Fin Can - LAD
One of the two Lead Designers.
Material: Aluminum 6061 - T6 Dimensions: 12" OD, 11" ID, 12.5" Length Mass: 5.96 lbm Structurally support loads from fins and Motor Retention Ring - Drag from fins - Pre-Load of motor retention ring bolts Minimized Fin alignment error to .056 degrees of vertical Lightweight construction: - Windows for Poly-carbonate insert to reduce mass - Second Moment of Area analysis to reduce weight and maximize strength Integration of partner components - Lower Air Frame - Motor Retention Ring, and Fins) |
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Attachment to Airframe
- Adhesive will be used for attachment to the lower air frame of the rocket.
- I am leading a 5 person team to qualify different adhesives, see Adhesive Testing
- I am leading a 5 person team to qualify different adhesives, see Adhesive Testing
- "Lobes" on shoulders allow for referance without interference of adhesive and a large adhesive area.
- To prevent a shift to one side during assembly, there will not be adhesive at the interface between the OD of the Lobes and the ID of the Airframe. The OD of the lobs are tolerance to have a .01" (diameter) interference fit with the lower airframe. This ensures that the Fin Can is perfectly concentric with the rest of the rocket.
- Both tight tolerances (+ or - .005" OD) with the airframe, tighter fit with airframe, and space for adhesive contact
- Tolerance to nominally have interference with the airframe of the rocket.
Adhesive Testing
I required an adhesive to bond the fiberglass body tube of a rocket to both the Fin Can, Thrust Ring, and Separation System. This meant an aluminum to fiberglass joint loaded in lad shear. The manufactures of adhesive generally test for aluminum on aluminum lap shear but not fiberglass to aluminum. I tested a variety of adhesives with a 100 grit surface finished for the joint. I discovered that of the adhesives tested, JB Weld was the strongest. I then performed tests with JB weld and different surface to isolate the optimal finish. 10 tests of the optimal set up were run to establish an average maximum value for lap shear of the joint. This allowed me to design my parts to a factor of safety of 1.5 to yield and 2 to ultimate.