Rust on Spar Carry-through

Rob58

Rob58

Moderator
Upon removing seats and floorboards I found the lower rear carry-through steel tube heavily rusted as shown. What puzzles me is that the other fuselage structure is free of rust. It is clear that the green primer and the black overcoat were factory original. I’m wondering if anyone else has seen this condition or can speculate why rust would be confined to the single tube? I proceeded to remove the rust and sanded to bare metal. This revealed a fair amount of pitting, as shown in the second picture. Does this pitting represent any serious problem? Should I keep sanding to remove the pits or perform some other remediation… or can I just go ahead and prime and paint. Any opinions or suggestions will be much appreciated. Just trying to be very careful here. Thanks, Rob (also posted on Viking forum)
 
Rob, I would probe those pits with a sharp scribe to see if they go very deep. If that works out, I would drill small hole top on on end bottom on the other. I would then load that with Tube Seal (03-14005) 14 bucks a pint @ACS. That stuff will also reveal if there are any thru pin holes. I had a fuselage cross member back in 08 that required replacement. The crate was uncovered at the time which showed the bad steel. Lynn the crate
 
Great advice, thanks Lynn. I never thought about it but some steel has internal flaws and porosity as you point out. I like the idea of the tube seal. Appreciate the feedback. --Rob
 
maybe hydraulic fluid spilled. that stuff can eat paint over time. looks like you already got a drilled hole on the top (just don't mention it to anybody), just need one on the bottom. i would check that diagonal at the weld too. but it sure doesn't look that bad in the picture. if your ai will sign it off, i think you will be good with a cosmetic repair and tube seal. i might seal up the holes after and paint over them so they aren't apparent. linseed oil was the old standby for internal tube corrosion. it still works real good.
 
There are electronic tools that you can probably rent that will tell you just how much wastage there is. If you cant find one get in touch with marine surveyors that test metal boats that way. It is a common procedure. Best of luck. Grant.
 
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