fmbettaguy

My Feedback: (7)

hello,
i was wondering if anyone can tell me how large of a helium balloon i will need to lift about 4lbs 1000-1500 feet? also where i could get such a balloon? i'm looking for something to take up an r/c skydiver.
thanks for any info
danny

smokingcrater

I would say a 1000 - 1200 gram balloon should give you a comfortable amount of lift, you will want at least two pounds free lift if not more, you have to lift all that line you are going to be hauling up, and want to maintain at least a pound or more of free lift above that to fight any wind. tethered balloons need VERY calm conditions! My balloon group has almost given up on tethered flights, it is just too hard waiting for perfect conditions.

also, 6 pounds of lift is going to run around $50 or so in helium...

[link=http://www.kaymont.com/pages/sounding_frmst.html]kaymont[/link] is probably the best place to get balloons now.

Ryan
[link=http://ND High Alt Balloon Group]http://blizzard.rwic.und.edu/~nordlie/balloons/[/link]

fmbettaguy

My Feedback: (7)

thanks for your info. wow, i didn't think it would cost so much for each fill up. at that cost its just not reasonable for droping an r/c skydiver. i guess i'll stick to the drop plane i have. thanks again
danny

B.L.E.

A cubic yard of air weighs about 2 pounds at sea level. Displacing a cubic yard of air with helium, which weighs about .25 pounds per cubic yard, results in about 1.75 lb of lifting power. Looks to me like you will need at least 2.5 to 3 cubic yards of helium to lift a 4 lb payload, depending on how much the balloon itself weighs.

One cubic yard= 27 cubic ft.