Fuel tank mystery hole

Freightdawg · #1 01-24-2015, 01:07 PM

This afternoon we were in the garage final drilling, well, a BUNCH of holes. (So, what's new, right?) But there is one hole (on each tank skin) that seems out of place. It's in the line of holes where the tank skin attaches to the the lower baffle flange, right in line with the middle rib. All of the other holes are evenly spaced, but this oddball evenly splits the "normal" spacing. There is no corresponding hole in the baffle flange.

Reading ahead, I can't find any reference to it, and though it appears depicted in the rivet diagram on page 18-5, it doesn't look like a rivet is called for.

I've left it undrilled for now. If anyone can clue me in on why it's there, I'd be most appreciative.

Thanks.

Jeff

Mike S · #2 01-24-2015, 01:30 PM

A photo might help.

By any chance is it where an access panel will end up? Trying to remember stuff, and taking a shot in the dark here..........

Jesse · #3 01-24-2015, 02:56 PM

I think it's so you can keep your rear tank baffle oriented correctly from top to bottom. Match drill the hole into the baffle and then you have orientation.

Freightdawg · #4 01-24-2015, 03:57 PM

Quote:

Originally Posted by Jesse

so you can keep your rear tank baffle oriented correctly from top to bottom

I thought that's what a Sharpie was for.

Freightdawg · #5 01-24-2015, 04:10 PM

The clecos are attaching the tank skin to the middle rib. The holes running left to right are in the skin and are where the skin attaches to the tank baffle lower flange. The four holes on either side of the rib are evenly spaced, then there's that one odd hole in line with the rib that has me ... ok, I'll say it ... baffled.

60av8tor · #6 01-24-2015, 04:30 PM

I think Jesse's guess is as good as any. Jeff, kudos for your attention to detail. I never noticed, but you're right - if you look closely, there is not a rivet symbol over that hole in the plans. That being said, both of my tanks are done with a 3.5 riveted in that hole

evmeg · #7 01-24-2015, 05:29 PM

That hole is there to make sure you don't put the baffle in upside down. There actually is a matching hole in the baffle flange...on the bottom only. Look again, I think you will find you have the baffles spun around 180.
Cheers.
Evan

Ron B. · #8 01-24-2015, 06:01 PM

If you look at page 18-4 rev. 0 figure 2 part number T-1002 the tank baffle. In the middle bottom you will see the three holes that correspond with the holes in the skin in your picture.
If you already have the tank zees in and pro-sealed and you have the baffle upside down you could match drill the top skin to the hole in the baffle and the bottom baffle to the skin. I'm pretty sure the remainder is the same. Just find some other way to keep things oriented properly.
I ended up sealing my zees incorrectly after having everything well thought out and marked very well, but then I had a brain fart and rotated the baffle for a second for something and got distracted and never turned it back. Returned after lunch and started pro-sealing. It's only after dropping the baffle down into the wet pro-seal and clecoing everything in place, I made a last check on orientation before riveting the baffle to the skins. I was pissed and worked very late that evening cleaning the pro-seal , drilling the offending rivets , cleaning all the rivet drilling chips thoroughly , new pro-seal and final riveting.
Goes to show me that no matter how careful I am I still screw up.

Freightdawg · #9 01-24-2015, 07:40 PM

Sure enough, I had the baffle in "upside-down."

Ron, I looked at the diagram, and sure enough, just as you described. Though, if Van's wanted to be completely accurate, they would have had matching holes illustrated on the skin. Not that I probably would have noticed it.

Now then, the question becomes--are the baffles symmetrical, except for this one hole? I final drilled the whole thing, so do I leave the baffle as is and match drill the one hole? I'll be sending off an email to the Mother Ship.

Fortunately, I only did this on one tank. We hadn't installed the second baffle.

Thanks for solving the mystery.

Jeff

aturner · #10 01-24-2015, 08:19 PM

Just a guess, but look to see if the location of the z-bracket mounting holes changes when you rotate the baffle. I am guessing they will, and that is why it is indexed.