I'm just about done fireproofing my firewall with titanium foil and fiberfrax -
Dave Paule suggested this method, and it turned out so well that I thought I'd document the process for y'all. Let me know if you'd like more detailed information!
Here's what the final firewall looks like:
The titanium doesn't crinkle at all, and is great to work with. This method is more tedious than the stainless foil method, but the results are worth it.
Bill of Materials:
You MIGHT be able to get by with 11' or so of foil by laying things out just right. Don't forget the firewall recess. I had to order a bit extra.
First, decide where you want everything on your firewall to go, add holes and nutplates, yada yada yada.
Then! Take it all off. Cut a big piece of cardboard so it fits onto the firewall inside the flanges. Do NOT cut out holes for anything other than the firewall recess in the center! Just create the big outline.
Next, use this template to lay out strips of fiberfrax. I managed to cover the firewall with two vertical strips of fiberfrax, side by side. I had no overlap between the two pieces of frax... I left a bit of overlap on the cardboard, then once I test-fitted the pieces against the firewall did the final cut to remove all overlap.
Then, lay out the Titanium foil on top of the fiberfrax. I used three horizontal strips, and cut the center strip to have roughly 1" of overlap with the top and bottom pieces. The Ti foil doesn't feel terribly sharp, but it WILL slice you badly if you let it!
Shears work just fine for cutting the Ti. You can use an exacto knife to cut out the firewall recess in the center. I'd recommend cutting out a square a little smaller, as you can use the dremel later to trim it back further.
Gluing on the Frax
First, lay your pieces of fiberfrax on the firewall to make sure they fit, mark any overlap between the two pieces with a sharpie and cut it off.
Next you'll want to clean your firewall off with some acetone.
Once it's dry, use a caulk gun with your Firebarrier 2000+ to lay out drizzles of firebarrier on the firewall. Stick one piece of fiberfrax on! It shouldn't move, it weighs nothing. Drizzle again on the other side and stick it down.
Next, you'll want to use an exacto knife to trim out all the holes for screws, nutplates, etc, anything that will penetrate. To find nutplate holes, get a partner to sit inside the cockpit and push a nail through the fiberfrax while you provide back pressure. Then, come at it from the firewall side with the exacto knife. For bigger holes you can run the blade around the edge of the hole and cut things nicely. For smaller nutplate holes you'll have to tear a little. Use your air hose to blow out any excess.
This is important - completely remove the fiberfrax from around the flanges of the oil cooler mount! I clecoed it on and used an exacto to trace around the edges, then took off the mount and completely removed the frax underneath and around the flanges. You could glue a piece inside here if you wanted; just make sure it doesn't sit under the flanges.
Adding the Ti Foil
Now that the frax is up and holes are all cleared out it's time to add the foil, one strip at a time. I started from the bottom.
Lay down some more firebarrier, this time on the Ti foil piece so you don't tear the frax dragging the caulk gun all over it. (Orient it so that the ends want to curl TOWARD the firewall so they don't lift up immediately!)
Place the Ti foil on the firewall, squish it down onto the frax and use some tape on the bottom edges to make sure it's held down. Run a strip of 3m aluminum tape along the TOP edge, taping the Ti foil directly to the fiberfrax.
Before you do the next strip you'll want to attach everything to the firewall that sits on top of this piece, including the bottom rivets of the oil cooler mount. Do that first.
Cleco the oil cooler mount through the fiberfrax using the top rivet holes. Then, use a #30 drill to match drill through the bottom holes, cleco-ing as you go. Remove the mount and give each hole a twirl with a countersink bit and make sure the hole's clear, then cleco the mount back on for support.
Clearing out the holes
Okay, now it gets sort of tedious! You'll want a partner to sit inside the fuselage with a nail or pop rivet shank or something. One by one, have your partner push the nail through various nutplate holes or larger holes to create a dimple on the front side while you provide back pressure. Mark the dimpled spot with sharpie.
Once you've marked all holes, take the nail from your partner and use a hammer to whack holes in the Ti foil at each sharpie-marked dimple.
Then, push an exacto knife into each hole so you slice across the full hole. On larger holes, like the holes for your heater boxes, you can cut all the way across and remove a good amount of material. On nutplate holes you're just trying to define the hole.
Finally, get out your dremel tool with its cutting bit:
and start cutting away to the perimeter of the hole. With nutplate holes you can do a pretty good job with the tip of the cutter, then go in and clear out the very thin foil with the exacto knife, then go back for a final pass. The results look like this:
For larger holes, make sure to hold the cutter perpendicular to the edge so the dremel doesn't kick and tear the foil. It's not that fragile so you should be fine!!
Finally, secure the foil by bolting or screwing on any components that below the top inch of this stretch of foil. (That was only the EFII fuel regulator in my case.)
Next Foil Strips
Okay, time for the middle strip. Same drill as before. I recommend an inch of overlap, a strip of aluminum tape along the bottom to join the strip to the bottom strip, and another strip on top to secure this middle strip to the fiberfrax.
DON'T cut out the outline around the heater boxes. You'll want to bolt them through this fiberfrax and Ti sandwich.
Cleco the oil cooler mount on to the new, cleared out bottom holes, and match drill the top holes, clear them out with the countersink and cleco back on.
It's the same drill for the top strip as well! Bolt on firewall components as you go.