As I discovered when I RockSimmed the ST-8 Centuri Chuter-2, sometimes the original designs have *very* high deployment velocities. The Centuri Scram-Jet displayed the same tendencies.

I noticed that when I upscaled the Chuter-2 1.48X to an ST-13, the performance on 18mm motors greatly improved. This led me to conclude that at least some classic designs may have simply been overpowered for given motor sizes.

To that end (and since I can't ever seem to leave well enough alone), I upscaled the Scram-Jet to ST-7 (1.40X) and ST-10 (1.37X) body tubes. I was surprised and pleased to find much better performance figures on standard 18mm motors.

Bill E. "Wallyum" and I have wrestled with making this particular design work in the 21st century *without* ejection charges burning through Kevlar thread. Finally it seems I have a solution: upscale to these dimensions, use 3/32" thick balsa (*not* basswood!), and use 600 lb. Kevlar on an ST-710 18mm motor mount.

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Scram-Jet_140X_RS9.rkt (117.3 KB, 121 views)

__________________
Jay Goemmer
"Centuri Guy"/"Tau Zero"
YORF Member 28
Semroc SAM #0029
NAR 86131


"I think about organizing things all the time. Never seems to happen. I find something that piques my interest and I'm off on a quest. Or a Centuri. "

--Bill Eichelberger, 02/22/2022


“Centuri fret buzz in an updated form.”
Bill “Wallyum” Eichelberger re: Estes Flutter-By
03 Sept 2014

Loved this design, but I never had any luck with any of the 2? 3? 4? that I built and flew. The last one was the big heartbreaker. It was beautiful when I finished it, then had the Kevlar break on one of the review pic flights. It was a hot day, so we were able to watch the nose cone and parachute thermal away toward Bellevue and the river for quite some time. Heavy sigh.

__________________
Bill Eichelberger
NAR 79563

http://wallyum.blogspot.com/

I miss being SAM 0058

Build floor: Centuri Design Contest F-150 Hurricane Estes - Low Boom SST Semroc - Shrike, Snake Jumper, SST Shuttle

In paint: Canaroc Starfighter Scorpion Estes F-22 Air Superiority Fighter, Solar Sailer II Semroc Cyber III

Ready to fly: Estes - Multi-Roc, Solar Sailer II Semroc - Earmark

One sheet with all fin pieces.

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Attached Files

1.4X Scram-Jet Sheet.cdr.zip (21.2 KB, 86 views)

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Craig McGraw

BARCLONE Rocketry -- http://barclone.rocketshoppe.com
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SAM 0044
AMA 352635