3 barb cluster head has anyone used one?

[CCspearo]

I am thinking of making a three barb cluster head (3/ 4.8mm stainless barbs) for my high powered roller gun. Has anyone used them? Do you loose more fish due to the less gripping power of 3 barbs compared to 5 or 6. I notice the large base on the larger cluster heads reduces shaft speed quite a bit I can get the base size down from about 35mm to 11mm by using 3 barbs. I am interested in hearing of anyone's experiences with this type of head. thanks in advance for you input.

 

[CCspearo]

well I bit the bullet and made a 3 barb cluster head. It should be quicker through the water than my old cluster head, perfect for shooting those fish that only give you a face on shot then turn around and dart off. here are the details: 316 stainless, 125mm long 4.8mm diameter prongs, 7mm barbs welded on for extra strength and holding power. 10mm base(1.5mm thick 316ss tube 7mm ID to suit 8mm spear shaft after thread tapping. The whole unit has been blackened for stealth by burning in sump oil. The spear tips have been tempered by heating to cherry red and quenching. The shafts have been left unhardened so they bend rather than snapping off if I hit a rock. I intend to use this head on my 1 metre rollergun for fish under 5kg that require stalking in open water. I have set my spear up so that I can quickly convert it to a point with a flopper if I see larger fish. I just open and hold on to the flopper and put my knife in the cluster head and wind it off the spear revealing the point. The cluster head fits nicely in the hollow handle of my modified seahornet speargun. Note the flopper retainer for shooting in caves with the cluster head prevents the flopper opening and getting caught up when pulling the spear from a cave. see the pics for more details. The point is a lot sharper than shown in the blury close up, my camera phone doesn't take good close ups.

 

[Mr. X]

Well done Interesting to read about your metal treatment. I am interested in hand tools and handmade tools, as a user rather than a maker. Sounds like you have hardened the tips to the point where they will likely be brittle but left the shaft soft/mild to help absorb shocks, etc.. I wonder if it might be better to anneal (is that the correct term?), i.e. soften just a bit, the tips? I read an article recently that gave some simple ways to achieve specific Rockwell hardnesses (I'll see if I can find it). Many of my tools have a Rockwell hardness of 59/60 so they take and keep a good working edge which is easily sharpened. Japanese blades are typically harder though, I forget the exact figure but around 64 I think(?) -- I wonder if that might be a good hardness to aim for (if you can find a reference on how to achieve it of course!). Such Japanese blades (plane blades, chisels, etc.) are often laminated with softer steel/iron to provide support/absorb shock/etc. - much as you are doing. Such blades are harder to sharpen but waterstones work well on them. Perhaps that is overkill though...gilding the lily!

 

[CCspearo]

Well done Interesting to read about your metal treatment. I am interested in hand tools and handmade tools, as a user rather than a maker. Sounds like you have hardened the tips to the point where they will likely be brittle but left the shaft soft/mild to help absorb shocks, etc.. I wonder if it might be better to anneal (is that the correct term?), i.e. soften just a bit, the tips? I read an article recently that gave some simple ways to achieve specific Rockwell hardnesses (I'll see if I can find it). Many of my tools have a Rockwell hardness of 59/60 so they take and keep a good working edge which is easily sharpened. Japanese blades are typically harder though, I forget the exact figure but around 64 I think(?) -- I wonder if that might be a good hardness to aim for (if you can find a reference on how to achieve it of course!). Such Japanese blades (plane blades, chisels, etc.) are often laminated with softer steel/iron to provide support/absorb shock/etc. - much as you are doing. Such blades are harder to sharpen but waterstones work well on them. Perhaps that is overkill though...gilding the lily!

Thanx Mr.X
I may have fluked the right temper or the burning in sump oil may have taken the temper off! I took the cluster head out for a test a few weeks ago. I shot 2 fish before I hit a rock. I had my rollergun on the lowest power setting (equal to a 110cm gun with 16mm band) The prong bent as designed and the point was slightly dulled I couldn't straighten the 4.8mm prong with my hands so I pulled out my DIY prong straightening dive knife only to find the hole I had drilled in it to straighten my old cluster head would not fit over the new larger prong. so that curtailed my dive. I drilled out the hole when I got home and it straightened the prong easily. I got the file out and the spear sharpened up nicely.

my DIY prong straightening knife handle is 3.5mm 316 stainless welded to an old stainless fishing knife blade

my dinner that night. The leatherjacket was shot from behind swimming away from me at about 3metres. A shot very hard to do on a thin fish with a single pointed spear but easy with a cluster head.

 

[Mr. X]

Excellent. Glad to hear it worked out I think cooling in oil is a good thing to do for tempering/hardening (generally preferred to water cooling for the sort of tools I use); that should harden it (as you already have). If you want to relieve some of the brittleness (perhaps unnecessary with your mild steel shafts but it might make sharpening easier) I think the process is called annealing & can be done simply by sitting the object in an oven (tricky for a long spear though) at a specific temperature for a specific time (I think something like 200 for 1 hour but I need to look up that reference still).

 

[CCspearo]

Excellent. Glad to hear it worked out I think cooling in oil is a good thing to do for tempering/hardening (generally preferred to water cooling for the sort of tools I use); that should harden it (as you already have). If you want to relieve some of the brittleness (perhaps unnecessary with your mild steel shafts but it might make sharpening easier) I think the process is called annealing & can be done simply by sitting the object in an oven (tricky for a long spear though) at a specific temperature for a specific time (I think something like 200 for 1 hour but I need to look up that reference still).

The type of tempering I did was to compensate for the hardening caused by welding the barbs on to the tip of the spear. Welding seems to make the metal hard and brittle. Tempering(dependent on the colour you heat the metal to i.e straw colour or cherry red) is a toughening process and gets a result some where between hardened and annealed.
here is a quote from wikipedia on tempering explaining what i tried to do.
"Welded steel
Steel that has been arc welded, gas welded, or welded in any other manner besides forge welded, is affected in a localized area by the heat from the welding process. This localized area, called the heat-affected zone (HAZ), consists of steel that varies considerably in hardness, from normalized steel to steel nearly as hard as quenched steel near the edge of this heat-affected zone. Thermal contraction from the uneven heating, solidification and cooling creates internal stresses in the metal, both within and surrounding the weld. Tempering is sometimes used in place of stress relieving (even heating and cooling of the entire object to just below the A1 temperature) to both reduce the internal stresses and to decrease the brittleness around the weld. Localized tempering is often used on welds when the construction is too large, intricate, or otherwise too inconvenient to heat the entire object evenly. Tempering temperatures for this purpose are generally around 205 °C (401 °F) and 343 °C (649 °F).[10]"

After many years of repairing prangers/clusterheads that end up looking like this one below I had enough and thought I could do better.

In some of the shop bought heads the prongs are too brittle and the often snap off, I think they use high carbon steel (hard but brittle)this is why I decided to make my own. The latest 3 prong model is the 6th one I have made over the years, the previous ones have been 5 pronged. My first was made from a stainless nut that screwed on to my spear and had 5 prongs welded on to it and lasted for years(and took hundreds of fish) til I cut the prongs of it and used them to make a more streamlined version. Now that I have it sorted, I cant wait to get out and use it again, but it has been raining heavily for the last 4 days on the east coast of Australia and I am starting to get cabin fever, even after the rain stops it will be a few days before the water becomes clear enough to dive. With 29 shark attacks in Oz last year I don't think I will be diving in dirty water. thanks for your interest in my little project Mr X

 

[Mr. X]

Basic forging is sometimes explained quite simply but there are many variables which can complicate things considerably. That wiki information about welds is interesting to me, as I bought a tool last year that would traditionally have been forged & forge welded but the (much less expensive) version I bought (by Narex, CZ) instead uses: their special steel, precision cryanogenic hardening and modern welding techniques. That allows them to produce the tool less expensively (not cheap tho!) however there is a problem*: one of the smaller versions of the tool snapped at the weld after just a few uses (according to an American Amazon reviewer), the special steel used is one of those prone to bubbles in the weld, according to wiki. Credit to Narex, they have withdrawn the tool from sale (hopefully only temporarily - perhaps they need to relieve some stresses as you have done). I have the larger model - & it works very well - and I am hoping the larger weld on the larger model will be enough to prevent the weld breaking on mine (I had a former professional welder check it out and he thought it looked fine); if not I will return it for replacement/refund.

*There might be a second problem. They might have uniformly hardened the whole tool head using their cryogenic technique (as it lends itself to mass production) - that would make the tool uniformly hard but that might also make it brittle. Alternatively they might have just hardened the blade before welding it onto the head. Not sure how this is done traditionally: forge weld then harden the cutting area or harden the cutting area & then forge weld that hardened bit into the head - the first seems like the simpler & safer approach (as the weld would not compromise the temper of the blade) but some old axes were made with the latter approach (perhaps because harden steel was then hard to make/come by).

 

[CCspearo]

The hardening, tempering and annealing of metals is a complicated process that has taken blacksmiths hundreds of years of trial and error to perfect, luckily with the help of the internet this info has become readily available to us. 20years ago I would be sitting in the library flicking through reference books trying to find out how to proceed with things like this. The other day I was reading how they get a very hard edge on a sword but keep the rest of the blade soft and flexible. Just the thing I needed for my clusterhead. We are very lucky to live in an age of information.