Eric and Darian:

I've seen a lot of theoretical discussions about pluses and minuses of hollow built bamboo rods, mostly how it lightens their weight (a good thing) and changes the action (some feel positively and some not), but I have not seen anything about change under stress compared with solid ones. I'm sure it has been looked at, but I'm not an expert on it. I know that one way to avoid problems with the hollow building was pioneered by E.C. Powell in the 1930s, when he made semi-hollow bamboo rods by removing the inner part of the strips and then gluing in "bridges" made of cedar at certain intervals. Now, some rod builders just scallop out certain lengths of the inner part of their strips, leaving short sections intact to form "dams", which are just intermittent solid portions of the rod - sort of like the nodes in the orginal culms they were split from.

Eric, I did a little reading about "Hexagraph" rods. It appears that Walton Powell (one of E.C.'s sons) was responsible for the advent of Hexagraph rods in the U.S., which were not made of bamboo at all, but of graphite sheets glued to a dense foam that was planed into strips, glued up into hexagonal tapered sections, and painted the color of bamboo. That is apparently what was used in the filming of A River Runs Through It. I don't know if the term Hexagraph was also used for rods made of bamboo.