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Tank removal - remove pushrods / access hole burrs?

sbalmos

Well Known Member
Two steps forward, one step back. I now join the ranks of those who have to re-seal the rear baffle. That was a nice constant drip going yesterday, after filling with fuel for the first time. Admittedly, the first time any liquid had been in the tanks since the balloon, and a water, test four years ago when I built them.

So, now I get to remove both tanks off my wings, which are already attached to the plane. Meh. For the bolts that you have to reach over into the next bay over from the inspection plate blindly, it feels like my aileron pushrod is either in the way, or greatly hampers my ability to rotate a wrench. Should I just go ahead and remove the pushrod for now?

Secondly, when I cut the rear baffle access holes, I'm probably going to do one in each bay. When you go to deburr the drilled rivet holes for mounting the access plates, I was going to try and vacuum out as much as possible. But the first pressure test would be another colored water test, which would then slosh out the rest of the loose burrs when I drain the water. Then let the tank dry out for a few days, and then do another test with maybe a gallon or two of avgas, which would probably be discarded also. Does this sound appropriate?

Maybe a third fuel test after they're remounted to the wings, in case the re-bolting flexes something on the baffle? Not sure how to really test that without filling the tanks full again, since the rear baffle in a mounted position is basically "on its side".
 
I had to pull my tanks recently to change fuel sender types, I feel your pain. I didn't remove the aileron pushrod but I sure right on the fence about it, not sure if I saved time or not by just fighting through the tight spots versus pulling the pushrod. Access to the bolts will certainly be easier with it out, there's no question there.
 
Ok, since I have had the glorious experience of removing and "attempting" to patch my left fuel tank 6 times and "successfully" doing so a seventh time I believe I am qualified to give some advice on tank removal. First off, you do not have to remove the aileron push rod. You will be able to get into those bolts via the access plates. Granted there is nothing pleasant about doing so but it is doable. And trust me, the second, third, fourth and every other time after that will be even easier. I am sure though that you will wish to only do this one time.

There are a total of 21 bolts to get to. Some will be easy, some will be difficult. The best thing you can do is get good tools with which to do the work. I use 1/4 ratchets of various configurations. One of the best is a round knurled Kobalt 1/4 ratchet that you can hold in the palm of your hand and turn it. I bought this at the Lowe's aviation tool department. The other is a short "stubby" 1/4 ratchet (similar to this one) that is about 2" long. I am sure there are many like this to find. I bought mine from Bob Avery, who is no longer selling tools. Both are very useful, and might I say, necessary to do the job.

You will be able to reach in to all of the bays from the two access holes. I have a large arm that found the edges of the lightening holes in the ribs very uncomfortable. The thinner your arm the easier it will be for you. You are right, it is a blind activity. You will have to develop a good sense of touch to tell you what is going on. Make sure to not drop any hardware. You will be able to get them out if you drop anything by using a telescoping magnet but do your best to avoid that frustration. Know that each bolt should have a washer on it so make sure to hang on to those washers when pulling the bolts out.

As for getting debris out of the tank. If you plan on using Van's fuel tank repair kit you will have a nice large hole to reach in and access every inch of the interior of the tank bays. Oh yes, while talking about that repair kit, you will need a good hole saw that you will need to cut those 4" holes for the repair plate. I used an adjustable hole saw that I believe I also bought at the aviation tool department of Lowe's. You should not need to worry a great deal about having debris after you seal it back up if you reach in and do a very thorough job of cleaning up any debris before you seal it back up.

Lastly, there have been a great many discussions on this forum about fuel tank repairs. Many of them I have posted to. I have even started a thread in which I detailed some of my experiences (If you wish to read it go here). Do a search and you will find a great deal of information. Here is what came up when I did the search.

Feel free to contact me via PM if you wish to discuss any more details.
 
Thanks Steve! Hopefully it won't take 7 times for me. :eek:

I'm aware of the other threads and have read a good amount of them. Actually did so before fueling yesterday, in anticipation of something happening. There was obvious comfort in knowing ahead of time that this is an extremely common issue - once you get past the "oh ****" moment of seeing fuel dripping out from the skin-spar seam at a not-insignificant pace and the hour or so of draining 36 gallons into cans. :rolleyes:

I've got long thin arms also, so reaching won't be a problem, and I don't mind doing things blindly. Thanks for the links for the tools. The palm ratchet I had never heard of, and Lowes doesn't sell them any longer. I'll see if Homeless Despot does, or something similar. Going to definitely pick up a stubby ratchet - been meaning to do so anyway. And yes, I was just going to end up ordering a number of the Vans patch kits, once I got the tanks off and got a proper look at the situation.

Hole saws are not a problem - Dad's an ex-industrial arts teacher. His basement shop is well-stocked. :)

Just another task... Was hoping to get to first engine start in the next few weeks, but probably not. Oh well.
 
Just a comment from someone who has been there. If I ever do build another RV fuel tank from scratch I will install the repair plates as part of the initial tank construction. I had a very hard time wrapping my brain around the idea of creating a container with a bunch of holes in it to hold a liquid. However, once I finally drank the Kool-Aid I realized these access plates should be the standard Modus Operandi for building fuel tanks.

Good Luck!
 
***AGREED PROFUSELY*** With as common as these rear baffle problems are, why not just make the rear baffle Swiss cheese to begin with (in a good sense)? My friend, who has a Diamond, had to have the equivalent done to his tanks last year. His repairman noted these kinds of per-bay access holes are actually now an actual orderable retrofit option.
 
I know this will ruffle some feathers, but.....

It bothers me just a little to find that people consider this all that common.
There are literally thousands of RVs flying that have never had a leak from day 1.
If you pay close attention to building the tanks, leaks should be very minimal.
 
No offense Mel, and I don't want the thread to diverge - I've got the information I need. And as I mentioned in my first post, the tanks didn't leak - when I tested them after building them 4 years ago. And before anyone asks, yes I gooped on the proseal quite heavily when installing the baffle. I knew that was a problem area to begin with. What happened between then and now, I don't know. It's useless speculation at this point.

I'm human, a first-time builder, not a mechanic or aviation-related by trade or profession, I was paying close attention in building at the time, having educated myself of the pitfalls from this forum... something happened after 4 years. *shrug* "Stuff" happens.
 
Find where it's leaking...

I've had to remove my left tank twice. One leak was on the cover plate and one in the rear baffle.

I had an RV-expert and A&P friend help me fix the leaks both times. He used the tank test kit, (ballon, etc.) to find where the leak was. Pressurize the tank using the test kit, then use water and soap to identify where the leak is.

Fuel can wick like crazy. It is sometimes not at all obvious where the leak is.

The rear baffle leak was in the bay where the fuel fill hole is. My A&P friend was able to remove old, softened sealant, clean and apply new sealant through the filler hole. He fabricated some make shift tools. 100 hours later, the repair is holding up well.

I had blue fuel stains all along the rear bottom seam of the tank, as well as the inboard edge. It looked like it was leaking all over the place, but it turned out to be one small spot on the outboard bay.

I was very happy that we did not have to tear into the rear baffle!

By the way removing the 21 bolts, is not near as bad as it is hyped up to be, once you've done it. The second time, I had all the bolts installed in less than 30 minutes. There's only 2 or 3 that are painful, even with the pushrod still installed. I fretted over this for some time, and even hired my A&P friend to do it the first time. The right tools, as have been suggested is the key.

Michael-
 
I've had to remove my left tank twice. One leak was on the cover plate and one in the rear baffle.

I had an RV-expert and A&P friend help me fix the leaks both times. He used the tank test kit, (ballon, etc.) to find where the leak was. Pressurize the tank using the test kit, then use water and soap to identify where the leak is.

Fuel can wick like crazy. It is sometimes not at all obvious where the leak is.

The rear baffle leak was in the bay where the fuel fill hole is. My A&P friend was able to remove old, softened sealant, clean and apply new sealant through the filler hole. He fabricated some make shift tools. 100 hours later, the repair is holding up well.

I had blue fuel stains all along the rear bottom seam of the tank, as well as the inboard edge. It looked like it was leaking all over the place, but it turned out to be one small spot on the outboard bay.

I was very happy that we did not have to tear into the rear baffle!

By the way removing the 21 bolts, is not near as bad as it is hyped up to be, once you've done it. The second time, I had all the bolts installed in less than 30 minutes. There's only 2 or 3 that are painful, even with the pushrod still installed. I fretted over this for some time, and even hired my A&P friend to do it the first time. The right tools, as have been suggested is the key.

Michael-
Michael,
I truly hope your A&P was successful in stopping your leak. However, if one only removes proseal from the exterior of the tank and replaces it, I am very doubtful that will end up being a long term resolution to a leaking tank. That was the real reason I became such an expert at tank removal/repair. The air/fuel mixture that exists outside a leaking tank will never allow for the proseal to effectively seal off a leak. The leak will eventually resurface due to the chemical makeup of the fuel/air/proseal.

Good luck with your existing repair. I hope your situation proves my statements wrong.
 
Interior fix...

The leak was fixed on the interior of the tank. The sealant was applied to the interior, rear, bottom baffle through the filler hole.

I agree that applying pro-seal to the exterior of the tank would not provide a long-term fix.

My main point is, that you need to find out where the leak is. Why cut holes in all the bays of the rear baffle, if the leak is only in one bay?

Michael-
 
The leak was fixed on the interior of the tank. The sealant was applied to the interior, rear, bottom baffle through the filler hole.

I agree that applying pro-seal to the exterior of the tank would not provide a long-term fix.

My main point is, that you need to find out where the leak is. Why cut holes in all the bays of the rear baffle, if the leak is only in one bay?

Michael-
Ok, gotcha. Very true as long as the leak is in a bay that is accessible. However, the only bay that is accessible without opening it up is the first inboard bay with its inboard access plate. If lucky enough to be able to reach through the fuel cap maybe you would be able to reach the interior seams with some difficulty in the outer most bay. Anything else though is going to require opening up the tank in some manner.
 
I have heard of this, but - - -

Michael,
I truly hope your A&P was successful in stopping your leak. However, if one only removes proseal from the exterior of the tank and replaces it, I am very doubtful that will end up being a long term resolution to a leaking tank. That was the real reason I became such an expert at tank removal/repair. The air/fuel mixture that exists outside a leaking tank will never allow for the proseal to effectively seal off a leak. The leak will eventually resurface due to the chemical makeup of the fuel/air/proseal.

Good luck with your existing repair. I hope your situation proves my statements wrong.

More information please. I sent pictures, descriptions, and cross section pictures to a 3M engineer for their version of tank sealant. She had never heard of it and was skeptical of it even happening. I never got a good explanation.

So, if I took a bowl coated in inside with proseal, then dripped fuel into the bowl enough to just keep it wet, (maybe a wick) it will soften?

BTW- thanks for sharing your tank experience, I just tested my tanks (made 2001) and they passed with 42" of water in a manometer. Dang that thing is sensitive to temperature.
 
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More information please. I sent pictures, descriptions, and cross section pictures to a 3M engineer for their version of tank sealant. She had never heard of it and was skeptical of it even happening. I never got a good explanation.

So, if I took a bowl coated in inside with proseal, then dripped fuel into the bowl enough to just keep it wet, (maybe a wick) it will soften?

BTW- thanks for sharing your tank experience, I just tested my tanks (made 2001) and they passed with 42" of water in a manometer. Dang that thing is sensitive to temperature.
Well, my 1st hand experience is that when the proseal (I believe I was using the FlameMaster brand) was exposed to air on the outside of the rear baffle and fuel made its way outside of the tank onto the surface of that baffle where the proseal was applied to the outside of the baffle flange there was a deterioration of the proseal over time. It was noted that even in areas where the proseal had properly cured there was a breakdown of the proseal. I observed proseal that was previously set and cured had broken down into a soft putty or peanut butter consistency and was allowing fuel to seep out from under that section of proseal.

It is my thought that a manometer is not a good tool for checking for leaks. Unless one can have a controlled environment where outside environmental temperatures and pressures cannot affect the reading of the manometer and in which one can isolate the cause of the rise or fall of the manometer strictly to the pressure inside the tank, I see little value in using it to check for leaks. The manometer, or for that matter, the inflated balloon will not be the beneficial tool for finding leaks. It will be the act of applying soapy water to all seams, rivets, etc. while applying small amounts of air pressure inside the tank that will allow one to find leaks. In that instance attaching the balloon is strictly serving as a relief valve for the pressure in the tank.

As for the manometer, as you said, it is an extremely sensitive tool that really is too sensitive for this task. One cannot isolate adequately all the variables that affect its movement to definitively state whether the movement would be do to a leak or to movement of temp/barometric pressure.
 
Manometer

Yes, Steve I agree on the manometer, but my tanks were already installed on the wing. The test was at around 44" of water and the first tank had me goosey as it dropped 2" over night, but when depressurizing, the zero had dropped 2" also. The second tank I measured temperature. It dropped an inch overnight and also dropped temp. The absolute temperature ratio and another zero change (smaller) got it within .2" in 24 hours - airport barometer was no change.

The tank exteriors were bubble tested as was the fuel sender and plate and other areas I could access short of removal. No leaks there. For the rest, it may leak but my logic is that I will be flying and the removal won't be any more trouble than it is now, and I have proof that it needs to be removed.

One day I will get some 3M tank sealant, in date, and set up a test. If it fails I will be back on the phone with 3M and get to the bottom of it. With a control sample of the fuel too. How long did it take yours to leak again - in calendar time? i.e. how long should the test run?
 
My problems persisted for approximately 2 years before I bit the bullet and cut the access holes for each bay. I would say in between each attempt was probably about 2-3 months before I again noticed blue staining from the leaks. I have now been 3 years since I made that last repair. Everything has been great for these past 3 years.
 
gents
I am buying wings that have the tanks done and tested from a previous builder that has given up on the project.. should I take any precautions on testing/ etc

Thank you..
 
gents
I am buying wings that have the tanks done and tested from a previous builder that has given up on the project.. should I take any precautions on testing/ etc

Thank you..
If it is still a project then I would do a test of the tank. It really is not a difficult process. That is if the tank is off of the wing. Once off the wing you will have access to every part of the tank. If it is attached to the wing, well, you have a decision to make. Do you remove the tank and do a proper test? Do you trust the builder and go on? Even though it can be a pain in the arm (LOL) to remove the tank, it really is the only way to know for sure. A spray bottle of soapy water, a balloon appropriately secured to one of the tank orifices and a 1psi squirt of air in the sealed tank is all you need to find out. If I were buying a second hand kit that was not flying yet this is what I would do.

Good Luck.
 
Just a comment from someone who has been there. If I ever do build another RV fuel tank from scratch I will install the repair plates as part of the initial tank construction. I had a very hard time wrapping my brain around the idea of creating a container with a bunch of holes in it to hold a liquid. However, once I finally drank the Kool-Aid I realized these access plates should be the standard Modus Operandi for building fuel tanks.

Good Luck!

I think it would be harder to remove the cover plate than it would be to cut in the holes. Why do this unless it is needed - you are creating a potential leak point, and you are making the repair harder.

As others have experienced; I have seen properly mixed and cured pro-seal turn to goop when exposed to air for too long. I don't know why, but I have seen it. It is probably a good idea to build the fuel tanks last and then keep them full all of the time after that.
 
If it is still a project then I would do a test of the tank. It really is not a difficult process. That is if the tank is off of the wing. Once off the wing you will have access to every part of the tank. If it is attached to the wing, well, you have a decision to make. Do you remove the tank and do a proper test? Do you trust the builder and go on? Even though it can be a pain in the arm (LOL) to remove the tank, it really is the only way to know for sure. A spray bottle of soapy water, a balloon appropriately secured to one of the tank orifices and a 1psi squirt of air in the sealed tank is all you need to find out. If I were buying a second hand kit that was not flying yet this is what I would do.

Good Luck.

Thank you sir...
 
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