# COMMUNITY : FORUMS : TECH

## blimp coming soon! but need help

i have restarted the blimp project and it will be coming soon....i hope. i need to know how many cubic feet of helium does it take to lift 1 pound (16 ounces). also need to know if mylar will melt to. please respond

Sun Gear (author)  Kiteman6 years ago
i thought i needed 16 cubic feet
6 years ago
You do - a sphere three feet across holds just over 14 cubic feet. Then you need to lift the weight of the balloon itself, so at least 16 cubic feet would be sensible. If you have more lifting capacity than you need, you can always add ballast to adjust the blimp's flight (angle as well as buoyancy). If you don't have enough lifting capacity, it's a lot harder to shave weight off your load.
Sun Gear (author)  Kiteman6 years ago
oh how long and how wide does cylinder have to be to hold 16 cubic feet
6 years ago
Volume of a cylinder is Pi x radius2 x length.

A cylinder 2 feet wide, five feet long, will have a volume of Pi x 1 x 5 = 15.7 cubic feet.

I'll let you work things out from there - working in feet instead of metres is making me grit my teeth, and I had a filling 5 hours ago.
Sun Gear (author)  Kiteman6 years ago
ok is 2 ft radius or diameter
6 years ago
Two feet is the diameter, making the radius one foot. Thus, r2=1.

Sheesh, Kiteman! Feet aren't that bad! It's furlongs and fathoms and gills and leagues and chains and rods and links and drams and hogsheads and minims and pecks and bushels and barrels and hundredweights and board-feet that are confusing.
6 years ago
Let's not forget English "stones" LOL
6 years ago
actually weight in stone isn't hard, it's 2.2lbs to a kilo, 14lbs to a stone. thereby to change from metric to imperial you take (weight in kilos)*2.2 / 14
6 years ago
Um, yeah, I have that memorized now (until I go to another page *sigh* ) the difficulty is not that it is hard, but it's unfamiliarity
6 years ago
Yeah lbs does the same to me, also american money can befuddle me now and again, we have 20p pieces no 25p pieces...
6 years ago
Is your 20p like 1/5th of a (what) pound ? 25 cents is 1/4 of a dollar (100 pennies in a dollar), but I see how that could be disheartening anyway.
6 years ago
just seems odd when adding up...
6 years ago
I understand. I know I had difficulties trying to figure the price of things in Canada, when the currency was the same, but the values were different *sigh*
6 years ago
Ah the simple complications of life...
6 years ago
That's Imperial...All of mine are official measurements that are part of the US system.

Vernors-No problem. Math with a purpose is actually fun. Arbitrary equations in a classroom that mean nothing aren't as much fun.

Well, except for the equation ei*pi=-1. That's a cool enough equation that it gets to be fun.
6 years ago
as can fooling about with: c2=e/m
;-)
Sun Gear (author)  CameronSS6 years ago
thanks sometimes to much math makes me go insane
6 years ago
Then wouldn't it have been easier to just work it out in meters and then convert ? :-)
Sun Gear (author)  Goodhart6 years ago
i don't know meters that well but i know feet and in the U.K. the use meters in U.S> they use feet
6 years ago
Yes, what I was say to Kiteman was that if he had difficulty doing the math in base 12 (inches in a foot), then he could use meters and then just convert the answers in the end, which is what you were looking for anyway.
Sun Gear (author)  Kiteman6 years ago
if i post this instructable should i message you to let you know
Sun Gear (author)  Kiteman6 years ago
crap back were i started but thanks this will help
Sun Gear (author)  Kiteman6 years ago
finally all the stress of getting materials is gone I'm soooo happy
Sun Gear (author)  Kiteman6 years ago
i just looked at the links and amassed that i need a lot less helium