Cabin fuel tank bracked failure

[Darrel Hanson]

I removed the top skin on my 415 C to replace with the stainless skin (D conversion) and found that both of the brackets that the fuel tank straps are attached to had failed on the 'closest to the pilot' end.  The bracket is an angle piece that runs from the firewall to the first bulkhead. The way it joins this bulkhead was accomplished by cutting away 1/2 of the piece angle and bending the remaining finger down and riveted onto the bulk head.  It is at this cut the  piece has failed. The turnbuckles that tighten to hold the fuel tank in position place a side load on this bracket and I think that this contributed significantly to the failure.     There was some evidence of this failure on the surface skin now that I look back at it with a bit of a deflection in the skin, and a broken rivet head where the skin and this bracket join the firewall. As this area is normally covered by the top cowl, it makes it even less visible.   I am a bit concerned as the heaviest portion of the tank was resting in the .002" skin, causing flexing fuel lines and all of the problems that this could cause.   Have any of you ever run into this before?      Thank you   Darrel Hanson 800-726-7086 http:\\www.perfectsolutions.com