Titanium Firewall Part I

While the engine was gone last year, I decided to take the opportunity to make a new firewall since the old one had many unused holes that were plugged. In fact it looked more like a slice of swiss cheese rather than a firewall.

The old material was a 0.025" thick sheet of stainless steel. When browsing on the biplane forum, I saw that some builders were using titanium to save weight! Since my airplane is a little nose heavy, switching to Titanium was killing two birds with one stone.

In order to select the material thickness, some guidance exists under FAA 14 CFR 23.1191 which says:

(h) The following materials may be used in firewalls or shrouds without being tested as required by this section:

[...]

(6) Titanium sheet, 0.016 inch thick.

I therefore proceeded an ordered a sheet of 0.016" thick titanium from Titanium Joe. Great service and quick shipping. First impression: ok Titanium is VERY light.

I used the shape of the old firewall to draw and cut the titanium sheet to the desired shape. I cut the biggest parts on a heavy duty straight shear and cut to final shape with curves using a shear similar to this:

Then I drilled the holes for the aluminum frame rivets them using a cobalt drill bit and the old firewall:

When looking at my neighbour Luc with his Pitts S-2C, I realized the lower edge of his firewall was actually bent with a large radius in order to reduce air restriction and make it easier for the warm air to get out of out of the cowl. My old setup had a sharp edge corner which obviously created a lot of turbulence and air restriction. I didn't especially had oil temperature or cylinder temperature problems, but since I may relocate my oil cooler eventually, I thought I was putting all chances on my side to make a large radius bend like on the S-2C. Easier to block air down the road rather than to unrestrict it!

In order to block the gap between the radius and the flat adjacent areas, I had to make small brackets using the leftover titanium:

Here is the result after the aluminium frame was transferred to the titanium firewall and the work on the bottom edge complete:

Next step was to locate and drill the required holes. I didn't want to blindly copy/paste the old hole locations so I prefered to wait until the engine was back before proceeding... To be continued!