The Effects of String Length on a Recurve Bow (a.k.a Wrapping 2020 Up With a Bow)

 
 

Overview of the Project

The Archery Manufacturers Organization creates standards for the manufacturing of archery equipment; this organization suggests that the standard length of a string for a recurve bow is 4” shorter than the length of the unstrung bow between limb tips. While this has become the standard for recurve bows, we couldn’t find documentation on why this length is ideal. The project was run with the intention of investigating the effect of varying string length on stringing, loading and shooting a recurve bow. I worked on this project with one other partner; together we created a model of a recurve bow in ABAQUS. We created the model in five steps: modeling the recurve bow, bending the limbs as if about to string the bow, attaching the string to limbs, letting the bow settle, and loading and releasing an arrow. We created a fairly complex model, but unfortunately the final results didn’t indicate why the suggested string length is best. An overview of each step can be found below.

 

  • Modeling The Bow

    The image above shows several iterations of our build for the top bow limb. Eventually we settled on a symmetric 3D model designed using actual measurements from a recurve bow. We input our best guess, after research, at the material properties of the bow primarily deciding to use yew wood.

  • Bending The Limbs

    To string a bow, you must first bend the limbs. This was particularly difficult to model in ABAQUS because when displacement was applied, elongation occurred. After some trial and error we decided on the boundary conditions shown in the image above to simulate bending the limbs.

  • Attaching The String

    This is traditionally the next step after bending the bow. We ended up combining it with the previous step, because otherwise the tension from the string would cause the limbs to snap. We added another fixed displacement to the bending step to account for the bow settling after stringing.

  • Letting The Bow Settle

    This is traditionally the next step in stringing a bow, but we ended up combining it with our previous two. We added additional displacement when bending the bow to account for both the stringing of the bow and allowing the bow to settle.

  • Loading And Releasing The Arrow

    The final step was to load the arrow and release it. We created an arrow of seemingly accurate density, length and material property after some research. We tied the arrow to the string, applied a displacment and let go to get our results.

 

If you are interested in looking at the model in greater detail or finding out more about the project, then please look at the attached document or powerpoint presentation which include both the process and the results.