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#11
02-20-2023, 04:22 PM
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Thanks! I appreciate that you've given this some thought. 
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#12
02-20-2023, 04:35 PM
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I did a fair amount of Centuri cloning back when Semroc first opened around 2004 and would concur with all of Earl's observations of parts/sizes.
__________________
When in doubt, WHACK the GAS and DITCH the brake !!! Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't ! Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY. ALL systems are GO for MAYHEM, CHAOS, and HAVOC !
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#13
02-20-2023, 05:56 PM
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I'm not too familiar with the Centuri stuff but from what it looks like to me, the pods go around the body tube, touching each other. The fins are glued to the tube joints. Am I just stating something that everyone else just assumed?
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Don NAR 53455 "Carpe Diem"
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#14
02-20-2023, 06:15 PM
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Over the years I have been up in the air on that point. At times I have thought just as you have stated; at other times I’ve thought “Well, maybe the fins ARE glued directly to the core motor tube”. Without just ‘hand modeling’ some tubes together (and some representative balsa fin stock) to see what could fit and what doesn’t, it is hard to truly tell. Earl
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Earl L. Cagle, Jr. NAR# 29523 TRA# 962 SAM# 73 Owner/Producer Point 39 Productions Rocket-Brained Since 1970
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#15
02-21-2023, 08:59 AM
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I was just looking around for a sort of body tube / cluster tube calculator, and I did come across the contention (with geometric proofs) that exactly 6 circles fit around 1 circle of the same size - leaving no space for fins to fit pass and attach directly to the main tube. Place 2 pods tight against the core tube (and each other) and you form an equilateral triangle between the 3 centers; sides = 2 * radius, all angles 60 degrees. Then it is a matter of 60 fitting 6 times around 360. I think that means fins attach to pod joints in the 6 fin/pod model. Based on the picture, what is the consensus then as to how many fins (and pods) there are? Five or six?
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#16
02-21-2023, 10:21 AM
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6 fins.
I'd do only 3 though.
__________________
When in doubt, WHACK the GAS and DITCH the brake !!! Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't ! Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY. ALL systems are GO for MAYHEM, CHAOS, and HAVOC !
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#17
02-21-2023, 04:09 PM
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All true assuming that the core tube is the same diameter as the surrounding tubes. Of course, if the core tube is larger, then there might be room for fins to pass between the surrounding tubes and be attached to the core tube. In any case, my gut feeling is that there are six tubes and six fins surrounding the core.
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#18
02-21-2023, 09:57 PM
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As GH and Mojo have stated, it probably is six. That would assume the core tube is the same diameter as the pod tubes, and as Mojo has observed, if the core motor tube is larger than the pod tubes (like the ST-8 as I mentioned above as a possibility for the core tube), then there could be enough room for direct attachment of the fins to the core motor tube. It is just too hard to truly determine which it is from the fidelity of the catalog photo. It would be interesting to know how many Centuri customers attempted to figure out this decal model and just what all part went into making it. One could assume Centuri received more than one letter over the years asking just what parts made up that rocket! All these years later, it is still fun to try to figure it all out! Earl
__________________
Earl L. Cagle, Jr. NAR# 29523 TRA# 962 SAM# 73 Owner/Producer Point 39 Productions Rocket-Brained Since 1970
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