Volume of Blimp

[WillowPtarmigan]

How do you determine the exact volume of the the blimp? I know it is not a perfect cylinder.

[Guga]

Try to use this web calculator or maybe search for volume calculation sites
http://homepages.ihug.com.au/~shane007/maths/surface.html

[Plantraco]

How do you determine the exact volume of the the blimp? I know it is not a perfect cylinder.

I should know this and have the perfect answer, but I don't. So take this advice as pure "farmers logic". This is what I do.

1. Weigh the uninflated balloon, flat, on the scale

2. Inflate the balloon with helium and add ballast weights to achieve neutral buoyancy. Do this at room temperature, and note your altitude as well - altitude is very important. The best place to do this test is at a place near sea level.

3. Remove the ballast weights and weigh them to see how much extra mass your balloon can lift. Add the mass of the uninflated balloon to get your gross lift. This is the total mass that your helium gas volume can lift.

4. You still don't know the volume of helium in your balloon, but you now do know exactly how much mass the sample volume of helium can lift. SO, now you can consult a chart and take a guess about the volume of the sample balloon. Most charts for helium lift show (in English Units unfortunately) 1 cubic foot of helium will lift 1 oz at sea level. If you are at sea level doing these tests, you might get pretty close to the actual volume of your balloon! Anyways, since you know the mass that you can lift, and know your altitude, you can have a chance to "accurately" estimate the volume of your balloon.

5. If you are above sea level, you will need to adapt your calculations - I have a chart somewhere, but I haven't looked at it for some time. Maybe someone else here can post it. If want to standardize things even more, you can get a nice spherical round latex party balloon, and inflate it to a known diameter, and calculate the volume of the sphere, and then use this calculation to determine what the lift of helium gas is at your location at your temperature and your barometric pressure etc. The key to doing this calibration would be that your latex balloon should be as close to a perfect sphere as you can muster.

6. Be aware that your measurements are all approximations. You can get close - probably within 5%, but to get the exact volume might require an improved method.

7. Repeat your test at a location with different altitude, but with the same helium supply if possible, and see if your volume calculations vary. They should be the same! If they are the same, you are doing something right and are probably accurately measuring the volume!


Good Luck and have fun with R/C Blimps - they are a Gas!

Bud
http://www.plantraco.com