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Nak
Since 19 May 2005
910 Posts
Camas
Opinionated
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 Thu Apr 05, 2007 8:01 pm Kite bladder volume |
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Just for grins I pumped up a couple of kites with an air tank this morning so I could determine bladder volume. The results surprised the shit out of me!
'04 19m Fuel 86 gallons!!!
Now I know why I like using an electric pump with big kites!
The math: 26 gallon air tank. Starting psi: 150 psi, End psi: 90
19m Fuel Starting psi: 0 End psi 3
P1 * V1 = P2 * V2
Nak
Edited because I messed up the math. I think I have it right now. Anyone want to check this?
Last edited by Nak on Thu Apr 05, 2007 9:43 pm; edited 2 times in total |
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EdG
Since 19 Dec 2005
304 Posts
Just a Kook that's
Obsessed
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| Thu Apr 05, 2007 8:43 pm |
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there are some strange people on the forum   |
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Nak
Since 19 May 2005
910 Posts
Camas
Opinionated
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| Thu Apr 05, 2007 8:48 pm |
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| EdG wrote: | | there are some strange people on the forum |
How true! 
There's actually a reason I wanted to know kite bladder volume. After all the talk of a compressor for the sand bar, just wanted an idea of what kind of tank would be needed!
Nak |
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jsj
Since 11 Sep 2006
40 Posts
Hood River
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| Thu Apr 05, 2007 9:41 pm |
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umm. you need to re-read your thermo book and maybe do a little reality checking:
6" dia cylinder 30' long, vol = 10179in^3 or 44 gallons
P1V1=P2V2 works for "work done at the boundary of a simple compressiible system in a quasiequilibrium process"*
e.g. - a moving piston. Hint: the fact that your tank pressure does not equal your bladder pressure should make you wonder whether there is some problem......
The right way to do the calc miiiight be to determine mass lost in the tank then apply ideal gas law (conservation of mass).
Or you could simple estimate based on geometry.
Electric pumps are a for girlie men.
jsj
* Wylen and Sonntag, Fundamentals of Classical Thermodynamics 3rd Edition |
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Nak
Since 19 May 2005
910 Posts
Camas
Opinionated
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| Thu Apr 05, 2007 9:52 pm |
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Hey jsj,
Yeah, thermo was 28 years ago... Obviously I need a refresher. Anyway that's why I edited the post. I think I have it right now at 86 gallons. What do you come up with? It seems about right just thinking about the volume.
Should have checked my math after first looking at it, but the opportunity to ride came up. Gotta have priorities! Still should have checked before posting. 
Electric pumps are for those who'd rather ride than spend time pumping. especially when time is limited! I'm pretty sure I've done enough in life to be assured of my non-girlieness without having to use a hand pump.
Nak |
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Hein
Since 08 Mar 2005
555 Posts
Possessed
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| Fri Apr 06, 2007 6:49 am |
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Might be better to determine the mean diameter and length
of the struts and LE and calculate the volume that way.
But if you are just wanting to figure the energy needed to
pump up a kite then the pressure drop and volume of your
air tank will tell you that. But that won't take into account the
frictional and heat losses it will take to pump the tank back
up.
Easy way:
Turn off everything in your house and use the compressor
to pump up the kite 10 or more times. Read your electric
meter before and after. KW-hours right there. |
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Reaper356
Since 10 Dec 2006
522 Posts
Salem / NewPort Oregon
Addicted
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| Fri Apr 06, 2007 7:06 am |
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| Quote: | | 6" dia cylinder 30' long, vol = 10179in^3 or 44 gallons |
You still need to add the struts tho right?
| Quote: | Easy way:
Turn off everything in your house and use the compressor
to pump up the kite 10 or more times. Read your electric
meter before and after. KW-hours right there. |
LOL, then you can find out how many PBJ's you need to eat to pump up your kite! |
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jsj
Since 11 Sep 2006
40 Posts
Hood River
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| Fri Apr 06, 2007 8:35 am |
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Nak, you've got got me there. My thermo was only 20yrs ago.
I hereby retract the bit about girlie-men.
cheers
jsj |
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