After lining the top holes up, I drilled the two end holes of the bottom firewall to the bottom skin. I ended up marking a new centerline on the bottom firewall angle that was 1/32" aft of the centerline. That gave the proper spacing of 5/8" from the face of the firewall of the edge of the skin. I called van's about this and they said a little thing like 1/32" isn't a big deal since it will be made up by trimming the cowl.
I noticed that the twist in the longeron didn't match up with the firewall bracket. After some work, I was able to match the bend perfectly.
I clamped down the firewall bracket to the longeron.
I put these holder rivets in the skin to longeron holes. Since the firewall bracket is behind here, you can't use a cleco. So, this is the only way to keep things lined up.
Once the firewall to side-skin spacing was checked about 100 times, I drilled it.
I then drilled the 7 #30 holes into the firewall bracket.
The hole edge distance was right on.
Next I drilled the auxiliary longerons to the side skin. Very straight forward, except the aft end needs to be trimmed.
I fabricated the F-719B clips that hold the firewall to the side skin stiffeners.
For some reason, I misinterpreted the drawings and trimmed 5/8 off the forward end of the F-719-L stiffener. I quickly realized that was wrong. It's only a 8 buck part or so, so I am not that pissed. Plus, its the first part I have screwed up since the trim tab.
I was on a real roll tonight. I broke off a corner of my workbench where my vice was clamped down. I think I pre-cracked it a few months ago, but I finally did her in tonight.
The right F-719 was a breeze to put on. These two holes between the stiffener and the clip were drilled by pealing back the skin and using a 12" #30 drill bit.
I didn't drill the hole in the F-719B clip that goes to the firewall because I didn't know how I would drill it back to the firewall. My solution is to drill the hole in the clip and firewall at the same time. I traced where the clip is on the firewall and marked a drill point.
Using the 90 degree drill, I drilled the clip.
The forward end of the F-719 fits terribly. The last rivet before the F-704 bulkhead looks like it will be exposed. I will have to do some creative countersinking on the F-719 stiffener to make this look good from the outside.
Finally, I fabricated the lower longerons. It took a ton of work to chop off one of the flanges of the angle and get it perfectly smooth. However, it was satisfying as hell with how good the outcome was.
Last Modified: August 13, 2023