Propagation tanks

[Delphinus]

I don't think an I-beam has more "rigidity" per se than a equivalent sized rectangular solid beam.. My understanding (which is very limited) is that an I-beam has similar load capacities (depending on the direction of force, which is either vertical or lateral) than the equivalent solid shape, but requires far less material. I.e., it's a more efficient structure in terms of function per unit mass, but that doesn't necessarily mean it's more rigid or has more load capacity overall. Plus, an I-beam is made out of "engineered lumber" whereas a 2x10 is just a piece of wood. You can make an I-beam based on byproducts of other products, but you need a tree for a 2x10, sort of thing.

(Maybe Carpentersreef, if he's out there, can elaborate.. Mitch??)