I wanted a gun to take southern blue fin tuna.
A gun should be tuned to match the fish and their environment. Where I hope to go, the tuna can be large, but it will be unlikely to encounter a real monster, so I built the gun with a 20 to 30 kg tuna in mind. The tuna are found near the edge of the continental shelf, so it’s a true blue water environment. I am unsure whether they will be encountered head on/from the top, or from the side, so I don’t know if the stalk will be “extend and shoot” or “swing and track”, or both.
I wanted a powerful gun, but nothing too heavy. My thinking was a four rubber gun, pushing an 8mm (5/16 inch) diameter spear, fronted by a slip tip. The stock length (from front of mech to tip of muzzle) should be about 1.35 metre.
Before starting the build, I named this gun “Death Descending”.
Since it was an experiment/prototype, I didn’t want to use fancy timber or joinery. I made it from DAR, KD, radiata pine, purchased from Bunnings. I tapered the central strip, and laminated it between two others. I used fibreglass plasterer’s tape as stringers. West epoxy holds it together. The pine strips came in a width of 40 mm, but I wanted a bulkier gun, so I laminated-on some side strips. Cheap timber or no, I still think the pine looks OK.
I don’t care what other people say, real men make their own handles. It is mortised into the under plate, and secured by a dowel. It fits my hand, and fits it exactly. I angled it back a little more than usual to assist in dissipating the recoil.
Seems to me there is a 1950s “spacey”, “ray gun” aesthetic to this gun’s appearance, and I like that. Not that that will impact on how well it shoots.
I used a Riffe mech, with a 5mm stainless steel push rod.
There are four 16 mm (5/8 inch) rubbers at 3.5 to 1 stretch. The bridles are “starter motor” braid.
The spear runs in a channel, about 8 mm deep. This was cut with a hand held router. In three places along the channel are “spear whip inhibitors” mini enclosed tracks, about 20 millimetres long. The spear hole through these is 9 mm. I fabricated them from acetal (delrin) plastic, fitting each individually to align the spear in the channel. This is an unconventional system, but it has worked for me in the past.
I plan two wraps of shooting line.
There is a hole above the handle to take a rubber break away, but I think that for my tuna fishing expedition, I will use a tethering rig.
I have not yet balanced and ballasted the gun. It has yet to get wet. I don’t know how much it will finally mass, and how it will shoot. Sticking my neck out and making predictions is a sure way to look silly, but it’s also the fastest way to learn how to build a better gun. My guess is that:
• Death Descending will shoot a little low, but once that is compensated for, it will be consistently accurate. I make the prediction based on the distance of the handle below the axis of the spear, and the length of the spear overhang at the front. I also suspect that if the spear overhang was a little shorter it should shoot flatter.
• there will be noticeable recoil, but nothing too obnoxious. I might have made the gun a little bulkier.
But, time will tell. I need to finalise the gun, and target shoot.
Once its done, all I will need is a boat trip out there. If anybody wants a paying passenger, I can be contacted on
ric.fallu@bigpond.com Ric