Should there be a projection beyond the tail of the plane (beyond the fiberglass) for
the outer pipe on a bypass system? If yes, then Why should it extend beyond the tail?

Thanks,
Dee

Outer duct should extend a little because until the ram effect of the inlet supples more air than the turbine can use, air is sucked in the rear.
Darryl Usher

No need to go beyond the tail.
Is ok with about 0.5 ~ 1 inch before the end, and cover that area with BVM heat shield.
This way it produce a diference in pressure that induce an cooling air flow inside the fuselage.
If you are using a double walled pipe from Tam ( the best), you can eather put the pipe flush with the rear of the fuse, but I consider is better not to do it.
Contact [email protected] , he will be happy to assist you.
Good Luck,
Miguel

Assuming that you have an air gap between the outer pipe and the fuse, I agree it should actually stop short of the end of the fuse, but I would not go (1/2" or more) inside the fuse, more like 1/4 to 3/8" to create the differential pressure to draw some air through that air gap and cool the fuse a bit. the BVM heatshield in that area is a good idea as well.
Regards,
Roger Shook
aka: Rocky Mountain Turbine Tailpipes

TO PROTECT AGAINST DAMAGE [HANGER RASH] OR INJURY [ LIKE THE RAZOR CUT I RECEIVED],, A 1 QUART MAYONAISE LID FITS IN MY TAM PIPE PERFECTLY ,THEN I GLUED ON COOL [REMOVE BEFORE FLIGHT FLAG]

2nd thought: you're right....1/4 to 3/8 is ok
Regards,
Miguel.-