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Remove Fuel Tanks

Plummit

Well Known Member
I'm getting ready to pull my tanks to repair some weeping rivets. As a buyer not a builder, how heavy are the tanks? Also, where is the access to the Z brackets to unbolt the tank from the spar? Any other tips?

TIA
-Marc
 
There are 3 inspection covers on the bottom of the wing just behind the spar. You can access all the attach bolts through there except for the most inboard 'Z' bracket (closest to the fuselage) which is accessed from the front. Nice to have an assistant to hold tank in place & help pry it off when all bolts removed. Tank itself is not very heavy, just awkward to hold.
Hope you have a set of plans or at least the fob version from Vans for $10
 
Yes I have both the original plans and the thumb drive Vans sells. The original plans show the Z brackets being attached prior to the bottom skin, which is why I asked about access.

-Marc
 
Both tanks are pretty light. 10 pounds? 15?

When you remove all the bolts and screws, the dimples on both the skin and spar will hold them in place a little. So, don’t drop them, but there is also little risk of dropping them since you need to “pop” them off that dimple friction with a little force.
 
Yes I have both the original plans and the thumb drive Vans sells. The original plans show the Z brackets being attached prior to the bottom skin, which is why I asked about access.

-Marc

A bit awkward but all the bolts are accessible thru those 3 inspection holes. Most folks can remove a tank in about 30 minutes.
 
A bit awkward but all the bolts are accessible thru those 3 inspection holes. Most folks can remove a tank in about 30 minutes.

I wish it only took 30 minutes. I had to take my tanks off my 10 a few times prior to first flight. It takes about an hour and a half. Also need to take the wing root fairing off as one of the zee brackets is under there.
 
A bit awkward but all the bolts are accessible thru those 3 inspection holes. Most folks can remove a tank in about 30 minutes.

That means it will take me 4 hours.... ;-)
Actually, now that I know what I know, it doesn't sound too bad. The only unknown for me is how to disconnect the fuel gage wiring. Hopefully there is a disconnect in the wing root so I don't have to pull the seats again.

I just did my C/I last month and opened all of those inspection panels on the wing. I thought they were there to aid connecting wiring or linkages. Gonna tackle it today.

Final question: I want to add a purge valve return line to a tank. The builder returned the purge valve to the tunnel, but not all the way to the QB tank. What fitting should I use at the tank and where is the best location?

-Marc
 
Final question: I want to add a purge valve return line to a tank. The builder returned the purge valve to the tunnel, but not all the way to the QB tank. What fitting should I use at the tank and where is the best location?

-Marc

What's wrong with how the purge is setup? I'm imagining it is set like mine:

You set the purge return where it tee's into the feed line from one tank. Let's say you set that up on the left tank.

So, to do a hot start, select the right tank, pump on, purge valve open, and the warm fuel is pushed back into the left tank.
 
Final question: I want to add a purge valve return line to a tank. The builder returned the purge valve to the tunnel, but not all the way to the QB tank. What fitting should I use at the tank and where is the best location?

-Marc

I used an AN4 bulkhead fitting. However, I had the fuel sender removed, so it was easy to get proseal on the inside. If you are pulling the sender, this is probably the simplest way to do it. Mine is high on the tank wall and close enough to the sender hole to get my hand in there. However, you will want to pick the spot before you pull the tank, as there are a few items that would create interference with the return line.

If you are not pulling the sender, you can buy one of the flanges used for the tank drain and install with closed end rivets. However, you will not have a means for clearing out AL chips from drilling.

Larry
 
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The fuel sender has a screw in the center that an eye for your wire is attached , no problem. Only caution I have is if all the fuel is not out it could shift when you remove the tank , just watch or be prepared for that. There should not be any fuel if you drain through the drain valve , but I would be prepared just in case. Much easier to have a friend to help, than deal with dropping the tank.
 
What's wrong with how the purge is setup? I'm imagining it is set like mine:

You set the purge return where it tee's into the feed line from one tank. Let's say you set that up on the left tank.

So, to do a hot start, select the right tank, pump on, purge valve open, and the warm fuel is pushed back into the left tank.

I'm pretty sure the purge tee's into the output of the A/P electric pump in the tunnel. That would seem to negate the benefit of the cool fuel in the tank. The purge instructions say you don't have to have a dedicated return to the tank, but then go on to say the port stamped as "return" should return to any tank.

-Marc
 
A bit awkward but all the bolts are accessible thru those 3 inspection holes. Most folks can remove a tank in about 30 minutes.

Sorry my time estimate may not apply to all, I base that from my experience of having removed & repairing a lot of tanks on a lot of RVs over the years. The removal job is awkward, not difficult.
 
I'm pretty sure the purge tee's into the output of the A/P electric pump in the tunnel. That would seem to negate the benefit of the cool fuel in the tank. The purge instructions say you don't have to have a dedicated return to the tank, but then go on to say the port stamped as "return" should return to any tank.

-Marc

Yeah, that isn't a good solution. Just use the same hardware and feed the return into either of the feed lines upstream of the fuel valve. That'll return it to that side's tank as long as that tank is *not* selected on the fuel valve.

Much easier (IMO) than pulling a tank and installing a new fitting.
 
Yeah, that isn't a good solution. Just use the same hardware and feed the return into either of the feed lines upstream of the fuel valve. That'll return it to that side's tank as long as that tank is *not* selected on the fuel valve.

Much easier (IMO) than pulling a tank and installing a new fitting.

Thanks Kyle. Unfortunately the tanks have to come off anyway as the top rivet(s) leak and the left tank looks like it has a small leak at the feed fitting at the bottom. I already purchased the Vans tank repair kits. Vans suggested I put some sealant on Top of the rivets but that just doesn't float my boat... The recent fuel tank build video supports my feelings that the repair should be on the inside of the tank.
These were Q/B tanks vintage 2008/2009, and the builder told me they leaked like a sieve and had to be repaired right out of the gate.

tank leak.jpg
 

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Final question: I want to add a purge valve return line to a tank. The builder returned the purge valve to the tunnel, but not all the way to the QB tank. What fitting should I use at the tank and where is the best location?

-Marc

My purge valve is returned in the tunnel. Works great. I installed a one way valve on the return line. If you take a look at the Airflow Performance instructions there is a diagram that shows exactly how this is done. Perfectly acceptable.
 
Well after 3+ hours I still don't have the tank off. Things were going pretty good until I tried to get this -3 bolt out:
stripped.jpg

Either the bolt or (more likely) the riv-nut insert is spinning but bolt no loosen. The only good news is that it's right up in the access panel so if I have to grind the head off with a Dremal it won't be too bad...

-Marc
 
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Well after 3+ hours I still don't have the tank off. Things were going pretty good until I tried to get this -3 bolt out:
View attachment 6189

Either the bolt of (more likely) the riv-nut insert is spinning but bolt no loosen. The only good news is that it's right up in the access panel so if I have to grind the head off with a Dremal it won't be too bad...

-Marc

There’s a nutplate on the other side of that bolt.. I would think the nutplate is probably not spinning, but I bet the threads on the -3 bolt stripped, leaving the bolt spinning in place. If the nutplate cleans up with a tap, that’s the better case. If you have to change the nutplate, you may have to use pulled 3/32 rivets, as the space under the Z-bracket is tight. If you use the Dremel to cut the head, be super careful not to nick the spar! I would probably tape some scraps of aluminum where I could just in case the dremel cutoff wheel jumps! The washer should protect the spot under the bolt head.
 
There’s a nutplate on the other side of that bolt.. I would think the nutplate is probably not spinning, but I bet the threads on the -3 bolt stripped, leaving the bolt spinning in place. If the nutplate cleans up with a tap, that’s the better case. If you have to change the nutplate, you may have to use pulled 3/32 rivets, as the space under the Z-bracket is tight. If you use the Dremel to cut the head, be super careful not to nick the spar! I would probably tape some scraps of aluminum where I could just in case the dremel cutoff wheel jumps! The washer should protect the spot under the bolt head.

Thanks for the excellent suggestion Tom. I'm thinking that I might try some scrap steel to protect the spar. I checked with a young A&P friend yesterday and he thought that the insert in the nut plat might be rotating, but either way, I'm not looking forward to this! I really need that guy that can pull these tanks in 30 minutes.... :D

-Marc
 
You might want to try a small pair of visegrips so you can pull while you turn , if the threads in the nutplate are stripped.
 
There’s a nutplate on the other side of that bolt.. I would think the nutplate is probably not spinning, but I bet the threads on the -3 bolt stripped, leaving the bolt spinning in .
+++
This has happened to me once. I attributed the cause to a bad nut plate or defective bolt threads.
 
Finally!

I happen to run into my A&P at the airport today and ran the problems with the -3 bolt by him. He discouraged me from using the Dremel, and said he thought we could get that bolt head drilled out with a 90* drill. He was right! Took all of 20 minutes.

tank off.jpg

Might need a new sending unit as the bolt that held the wire terminal just rotates...

-Marc
 
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