Sergiy Kravchenko & Peter Currer
This article has been published in magazine "International Freediving and Spearfishing News" (April/June 2005 № 41) . www.diving-action.com
Hi-Power Speargun: At the Cutting Edge
Experienced spearfishermen soon learn that different conditions and the types of fish being hunted require different weapons. While it is possible to successfully hunt a wide range of species with one "all-purpose" gun, there are times when it cannot do the job. In murky water the gun may be too long for safe shooting, you may not even be able to see much past the muzzle of the gun, plus confined spaces may make the barrel length a problem. In such circumstances manoeuvrability of the gun will be more important than long shaft length and greater shooting range. Conversely in clear open waters a shorter gun will not have the range and striking power for targets located at extreme range. Bluewater hunting generally requires stable and accurate shaft flight and considerable energy at impact to facilitate penetration of the target at the desired body location, unless the diver can work his way in closer to his target. Of course if the target is overly curious, then it may come to him instead, a pleasing situation.
This article is about a new long range weapon for shooting fish at extreme range. Readers of this magazine will already be familiar with multi-band spearguns which use incremental band loading onto the shaft to achieve high energy storage. The aim of these weapons is to provide a reliable launcher which can eject the shaft so that much of this stored energy is imparted to the spear. By storing the energy in multiple bands this enables the loading effort to be split so that the spearfisherman only need summon the strength to load one band at a time.
Another energy storage medium is compressed air. In the pneumatic speargun the diver's loading effort is used to push a spear shaft down into the muzzle of the gun while working against the high air pressure already stored within the gun. The spear tail usually pushes a moving piston in the inner barrel which latches onto a catch mechanism at the rear of the gun once the loading stroke is completed. The moving piston is equipped with rubber seals to stop any compressed air from escaping and also acts as a carrier to push the shaft back out of the barrel when the gun is fired. This seems like an ideal system, but it is limited by the force that can be transmitted to the spear during loading. In all manually loaded spearguns you only get out what energy you have put in, and not always that as there are often inefficiencies in the gun's storage system and overall operation. Muzzle loading a spear into a compressed air gun pumped up to high pressure can flex the spear to the point where it will permanently bend, which is the last thing you want. You cannot shoot bent spears out of a pneumatic speargun, even if you could force them in, as the spear will soon irreversibly damage the smooth inner barrel and result in big compressed air leaks.
In an earlier article I discussed the hydropneumatic speargun which also uses compressed air as the energy storage, but utilises a flooded barrel to inject water into the gun when the spear is inserted. The compressed air is held back by a moving bulkhead or piston arrangement located elsewhere in the gun body. The water pushed into the gun displaces this bulkhead or piston and causes the compressed air reservoir to be reduced in volume, thereby further increasing the air pressure stored within it. Firing the gun releases the injected water, driven by the re-expanding compressed air, pushing it out of the gun and propelling the spear from the barrel. Although the gun is subjected to sea water inside it when loaded, it has one big advantage. Water is incompressible. If you pump water you quickly reduce the air volume inside the gun. The force acting on the spear is given by the pressure in the gun multiplied by the cross-sectional area of the barrel. A gun with a large cross-section barrel can be difficulty to load if it is pumped up to very high pressure, whereas a smaller diameter barrel can be loaded more easily at the same pressure. The ideal situation would be to have a small diameter barrel to load the gun and a larger one to shoot from. This is not possible unless the gun has separate barrels, the smaller barrel serving the function of a loading pump. Then the gun can be loaded by a number of pump strokes of the smaller diameter barrel to provide a very high power shot out of the larger diameter barrel.
Although not common today, this self-contained water pumping principle has been used a number of times by speargun designers to generate greater air reservoir pressures while keeping the in-water loading task at a realistic level for the diver. One of the most recent examples is the Aquatech "Black Sea" model, a hydropneumatic speargun of novel design which also utilises a hydraulic trigger release mechanism. The latter greatly simplifies the mechanical layout of the gun and reduces the trigger pull, a necessity for steady aiming when shooting very high power weapons. As such it offered an ideal basis for the creation of a very high power speargun for specifically targeting large, fast fish; hence the "Black Sea" designation.
With the "Black Sea" speargun the spear is loaded into the main barrel with little effort, then the necessary water injection is carried out by using a small bore hydropump built onto the rear of the gun. The hydropump uses a lever system to further improve its mechanical advantage and reduce the loading effort. By working this pump in the manner of raising up a car using a hydraulic lift jack to change a wheel, the "Black Sea" speargun has water injected to enable the internal air reservoir volume to be progressively reduced and the stored air pressure raised to extremely high levels. This elevated air pressure is then available to push against the water connected to the speargun's main barrel. On pulling the trigger the release valve opens and the spear and previously trapped water is ejected at high speed, being driven by a pressure which would be virtually impossible to load against by normal muzzle loading of the spear down the barrel. Even if the diver was strong enough the spear would be in danger of bending as it tried to overcome the enormous resistance created by the gun's air pressure system.
Thus a high power air gun is available which can be loaded progressively in the water with no danger of spear bending during loading. As the diver works the hydropump at the rear of the gun he can also stay away from the muzzle of the gun, a big safety consideration. The "Black Sea" speargun is a very high power gun, yet is manually loaded without one having to posses superhuman strength. Designed to hunt some of the largest fishes, it advances the hydropneumatic powered speargun to new performance levels. It has already been used to hunt record size Tuna, easily driving its high speed shafts deep into their bodies.
The accompanying photos show the details of the latest prototype. This is the new titanium "Black Sea 1300x10B" model, designed specifically to shoot large Tuna. The rear mounted hydropump is shown in the various positions of its pumping action.
A record fish will no doubt be taken once opportunity and preparation coincide, it is only a matter of time. A record Tuna was shot last year, but sunk before it could be retrieved by the hunter. A lucky fisherman found and sold it a few days later!