Big Idea calculation:
Treat boom(s) as a cantilever beam with the load of the empennage being applied at the end of the beam
Make and equation relating the load applied and the length of the boom to the cross-sectional area of the rod.
Look at ENG 104 Stuff?
Flexural Strength formula (Maybe related?)
Can find flexural strength value for different materials
Second Moment of Area of a circular cross section:
Where ro is the outer radius and ri is the inner radius
Plugging the second moment of area into bending, and y = outer radius
With a solid cylindrical rod (wooden dowels) the equation becomes simple and where moment is the force applied at the end times the length of the beam
$r_o=\sqrt[3]{\frac{4M}{3\sigma}}$
If keeping to the hollow cylinder, the equation becomes still complex with two variables
$r_o^3-\frac{r_i^4}{r_o}=\frac{4M}{\pi\sigma}$