Monday, June 18, 2018

Chapter 15 Firewall - cutting and fitting

A deviation from plans is to use Stainless Steel rather than Aluminum.   
Made a template from cardboard.   Cleared off one of my 4x8 workbenches, placed scrap board to put underneath while drilling.  Borrowed a set of knock outs from a neighbor to make clean hole cuts.  The electric shear cuts wider sheets well but didn't work very well for trimming edges.  An angle grinder with a cut off wheel works pretty well for trimming the edges, but have to be careful not to heat the metal up to much.  The shavings from this are like little razors.  

Stainless can be hard to work with.   The hole saw grabbed and tore the metal a little here.   This hole was just for the knock out bolt.  Fortunately, the knock out cut this part out.

The sheet is clamped in place.   The cardboard helps align the knock out.

A uni-bit seemed to drill holes pretty well without tearing.  A sharpie marked the stop depth on the bit.

Still needing a little trimming, but is lining up pretty well.
Holes not cut yet that are needed are for the EMS system's D37 and D25 cables, alternator wiring, SDS EI/EFI, AFR probe wires, cabin heat, throttle, fuel source and fuel bypass return.

Stainless Steel parts from Cozy Girrrls.  Not all holes are drilled.  
Saw this technique either on an EAA video or another metal builder's site.
Cleco clamps hold the paper to the pulley so the holes can be marked with a sharpie.   Small dots mark where the cotter pin holes need to be.
  Keep the drill bit cool (I used water) and take your time.  These little holes each took about 10 minutes.   Black carbide drills work.   

The sections covering the spar were added and fastened using rivets.   Some of the holes needed to be elongated slightly and edges trimmed in a few spots.   I put electrical tape on the inside edge of the holes for the vent lines to try to protect the aluminum from scratches when putting the firewall on and taking it off.    There is still a protective plastic sheet on the stainless steel that will be left on.   A few more holes need to be cut.