09-26-2016, 12:28 AM
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Contest, Sport, it's all good......
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Join Date: Jul 2008
Location: West of Minneapolis, MN
Posts: 760
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Regarding finless, in 1971 I made a finless egglofter for a North Georgia Regional Meet (NGRM) in Atlanta.
It used a CMR egg capsule, and 18" of BT-50. The liftoff CG was about 1 to 2” behind the capsule, so there was 16-17” of BT-50 behind the CG (I THINK it was 1" behind the capsule)
The main idea was to use it launched “inside” of a plugged Centuri #10 body tube, for a simple “Closed Breech launcher”, as pistons had not come into use, or were not well known at least, in 1971. The model worked, but did not fly very well, a rod-launched model with 12” of BT-20 and fins would have flown a lot higher. Hey, it was my first contest, I learned a lot.
Years later I duplicated the design just to fly it as a novelty. It was notable in that when it flew, it would very slowly wobble back and forth. The lower part of the body had to “stick out” into the airflow at a significantly visible angle of attack to finally stop the pitch or yaw motion and get pushed back the other way where the slow oscillation cycle repeated a few times. I have never seen a finned model do anything like that. It would have been interesting to have replaced the large diameter egg capsule with a say a 4-5” long BT-50 payload section and add the weight of an egg inside, or whatever was needed for the 1-2” CG below the top of the 18” BT-50, just to see if it would wobble as much or wobble a lot less (likely the latter).
Would also make for a pretty neat “surprise” 2-stage rocket, like A8-0 to B4, or full blown C6-0 to C6, when with a finned booster it would look like a single stage rocket.
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