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Old 08-19-2021, 01:11 AM
scott_mills scott_mills is offline
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Default Saturn 1b scratch build 1:70 discrepancy

I'm having a little trouble with my scratch build on this project, and I seek the help of those in the know. My problem is that starting with tube sizes from estes k29, the bottom bt101 is 2 .78" but according to George Gassaways drawing the same section of tube is 1.98". So which is the correct measurement?
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Old 08-19-2021, 06:35 AM
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Flash Flash is offline
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If you are building an Estes clone then the taller ring is correct. I think they did this to give the fins a little better protection. If you are building a true scale model, then George’s measurement is correct.

Estes model was a semi-scale model with larger fins also.

So if you are going for true scale, then you will have to change the fin size and a few other things from the old K29 kit plans.

Unless you are really stuck on true scale, go with the Estes - SEMROC plans. It will look better and fly better.
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Last edited by Flash : 08-19-2021 at 05:11 PM.
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Old 08-19-2021, 09:25 PM
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georgegassaway georgegassaway is offline
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Flash nailed it.


For those wondering about my drawing(s), here is the page link:

http://www.georgesrockets.com/GRP/P.../Saturn-IB.html

Based on NARTS drawings, other NASA sources. And NASA photos plus my own photos of the IB at Ardmore Alabama, and the interstage adapter that used to be at the US Space & Rocket Center before the tourist gimmick thing inside of it caught fire and burned (I do not know if it was scrapped or moved out of sight after that. IIRC it was not there when I visited in March 2019).

A Saturn-IB with Scale sized fins, needs for the CG to be about at the middle of the interstage adapter. The more aft of that, the greater the odds it may go unstable. Notably the Centuri 1/100 kit, and Cox kit had more scale-sized fins.
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Old 08-20-2021, 11:14 AM
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ghrocketman ghrocketman is offline
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I much prefer scale-size fins on scale kits.
If it needs 8oz of lead shot/epoxy mixture in the nose and a 29mm F to fly safely, fly the darned thing on a F motor.
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