On selecting spears:

A common question from our customers is what is the best spear? Our customers are usually quite disappointed to hear our standard answer, which is “that it depends on what you are trying to do with it.” As we have intimated elsewhere on the site, the key to selecting a spear (and indeed to selecting any diving gear) is to always match the tool to the job at hand. No single tool is best for all jobs, they each have their specific pros and cons, and no single spear is the best for all hunting environments.

The key to a successful dive is to match the gun to the dive, and then select the correct spear to match the gun. So the spear you select will be determined by the gun you are using.

Spear Thickness:
The thickness of the spear will be determined by the rubbers. If you are using a multi-rubber gun, or heavy rubbers, we recommend that you select a heavier spear, in the 7mm to 7.5mm range. The reason for this is that a heavier spear will have more momentum (kinetic energy), and will go deeper into a large fish than a thin spear will. It will also be stronger so less likely to bend at impact, and will be stronger as you battle the fish to the surface, and less likely to tear out because the spear-barb is larger. But the most important reason for correct spear selection is that the spear will fundamentally determine accuracy. If your spear is too light for the rubbers, the gun will become inaccurate. The reason for this is that at the moment of release, the spear will bend slightly and start vibrating as it screams down the barrel towards the target, developing a slight U-bend. (You should visualize this as the back of the spear trying to catch up with the front of the spear). This phenomenon is called “spear-whip” and the net result is that the spear will not fly true, and the gun will usually shoot low. This is one of the major reasons why over-powered guns are inaccurate, but there are many others. We have tried to minimize this effect, and experimented with making our notches slightly deeper than other manufacturers such that the wishbone is actually applying the force directly in the horizontal plane. However, the Sumora jury is hung on how effective this is, and if it is worth the additional weakness that it creates in the spear, so we are conducting further tests.

Spear Length:
The length of the spear will be determined by the length of your gun. Clearly a longer gun requires a longer spear, allowing you to get more range and stopping power. The support given by railguns allows the guns to use a shorter spear than a normal gun. The benefit of having a shorter spear is that the gun is more maneuverable, and the spear is stiffer and less likely to bend, but these effects are marginal in shorter guns. To make a standard gun accurate, the length of spear has to be such that the section protruding from the muzzle will counter the sag in the middle section, such at the moment of release the spear is straight and in the correct horizontal plane. The effect of having an overly short spear will be apparent, because the gun will shoot high. The opposite is true if too long a spear is used, as the gun will shoot low. The reason for this is that in a standard gun the spear is only supported in the mechanism and in the muzzle, while in a railgun the entire spear is supported.

In general, we recommend the following general configurations for our railguns:

  • Length:
    The rule of thumb is that spears should be 40 cm longer than the barrel length For example, a 120cm Railgun needs a 160cm spear.
  • Thickness:
    For guns up to 130 cm we recommend a 7mm to 7.5mm spear. However, for guns longer than this, we recommend a 7.5mm to 8mm spear.

Spear Composition:
Another major consideration when selecting spears are stiffness and corrosion. Spear bending is primary a function of the material the spear is made out of, and the length of the spear. The tougher the material, the less it will bend. Our Spears are oil quenched carbon spring steal, and are then galvanized in a zinc solution to combat corrosion. We  believe that the net result is a cost effective and tough spear that won’t bend. Review Sumora Founder, Craig Heslop's and his "test drive" of the steel spears.  

Straightening a spear is a non trivial process, and involves hitting and repeatedly rolling the spear on an anvil, so it is often better to get a stronger spear that is less likely to bend than spending a lot of time hammering away in your garage when you could be diving.

If you are interested in more detailed description related to our spears please see Our Ode to Steel Page.