© Tapani Salmi 2002

Typically when building hexaconal shaped split cane bamboo rods we try to have the strongest part of bamboo, the power fibres, originally located near to the surface of the cane to be located on the surface of the final rod.

Accidentially I build a hex bamboo rod with some of the hex strips turned 60 degrees. This resulted in some of power fibres locating INSIDE the rod. To my surprise this did not result in a weak rod or some significant asymmetry in function of the rod.

Thereafter I made some experimentation building some shorter and longer rods with both traditional (A.) and INSIDE - OUT (B.) construction, ie. with all the strips turned 60 degrees and all the power fibres inside the rod. Again the rods were of identical properties and the inside-out rods with the power fibres as "STAR" like configuration were not weaker than the traditionally builded.

If we think that the rod acts like a "tube" (or a living bamboo) with the strong material as the walls of the tube, the inside-out sturcture should be significantly weaker than the tube-like traditional construction. The bending of the rod is, however, more complex with the fibres on the outer curve stretching and the material in the inner curve compressing. This causes change in the shape of the cross section of the rod. This is certainly effected by the "hardness" of the cane, which we try to increase eg. by heat-treating the material during the building. If we use glue of good quality and have the strips either outside-out (traditional structure) or inside-out (power fibres inside the rod) the change in the cross section is about identical in different parts of the rod and it is easier to understand that the functions of the rods builded with two different ways are about equal.

If there is no difference in action of inside-out and traditional rod why should somebody like to build a inside-out constructed rod?
There are some potential advantages especially if you would like to make some experimentation with rod tapers: the taper of the inside-out rod may be modified after completing the rod simply by sanding or planing the rod thinner! If you try to sand, plane or file a tradional rod you lose the valuable power fibres first. In inside-out rod the power fibres are inside the rod and the modification does not change the amount (portion) of these fibres. You could easily change a #5 rod to a #4 rod or make modifications only to tip or butt part of the rod!

There are some disadvantages in the inside-out structure: it is more difficult to have really thin glue lines and the outlook of the rod is not as nice as the traditional.

If you are interested to make new tapers or modificate some old one, I would recommend you to try an inside-out builded rod!

Experiments with asymmetric (extra spine, "backbone") -tapers
Typically the strips are planed and glued to get as symmetric rod as possible without a strong "backbone" -action. I, however wanted to further improve the weight / power relation of the cane fly rod by intentionally building an asymmetric rod with a strong "spine" action. When testing manually the strength/bending of a single planed triangle shaped strip it seems to be strongest in direction (tangentially) of the surface or tangentially against the power fibres, i.e. the strip dont want to bend "sideways". Therefore I put the strips asymmetrically, with four strips inside out and two outside-out.
I made actually two different asymmetric (and one traditional) PH Young Driggs river special rods with the arrangement showed in picture C. and D.
The both experimental rods (C and D) resulted in an asymmetric action.
I put the guides opposite to the strongest (spine) side. To my disappointment the difference is however quite small and I did not get any huge additional power the action of the taper.

Five quad strips for an asymmetric penta rod - experiment in Autumn 2003
To make a really asymmetric and powerful action I made an experiment by making a PENTA (five strip) rod using strips originally intended for a QUAD (four strip) rod. The taper was again PH Young Driggs river special. To transform it from HEX to QUAD you have to use a 93% formula and to transform to a five-strip-quad you have to make the strips 10% smaller (90% of the original) (to get the area and mass of each strip 20% smaller or 80% of the original).
I glued the strips as in figure, there are three "normal" quad strips and two strips glued with power fibres against each other on the casting axis.
The line guides are fixed on the "base" (lowest) strip. As the power fibres of two strips are glued together and are on the casting axis it gives a lot of extra power to the rod. When I fixed the ferrules and guides it was obvious that the rod had a tendency to twist to side easily - it was too asymmetric!
Therefore I sanded (rounded) the upper part ("roof") of the rod to diminish the asymmetry.
The rod has now a lot of extra power, it has only mild tendency to twist and it is very light. I think that it could be used for flyfishing and I am waiting for the next summer!

Eight strip rod (OCTA) with an INSIDE-OUT structure - experiment in Autumn 2004
One of the ideas in developing and experimenting in cane rod building is to increase the weigth / stiffness ratio of the rod. Therefore eg. the hollow rods are built.
I wanted to try another method to increase the realtive amount of the power fibres in the rod. The power fibres are situated just beneath of the surface of the bamboo. I looked for different possibilities to construct a rod a noticed that an OCTA (eight) strip rod with every strip flipped so that the outside (power fibres) are inside the rod results in bigger amount of the surface and power fibres compared to a traditional hex rod. There could be even 10-20% more of power fibres in that manner! Therefore the resulting rod should be more powerful. See the picture of the rod cross-section in the picture!
The geometry of the octa rod is quite simple. The inner angle is 45 degrees and the outer angles are 67.5 degrees each. The planing with hand-tools makes some requirements: you have to build a new planing form with a 45 degree groove. I made it from nylon (Ertalon). I made the calculations and build the octa version of PH Young Driggs River special.
To my surprise and disappointment the difference compared to the traditional HEX rod was really minimal! I even measured the stiffness using Common Cent System and the hex rod was one coin stiffer! How is this possible. I suggest that the geometry explains it: the power fibres are however more near to each other compared to hex rod.
Presently I could recommend octa inside-out rod as the but part of thick salmon / two-hand / Spey rods. It is difficult to find really thick cane with thick power fibre layers. In an octa inside-out rod the strips do contain more power in very thick rods.