On Aug 28, 4:10 am, Stealth Pilot
wrote:

personally I think they've drawn the length of the round tube a little
short. this may give welding problems that can be obviated by making
the round tube a little longer.
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Roger that.

The cited 1.5C is the accepted MINIMUM. In practice I believe you'll
find the PRACTICAL minimum to be 1.5C + B (ie, 3C + 2B for the
insert's total length). This reflects the fact that the fishmouthed
ends tend to absorb heat more quickly. To keep from having to chase
the weld-pool you'll find it best to have the full diameter of the
doubler under the end of the notch.

Also, because stresses in the streamlined tube will cause the material
to spring out of position once you've created the notches, this is one
of those cases where you'll need lots of clamps & tack-welds to
maintain alignment. Note the recommended eighth-inch gap along the
diagonal. I believe you will find this too is a minimum.

Finally, while TIG does fine for the tacking, you'll probably have
less trouble if you do the weld with O/A. If TIG is used for the
whole job you're liable to get some cracks on the LE side of the
groove unless you can bring the whole thing up to red heat and allow
it to cool in still air. (O/A pretty much guarantees the whole damn
thing heats up.)

-R.S.Hoover