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  #11  
Old 07-16-2017, 06:39 PM
PilotjohnS PilotjohnS is offline
 
Join Date: Jan 2016
Location: Los Angeles
Posts: 302
Default My way

I just finished my tanks. Here is how I did it. I bought some 1/4" plactic tubing from home dpeot. Heated the end upmand pushed it over the tank's vent to flare it. Added a B nut and AN sleeve and hand tightened it onto the vent fitting. Blew into the tank until i couldnt blow any more, took a swige of water and blew that into the tube for about 30 inches then kept on blowing until it filled up the manometer half way ( both sides level) . Stopped blowing and the manometer settled at about 24 " of water, which is just shy of 1 psi. Then i bubble tested all the joints and let it sit over night. My breath in the tank cooled over night and I lost 1.5" of water, but the bubble test showed no leakage.

After reworking the second tank, i add a second tube on the fuel pickup. One with water for the manometer, one to pressurize. This made it easier to fill with my breath without have to push a swig of water into the tube. I just used a 1/4 inch punch to seal up the pressurization line. Easy peasey.
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WARNING! Information presented in this post is my opinion. All users of info have sole responsibility for determining accuracy or suitability for thier use.

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Last edited by PilotjohnS : 07-24-2017 at 10:48 PM.
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  #12  
Old 07-19-2017, 03:48 PM
amaris amaris is offline
 
Join Date: Feb 2015
Location: Santa Ynez, CA
Posts: 106
Default

After about 4 days, I've lost about 5" of deflection from my initial pressure. Which was about 12" total in a 3/8" ID tube. The tank is obviously holding at this pressure and I couldn't find any leaks at the full 12" of pressure.

Is it possible to have a leak only at higher pressure and be leak free at the lower pressure and still be okay?

I want to do one more full pressure bubble test to see if I can find anything. I'm also worried about over pressurizing the tank and doing damage.
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  #13  
Old 07-19-2017, 04:05 PM
Gusmax Gusmax is offline
 
Join Date: Jun 2014
Location: Sherwood Park, Alberta
Posts: 11
Default

I'm not sure if this has been mentioned in the past, but has anyone had success building a plastic lined water tank and submerging the fuel tank under water to look for leaks?

Cheers,

Phil
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  #14  
Old 07-23-2017, 08:23 PM
JimWoo50 JimWoo50 is offline
 
Join Date: Oct 2005
Posts: 343
Default I poured fuel in them

About a gallon and a half. Left it on ends overnight, standing with aft side down leading edge up and leading edge down in the cradle. I tried to orient the tanks over about a week so the fuel would be concentrated on every seam or rivet hole.
I did try the balloon method on my first tank but was leery of over pressurizing the tank and was not confident in the result because it showed my first tank being leak free. And lo and behold it was!
The second tank was a different story and required access holes in the baffle where I squeezed the proseal out of the seam and set up a minor seep.
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  #15  
Old 07-23-2017, 09:05 PM
PilotjohnS PilotjohnS is offline
 
Join Date: Jan 2016
Location: Los Angeles
Posts: 302
Default Bubble test?

Quote:
Originally Posted by amaris View Post
After about 4 days, I've lost about 5" of deflection from my initial pressure. Which was about 12" total in a 3/8" ID tube. The tank is obviously holding at this pressure and I couldn't find any leaks at the full 12" of pressure.

Is it possible to have a leak only at higher pressure and be leak free at the lower pressure and still be okay?

I want to do one more full pressure bubble test to see if I can find anything. I'm also worried about over pressurizing the tank and doing damage.
I used 24" of water and only lost 11/2". But the soap bubbles are what showed the leak. Inwouldn tworry about over pressurizing if the pressure is less than 27" which is right about 1 psi.
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WARNING! Information presented in this post is my opinion. All users of info have sole responsibility for determining accuracy or suitability for thier use.

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  #16  
Old 07-24-2017, 05:57 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 3,915
Default

Quote:
Originally Posted by amaris View Post
After about 4 days, I've lost about 5" of deflection from my initial pressure. Which was about 12" total in a 3/8" ID tube. The tank is obviously holding at this pressure and I couldn't find any leaks at the full 12" of pressure.

Is it possible to have a leak only at higher pressure and be leak free at the lower pressure and still be okay?

I want to do one more full pressure bubble test to see if I can find anything. I'm also worried about over pressurizing the tank and doing damage.
IMO 12" is not enough to begin with, and with 5" loss you likely have a leak. Be sure to check around the cap too. 24-30" range is ideal (agrees with latest Vans instructions), I ran 44". Lost 0.2" in 24hrs. I also put some tape on the tank and used it to shoot the temperature. The pressure changes a good bit with temperature. Also, be sure to re-zero the manometer at the end of the test. It will change. Dissolved gasses in the water come put and change the level.

Dunking in a tank may seem like a good idea but holding the tank underwater to displace 42 gallons will take 345 pounds of force. Just not practical. Way more work than the manometer.
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  #17  
Old 07-24-2017, 06:06 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 3,915
Default Temperature Compensation

Using ideal gas laws and the ratio of absolute temperatures would seem to be a good correction factor, but it is not. It is close, but not perfect. The tank is a spring too, so the volume of the tank changes with pressure. It is, therefore, also affected by barometric pressure, but not predictable. I did not try to make a perfect correction factor, but by measuring the temperature, keeping in a stable environment, out of the light and getting lucky to catch the temperature at the same (as initial stabilized) point (and no barometer change-AWOS) yielded good results.
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  #18  
Old 07-24-2017, 01:58 PM
YoVuelo YoVuelo is offline
 
Join Date: Sep 2015
Location: Tucson, AZ
Posts: 14
Default

Quote:
Originally Posted by amaris View Post
After about 4 days, I've lost about 5" of deflection from my initial pressure. Which was about 12" total in a 3/8" ID tube. The tank is obviously holding at this pressure and I couldn't find any leaks at the full 12" of pressure.
I tested my tanks using the manometer method. I waited till both were completed and set them up side by side on individual manometers. I "calibrated" the fluid level in each side so they were equal and then pressurized each tank to 27". You don't have to worry about over pressurizing the tanks as the water will just vent out of the manometer if you get carried away. I watched my tanks track within 1/2" of each other over three days. As they tracked together for that length of time, they are either leak free or both leak at the exact same rate. I'm working in an AZ hanger and saw some pretty wild swings with the daily temp changes, but they always tracked true with each other.
If the 5" change can't be explained by temperature, then I would suspect a leak in the tank or in your test system. I used a bit of fuel lube on all of the joints to ensure leak free connections.

https://www.dropbox.com/s/pr5olsz13o...70518.JPG?dl=0
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  #19  
Old 07-24-2017, 02:09 PM
jwilbur jwilbur is offline
 
Join Date: Dec 2010
Location: Warrenton, VA
Posts: 559
Default control balloon

I did the balloon test. One for each tank. Then I got a third "control" balloon, blew it up to approximately the same size and tied it off as just a balloon. I left them in a quiet room in my house for several days. Theory: if the tank balloons change the same as the control balloon, no leaks.
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  #20  
Old 07-24-2017, 02:10 PM
amaris amaris is offline
 
Join Date: Feb 2015
Location: Santa Ynez, CA
Posts: 106
Default

I re-pressurized my tank and increased the pressure another 2" and moved the hose clamp, which revealed a small leak. I tightened that down which stopped the leak so I will check it next week when I return from OSH. I hope to find there's plenty of offset in the tube still!
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