Here's a little "cup" type washer I made for a friend's -8 that had a very (very) slow seep coming out of his left hand fuel tank drain flange.
There is a 1/8" margin around the perimeter and a 1/32" gap between the flange and the underside of the "washer". Cleaned up and bonded on with 3M-2216 epoxy adhesive. Before you shoot me and tell me this won't work, I called 3M engineers back in 2011 and ask about the durability of their product in 100LL AvGas. At that time I was told that it would stand up to the aeromatics in the fuel just fine - but to be sure, I have had an ongoing test since then (2011 - 2026 +) of some cured 2216 in a jar fuel of AvGas and have never seen any deterioration of it.
I have used it (2216) for more than 40 years with very good results.
YMMV - but I bet not by much ...
HFS
There is a 1/8" margin around the perimeter and a 1/32" gap between the flange and the underside of the "washer". Cleaned up and bonded on with 3M-2216 epoxy adhesive. Before you shoot me and tell me this won't work, I called 3M engineers back in 2011 and ask about the durability of their product in 100LL AvGas. At that time I was told that it would stand up to the aeromatics in the fuel just fine - but to be sure, I have had an ongoing test since then (2011 - 2026 +) of some cured 2216 in a jar fuel of AvGas and have never seen any deterioration of it.
I have used it (2216) for more than 40 years with very good results.
YMMV - but I bet not by much ...
HFS
