rocketman1988

rocketman1988

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I have the factory built tanks. After hearing that some have had leaks in the factor built tanks, I decided to test mine.

In order to eliminate any potential leaks, I used AN6 gauge fittings on the two AN6 tank fittings. On the first, I mounded the Schrader valve. The second, a 0-5 psi gauge was installed. the two AN4 fittings were capped with AN caps. The fuel sump was plugged with a brass NPT plug. All NPT threads were sealed using loctite 567.

The fuel caps were adjusted and the o-rings lubed with Krytox.

The tank was then pressurized to 0.8 psi. The plans say no more than 1 psi.

The tank leaked down in about 24 hours.

Pressurized the tank again. This time, I went over ever rivet and every seam with Camco gas leak detector fluid. No bubbles at all. The tank leaked down in 24 hours.

Next, I transferred the AN fittings to the right tank and performed the exact same process. Tank leaked down in 24 hours...basically the same rate as the left tank.

I have sprayed all of the AN fittings, the valve, and the gauge...no bubbles.

I am at a loss, and two days wasted.

Didn't have this much trouble with the -10 tanks...

The worst part was looking at the "inspected by" stickers, while the tanks leaked down.

So, has everyone tested their tanks? What are you seeing?
 
What are people doing for temporary gaskets for the access panels and fuel sender during the tank pressure tests?

I finished building the right tank. I want to pressure test it before I go any further but don't want to mess with pulling sealant off the access covers if I can avoid it.
 
bigmikeh24 said:
What are people doing for temporary gaskets for the access panels and fuel sender during the tank pressure tests?

I finished building the right tank. I want to pressure test it before I go any further but don't want to mess with pulling sealant off the access covers if I can avoid it.
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You will have to test it again after you do the panels, right?
 
bigmikeh24 said:
What are people doing for temporary gaskets for the access panels and fuel sender during the tank pressure tests?

I finished building the right tank. I want to pressure test it before I go any further but don't want to mess with pulling sealant off the access covers if I can avoid it.
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I only tested after final closure and sealing of the access panels.

Unfortunately this means if you find a leak (like I did), at least one panel is coming back off…
 
justa6ereh said:
Hard to beat a balloon…I’ve seldom used a gage…but a Schrader valve and a balloon zip tied on a brass nipple works
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That balloon is there to prevent over pressurizing the tank, though it may show a relatively large leak. I prefer a gauge or manometer...well, unless the gauge is leaking. :unsure:
 
rocketman1988 said:
Honestly, a pre welded integral tank would have been so much better.
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THIS. But I get it, it's a 'homebuilt' after all, designed to be done on the cheap by builders like me who have never built an airplane before.

I'm a few weeks out from testing my tanks so I'll be watching this thread.
 
Why aren’t we using “fuel cells” like they do in the racing world? I think Extra Aircraft is using plastic (some form) for their fuel tanks. My 70 year old Bonanza has fuel bladders and the reliability and crash worthiness far exceeds the wet wing design. Maybe the new folks running vans will turn their attention to making improvements to their old designs instead pushing out another new product every several years. It was such a great design to begin with, seems like low hanging fruit to me.
 
Have you leak checked the schrader valve? Notorious leak points. Might also try soappy wayer from a sprayer. I have almost been dupped a couple times where the flow was great enough that the bubbles won’t be seen unless the area is floode with fluid. With a light coat, the air just pushes away the water without making a bubble. Losing 1 psi in 24 hours with that much tank volume is not a tiny leak.
 
Use an aircraft hydraulic Schreder valve…they are good for 3400+ psi and don’t leak.

The balloon is very practical, as you can inflate it pretty large and let sit for days…I zip tie them and then wrapped with a couple wraps of gap seal tape from sailplanes, but electrical tape works fine too.

The most likely place you find leaks are the aft corners and then fuel senders and access plates.

The easiest trick ‘I’ve found for finding leaks, is to fill the tank with a quart of isopropyl alcohol and rotate it around…if you have a leak, isopropyl is way finer than air and in short order, you will find your leak…ISO won’t hurt the Pro Seal and evaporates rapidly once you drain it.
 
rocketman1988 said:
That balloon is there to prevent over pressurizing the tank, though it may show a relatively large leak. I prefer a gauge or manometer...well, unless the gauge is leaking. :unsure:
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The air volume in the tank is large enough that it doesn’t take much of a change in ambient temperature to show a very noticeable change in the balloon inflation.
That is why the instructions from Vans has never included, referencing the balloon as evidence of a leak. As others have mentioned, it is a pressurization indicator and to help prevent over pressurization. Using a leak indicator solution while the tank is pressurized is the only reliable method in my opinion.
 
I had a slow leak in the centre of the gas cap even though it was adjusted correctly and had duct tape over it. The air still managed to get out. I switched gas caps and it solved my problem.
 
The tanks are in an air conditioned shop so temp shouldn’t be much of a factor.

Can’t control the barometric pressure but it is highly unlikely that it changed enough to cause a 0.8 psi change.

Schrader valve has been changed to a new one.

I have been through almost two bottles of Camco Gas leak detector fluid which works much better than soap and water. Almost no way to miss bubbles.

I really do not want to fill the tanks with gas and the have them sit full of fumes in my shop for the remainder of the build. That will be a last resort.

I am considering using one of the crates and lining it with plastic sheet. Secure the pressurized tank in the crate and then fill the crate with water. Kind of like how they find a leak in a tire.

Very frustrating, but building the tank into the wing and then finding a leak would be worse.
 
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rocketman1988 said:
I am considering using one of the crates and lining it with plastic sheet. Secure the pressurized tank in the crate and then fill the crate with water. Kind of like how they find a leak in a tire.
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that was going to be my next suggestion. There is a reason shops sacrifice space for a big tank. just too easy to miss leaks with spray on solutions. obviously a major hassle, but sounds like you are out of options. should be able to buy a cheap kiddie pool.
 
lr172 said:
that was going to be my next suggestion. There is a reason shops sacrifice space for a big tank. just too easy to miss leaks with spray on solutions. obviously a major hassle, but sounds like you are out of options. should be able to buy a cheap kiddie pool.
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I hate to say this, but what about pressurizing the tank and them putting it in a blow up wading pool> hey Bob--you have a swimming pool? Hot Tub? :unsure:
 
rocketman1988 said:
That balloon is there to prevent over pressurizing the tank, though it may show a relatively large leak. I prefer a gauge or manometer...well, unless the gauge is leaking. :unsure:
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The balloon could be a leak source. I didn't used one. Also, I needed to put packing tape over my gas caps to stop a very slow leak there. I used the manometer method and left it set up for a few days. It's a very sensitive test that worked for me. YMMV....;)
 
RV7CardenMike said:
The balloon could be a leak source. I didn't used one. Also, I needed to put packing tape over my gas caps to stop a very slow leak there. I used the manometer method and left it set up for a few days. It's a very sensitive test that worked for me. YMMV....;)
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Not using the balloon. All fittings are hard plumbed with a gauge.
 
Seems like you’ve covered all contingencies…pretty great sounding plan to dunk it, find it and resolve the issue. Despite all the effort, I’m sure you’ll be happy in the end and will make it all worthwhile.
 
justa6ereh said:
Seems like you’ve covered all contingencies…pretty great sounding plan to dunk it, find it and resolve the issue. Despite all the effort, I’m sure you’ll be happy in the end and will make it all worthwhile.
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Yes, for sure. I am really hoping that it is a plumbing issue and not a structure issue. Again, frustrating to look at those "Inspected" stickers while the air leaks out of the tank...
 
I remain naively puzzled by why folks won’t use a manometer. I have yardsticks and clear tubing in my hangar as well as tape. I do not have balloons. The manometer is easier to make, it is far more accurate than the balloon or gauge needing no calibration and will not leak down over time unless the tank or fittings are leaking.

As far as submerging the tank I can’t imagine how to submerge 4.5 cubic feet under water without bending some element of the tank. Think about taking six empty 5 gallon gas cans and holding them under water at the same time. If memory and math serves me that will require over 250 pounds of force.

Water with some food coloring or fluorine dye might be better to use if you fill it with liquid to isolate the leak. But it will be very heavy if you fill it full. Otherwise a partial fill will require rotating over time.
 
Alphalpha said:
I remain naively puzzled by why folks won’t use a manometer. I have yardsticks and clear tubing in my hangar as well as tape. I do not have balloons. The manometer is easier to make, it is far more accurate than the balloon or gauge needing no calibration and will not leak down over time unless the tank or fittings are leaking.

As far as submerging the tank I can’t imagine how to submerge 4.5 cubic feet under water without bending some element of the tank. Think about taking six empty 5 gallon gas cans and holding them under water at the same time. If memory and math serves me that will require over 250 pounds of force.

Water with some food coloring or fluorine dye might be better to use if you fill it with liquid to isolate the leak. But it will be very heavy if you fill it full. Otherwise a partial fill will require rotating over time.
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lets get Bob a swimming pool
 
Alphalpha said:
I remain naively puzzled by why folks won’t use a manometer. I have yardsticks and clear tubing in my hangar as well as tape. I do not have balloons. The manometer is easier to make, it is far more accurate than the balloon or gauge needing no calibration and will not leak down over time unless the tank or fittings are leaking.

As far as submerging the tank I can’t imagine how to submerge 4.5 cubic feet under water without bending some element of the tank. Think about taking six empty 5 gallon gas cans and holding them under water at the same time. If memory and math serves me that will require over 250 pounds of force.

Water with some food coloring or fluorine dye might be better to use if you fill it with liquid to isolate the leak. But it will be very heavy if you fill it full. Otherwise a partial fill will require rotating over time.
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You don't have to submerge the whole tank. In fact, putting it in just a couple of inches of water will test the entire side that is submerged, as well as the rib flange seams. Then you flip it over and do the same thing.

Not a fan of filling the tank with water...
 
Alphalpha said:
I remain naively puzzled by why folks won’t use a manometer. I have yardsticks and clear tubing in my hangar as well as tape. I do not have balloons. The manometer is easier to make, it is far more accurate than the balloon or gauge needing no calibration and will not leak down over time unless the tank or fittings are leaking.

As far as submerging the tank I can’t imagine how to submerge 4.5 cubic feet under water without bending some element of the tank. Think about taking six empty 5 gallon gas cans and holding them under water at the same time. If memory and math serves me that will require over 250 pounds of force.

Water with some food coloring or fluorine dye might be better to use if you fill it with liquid to isolate the leak. But it will be very heavy if you fill it full. Otherwise a partial fill will require rotating over time.
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Naivety? It really does not sound like you are naive at all. Considering your description of understanding that those not following your plan of leak detection still continue to follow some different plan than yours.

As for manometer use, again, I turn your attention to my earlier statement. The balloon IS NOT a tool of measurement in any sense of the word. That goes for attempting to use it as a “gauge” or as a “substitute for a manometer”. It is a mechanism that will protect the seams on a tank from breaking free if too much air pressure is introduced into the tank. IT IS AN EMERGENCY RELIEF VALVE! PERIOD!

So to continue further discussions about how to set up and use a manometer instead of a balloon totally misses the point. It is completely acceptable to set up a manometer to “measure” changes over time inside a sealed tank. If that is your goal then go for it. Just be sure to understand though, that mechanism will NOT give you information on whether you have a leak, or where the leak may be. Neither will the balloon. I would suggest that even if one uses a manometer I hope one is also using some form of protection that will prevent damage to the tank if too much pressure is introduced into the tank. So be safe out there. Practice safe “testing” and: “USE A RUBBER!!”

LIVE LONG AND PROSPER!
 
Manometer is safest method for checking with air. I wouldn't try to submerge an RV-4 tank let alone an RV-15 wing. Ive fixed a bunch of RV tanks, and maintained the AF KC-10 tanker fleet Depot maintenance for 15 years (330,000 lbs of fuel). The BEST check is done with the fuel itself, and I do all my RV tanks, new or repaired, with 100LL. I understand the RV-15 is a built wet wing and is large. I'm not building one, so I don't know all the details, but I leak check other tanks with only a few gallons of 100LL and rotate the tanks to cover all the leak areas in stages. An RV-15 wing could be bench shored to mimic the installed static position and filled...I know its a lot of gas, but it will tell the truth.
 
fixnflyguy said:
Manometer is safest method for checking with air. I wouldn't try to submerge an RV-4 tank let alone an RV-15 wing. Ive fixed a bunch of RV tanks, and maintained the AF KC-10 tanker fleet Depot maintenance for 15 years (330,000 lbs of fuel). The BEST check is done with the fuel itself, and I do all my RV tanks, new or repaired, with 100LL. I understand the RV-15 is a built wet wing and is large. I'm not building one, so I don't know all the details, but I leak check other tanks with only a few gallons of 100LL and rotate the tanks to cover all the leak areas in stages. An RV-15 wing could be bench shored to mimic the installed static position and filled...I know its a lot of gas, but it will tell the truth.
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…and then you have two empty fuel tanks full of fumes in the workshop for 2+ years while the rest is being built. Not a fan, however, that may be the only way to be sure there are no leaks.
 
RVbySDI said:
Naivety? It really does not sound like you are naive at all. Considering your description of understanding that those not following your plan of leak detection still continue to follow some different plan than yours.

As for manometer use, again, I turn your attention to my earlier statement. The balloon IS NOT a tool of measurement in any sense of the word. That goes for attempting to use it as a “gauge” or as a “substitute for a manometer”. It is a mechanism that will protect the seams on a tank from breaking free if too much air pressure is introduced into the tank. IT IS AN EMERGENCY RELIEF VALVE! PERIOD!

So to continue further discussions about how to set up and use a manometer instead of a balloon totally misses the point. It is completely acceptable to set up a manometer to “measure” changes over time inside a sealed tank. If that is your goal then go for it. Just be sure to understand though, that mechanism will NOT give you information on whether you have a leak, or where the leak may be. Neither will the balloon. I would suggest that even if one uses a manometer I hope one is also using some form of protection that will prevent damage to the tank if too much pressure is introduced into the tank. So be safe out there. Practice safe “testing” and: “USE A RUBBER!!”

LIVE LONG AND PROSPER!
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Actually, a manometer will tell you if you have a leak but it won’t tell you where the leak is.
 
I’m a little confused too, is the leak down test over a 24 hour period the new standard for testing alum fuel tanks? At less than 1 psi. Does that even allow for expansion of the tank or atmospheric changes?
 
fixnflyguy said:
Manometer is safest method for checking with air. I wouldn't try to submerge an RV-4 tank let alone an RV-15 wing. Ive fixed a bunch of RV tanks, and maintained the AF KC-10 tanker fleet Depot maintenance for 15 years (330,000 lbs of fuel). The BEST check is done with the fuel itself, and I do all my RV tanks, new or repaired, with 100LL. I understand the RV-15 is a built wet wing and is large. I'm not building one, so I don't know all the details, but I leak check other tanks with only a few gallons of 100LL and rotate the tanks to cover all the leak areas in stages. An RV-15 wing could be bench shored to mimic the installed static position and filled...I know its a lot of gas, but it will tell the truth.
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Sorry for the drift, but how do you use fuel to find the leaks, especially tiny ones? Are you just looking for the fuel to appear on the outside? Curious, as I have never done it that way, but see the upside.
 
lr172 said:
Sorry for the drift, but how do you use fuel to find the leaks, especially tiny ones? Are you just looking for the fuel to appear on the outside? Curious, as I have never done it that way, but see the upside.
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It will show wet spots and leave blue stains.
 
rmarshall234 said:
I’m a little confused too, is the leak down test over a 24 hour period the new standard for testing alum fuel tanks? At less than 1 psi. Does that even allow for expansion of the tank or atmospheric changes?
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One psi would equate to over 2 inches of mercury so unless a really nasty storm rolls through, atmospheric changes should be minimal. Even so, it should not leak down to zero.
 
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