R/C Blimp question? ?

Question

I want to make my own from scratch with a hard shell (very thin but solid plastic, maybe a thin rubber coating. either way, does anyone have any EASY TO UNDERSTAND converstion numbers for me to figure how much helium I need to cover Weight? (assuming avarage 10 feet above water area), and for use inside? I want to make it remote control and round with a webcam. just cant figure out how to figure how much helium is needed to cover wieght and if its solid ,how much pressure to add.

thanks

Answer 1

A good approximation for lifting capacity is 1 ounce per cubic foot of helium, you don't want any pressure, just enough helium to fill the blimp, you can use a plastic bag and let the helium fill it to it's shape.  A hard shell will add a lot of weight for no benefit.

I spent many hours of my youth doing this.  I used hydrogen and natural gas as this was before I knew where to get helium.  I also had some fun putting a fuse on some of my homemade Hindenburgs.  The lift from helium and hydrogen is about the same but natural is less than half.  The math says that the closer your blimp is to a sphere the more lift there is for the weight of the gas bag.  Blimps are cigar shaped to reduce drag from the air.

Your probably looking at blimp that's at least 6-8 feet long and a couple of feet in diameter to lift a remote control, battery, and wweb-cam  Good luck, email me if you need some more information.

Answer 2

basically 1 cubic meter of He provides 1 kg of lift.

0.1 cubic meter gives you 100g lift

The gas cannot be compressed in any way, or the lift goes down, which is why He is stored in flexible bags of some sort in real blimps.

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Answer 3

For each liter of He, you will get ~1.11 g of lift in air at STP.

You must then subtract the weight of the envelope to find the remaining useful lift.

Ergo, for 50 g lift you would need 50/1.11 = 45 L of He.

If your shell is hard enough to maintain its shape without a pressure differential, so much the better; otherwise you'd have to use more volume to account for the increased density of the helium.