Firewall

This site was last updated on February 15, 2008.

The radial-mount backplate bolts to the firewall and the firewall is contained and supported by the front end. The picture above shows a few firewalls. The rest of this page is a discussion of how we produce them.

The firewall is assembled from 3 pieces of carbon fiber. Some of the parts were cut from a sheet we picked up at Boeing Surplus. The rest were cut from a slab, 1/4" thick, that we made up especially for the occasion. Unfortunately, we neglected to document the process.

The parts are glued together on a fixture that holds everything square while the glue dries. The parts are all sanded to remove the sheen.

We use epoxy, mixed by weight, to glue the parts together.

Alternatively, CyA works too, especially in the "tough" varieties, with rubber added to make it more shock resistant. We got this bottle from Small Parts. An alternative is Black Flash, available from Darrol Cady.

What's tough enough? At a minimum, the part needs to survive all the sanding and drilling to come.

The fixture will hold up to 4 assemblies at a time (basically limited by the number of clamps we had in the shop). Note the square, used for alignment.

The engine mounting holes are drilled using a simple template. After the center alignment hole is drilled, the template is pinned in place. After a second hole is drilled, a second peg is added to ensure alignment of the remaining holes.

These pictures give front and back views, showing the rough shape after the parts are glued, rough cut, and drilled. The center hole will be used for alignment at a later stage of assembly.

We use a disc sander to quickly reach the final shape.

Here's Howard at work. When he sands CF parts, he prefers to wear an air filter to avoid the dreaded black-booger syndrome.

A little fixture holds the part at the correct angle.

Here's how it fits together with the sacrificial foam part. Together, they define the shape of the front end.

We add a special sort of blind nut (PEMnuts) to receive the engine mounting bolts.

If we carefully hold the part using a machinist's clamp, we can avoid having the fibers tear out of place when drilling. This approach slows things down a bit, but the results are better.