Chapter 15 - Firewall
Start: 5/29/09
Finish: 6/3/09
Total Time: 8 Hours

This chapter is a bit of an odd one. Most of this chapter tasks happen at various points after the installation of the spar, and usually in conjunction with some other task. For example, the installation of the rudder cable brackets we (somewhat incorrectly) documented in Chapter 16 when we were installing the rudder cables, where it should have been documented as part of Chapter 15. For our purposes though we going to make the installation of the firewall insulation and aluminum the main focus of this chapter. It doesn't leave much to discuss, but we believe the other items are better left in the chapters with which their installation relates.

Before we install the Fiberfrax insulation we needed to make a small modification to the firewall. After installation of the spar and the side firewall pieces, the middle section (back side of the main spar) is filled with 1/4" Clark foam to make everything level. As we were fitting our engine, we discovered that the clearance between the back of the engine, and the aft face of the firewall is very small. Our particular problem was in trying to fit the prop governor in place. Distance from the prop governor pad to the firewall is only 5.25". The Hartzell governor that came with our engine is over 7" in length. There was no way it was going to fit. We learned that some Van's RV builder cut holes in the firewall and than build a box around the hole on the inside to accommodate the governor. This wasn't going to be an option for us, as the governor lines up with the aft face of the main spar. We did learn of another brand of prop governor that would clear though. Jihostroj makes a light weight prop governor that is only 4.9" in length. This was still going to be a little close against the firewall though.

In order to gain just a little more space we decided to sand away the 1/4" Clark foam in the area where the prop governor would be. This will get us a little better than 1/2" total clearance with the governor. We'll need to do a little more work to insulate and aluminize this area neatly, but the added clearance will help tremendously.

Next we cut Fiberfrax insulating material and transferred all needed holes. We then used the Fiberfrax as a template for cutting an aluminum heat shield to go over it.