When I was a high school student, I wrote research papers on "The Krushnik Effect" and "Determining the Efficiency of Ducted Systems in Model Rocketry". I don't think that either of these phenomena had anything to do with my plastic flower pot-turned fake engine bell being ripped from Marvin Martian Jr., but I thought I'd put it to guys & gals much smarter than I as to what happened.
My obvious first thought is that there was more airflow stress on the engine bell than the security that the three screws holding it to the bottom of the rocket provided. I noticed that the ends of the screws only stuck out maybe 1/4" past the bottom of the attachment points to the rocket. The answer is probably as simple as that.
However- it seemed that the St. Louis Rocketry Kaboom Krewe, who successfully flew the ten foot tall/ 400+ pound big brother of my rocket, noticed that the airflow didn't follow the shape down the bottom half of the football-shaped rocket. So I wondered if my fake engine bell was in a "dead air" zone. They were pretty certain that much of their fin surfaces weren't in contact with airflow.
I also noticed from one attached photo that the tip of the engine nozzle extends past the fake engine bell. I didn't know if some funky low air pressure area could have been set up inside the engine bell which caused the bell to be ripped off. The other attached photo shows the bell being ripped off.
Any thoughts? For me, this was one event that is kind of fun to ponder. Not really imprtant, but fun nonetheless.
My obvious first thought is that there was more airflow stress on the engine bell than the security that the three screws holding it to the bottom of the rocket provided. I noticed that the ends of the screws only stuck out maybe 1/4" past the bottom of the attachment points to the rocket. The answer is probably as simple as that.
However- it seemed that the St. Louis Rocketry Kaboom Krewe, who successfully flew the ten foot tall/ 400+ pound big brother of my rocket, noticed that the airflow didn't follow the shape down the bottom half of the football-shaped rocket. So I wondered if my fake engine bell was in a "dead air" zone. They were pretty certain that much of their fin surfaces weren't in contact with airflow.
I also noticed from one attached photo that the tip of the engine nozzle extends past the fake engine bell. I didn't know if some funky low air pressure area could have been set up inside the engine bell which caused the bell to be ripped off. The other attached photo shows the bell being ripped off.
Any thoughts? For me, this was one event that is kind of fun to ponder. Not really imprtant, but fun nonetheless.