Can you confirm that the “Black“ rotted wood in your firewall was, for sure, saturated with engine oil? Could it have instead been fungi/black mold from exposure to moisture instead? I am asking because I associate wood rot with moisture and mold and I think of oil as inherently a preservative since it is common to treat wood with oils (like linseed oil).
Fiberglass should be impervious to oil penetration in any absence of voids or pin holes.
What should owners/builders be expected to do to insure the structural integrity of the firewall and airworthiness?
Inspect the firewall -how to
Drill a hole or core sample hole and inspect the wood for???
Degradation, softness, sponginess , oil, moisture, mold?
What is the acceptance/rejection criteria?
Should owners ground their aircraft immediately if they should encounter what conditions?
This reminds me of a British Car Enthusiast who took his Morgan to the shop for peculiar handling issues, later to find he had termites.
The Q-list needs a file or folder to store issues that are found.
In the first few years of my Q200 I was sharing a hangar with a high wing aircraft. I would pull the Q into the hangar, put a wheeled hydraulic jack plus a support that spread the load out over the lower firewall and body of the plane, about 2 square feet of area. Then I'd jack the plane up and roll it sideways into the hangar.
I knew I had a slight amount of fiberglass cracking at the firewall/lower body point.
Slowly over 37 years, engine oil had penetrated into the firewall plywood. The firewall wood was found to be black and rotted. A few of the triangular load spreaders also had rotted.
Inspection of the lower firewall to body joint should be done looking for cracks. Additionally a tap test looking for softness should be performed. It is possible that the fuselage can trap moisture in the area under the canard at the firewall due to it's design.