augmented thrust of slightly divergent pipes (larger end of the cone towards aft)
The divergent section is only in the very front section of the pipe. The rest of the pipe is the same diameter all the way to the exit.
The thrust augmenting pipes work well for the larger turbines as well, but the pipe size at the exit end gets too large to fit into some scale planes. I have built a couple of augmenting pipes for a Jetcat Titan and a Merlin 160 with excellent results.