Hello everybody,
if one looks at this 12’’ outlet more closely, one can see that it is still too much rounded at the kink, 
which is why I have this pronounced even stronger, as can be seen right in the image.
And from these outlets I need a total of six pieces that I need to scratch now.
Since the 18’’ bows of these tapered outlets but are slightly narrower than those of the other four 18’’ outlets without taper, I had to create a new Balsa template for bending. 
For further handling, it was skillful, initially to file the rounding at the left end of the bow and only then to remove the right end of the bow. 
How now the test fitting in the next image shows, the new bow is but still a bit too long and still needs to be shortened somewhat, so that the outlet comes closer to the shaft wall. 
And then I have tried to also represent the outflow opening opened at the 18’’ outlets, whereto I drilled out the end with Ø 2,5 mm and sanded a bit at the inside.
Then I have heated the opening and pressed together in the sliding caliper.
And this opening really appeals to me actually completely well,
especially as it looks more realistic than the first attempt. 
Maybe I’ll find even a slightly larger drill to reduce the wall thickness a bit more without having to smooth the opening yet. 
