28-02 -> 04: Forward Fuselage Bottom Skins & Exhaust Tunnel

Chapter 28 starts like all the other chapters - preparing parts! First up, was the bottom skins, skin stiffners and antenna doublers. At the same time, i prepared the stainless tunnel sides and tops. The muffler hangars are made of steel - so these were primed with black high heat paint. 

One of the antenna doublers

The aft part of the tunnel sides is trimmed to be flush with the top flange surface.

Trimmed end of stainless tunnel sides.

Hot Finger!

Bottom skins and other small parts primed

Muffler hangars were cleaned with a scotchbrite wheel

This was the paint used for the muffler hangars

The tunnel sides were polished similar to the firewall, and the muffler doublers and hangars were riveted on. 

Shiiiiiny.

The muffler doublers were backriveted to the tunnel sides

The squeezer was used to attach the muffler hangars

Fuel pump attach brackets were also backriveted

The skin stiffner and antenna doublers were also backriveted.

The tunnel sides were then clecod onto the bottom skins, using Firebarrier 2000+ firewall sealant to seal between the tunnel sides and the bottom skins. 

I made sure there was a little bit of squeeze out along the entire length of the parts.

Once the sealant had cured overnight, the tunnel sides were riveted to the bottom skins. Most of the rivets were backriveted - and in some cases i had to be pretty creative! The aft most 6 were unable to be backriveted due to the angle of webs of the tunnel sides - so these were done with a gun and the bar. The very last 2 aft rivets i could not fit a bucking bar in between the flanges of the parts - so ended up backriveting using a cold chisel, by using the gun on the chisel itself. Worked actually pretty well! 

I used my big backrivet plate - with wooden spacers.

The muffler hangar just extends past the bottom of the skin, so i had to be careful to hang it off the sides of the backrivet plate. 

I was able to fit the tungsten bar onto this rivet

and tried all my bars for the last 2 rivets..

but this was the best way in the end!

Nothing like a good Cold Chisel!

Once the sides were riveted to the bottom skins, i was able to rivet the top of the tunnel onto the sides. I tried using my squeezer, but it really didn't work. There was not enough room due to the angles of the sides / tops. In the end, i used the gun and bar. This was a lot better then trying to use the squeezer and damaging the tunnel sides. 

I used my ground down squeezer yoke, but it still didn't fit well, and was damaging the tunnel sides.

Once both sides were riveted, i turned the assembly upside down and applied a fillet of Firebarrier 2000+ to ensure no exhaust gas and/or oil could seep into the cockpit. 

Next up is to attach this part to the firewall assembly.