I completed the remaining match drilling of the forward fuselage skins today.
There is a fair bit to do here and a lot of tricky drilling.
The firewall brackets aren’t welded perfectly straight so it takes some creative clamping to keep edge distances correct.
I used 1/8 inch aluminum as shims to keep the bracket centered in the channel.
I was worried about messing this one up and happy that everything came out evenly balanced.
I used the same technique on the right side.
The lower brackets are more difficult to get to and I created two small shims to use here.
These also came out really well.
The next step is drilling the longerons. The plan have you start at the gussets but I started at the mid fuse seam to keep the skin tight as I drilled towards the firewall. I did clamp the longerons to the firewall gussets first to set the vertical position.
I then match drilled the gussets to the longerons. This also took some creative clamping and drilling. I used a long #30 bit from below and kept it bent while drilling to keep the hole perpendicular. There isn’t much room here and it got challenging towards the firewall but everything worked out well. The last thing I wanted to do was mess up one of these longerons so I took my time with planning and drilling every hole.
The result looks tidy but the process is a bit more involved (mirror to see underneath, blanket in case I drop anything, wood to press against the gusset, air to clear out chips).
I then matched drilled the side channel tabs to the lower channel. I also used a long #30 bit here.
That’s it, all of the side skins have been match drilled! Now to take things apart..