If it breaks it usually happens at the flopper pin hole, or if it's a notched shaft at one of the notches. Otherwise mighty suspicious 
Hahaha now you can make a shark spike, a stringer, and other acc that you might not need hahaha
Better for gear to fail when it doesn't cost you fish or health
I've seen a couple spears broken like that. Like Dan said usually it's at the flopper pin or at the threads but under the right circumstances (blasting into rock) it can happen.
Was it stainless or spring steel?
I have seen spring steel shafts brake a foot back from the tip on point blank rock impacts.
Cheers, Don
If anyone wants a more technical explanation of why this happens PM me. Ill reply tomorrow after my last Final Exam.
If anyone wants a more technical explanation of why this happens PM me. Ill reply tomorrow after my last Final Exam.
I don't type as fast as I can speak, so here's mine.....
Hard shaft and hard.... Rock.:D;)
Leading to catastrophic failure of the Hanks shaft.:@:@
If anyone wants a more technical explanation of why this happens PM me. Ill reply tomorrow after my last Final Exam.
Is it too hardcore to post?
When a spear is fired the bands convert their potential energy into kinetic energy which causes the shaft to move. Not complicated. When the shaft strikes a rock or some other rigid object, this energy cant be transferred to the rock and so it is converted into heat and sound in the form of a vibration. You have all heard the ping when the shaft hits and if you have every repeatedly bent a wire you know it will warm up. However, these deformations and vibrations cannot occur instantaneously. A high-velocity collision (an impact) does not provide sufficient time for these deformations and vibrations to occur. As a result the material behaves as if it were more brittle than it is. Thats why steel which is usually a ductile material snaps as if it was brittle.
You may wonder why this doesn't happen more often. Kinetic energy is proportional to velocity squared v^2. If the velocity is cut in half the kinetic energy is cut by a factor of 4. Drag, the force that slows the spear down, is also proportional to the v^2. The force of drag is highest when velocity is highest. As a result, the kinetic energy of the spear drops fairly quickly after the shaft leaves the gun. Once the kinetic energy has dropped below a certain point it can be more easily converted into the deformation of the material. In the case of steel which is malleable the tip gets smashed or dulled.
Other factors such as fatigue - microscopic cracks from repeated impact, impurities and irregularities in the steel, type of rock, angle of impact, and others also effect the this scenario.
Please do xan. I love a good physics lesson
Which brand was the shaft? I suspect I guess...
Which brand was the shaft? I suspect I guess...
Pursuit
Only time I ever had any problem with one of that brand. And that was no virgin shaft. I think it'd been bounced off more than one rock as Mo and Tino were honing their aim on unsuspecting hogfish. 
Pursuit
Only time I ever had any problem with one of that brand. And that was no virgin shaft. I think it'd been bounced off more than one rock as Mo and Tino were honing their aim on unsuspecting hogfish.
Ups! I had another guess...
I suggest you put a flopper pin hole in it and shape another point. This tool does a great job Speardiver Spear Shaft Drilling Jig .
Other factors such as fatigue - microscopic cracks from repeated impact, impurities and irregularities in the steel, type of rock, angle of impact, and others also effect the this scenario.
Nice post. Thanks.
The shaft had probably been bent a couple times and straightened. I lay them on a flat slab of concrete outside and pound them straight as a fine tuning method. If it doesn't work, I get a bigger hammer. The boys have had this shaft stuck in holes, banged on rocks....it's their training shaft and it's been on a Riffe C3
Dan I still have 4 more of the ones you sent. It's about time to place another order. I'm maintaining about 6 guns now.
Pretty funny to see someone get a new gun. They're all stoked and I'm thinking, "it begins". My friend just bought a nice gun and I'm telling him to order shooting line, crimps, crimp tool, band rubber, wishbone line, dyneema, pigtail. And they were scuba divers so now they need low volume masks, long fins, computer,....haha. He looks at me like..."seriously"? Expect a big order soon. :thumbsup2:
Thanks xan. Very cool.
Hank you are so right!! It is a money pit
Drag, the force that slows the spear down, is also proportional to the v^2.
That's correct for high speeds (and turbulent flow -> high Reynolds number) but at low speeds it's proportional to v...
I just tough I'd mention it so people don't get confused while calculating their diving drag :laughing:
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