On Oct 9, 2006, at 11:10 PM, Joe Hull wrote:

>Just a heads up - it looks like your new "header flange to pipe" (picture 5) was welded on the >outside.  I think that 'acceptable practices' state that there should only be a tack weld on the >outside and the actual structural weld should be on the inside.  What does everyone else say?   In >any event be sure to keep an eye on the welds.
>
>Ken Powell
 
Ken,
Yes, I’ve heard that from PL’s list – but haven’t seen pictures of any other flying Rotary that is welded that way. I was going to tell Aircraft Exhaust to only weld it on the inside but forgot. But I’m not sure there is agreement about this among the rotary flyers.
 
Joe Hull

It is recommended in Bell's book on turbocharging. All the discussion made me go look at the Racing Beat headers sitting in my garage, and they are bead welded on the outside only.