Today, the weather was absolutely beautiful.  The hot temps and high humidities we have had over the last week were gone.  This made a great day for working in the garage on the plane.

First thing I did today was figure out where I was going to place the rivet holes for the T-410 reinforcement plate ( T-405, tank attach angle).  Van's does not give you any real information on where to put these rivet holes.  They just say "fabricate it".  I just tried to come up with the same number of holes they show on the print.

The key here is that if you are installing a flop tube, placement of these rivet holes more restrictive as you have to drill a 9/16" hole to accommodate the flop tube AN fitting.

Here are the rivet locations match drilled to the attach angle.  Everything looks pretty good here, however, the three holes in a line by the angle are a little close to the bend.  If I put the factory heads on the reinforcement plate side (T-410), I will have plenty for the shop head on the T-405 attach angle.  The big question is:  Will I be able to orient those rivets that way when it comes time to shoot them?

The other thing worth mentioning here is that the T-405 attach angle does NOT go all the way up to the flange of the rib.  The reason being is that there are rivet holes along the T-405 that sits on the flange of the rib.  I left room for the shop heads of the tank skin-to-rib rivets.  Van's instructions do not make any mention of this and if you are not thinking ahead (my typical problem), you could be inventing new cuss words later on.  I guess they figure that if you are this far on the plane, you should just know those things.  Okay, but I am going to miss something sooner or later.

I decided that I would install a flop tube in the right wing.  Therefore, I needed to drill a 9/16" hole into the T-405 attach angle, the rib, and the T-410 reinforcement plate.  Don't ask me why I drilled the attach angle in this orientation...  Ooohh yea, I remember why....  The drill chuck was going to rub on the attach angle when I went to drill from the other side.  I just used a couple of quick clamps and C-clamps to hold the angle to some scrap wood.  Worked great. 

Just another close up picture of the measures I had to take in order to drill this hole.

Hey, what do you know...  The flop tube fits.  I looked at my rivet hole placement to make sure that the rivets would not interfere with the flop tube AN fittings.

See Dan Checkoway's hole placement.  This link illustrates why placement of the rivet holes is important.  I left my holes as close to the edges as I could and I probably do not have any more than 1/16" from any rivet to the nut that secures the flop tube AN fitting.  Builder beware...

Next, I moved on to drilling the reinforcement ring for the inspection cover.  Nothing really high tech here.  To figure out how / where I was going to orient the plate nut holes, I used the aft flange of the rib and measured to the edge of two screw holes and rotated the plate until two screw holes measured equally.  Now ask me if it matters....  I don't think so.....

I then proceeded on to dimple the plate nut RIVET HOLES in the rib and countersunk the plate nut rivet holes on the reinforcement ring.  Note the location of one of the aft plate nuts highlighted with the arrow.  It sets right next to the tooling hole in the rib.  You cannot see this when the reinforcement ring is placed on the rib.  I would consider re-orienting the plate nut locations to give me more distance between the plate nuts and the tooling hole.

I had bought these floating, sealed plate nuts a while back with intentions to use them for the inspection hole plate nuts.  The idea here is that the inspection plate screws are sealed off from the tank eliminating them as a source of leakage.  If you need to open your tank up, it is no big deal as you shouldn't have to take any extraordinary measures to seal it back up.

I got these from Wicks Aircraft Supply.  (Floating Plate Nuts:  NAS1473A08)

Okay, I got all the plate nuts installed and was admiring my work.  These look pretty good.

The one trick here is that the rivet holes are so close to the screw cavity, it was difficult to rivet these on.  I could barely get the squeezer square.

Then I realized I had somewhat of a problem.  I held the rib up to the light and I could see light between the rib and the reinforcement ring.  Okay, why did I spend money on the fancy plate nuts if I am not going to have a fuel tight seal between the rib and the reinforcement ring?  There are four major locations where a leak can occur in the inspection plate area:

1. Gasket between the rib and the cover plate
2. Plate nut rivets
3. Cover plate screws
4. Small tooling hole that sits under the reinforcement ring.  It would be covered by the cover's cork gasket, but not by much.

Considering my options here, I decided tooooo.....  drill out all of the plate nuts and prepare for my first session playing with tank sealant.  I decided that this would be a good practice session.  Since it is really not required to be sealed, I didn't have anything to lose if the tank sealant kicked my butt.  I got prepped up for the NEW experience I was about to under take. 

1. I soaked the rivets in MEK
2. Scrubbed all my parts down with a scotchbrite pad and Alumiprep. 
3. Wiped down all my parts with a clean rag and MEK (not required if you cleaned/etched with Alumiprep).
4. Measured out and mixed up a batch of tank sealant.  (10 to 1) ratio using a digital cooking scale I got from Wal-Mart (Worked GREAT).
5. Organized my tools and equipment so I wouldn't have to go searching for them with messy gloves.
6. Recruited Tami to help clean parts as I finished.

I didn't get a lot of pictures while doing this as Tami doesn't usually want to run the camera.  However, today she thought that was a better deal that using the little spatula's to spread sealant. 

Here I am only a little over half way done installing the 12 plate nuts for inspection hole.  Dealing with tank sealant was definitely a new experience.  Once the sealant gets on your gloves, you stick to EVERYTHING.  I tried to pick up a rivet and 10 rivets would stick to my glove. 

I frosted up the mating surfaces of the rib and reinforcement ring, clecoed them together.  I then frosted the plate nut flanges then clecoed them to the reinforcement ring.  Last but not least, I put a little sealant in the dimples for the flush rivet factory heads.

With sealant all over (by this time), I had a hard time finding my rivet holes and the rivets I put in them.  As sticky and gooey as this stuff is, try and put your squeezer on it.  It was like trying to hold a GREASED PIG.  The squeezer dies slid all over the place.  I couldn't believe it !!!

In the picture below, you can sort of see how messy this was getting.  I had to wipe some of the sealant off the shop heads after setting them as I wanted to see if I got the rivet set properly.  I gave up trying to keep this looking neat until after I got done setting all of the plate nuts...

I had Tami cut my painters rags up into little "swatches".  As soon as you get sealant on the rags, it was just better to toss them.  When dirty, they just smear sealant around.  Alot of trash for such a small sealant effort.

Here is what the inspection hole looked like after I got everything frosted up and cleaned all the excess sealant off.  Can you figure out what I forgot in the picture below?

Yep, you guessed it...  I need to install an anti-hang up bracket over the inspection hole since I am using a flop tube in this tank.  I will wait until the sealant sets, otherwise I would never get all the aluminum shavings out of that new sealant.  I couldn't even imagine....

If all goes well here, I have eliminated 3 of the 4 leakage paths I discussed above.  All I have to worry about is the large hole.  Van's has you seal the cover plate with a cork gasket.  I know some builders who use tank sealant to seal the cover plate and throw the cork gasket away.  I am not sure what I will be doing yet.