|
-
POSTING RULES

-
Donate yearly (please).
-
Advertise in here!
-
Today's Posts
|
Insert Pics
|

02-10-2009, 01:43 PM
|
 |
|
|
Join Date: Feb 2006
Location: Vancouver, Wa.
Posts: 57
|
|
You are aware that "air" is about 78% nitrogen right?
__________________
Randy Griffin
RV-8
N925RG
Vancouver, Wa.
|

02-10-2009, 02:37 PM
|
 |
|
|
Join Date: Sep 2005
Location: Dothan, Alabama
Posts: 1,487
|
|
Quote:
Originally Posted by Griff
You are aware that "air" is about 78% nitrogen right?
|
I was gonna say that.
__________________
Alton DeWeese
N526RV RV7A Tip Up, IO360 180 W/Hartzel BA prop.
Flying ~950 hours since Aug 2010
N4IDH
Construction Log
?The secret of getting ahead is getting started. The secret of getting started is breaking your complex overwhelming tasks into small manageable tasks, and then starting on the first one.?
?Mark Twain
|

02-10-2009, 02:38 PM
|
 |
|
|
Join Date: Jul 2006
Location: Corvallis Oregon
Posts: 3,547
|
|
That 21% O2
Just messes everything up don't ya know... 
|

02-10-2009, 08:25 PM
|
|
|
|
Join Date: Mar 2007
Location: Sonoma County
Posts: 3,821
|
|
Quote:
Originally Posted by Griff
You are aware that "air" is about 78% nitrogen right?
|
NOT IN CALIFORNIA.......... 
|

02-11-2009, 04:35 AM
|
|
|
|
Join Date: Jan 2005
Location: Oklahoma City, OK
Posts: 924
|
|
Quote:
Originally Posted by gasman
NOT IN CALIFORNIA.......... 
|
I'm an "OKIE" what is it?
Marshall
|

02-11-2009, 09:26 AM
|
 |
|
|
Join Date: Jun 2005
Location: SoCal
Posts: 2,452
|
|
I live in the Mojave Desert and it is not uncommon for temp swings in one day of 30 deg or more. When I tested my tanks I used the Vans kit and clear tubes full of water. The way I made sure temp was not much of a factor was by taking the temp at start of test. Then the next day at about the same time I took the temp and waited until the temp was the same. I also kept the tanks away from the sun and in the same location.
http://www.mykitlog.com/users/displa...og=47689&row=4
__________________
Axel
RV-4 fastback thread and Pics
VAF 2020 paid VAF 704
The information that I post is just that; information and my own personal experiences. You need to weight out the pros and cons and make up your own mind/decisions. The pictures posted may not show the final stage or configuration. Build at your own risk.
|

02-11-2009, 11:33 AM
|
|
|
|
Join Date: Feb 2008
Location: Thousand Oaks, CA
Posts: 183
|
|
Fuel tanks and balloons
If you left the balloon on there for 24 hours or more and it contracted and expanded with the temp changes and Barometric pressure consistently and never deflated wouldn't that be sufficient to prove it wasn't leaking?
I had a balloon on my tank and it was filled up when I left it. Came back in the morning and it was deflated......came back in the afternoon (same time I started the day before) and it was inflated again back to normal.
I took that as a confirmation the tanks weren't leaking. This is on a composite Lancair tank however. No rivets.
|

02-11-2009, 11:47 AM
|
|
|
|
Join Date: Jan 2005
Location: Austin, Tx
Posts: 333
|
|
I think lots of guys have used balloons to test, but it is pretty hard to get an accurate test with a balloon. With an manometer, you can mark the water level, and note the temp. Then you can come back 24 hours later and mark again, and note the temp again. It is possible to actually calculate if any pressure has been lost, but doing this over a few days gives you a pretty good feel for whether the tanks are leaking or not.
With a balloon, you have to kind of eyeball whether or not the pressure has gone down, and if so, then how much. I suppose you could get out the calipers, and get a little more accurate, but a balloon is not a perfect shape, so it is hard to calculate the volume to any level of accuracy. I suppose if you leave the balloon on for several days, you should get a good feel for whether the tanks are leaking or not, just not as accurate as a manometer.
Of course, you balloon guys do not have to deal with the problem where you go out in the shop 24 hours later, and all of your hose is lying on the floor because it got too hot and the glue on the duck tape melted and let every thing drop, so you have to use a whole bunch of duck tape to hold everything together for the next few days, so you can get an "accurate" reading. Everything has compromises.
Cheers,
Tracy.
|

02-11-2009, 01:47 PM
|
|
|
|
Join Date: Apr 2006
Location: Santa Monica, CA
Posts: 325
|
|
Can't beat the laws of Physics
Edit: Should of read the whole thread before responding...I thought this was my chance to sound smart!
Quote:
Originally Posted by danielhv
oh...  I was under the impression nitrogen did not expand or contract as much as air... guess that rules that out!
|
Air is 78% nitrogen to begin with. But all gasses obey Boyles law which states that volume and pressure are proportional to temperature.
People like to put nitrogen in their car tires because nitrogen molecules are bigger than the molecules that make up the remaining 22% of air, so theoretically you won't need to refill your tires as often.
__________________
-John
Flying a Glasair I FT
Planning to build an RV...someday
Last edited by jtrusso : 02-11-2009 at 01:51 PM.
Reason: read the whole thread
|

04-18-2011, 01:41 PM
|
|
|
|
Join Date: Jul 2009
Location: Ankeny, IA
Posts: 210
|
|
Geekery
A datapoint just for fun:
Expensive laboratory leak detection apparatus use helium as the test gas because helium flows very quickly out of very small openings.
If you happen to moonlight as a clown and have a bottle of helium lying around, you could probably use it for a very fast and effective leak test, obviating the need to maintain pressure overnight. This way, temperature and pressure variations in the environment wouldn't matter.
M
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
All times are GMT -6. The time now is 06:54 AM.
|