This is the second service bulletin issued for this ridiculous fuselage gas tank in just over two years - two years and 5 days to be exact. Gee, Tom, tell us how you really feel about the tank. Yet another of the "infinite" number of failure modes has emerged for the engineers at Vans to subdue. They need just a bit more reinforcement of the forward attach points on the tank after another RV-12 had its tank breached. Seems this failure mode was worse than the previous one. Seems the frangible bolts weren't "frangible" enough. So now, all RV-12 builders and pilots get to dismantle their tanks and insert some more doublers into the corners of the forward bulkhead of the tank and replace their existing frangible bolts with some new more frangible ones.
Quoting the last sentence of the 2013 SB's synopsis: "Adding more robust hardware in conjunction with doublers inside the tank will help the frangible head of BOLT-00002 to fail before significant distortion of the tank and make the tank more resistant to a breach."
And quoting the last sentence of the 2011 SB's synopsis: "While the severity of the impact was such that a breach of the fuel tank is not surprising, the tank can nonetheless be made more breach resistant by the addition of clips and by the use of frangible bolts."
Am I the only doubting Thomas out there? I am so frustrated about the prospect of tearing up a perfectly good and tight tank. If I had to do it all over again, I would definitely go with the group of EAB builders who have/are pioneering wet wings - where the fuel belongs in an airplane. I know of at least 1 RV-12 currently flying with wet wings. Not exactly a compelling statistic but the work I have seen on those in progress is stellar.
Okay, I am tired to griping so I'll get on with the start of my teardown saga....it is still very early in the process. The first pictures show the T-1209 sender plate in surgery. Below shows all but 2 of the sender plate screws removed. The remaining 2 had to have their Phillips head converted with a Dremel tool into a deep slot configuration so I could get enough torque for their removal.
After slotting the heads, I was able to remove the two problem screws and now the ProSeal removal debacle begins. I had some success earlier in the project using some heavy duty stripper (methylene chloride-based product) for softening the ProSeal in cleaning up the tank after assembly and before painting. That is what you see around the perimeter of the T-1209 below.
Now, I have to figure out how to break the seal without destroying the tank bulkhead and the sender plate. I am having no success with anything plastic, so I will probably have to resort to something sharp and metallic...which will probably not end well. More to come.
Fast forward a few hours. I got some reassurances from others at VAF.com to go ahead and use a sharp metal tool, as shown below to pry apart the sender plate and bulkhead. It actually worked okay.
Progressing nicely.
Victory!
Cleaned up the bulkhead and sender plate (not shown) with my drill and wire brush attachment.
Next, came removal of the rivets for the nutplates and then more rivets from the tank bulkhead where the doublers are to be installed. Below is the attach bracket with the nutplate rivets and adjacent rivets removed and the area cleaned of the ProSeal and finish paint.
More rivets, nutplate, and paint removed from the other attach bracket.
Stay tuned...or just watch the photo's date stamp to get a feel for the duration/time lapse of the events.
The next step in the process is removal of the ProSeal from the interior of the tank, where the doublers are to be installed. This is definitely hard, long work exacerbated by the long, blind reach into the tank to do the work.
And this is the objective: the two doublers that will strengthen the tank to the point that the frangible bolts will fail before the tank breaches.
I didn't take too many pictures during the final sealing of the tank. In particular, I failed to snap pictures of the doublers, coated with Proseal going into the tank. I think I lose part of my sanity when I am working with ProSeal, as all HE** seems to break loose as soon as I start applying it to aluminum!
The picture below also appears on the tank vent modification page, but gives a good perspective of the amount of ProSeal I applied to the doublers.
Spreading the "love" on the face of the tank bulkhead in preparation for the sender plate and its dozen screws. All internal mods have been completed including re-connecting the vent line, which I was certain I would somehow forget to do!
Now comes the waiting game: letting the ProSeal setup for a week or two before conducting round 2 of the fuel tank leak testing.
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