Description of a speargun for freshwater fishing

In the following we will briefly describe a specific speargun for freshwater fishing, which I bought from a fisherman in the northern suburbs of Bangkok, Thailand. It is neither as primitive as many of these guns are, nor is it too over-sophisticated. Besides of the reel, everything was made locally by himself and just for the practical purpose of catching fish for his family’s table.

General description

With a total length of 186cm / 6 ft 1.23’’ (73 ¹⁵/₆₄’’), this is a pretty long piece of equipment. But it can be easily handled from an elevated position over water, where there are no obstacles around. Main components of this speargun are:

  • Wooden stock, which also acts as the guideway for the spear
  • Rubber bands with fastening bar
  • Trigger mechanism
  • Reel and line on mounting brackets
  • The spear

Wooden stock

The stock assures convenient handling of the speargun. It is made from straight grown teak heartwood. For closing the wood pores and making it water resistant, the stock was varnished after final assembly of all parts.

The guideway (or guiding groove) for the spear is often called ‘barrel’ – like at a real gun. But it is not a barrel, as it is open on the upper side. Length of this guideway from the hooking point of the rubber band wishbone to the muzzle is 120cm / 47’’. The width of the groove is 6mm over the whole length. Depth of the groove is 5mm / 13/64’’ at the hooking point and tapers up to 3mm / 1/8’’ at the muzzle end. With a spear thickness of 4mm / 5/32’’ over its whole length, the spear has got a tolerance of 1mm / 3/64”on either side within the groove, when propelled forward.

Reason why the spear flies straight

Here we can see the necessity of a long guideway. When the spear is released at its backward position, the rubber bands convert their stored potential energy into kinetic energy. Friction on the sidewalls would reduce this kinetic energy. In order to reduce friction, a wider groove was chosen compared to the spear thickness. But the spear will snake around sideward when propelled forwards. When rubbing on the wall, friction is created, and the spear moves the other side. And does the same on the opposite side.

At a good length of the guideway, this sideward snaking will be reduced, and the spear is taking the path of least resistance – which means moving straight horizontally in between the sidewalls. A vertical movement of the spear is not possible due to the eccentric location of the hooking point. This assures that the spear is always pressed to the guideway bottom. And is further reduced by the tapering-up of the groove bottom.

Stock decoration

On both sides of the stock a picture of a Thai mystical figure was added for spiritual purposes. And the head of the same figure is depicted on both sides of the forend. Depicted is the ‘Respected Mighty Hermit Dern Deng’ (Thai: พ่อแก้วเลอซี่เดินเด่น, Por Gae Lersi Dern Deng).

In Thai folklore, Lersi (yogi or ascetic hermit) Dern Dong is believed to possess various supernatural powers, including:

  • Control over the elements of fire, wind, and rain, and can use these powers to create or destroy.
  • Healing abilities: it is believed he has the power to cure physical and spiritual ailments.
  • Lersi Dern Dong is believed to possess great knowledge and wisdom and is often sought out by those seeking guidance or answers to spiritual questions.
  • He is also considered a protector and is often invoked for protection from harm or danger.

All-in-all, Lersi Dern Dong is revered as a powerful and wise hermit with a wide range of supernatural abilities. The builder of this speargun obviously considered him a suitable protector of the bearer and his gun.

Rubber band tubes with fastening bar

Distance from the hooking point of the spear locked in the gun to the fastening bar is exactly 1m / 39’’. And the distance of the fixation points of the rubber band tubes from the forend are 9cm / 7.5’’ either side of the forend wooden walls. Total distance between both fixation points is 20,5cm (9 + 2,5 +9) / 8’’.

The rubber bands got tube shape with an outer diameter of 12mm / 15/32’’ and a wall thickness of 3mm / 1/8’’. The wishbone between both rubber band tubes is made from a densely weaved, strong polyester band with a total open length of 16cm / 6’’. And both rubber band tubes are connected to the fastening bar with the same type of polyester material.

Trigger mechanism

Also, the trigger mechanism is homemade. It works as follows: A round tap locks into a hole in the rear end of the spear. When the tap is vertically moved downwards, the spear is getting released.

Vertical downward movement of the tap is initiated by a lever, which is a fixed part of the trigger. This lever connects to a cam at the lower end of the tap. And the tap will be pushed upwards again by a spring below the cam. Therefore, pulling the trigger will move down the tap, releases the spear, and be put back in the initial position by a spring. There are only two moving mechanical parts and a coil spring. The whole mechanism is held together by a trigger plate and secured by a trigger guard.

Reel and line

A ‘Closed face’ spincast reel is mounted on two aluminum brackets above the stock. It looks like the mounting brackets were intentionally angled backward and not by an accident or outside pressure. The spincast reel bears the name and logo of ‘Marukyu’ brand. Gear ratio is 4.1:1, which is impressive for such a simple reel. Most of these reels got ratios of either 3.1:1 or 3.3:1.

The fishing line got a thickness is 0,4mm / 1/64’’ in monofilament. The distance from the knot around the spear and the mono-line are bridged by a 20cm / 8’’ long double-braided nylon-twine. Purpose of this twine is an increased protection against abrasion at the spear cover bracket in front of the reel bracket.


Basically, the so-called ‘spear’ is an arrow with a latching hook on it. Length of this spear is 29cm / 11.4’’ with a uniform thickness of 4mm / 5/32’’. It got a sharp, pointed nose and a latching hook 4cm / 1.6’’ behind the tip. The rear end got a hole for the trigger tap. About 5cm / 2’’ from the rear end there is a constriction, which is holding the braided line. Spear material is mild steel, and the latching hook was welded on in Inox.

Loading and shooting

The speargun for freshwater fishing is loaded by connecting the rear end hole of the spear into the trigger tap and fastening the line by the reel. In preparation for shooting, the clutch button on the reel has to be pressed, so that the line can be spooled off freely when shooting. After hitting the target, the arrow is often completely penetrating through the fish and the target can be reeled in easily.


Unobstructed aiming of the gun on a target is difficult, as there is always the latching hook with the wishbone band in the line of sight. But due to the long wooden guideway, it is possible to level the upper surface of the wooden forend with the horizon of the muzzle and the target. And it can be seen at practical fishing applications of such spearguns, that the likelihood of striking fish is high.

Lessons learned about a homemade speargun for freshwater fishing:

  • Presented speargun for freshwater fishing in Thailand is 1,86 m / 6 ft 1.23’’ long but still lightweight and easy to handle.
  • All parts, with exception of reel and line, are handmade.
  • For spiritual protection of bearer and gun, stencils of the ascetic hermit Dern Dong were added to stock and forend.
  • Exact aiming a target is difficult, as the latching hook of the spear and the wishbone band are in the line of sight.