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Old 09-01-2018, 04:37 PM
Navy76 Navy76 is offline
Join Date: Apr 2018
Location: Corvallis, OR
Posts: 12
Default QB Fuel tank stripped threads

Recently Iíve been trying to install fuel level sender on my RV-14A QB right wing. I called Vans for help and tips. Itís very difficult to see whatís going on inside the completed tank. Vans suggested that things would be much easier if I removed the tank from the wing first. This would also facilitate the pressure test to follow.

This seemed reasonable, so today I built some cradle supports for the tank then attempted to remove it. Everything went fine except that two to the bolts that connect the rear of the tank to the spar appear to be stripped. They spin freely but never back out. I thought that if I applied some rearward pressure while turning the bolt tha maybe I could get it to reengage the thread. I put a pair of small vice grips on the head and pulled as I tried to back out the thread but no joy.

Both bolts are very difficult to get to. One of them I canít even see without a mirror. The second one I can see and I can even see the threaded end of the bolt where it comes out of the nut plate. It just spins and spins in both directions with no axial movement.

I am really at a loss as to what to do. Both bolts are so inaccessible I donít think drilling them out is really an option. Any ideas?

I am also wondering if anyone has experience with getting Vans to do the work? I paid a lot for the quick build kit and donít relish the thought of having to pull a wing skin to repair a problem that I didnít create.

Lyn Robertson
Corvallis, Oregon
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Old 09-01-2018, 05:10 PM
BobTurner BobTurner is offline
Join Date: Dec 2011
Location: Livermore, CA
Posts: 5,494

Call Vans. I think you have a good case for shoddy workmanship here. For the record, my QB -10 came with those same bolts being too long. This was Ďfixedí by the QB guys by using a stack of washers under each bolt head. Since I needed to remove the tank anyway (as you found out) no real harm other than using the correct size bolts from my spares.
Be careful trying to remove these. You do not want to damage the spar in any way.
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Old 09-01-2018, 05:11 PM
Paul 5r4 Paul 5r4 is offline
Join Date: Oct 2006
Location: Foley, Al
Posts: 355

That sounds like a major problem. I was a machinist for 15 years before becoming an RN. I've taken out many many broken and stripped studs/bolts.
I don't know about Vans doing any work so someone else more in the know will have to speak to that.
As far as your problem. I can't visualize whats going on. It sounds like the bolts were overtightened when assembled which broke the threaded part of the nut plate off which is now acting like a nut holding the bolt in place. Only suggestion is if you can somehow get a pair of thinly ground down pliers to grip the barrel of the broken nut plate then back the bolt out. Easy to say but can you get something like that up in there along with two hands??? There's no really right way here.... it's what ever works without any damage to the tank, wing spar etc.
With that said, the only other way which is my guess what you're going to end up doing is what you've mentioned. Just like the other access holes in the wing skins... cut another one. I don't see where you have a choice. The + side of this would be easy access when reinstalling or removing the tank if ever needed.
Paul Gray
Foley, Alabama
N729PG..... 300+ hrs
RV 7A, Lycoming 0 320 D1A, Sensenich FP propeller
VAF supporter $$$

Last edited by Paul 5r4 : 09-01-2018 at 05:13 PM.
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Old 09-01-2018, 05:54 PM
rocketman1988 rocketman1988 is offline
Join Date: Jun 2010
Location: Sunman, IN
Posts: 1,336
Default Help

Can you get a nut splitter in there?

If you can get this tool over the nut, it will split the side of the nut and you should be able to remove it from the bolt...
Aerospace Engineer '88

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Old 09-01-2018, 06:47 PM
N804RV's Avatar
N804RV N804RV is offline
Join Date: May 2013
Location: Mount Vernon, Wa
Posts: 410

Originally Posted by rocketman1988 View Post
Can you get a nut splitter in there?

If you can get this tool over the nut, it will split the side of the nut and you should be able to remove it from the bolt...
If its the bolts I'm thinking of. A nut splitter won't do it. These are AN3 bolts that go through the spar web into the L brackets on the rear web of the tank. The ones in between the most inboard ribs, where the wing walk goes are very tough to get anything on other than a socket on an extension. They are retained by K1000 nutplates. My bet is the nutplates are spinning. Its a bit scary to consider why they became that way.

Definitely talk to Van's. If you can get a video camera down in there even better.

----------PS: The only reason I risk opening my pie hole on this is, I'm the guy that bought the "barn-find" wings and went through similar problems. -KW
Ken W.
Mount Vernon, WA
2018 VAF Supporter

Last edited by N804RV : 09-01-2018 at 06:52 PM.
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Old 09-01-2018, 06:59 PM
mturnerb mturnerb is offline
Join Date: Apr 2015
Location: Ponte Vedra, FL
Posts: 847

The good news is that you are close to the mothership - hopefully they'll step up and fix this problem. This could be a big challenge to disassemble enough to access the brackets on the fuel tank that hold the nutplates.
Turner Billingsley
RV-14A In Progress
N14VB Reserved

Last edited by mturnerb : 09-01-2018 at 07:08 PM.
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Old 09-01-2018, 07:14 PM
jask jask is online now
Join Date: Feb 2018
Location: Ramona, CA
Posts: 109
Default Nut plate

I would get an inspection camera from harbor freight and see if you can get a look at what is going on. 25% off on monday. It has a 38" reach.
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Old 09-02-2018, 12:46 AM
Navy76 Navy76 is offline
Join Date: Apr 2018
Location: Corvallis, OR
Posts: 12

Thanks for the feedback! Iíll call Vanís Tuesday and see what they say. These particular bolts are in the most inaccessible spots, almost anywhere else and Iíd have more options. Murphyís Law holds true again!
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Old 09-02-2018, 12:53 AM
Paul 5r4 Paul 5r4 is offline
Join Date: Oct 2006
Location: Foley, Al
Posts: 355

If the entire nut plate is spinning..... That might be a better scenario than the nut plate barrel broken off. At least it gives you something to grab onto. If that is the case then maybe a long piece of safety wire through one of the holes. I know that would be a mother bear to do! Like others have suggested, maybe a scope. I've blindly stuck my phone in camera mode way inside places and snapped a bunch of random pics to get a close up look. It may take several to get the one or two that yields some good information.
Paul Gray
Foley, Alabama
N729PG..... 300+ hrs
RV 7A, Lycoming 0 320 D1A, Sensenich FP propeller
VAF supporter $$$
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Old 09-02-2018, 02:06 AM
scsmith scsmith is offline
Join Date: Jan 2008
Location: Ashland, OR
Posts: 2,002

It seems to me there are two possibilities here.

One is that the plate nut is spinning, presumably because it wasn't riveted properly to the Z-bracket, or it was overtorqued and that broke the rivets, or possibly the ears off the plate nut.

The other possibility is that the bolt is actually broken, most likely at the root of the threads, which could be caused by the bolt being a little too long and the assembler just kept turning it to try to get it to draw tight when the plate nut was bottomed on the threads, and that broke the bolt. This seems like the most likely scenario to me, especially after the other comment above about finding one assembled with too long a bolt with some washers under the head.

If you can snake a small camera in there and watch, it would help answer which case you have.

It seems unlikely to me that the threads of the plate nut are stripped. It is pretty hard steel.

If it is the second case (broken bolts), then your idea of getting some rearward pressure on it as you turn it is the right idea, and maybe you just didn't get enough. See if you can get a straight-blade screwdriver in under the head, being careful not to gouge the face of the shear web of the spar. But also, if it is the case that both bolts are actually broken off, then it should be possible to remove all the other connections of the tank to the wing, and just remove the tank, leaving the broken bolts in place. The Z bracket would just slide off the ends of the broken bolts. Then with the tank off, you can punch the broken bolts out from the front, remove the broken bolt ends from the plate nuts (might be easier to just install new plate nuts) and it should be straightforward to reassemble everything, with proper-length bolts.

If it is the first case, you have to find a way to keep the plate nut from turning. I think you can drill a hole in the tank skin in the area between the spar and the rear tank baffle so you could feed some kind of tool in there. (*)

The safety wire idea mentioned above might work. If that isn't strong enough, then make a tool from a narrow strip of steel with a pin near the end that would fit into one of the rivet holes in the plate nut. with the plate nut turned perpendicular to the long tool, you hopefully can get enough torque to loosen the bolt. Otherwise, make a tool with two pins at the right spacing to fit into the rivet holes in the ears, and a semi-circular cutout between them for relief around the barrel of the nut. This tool would engage both of the holes in both ears of the plate nut. It might not even be necessary to actually get the pins into the rivet holes, it might work to just have the sides of the ears bear on the pins.

If you need help visualizing what the tool would look like I can make you a sketch, just send me a PM. But I'll be away until Wednesday.

(*) As I think about it, the rear-facing flange on the rear tank baffle probably comes back pretty close to the forward face of the spar? If so, then drilling a hole there will remove some of the bond area that is sealing the tank. If the flange is something like an inch wide, it may be OK to put a 3/8" hole in the middle of it without causing a leak.

I can't think of any other way to get access in there to grab the plate nut.
Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet"
Hobbs 525 in 9 years (would have flown more this year if not for fire smoke)
also LS-6-15/18 sailplane
VAF donation Jan 2019

Last edited by scsmith : 09-02-2018 at 02:19 AM.
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