Speargun design: Chapter 1

Square stock guns have been around for ages and work, so why do we love the cuttlefish? The easy answer is that the cuttlefish design optimizes the shape as a result of the forces acting on the gun from the power bands, as well as provides a more hydrodynamic profile when tracking a fish though the water.  Oh, and it looks great too!




In today’s blog, we will discuss the strength aspect.  From an engineering aspect, a speargun is nothing more than a simple column problem. There is one major force acting on both ends of the gun; band tension between the band hole and the trigger mech (i.e. compression force on the gun/column).  I’ll spare you the math, but the resultant bending moment (the reaction induced in a structure by an external force, causing the structure to bend) increases as you move away from where the force is applied. Therefore the maximum bending moment occurs at the midpoint between the bandhole and the trigger mech. The OSS cuttlefish moves the traditional location of the cuttlefish bulge forward to the midpoint to ensure the maximum amount of material is located in way of the maximum bending moment.


In following posts we will delve into fluid dynamics and how the cuttlefish shape allows the gun to track easily through the water.

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