A couple of days ago the fuselage team completed the important step of bonding the firewall to the fuselage. This was a very work-intensive process that began almost as soon as we got the kit and will only be completed when several reinforcements ribs are added to the assembly. read on for more details about what the firewall does and how we built it.
For those uninitiated in the addiction of flying the firewall is the bulkhead to which the airplane’s engine is attached. It is called a firewall because it is required to be fireproof to stop a fire from spreading to the rest of the aircraft. It also performs a few other VERY important roles that make it key that it is installed properly on the aircraft. For instance, the firewall transfers all of the “pull force” from the engine into the fuselage so it must be strong enough to handle these stresses.
Also, since the engine is mounted to the firewall, if the firewall is not perfectly straight the engine is not pointing straight forward which creates some side thrust. As you can imagine this could lead to a squirmy airplane. (In reality the engine is tilted on purpose to counteract things like P-factor and slipstream effects). Here is what an engine mounted on a firewall looks like.
In single-engine tractor aircraft (like the Glasair) the engine is located at the very front of the fuselage. This means that the firewall is the forward-most structural bulkhead in the fuselage. This gives it the additional task of handling loads from the fuselage so it has to be strong enough to hold it. For all these reasons the firewall is a key component and the greatest care was taken to ensure that we built it properly and installed it properly.
The first step was to laminate the fireproof foam that is used in the firewall and cut it to shape. We then beveled the corners to be able to install the engine mount screws and the bottom for the nosewheel mount. This is what it looked like at that point.
We then made VERY sure that the fuselage and firewall were level relative to each other using the laser level that Chris Yeeles so graciously lent us. You can see it in the first picture of this post. We temporarily affixed the firewall using hot glue and began applying fiberglass to secure the two surfaces.
At the end of the process the firewall looks like this:
The next step in the process will be to add reinforcement ribs at the bevels to transfer the loads from the engine mount and an overall rib to stiffen the front end of the fuselage. As always, you can follow daily updates to our build in the FAA build log.