This chapter is relatively short, but most important.  The firewall is just ¼” thick aviation plywood and fiberglass.  Plenty strong enough for its intended use, but if there is a fire in the engine compartment, the fiberglass would melt around 150 degrees F.  The wood would not be far behind that.  So, we have to install a proper fire barrier.  The plans call out 1/8” fiberfrax.  It kind of looks like asbestos but without the bad chemicals I guess.  This material is what provides the bulk of fire resistance.  It is easily ripped though, almost like paper, so it needs a protective barrier to keep it in place.  The plans call for .016” aluminum sheet to be used.  Other builders have suggested using .016” stainless steel for the additional protection.  This sounded prudent to me, so that is what I went with.  It’s a couple pounds heavier than the aluminum, but I felt it was worth it.

 

I held off doing this chapter until I could get my electrical components placed where I wanted them on the inside portion of the firewall.  That way, if I made any changes in location, there wouldn’t be unused holes in the liner.

 

Once everything is located, the plans say to make a paper template of the firewall including all the holes for mounting the rudder pulley’s, aileron bell horns, and electrical conduit.  Accuracy here pays of when cutting and fitting the stainless steel.  I just used some poster board material purchase in Target’s aviation department.  After the paper template is done, cut out the fiberfrax and stainless steel to match.  High temp silicone is used to attach the fiberfrax to the firewall as shown below…..

 

 

next apply the fiberfrax…..

and finally, another coat of high temp silicone is applied to the back of the stainless steel. It is then placed over the fiberfrax.  I fabricated a clamp that uses the engine mount hardpoints to hold everything in place while the silicone cured.

 

 

The only problem I see already using the stainless steel is it looks worse than my Mother’s oven did when we were growing up……fingerprints everywhere!

 

Like I said, a quick, but important chapter.