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Old 01-28-2019, 11:15 AM
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Default Saturn V with clear fins

Has anyone run the CP on the Saturn V with and without clear slip-on fins that were supplied with the old Centuri (or early Estes) kit? I'd like to know how much difference there is.
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Old 01-28-2019, 10:38 PM
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I have attached the RockSim files I created for both of these scenarios with the Estes K-39 Semi-Scale Saturn V. The CP is better with the plastic fins, 13.89" and the stability is 0.60 on a C6-5 motor, the more scale like fins give a CP of 13.26" and 0.43 caliber of stability. I simulated the 4 engine shrouds as a single transition. The more scale like fins (paper) are slightly distorted by RockSim, they are slightly larger in size, so the actual CP would be less and stability margin would be worse. I don't know of any other old Centuri/Estes Saturn V kits that have clear plastic fins and the ones in this kit don't "slip on".
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Old 01-28-2019, 11:45 PM
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The K-36 Saturn V had clear plastic slip on fins that fit over the scale balsa fins. The clear fins were necessary because the back of the motor mount was at the bottom of the BT-101, rather than nearly 4" from the bottom like the Centuri KS-12, Estes 2001, and Estes 2157. I haven't seen the new Estes 1969 version yet, so I can't comment on it at this time.
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Old 01-29-2019, 07:41 AM
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Both the Estes K-36 and the Centuri Saturn V had clear add-on fins. The Estes kit used a sandwich of two pieces that the modeler glued together on three of the edges. The Centuri kit used a single sheet with a pair of slots that you bowed out to slip over. This made the fin have a slightly cambered shape and gave the Saturn a nice slow rotation. IIRC, on a single D12, by the time it ejected it had rolled somewhere between 1/2 and one full rotation. Since the real Saturn had a roll program, it should give it mission points!
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Old 01-29-2019, 12:35 PM
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Quote:
Originally Posted by tbzep
Both the Estes K-36 and the Centuri Saturn V had clear add-on fins. The Estes kit used a sandwich of two pieces that the modeler glued together on three of the edges. The Centuri kit used a single sheet with a pair of slots that you bowed out to slip over. This made the fin have a slightly cambered shape and gave the Saturn a nice slow rotation. IIRC, on a single D12, by the time it ejected it had rolled somewhere between 1/2 and one full rotation. Since the real Saturn had a roll program, it should give it mission points!

Correct me if I'm wrong, since I'm still a relative sim newbie, but if the outer design remained the same, wouldn't the CP of the older kit (without the clear fins) be the same as this one?
https://www.rocketreviews.com/unkno...1100-scale.html
I'm assuming the balsa fins of the older kit were the same size as the styrene fins of the newer ones. And moving the motor mount up 4 inches would only affect the CG, not CP right?

Finding the CP with the clear fins on can be done by adding them onto the components of the Rocksim file. The template is on the shroud templates page here:
http://www.spacemodeling.org/jimz/k-36.htm

As far as kits with clear fins, I know of 3 by Estes: Thor Agena B (K-28), Gemini Titan (K-21) and the aforementioned Semi-scale Saturn V (K-39).

BTW the smaller Saturn had permanent TTW clear fins with the scale fins emulated by a glue on paper silhouette. So I did a small mod on my clone by gluing a strip of tubing just above the fairings to act as a rear flange, and slipping the clear fins down from the top. Replaced the paper silhouette fins with fiberboard scale fins. This way I could remove the clear fins for display. And if I had to do it over I would replace the printed paper wrap ons and instead print the pattern onto decal paper. Woulda, coulda, shoulda. Cheers.
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Old 01-29-2019, 12:48 PM
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Quote:
Originally Posted by BARGeezer
Correct me if I'm wrong, since I'm still a relative sim newbie, but if the outer design remained the same, wouldn't the CP of the older kit (without the clear fins) be the same as this one?

The K-36 had smaller fins than more modern releases. I don't know if the 2001 (balsa) 2157 and 1969 all have the same size fins. I only have a 2001 and a Centuri kit built so I can't compare the 2157 and 1969 versions.
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Old 01-29-2019, 01:26 PM
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Quote:
Originally Posted by tbzep
The K-36 had smaller fins than more modern releases. I don't know if the 2001 (balsa) 2157 and 1969 all have the same size fins. I only have a 2001 and a Centuri kit built so I can't compare the 2157 and 1969 versions.

Then how about this: take the balsa fin template from the K-36 plans and sub it in for the styrene fins in the components section of the linked Rocksim file. Do the same with the clear plastic fin template. Should give you the two different CPs.
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Old 01-29-2019, 01:47 PM
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Weeeell, that's why I posted it. I don't have Rocksim.
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Old 01-29-2019, 02:53 PM
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I made a better simulation for the K-39 kit with the paper fins (no distortion), I also attached the simulation file that includes both fin sets (paper and plastic).

I am working on the Estes Saturn V K-36 simulation, I hope to include as much detail as possible, the Saturn V .rkt file at rocketreviews.com is very basic, it does not even take into account the fin fairings and escape tower.
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Old 01-30-2019, 12:42 AM
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Attached are my preliminary simulations for the Estes Saturn V, K-36, 1/100th scale with and without the plastic fins. I still need to size and place the body wraps better and include the electrical, pressurization and systems tunnels as well as all the other surface details.

CP with plastic fins is 32.903", stability margin with 3 x C6-3 motors 1.06, altitude 183' AGL. CP with just the balsa fins is 29.770", stability margin with 3 x C6-3 motors 0.52, altitude 208' AGL. Although this suggests that the clear plastic fins might be needed for flight stability RockSim gives a stable flight in 7mph winds with just the balsa fins.

Again I simulated the engine shrouds as one transition section of the same length and overall base diameter. You should be able to open and use these files with Open Rocket freeware http://openrocket.info/.
Attached Files
File Type: rkt oop_estes_Saturn_V_K36_Balsa_Fins_Only.rkt (106.2 KB, 24 views)
File Type: rkt oop_estes_Saturn_V_K36 Plastic Fins Only.rkt (106.2 KB, 16 views)
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Last edited by teflonrocketry1 : 01-30-2019 at 07:34 AM.
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