Fuel Tank Bracket & Finishing Up Firewall Prep

Last week I read up on the process for fitting the wings, since that'll be one of the big tasks to do next week.  In doing so, I realized that I had never made the fuel tank attach brackets that mount to the fuselage.  These are very similar to the brackets that are attached to the fuel tank itself.  Unfortunately I didn't have enough 3/16" thick aluminum angle to make the brackets.  I'm sure I had enough material originally, but over the years used it up remaking some other parts or something.  Thankfully there's an onlinemetals.com location in Seattle, so I was able to buy a 12" piece of the 2 1/2" x 2 1/2" angle without paying insane shipping costs from Aircraft Spruce or Van's.  I was surprised that onlinemetals actually carries the right structural angle (vs architectural angle) in the right composition.  The structural stuff has the radiused angle vs just a 90 degree angle with no radius.

The brackets aren't complicated to make, but they take a while just because of the thickness of the material.  Even though aluminum is pretty easy to work with, when it's 3/16" thick, it takes a while to cut and shape it.  That's all I can do on the brackets for now.  They will be match drilled to the fuselage and fuel tank bracket once the wing is in place.

I'm still chipping away at the firewall.  Today I fixed a problem that the plans caused a year or so ago.  When I first built the firewall, the drawings showed to make a doubler for the aux fuel pump that sets below the fuel line fitting.  I dutifully followed the instructions, riveting the doubler and drilling the two big bolt holes.  Sometime down the road I discovered that this was only for the fuel pump used for a carbureted engine.  I hadn't gotten to the point of working on my boost pump setup yet, so I didn't know there was a different setup for an injected engine.  Now I've learned that virtually all of Van's instructions are for the carbureted engine.  I don't think the injected engine was a common choice 25 years ago when the 9 came out.  So now I have two empty bolt holes in the firewall.  I went ahead and riveted a couple of nutplates in place.  I will wait to fill the holes with bolts until later.  Maybe I'll figure out a use for some clamps in that location or something.

Yesterday I put the ground block in place, but I don't think I took a picture.  It's a brass, forest of tabs on the aft side of the firewall.  There is a big, brass bolt that extends through the firewall - the battery ground and engine ground will attach here.  I will actually use very few tabs for grounds, unlike a typical wiring scenario.  For the most part, the ACM takes care of the device grounding internally, so the ACM only needs one big wire going to the airframe ground.  There are a few grounds that the ACM doesn't handle that I'll have to run though, and for anything (like the heated seats) that doesn't go through the ACM, I'll use the forest of tabs.

I think most of the firewall penetrations are sorted out, aside from the control cables (throttle, mixture, alternate air and oil cooler shutter).  I made a poster board template of the firewall and cut out the locations of all of the penetrations.  Some of these spots will have the insulation removed completely because the item is already mounted directly to the firewall, and for other spots I will punch small holes for bolts that will mount objects on top of the insulation.  I'll use the template to cut out the fiberfrax and stainless overlay - hopefully accurately!

I've been putting off riveting the firewall recess in place just because it's handy to have a big, open hole to reach through.  I'm sure I'll regret it at some point, but I think now I'm at the point where there's not really much else to do that I can't easily do just reaching over the top.  So riveting it is!  The recess is full of seams and has gaping holes in the corners, so I ran a bead of sealant under the outside edge and then filled the corners after it was riveted together.  Sticky stuff!