Re: Centering Ring Placement

Gary Slater

Let me add some information. 
The motor tube option is to accommodate up to a 38/720 case. So about 14 inches. 
What I want is all 3 CRs but I only have 2. 

On Jun 10, 2021, at 5:50 PM, Greg Smith <gregs@...> wrote:

Agree completely with Mark. A third, forward ring is useful because it provides a convenient anchor point for a U-bolt or other recovery attachment, and it makes construction easier because it holds the motor tube in good alignment while you work on the internal fin tabs and fillets. But its structural contribution is minor.






From: [] On Behalf Of Mark Joseph
Sent: Thursday, June 10, 2021 5:45 PM
Subject: Re: [cia-rocketry] Centering Ring Placement


Interesting points, Kevin.

One concern in not having a truly "forward" centering ring has to do with conveniently and securely anchoring the recovery harness. If you've got that worked out in some other way, then I wouldn't give this a second thought. My opinion is that supporting the forward end of the motor mount (or even motor mounts long enough for the range of intended motors) is a somewhat overrated concept. I think that the structural integrity gained by creating the mechanical "system" of airframe/fin tabs/centering rings/motor mount/epoxy is the bottom line.

Thanks for letting me ramble. Again.


From: <> on behalf of Kevin A <kauskings@...>
Sent: Thursday, June 10, 2021 5:22 PM
To: Group Moderators
Subject: Re: [cia-rocketry] Centering Ring Placement

I would think at the top of the TTW fin tab would give the best support... But how far past that point does the MMT extend?

If that ring is not at least slightly past the midpoint of the MMT, I'd be looking at other options... Perhaps some shims at the leading end of the MMT tube vs a full ring?

Just my noob thoughts.



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