some interesting comments and pictures in that old post. SO now we know that Estes as Early as 1971 experimented with spiral-wound motor casings.
https://oldrocketforum.com/showthre...23&page=1&pp=10
Gus shows pics of the original 2.5" Centuri along side a later 1.75" Centuri (Estes made)
And look at the size of those nozzle cores ! looks like a smaller version of the B4 throat
Jeff Flygare authored an article about ( I believe Flygare either worked at Centuri or Estes at one time later) 8th Annual Pittsburgh Spring Convention on March 16-18,1973.
"Randy Gilbert was there for Centuri and Enerjet, and both of the product lines were very popular. .......The Centuri mini-motors will be 1/4"(.250)in longer than the AVI Minijets, and the same diameter as both the Minijet and the Estes minibrute. Centuri plans to produce both a 1/4A engine and a full-range B in their small casings, which are spiral-wound to reduce weight."
Estes spiral-wound in 1971....now Centuri spiral-wound in March 1973
Wasn't BOTH Estes and Centuri owned by Damon Corp. during this time frame?