Tailcone or Flat Retainer?

[jms]

Hey all, I am looking at my first real HPR kit, the Super DX3 from Madcow. I like the look of the tailcone style Aeropack retainer, but I am really more interested whether there is a benefit to using a tailcone style over a flat retainer other than having the tailcone match up perfectly to the OD of the body so that you get better aerodynamics.

Is it just an aesthetics thing when looking at the Super DX 3?

 

[gpoehlein]

In mod-rocs, conventional wisdom is that using a boat tail to take the aft end of the rocket down to motor diameter reduces drag quite a bit - and it very useful when building competition models. (You can either transition from a larger tube to a minimum diameter tube and mount the fins on that, or put on a boat tail and either mount the fins to the larger tube or a combination of the large tube and boat tail.) I can't say whether this rule applies to high power rockets or not, although my gut instinct is that it does. Besides, it usually does make the rocket look cool!

 

[cjl]

It reduces drag and looks cool. It also sticks out farther from the back, and forces the motor to stick out farther as well, which pulls your CG back. Make sure that if you get the tailcone, the rocket is still stable with the extra weight at the back.

 

[jms]

Yeah I definitely like the look of it, I guess with the super flat aft of the Super DX 3, I wondered if there was going to be any real gains in doing a tailcone or not. I was more worried that it would look silly than anything. I'll RockSim out moving the retainer further back and make sure everything looks ok.

 

[jms]

Oh and I don't plan on boattailing either. Just keeping it stock.

 

[gpoehlein]

Oh and I don't plan on boattailing either. Just keeping it stock.

Perhaps I was using the term wrong, but I've always used the term boat tale and tail cone interchangeably - to me, at least, a boat tail is a tail cone (could be cone, ogive or parabolic) that goes from body tube diameter to motor tube diameter at the reattach of the rocket, and behind or even with the fins.

From what I understand, though (and just for general info), a tail cone that goes down to the motor tube diameter is aerodynamically the same as a rear transition that goes down to the motor tube diameter ahead of the fins. The nes result is pretty much the same (although placing the fins behind the transition may not work quite as well as those on a tail cone since they are "partially hidden from the airstream" behind that transition.

 

[jms]

Yeah I was strictly referring to the tailcone style Aeropack motor retainers on a flat-aft Super DX 3. Not planning on making any modifications to the body of the rocket.

 

[jms]

Although now I'm looking at Mad Cow's fiberglass tail cone, fired them an email to get some thoughts on popping that on the after of the Super DX 3. I'm sure pulling all that weight backwards will require some additional nose weight, but we'll see!

 

[Fe Dude]

If you rather Giant leap has a more ogive style retainer, rather than the cone shape of aeropack.

https://giantleaprocketry.com/hpdefault.asp