LV3 Fin Design Parameters

The drag and velocity data from OpenRocket for the Brothers, OR flight was imported into Solidworks. The worst case form drag loading of 1030 N on the entire rocket was recalculated to 130 N on the fins only. The maximum von Mises stresses experienced by the truss in the static and dynamic cases are shown:

Syield   = 275e6 # Yield stress (Pa)
Stensile = 310e6 # Tensile strength (Pa)
EAl      = 69e9  # Elastic modulus (Pa)
v        = 0.33  # Poisson's ratio
rhoAl    = 2700  # 6061-T6 Al. density (kg/m^3)
SmStatic = 13e6  # Static max stress (Pa)
SmDynami = 0.3e6 # Dynamic max stress (Pa)

The first four modes of vibration are shown below, representing the resonant frequencies of the 6061-T6 Aluminum fin truss:

Truss Parameters

The following data represents the various relevant truss parameters used in the Solidworks model:

Tt = 0.25   # Truss thickness (in.) 
Fw = 0.25   # Fin width (in.)
fr = 0.25   # Fillet radius, universal (in.)
Mt = 0.10   # Mounting rail thickness (in.)
m  = 0.2794 # Fin mass, new (kg)
m  = 0.2631 # Fin mass, short (kg)