[aerohead]

Looking back over Hoerner's book,'Aerodynamic Drag' I ferreted out some tidbits.
The following info is for streamlining 2-D flow around aircraft machine gun barrels,conducted by the German DVL,and also Junkers (aircraft company).
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The 1934 DVL research was for super-critical Reynolds number:
*The un-faired barrel had------------------------------------------- Cd 0.4
*A simple prismatic fairing,with gap rendering L/D=3 gave------------- Cd 0.29
*The same fairing,but with sealed gap yielded------------------------ Cd 0.16
*A classical 'teardrop' fairing of same L/D ratio yielded --------------- Cd 0.13
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The 1943 Junkers research was measured at critical Mach number:
*The un-faired barrel measured-------------------------------------- Cd 0.50
*A L/D=3 teardrop fairing gave-------------------------------------- Cd 0.08
*An L/D=3 teardrop,but with 20% of the tail chopped off =------------Cd 0.17
*An L/D= 4.2 teardrop,but with 10% of the tail chopped off = ---------Cd 0.20
-------------------------------------------------------------------------- I'll do the graphics when time allows,but you can get a sense of how sensitive the boat tail is to either gap or truncation.