18-06: Aft Root Rib #1 / Fuel Vent Union Install

 Next up was the aft root rib (Rib #1) in each tank - which is the LAST rib in each tank! 

Basically this was installed in the same manner as all the others, except the skin to rib rivets could be squeezed with the pneumatic squeezer and there were 6 x AN470-AD4 rivets that needed to be set between the aft rib, the tank attach bracket and the forward rib. 

For these larger rivets, i used my offset cupped set which was a very tight fit as the rib could not be pushed out of the way and the rivet gun was touching the rib, but it was just doable. I used 60 PSI and the long tungsten bucking bar on the shop heads. One rib i had a lot of trouble getting the rivets in and i had to run a reamer through the holes (stressful with sealant going off!), but i checked the other one beforehand and made sure it didn't happen again. 

A large sealant fillet was placed on the inside of the rib as i did with the tip #7 ribs. I probably didn't need to add sealant to the shop heads in this case, but i had on all the others so why not! I used the flared fuel tube trick once again which i wish i had learned much earlier in the build!

These took a long time to get to this point!

It feels like a milestone has been reached to get to this point - just the rear baffle to go! The tanks have taken 88.7 hours so far over a period of a bit over 3 months. So far i have used 2 and a half pint cans of sealant and i reckon i will need probably 3.5 total by the end but i might be able to get away with 3. 

So far: 1085 rivets set on these 2 tanks! (the vast majority done with gun and bar). 

Fuel Vent Bulkhead Union

The fuel vent bulkhead union was installed with a little proseal under the inside flange of the 'nut' on the union, which squeezed out through the hole and provided enough proseal to also seal the nut on the outside of the rib. I also covered the inside of the flange of the bulkhead union with sealant. Both the outside nut to mount the union, and also the flare nut on the vent line inside the tanks were torqued as per my mechanics handbook. 

On recommendation of my TC, i bent the end of the vent line to be a little toward the top skin, so it is as far above the fuel level as possible - just in case i ever leave it full one day in the hot sun, and the fuel expands; you don't want it leaking out the vent and syphoning onto the ground.

This shows the amount of sealant which squeezed out the hole - i didn't add any additional on the outside. 

I used 55 in/lbs to torque the aluminium flare and bulkhead union nuts (pictured)

This was the final sealant application on the inside of the tanks. None is needed on the flare fitting - it is supposed to be fuel tight! 

I bent the end of the fuel vent line up toward the top skin.