Structural rationalities of tapered hollow cylindrical beams and their use in Japanese traditional bamboo fishing rods

Ryo Nishiyama,Motohiro Sato

doi:10.1038/s41598-022-06426-x

Abstract

Bamboo has historically been used in Japan as a structural material and for building tools such as fishing rods owing to its remarkable structural properties. In recent years, the materials used for manufacturing fishing rods have changed greatly owing to the development of composite materials; however, the basic slender tapered hollow cylindrical fishing rod design has remained unchanged throughout the long history of fishing. However, the mechanical rationale behind this structural design has not yet been sufficiently verified, and this study clarifies this. The analysis was performed by solving the nonlinear bending equation of a slender tapered cantilever beam with a concentrated load at the tip, which causes large deflection, using the Runge–Kutta method. The deflection curves and bending stresses were obtained, and the structural design to minimize the stresses was explored. Our results may prove useful for bamboo-inspired bionic design and bring to light our ancestors’ deep knowledge of natural materials and their advanced technological capabilities.

Highlights

Bamboo has historically been used in Japan as a structural material and for building tools such as fishing rods owing to its remarkable structural properties
A familiar example of utilizing the flexure of such a slender rod is the fishing rod. Composite materials such as carbon fiber-reinforced plastic (CFRP) and glass fiber-reinforced plastic (GFRP) have made remarkable progress, and they are used in fishing rods
The basic slender tapered rod design of the fishing rod has remained unchanged throughout the long history of fishing

Summary

Introduction

Bamboo has historically been used in Japan as a structural material and for building tools such as fishing rods owing to its remarkable structural properties. Amada and N agase[15] focused on the characteristics of flexure and estimated the wind load applied to the trunk by the branches and leaves and their own weight from the projected area of the photographs, and conducted a large deflection analysis based on the measured data of bamboo They confirmed that the bamboo effectively suppressed the stress increase by shifting the position of maximum bending stress generation toward the root, which is more rigid, by bending the whole trunk at high wind loads. Turning to the history of fishing, the origins of the fishing rod is bamboo rods (Fig. 1) This is probably because bamboo provides a naturally slender tapered hollow cylindrical structure, such a structure provides useful properties for fishing. This study optimized the shape of rods by deriving the optimal taper that minimizes the bending stress under

Methods

Results

Conclusion