Firewall mounting part 1

TLDR

• Test fitting firewall

Details

Components

There are 4 layers to be sandwiched together for the firewall, from outermost layer to innermost:

• The side skin
• The spacer
• The firewall
• The dzus strip

And the top skin will later sit on top of the firewall, with both left and right sides rest right on top of the spacer. So it’s important to test fit the top skin at this stage in case I need to trim the top end of the spacers.

The test fit

It’s a real struggle to get all the holes to line up between the 4 sandwich layers.

So far I’ve managed to line up most of the holes with just the 3 layers (no dzus strip yet). I’m pretty sure I’ll have to match drill every hole, so right now I’m just trying to minimize the amount of drilling in this area.

Step 1: I mounted the firewall with just a few clecos to allow some flexibility

At this stage there are still visible gaps between skins

Step 2: more clecos, but more holes starts to be misaligned

Step 3: I took off the firewall, and trimmed off the front end of reach longeron so I can push the firewall further back

Step 4: Mounted firewall back and threaded clecos around the side skin. I marked every hole for sure won’t fit with an X.

Step 5: Test fitting the top skin. I have cut off some spacer so there is plenty of clearance between spacer and top skin.

Riveting

Step 6: Start riveting the firewall to fuselage

Step 7: Rivet the spacer and dzus strip last

As I riveted the strip, the bottom portion has a noticeable gap with the skin. I wrapped some duct tap on a light hammer, and gave the skin some light tap to shape it to the strip. In retrospective, this would have been easier done with a fluting tool before the strip was riveted.

Used a hammer to lightly tap the skin to close gap

Result: still has some gap but IMO acceptable

Final result