Estes Saturn V Build Part 5 Engine Mount

The instructions say to recess the mount inside the lower end of the BT-101 by 3 3/8". Many forums posts think this is too far inside and may cause the Krushnick Effect.

Here's an explanation I found online for the Krushnick Effect:
"Krushnic Effect: A very dramatic phenomenon where your rocket makes a tremendous amount of noise and smoke but doesn’t go anywhere! This happens when the motor is recessed into the body tube by more than one tube diameter. If so recessed, the cylindrical volume below the motor forms a secondary expansion chamber which allows the exhaust gasses to expand below atmospheric pressure before leaving the rocket. Surrounding air aspirated into the exhaust stream causes turbulence which negates much of the thrust, along with creating the characteristic roar. A multi-stage model that ejects its booster motor, but not the airframe, is a perfect example. Very damaging; it almost always destroys the lower body tube beyond use. Named for Richard Krushnic, the rocketeer who characterized the effect in the late ’60s."

It's hard to mark a tube at the 3 3/8" distance. I used a strip of card stock cut to exactly 3 3/8" long.
I'll be able to check the correct recess even while the glue is drying.

TIP: Be careful how much glue you use on this big, thin walled tube. A heavy glue fillet will shrink and pull the tube in where the centering ring contacts the tube wall. You could see a round recess around the tube at all the centering ring locations.

Time spent on build: 1:00 gluing engine mount and fillets
Total time on build so far: 4:15