"Fortunat1" wrote

Sorry. Scroll down to 4-84.
There's a whole section on the type of repairs you're talking about.
4-84 specifically mentions including the innner tube into the weld. It
seems to me that the weld area would be at least as strong without
welding across the inner tube like that. If you weld a doubler on the
end of a strap, for instance, you don't lap weld across the widthe of
the strap where the thickness steps down, you only edge weld around the
outside perimeter. That would indicate to me that welding across a piece
of tubing, unneccesarily, only puts stress risers around the weld. If
it's a snug fit, you've got to have at least the same strength there you
had with the original tube.

The repairs detailed in the "acceptable repairs" publication are time tested
and true. There have been tube and fabric planes being repaired in this
manner, for a very long time.

I would tend to believe that if it is outlined in a certain way, then there
is a good reason for it. As far as stress risers, gas welding done
correctly will not create them.
--
Jim in NC