will depend on the type of balloon and the type of balloon-to-balloon connections, etc.
I watched a balloon arch get put up once. They already had the balloons inflated and assembled when they arrived at the event, as a long “column” basically. The balloons were packed tightly enough that they would keep this column straight through their own pressure. When the arch was put up, securing the two ends was all they needed to do. The arch didn’t collapse because the only motion that would have relieved tension would be to spring back to a straight column and the ties to the ground prevented that.
If it doesn’t hold itself up, the problem would be loosely packed balloons, not a lack of buoyancy.
Certainly Not!
Helium-filled balloons are territorial.
I have built many balloon arches, we always used all Helium and as the other poster mentioned we just built a column and bent it over on site. I think you could get away with a 1 to 1 ratio but I have zero experience with that method. I think that is a little pricey for helium you might want to try a welding gas place and see if they would give you a better deal
Cheers and have a fun party
Capt
Never built a balloon arch, but I did study structures in school. If you want an arch, you should distribute your helium balloons evenly along the string. This will form a catenary, which is pretty close to a parabola, which is pretty close to an arch. If you put all the helium balloons in the center, you’ll get something like a triangle, and if you put them near the ends, you’ll get two columns with a string dangling between them. I’m not sure what the weights of air- and helium-filled balloons are, but the closer you get to neutral buoyancy, the less stable the arch will be - which means on a windy day, it’ll collapse easier.