Long taper vs. transition?

[SolarYellow]

I'm wondering what would be the better aerodynamic (less drag) result:

A long, very slight taper or just running at the average diameter of the taper for most of the length and having an aerodynamically optimum (~4.5 degrees/side or 9 degrees total included angle) transition to the required larger diameter at the end.

They will probably be about a wash on surface area. The taper will end up with a smaller nose cone, so less form drag there, but will have a slight increase in pressure drag along the full length. Theoretically, the cylindrical form should have no pressure drag, only friction, but then the transition would have more form drag. The long taper will have slight (barely more than zero) pressure drag along its length, but I wonder whether that might actually resist the transition to higher-drag turbulent flow?

I do have a citation somewhere in a reliable source that indicates the optimum taper angle for boat tails is 4.5 degrees/side for a straight taper, or the equivalent average reduction if parabolic (which will form a 9 degree angle at the small end). But I don't know if that applies the same to expanding transitions.

I think it would probably be lighter and easier to consistently/reliably/accurately construct the long taper vs. the straight wall plus transition, as a single cone can be rolled out of flat material vs. a straight and a cone needing to be two different sheets that have to be joined.

Also, thinking through this post has already given me further ideas to try out in the design.

Figured I'd throw it out there for discussion and see if anyone knows something that sounds good.

 

[jqavins]

Pictures please. I only think I understand the choices.


In the tired old trope of school science fair projects finding the "best" nose cone shape for low drag in subsonic ascent, longer is always better. A long straight cone is better than a short one, a long ellipse is better than a short one, etc.

 

[OverTheTop]

The long straight taper will act more like a cylinder, and the transition will act more like a small concentration of lift at the transition for non-zero angle of attack.

The slow taper will be more aerodynamic IMHO.

 

[jqavins]

Pictures please. I only think I understand the choices.
View attachment 628739

In the tired old trope of school science fair projects finding the "best" nose cone shape for low drag in subsonic ascent, longer is always better. A long straight cone is better than a short one, a long ellipse is better than a short one, etc.

Also, as a side note, my second picture makes me want some wine.