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Speargun sling problems...

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.

icarus pacific

Nov 7, 2001
OK, all you spearos, engineers and diver-types with nothing else to ponder...

Went out the other day to Monterey, CA and went looking for a couple of dinners. I had my usual rock/hole gun, a Voit/Mares/JBL 4G32 with my 5/8" diameter, 14" rubber slings, and a rock tip. I came up on and shot 4 fish, 2 red snappers a ling cod and a cabezone.. Now I like to get real close to my fish, a choice often dictated by the confines of the hole they're in. I shot them all in the head and two through the eyes and only once did the tip exit the fish's other side, allowing the barbs to open. The other shots pretty much went in half way and stoned 'em.

Now I'm not bitching- I strung them all and life is tasty, but I recall the shaft only leaving the muzzle of the gun once, and that wasn't when the shaft cleared the fish. So my question is, at what point is the velocity and therefore punch of the shaft the greatest? At the moment the trigger is pulled, when the bands are slack and the shaft released....?

Lets here from all you old timers that have answered the same question, and you techie/NASA types!

And remember to post your caption for the contest, see the "It's a Contest! thread.

Shaft speed

Hi Sven,
Well my math sucks so I'll just have to go w/ common sense. The shaft should have the greatest speed at the moment the bands have stopped pushing the shaft, or just shortly there after.
Somethings that could be effecting your penetration(no jokes). Your JBL probably uses a heavy shaft w/ a screw on tip. All this causes drag. Is the 14" band total length or just one half? If it's only half the length then your band may be a bit long to develope all the power that the gun could handle. At that close distance your shaft should be punching all the way through unless it is pinning the fish against the walls of the caves. Hope this helps.

Hi Jay!
gee, I was hoping to have Cliff answer...:blackeye

Seriously, yeah the shaft is 5/16" and all, but seeing as how I'm shooting in the holes at less than 5 feet away, the drag doesn't seem like it'd be an issue as much as when I'm 12' away. Thus my only having a single wrap of line too. The total length of the band is 14" so it's shorter than what comes stock, which adds to the punch, but I wonder if it's a function of the relative inelasticity of the stiffer, thicker rubber, (there's a sure trigger for Anderson...) Granted the lings and cabs are hard heads, and come to think of it also look and exhibit other behaviors of an ex Mother-in-law.

Tip ...

It might have to do with the tip you're using - actually it's quite possible that this is the reason.

Are you using a diamond - shaped or a bullet - shape tip? Or are you using a trident / fork tip? For cave / hole diving I'd definitely recomend using a multi prong tip - it's got fixed barbs right at the tips, so that even if you don't get a stone shot the fish won't escape hurt.

For the math bit, I've noticed that during my own misadventures into murky holes that ultra short range is no good. Best distance if it had to as short as possible was if the spear was out of the front guide by around 5 cm or so. Any shorter and it just wouldn't do.

Hope this helps.
Nope, went the tip route first thing. I've found that multi prong tips don't do the job on these lings or cabezones, unless you gut shoot them or aim for the body rather than the head, which kind of defeats the purpose of shooting them for the meat. They're good though for snap shots at the midwater fish like the black and blue rockfish. I call them bait... I agree that the greatest velocity is probably at that point where the slots in the shaft have gone past the line made by the muzzle and the rubbers.

Lighter shaft?

You could try a 6.7 mm shaft w/ a tahitian tip,( the barb is fixed to the shaft and the point is the end of the shaft). This lighter more streamlined set up would be good for the small to midsized fish, is should have better speed and penatration. If the shaft is jerking on the gun after a long shot maybe another wrap on your shooting line wouldn't hurt. Good shooting.

Hey Sven
Nice catch. Can you e-mail me a few steaks from that Ling? It's been a long time. I'll trade you for some of the 'pond scum' that they produce in the billion dollar, subsidized acquaculture facility here.
"So my question is, at what point is the velocity and therefore punch of the shaft the greatest?" Easy answer for velocity; at the point where the rubber returns to a relaxed state, where would the force come from to accelerate the shaft. Nothing but drag from there on. Max shaft speed.
Punch is a funny word. If you're talking penetration, a smaller shaft moving faster doesn't change much, momentum is vel x mass. If you want 'shock' power (the shaft stops with the point in the fish), a lighter shaft might help, energy is vel^2 x mass.
My way is 3/8" and 5 prong. One of the first meets I went to, it took two big guys about fifteen minutes (in the parking lot) to get the 5 prong out of a Ling's head.
If you really want to be safe, use more rubber.

stiffer, thicker rubber

i thought blow-up dolls were made of vinyl? didn't know they came in industrial strength material?! :D

sorry, sven... couldn't dissappoint you. rofl

anyways, here's mi dos pesos:

get a 5/16 tahitian shaft and grind down the tip so you have just an inch or so of a nub beyond your flopper. (ok, go ahead...) make the tip blunt for more damage. modify the flopper too, if you want. shorter flopper, less penetration distance to clear it beyond other side of fish.

about the whole 'power thing'. yes, you can say how your kin. energy is equal to .5mv^2, but you have another factor in the equation.

here's a preface. i teach golf (shut up, sven) and i'm pretty keen on the physics behind the swings of diff players. some of the bigger guys might have a slower clubhead speed on their drivers at impact than some of the lighter dudes. let's just say that the lighter guy has a swing speed of about 120mph and the beefy muscle dude has one of about 105. well, the balls end up going pretty similar distances. yeah, i know it's wierd since the ball's only on the club face for a micro second, but it proves the point of added factors to the momentum/energy theories....

the velocity of the spearshaft will continue to increase until the bands approach their normal length. but, the shaft's acceleration will decrease once the bands have passed a certain stretch. so... you actually have a third concept of motion here called the 'jerk'. of course this is linear and not angular jerk. (remember, as long as you have positive acceleration, you will increase velocity even if your acceleration is decreasing)

so anyways, shaft momentum should theoretically increase till the end of the shaft nears the end of the gun. but, in order to calculate the momentum, it would have to be measured at points in time, like snapshots, without the bands present(hypothetical). this is just to make the momentum equation true. but, since you still have the bands present, you have to add their force into the equation, just like simple physics equations of falling objects and gravity's effect on them.

so, back to the golf thing. the beefy guy is compensating his slower swing speed w/ his ability to power through the ball as apposed to the thin guy just whipping his club up to high speeds. anyone get this? so, .... i'd imagine the spearshaft should have maximum energy around half of the band's recoil length(of course bands differ) since acceleration decreases around this point.

so sven, you'll just have to have about half the gun's distance from the tip of your spear to the fish for the most damage possible. a bit easier in holes, i'd imagine. :D

good hunting,

your loyal techie, anderson ;)
you're jerkin me...

Hey Anderson, aren't you supposed to be in FL?

Hi Bill, glad you're feeling better. A little time in the bait ball will do that I agree... I've got to get over there one of these years.

I actually understand both of your takes on this topic. Must be the public education system or my time swanging my Big Bertha. Don't laugh; next to holding my breath, it's my game. I've gone the prong route and the thinner shaft scenerio several times in my past. Maybe I just noticed it lately or maybe like everything else these days, the fish's heads are getting harder. I'm going to swap the bands for some fresh ones, slide in my 3/8" meat eater and give it a, uh, er, shot.

I do try to have at the most, the gun's 28" length from the fish, thus my only having one wrap. It leads to some lost fish in terms of not being able to reach, but those that I hit are history. The notion of even being in water with the viz to allow a 10-12' shot makes me moist. But enough about shooting in holes. ;)

My kids are e mailing me when the funny entries are going to appear on the caption contest:t

andrsn said:
get a 5/16 tahitian shaft and grind down the tip so you have just an inch or so of a nub beyond your flopper. (ok, go ahead...) make the tip blunt for more damage. modify the flopper too, if you want. shorter flopper, less penetration distance to clear it beyond other side of fish.
anyway i think that using a heavier shaft would take "more punch" issue, if you want to make a heavier shaft move faster then add more bands to your gun but if you have more punch i imagine it would stun the fish more

i think my logic is right (we havent covered this in science yet)

i don't think they make a thicker tahitian shaft for his gun. :confused:

sven, what you need is this! :D
shaft speed

I'm still of the euro thinking of lighter shafts, more speed although the distances aren't great. Some of the problems I've had w/ heavy shafts and large heads were poor penatration on bony parts of fish. The last 6 grouper I've shot I was using a 48" arbalete w/2 bands. All were head shots at not extreme distance. None were pass throughs and all either stoned the fish or paralyed it. The drawback is at least half took two people to pull the shaft out of the fishes head. On all of them the tip of the barb wasn't even in the fish. The shaft just jammed in the bone. All of these fish were 15-20#. The brain pan is a hard place to punch through. You could also try a 7mm shaft. Thats between 5/16 and 1/4". Just my experience. Take it for whats its worth.
Nice Bible-action Jay. I oughta read more of that work one of these days.

I've gone the light shaft route before and really, REALLY regretted it when the halibut came around. When that happened, I was thinking of turning down a 1/2" piece of re-bar..
I also think, as you experienced that the mass of the heavier shaft did as much in stopping the fish as did the penetration. I was able to follow the shaft down and pin the things while I strung them. Hell, all I had to do was reach out with my left hand.

Yeah Anderson, I can see that .22 powered Rambo-ette strapped around my massive, uh, limb, terrified babe in torn wetsuit and windblown hair gtipping me tightly... (cold shower smilie-face). I get enough grief from my friends when I roll out in my camo suit. The bazooka would pretty much seal my doom. Years, and I mean years ago I tried a setup that took an air charge from a tank on your back, all 3000psi of it. The clowns in Louisiana just dug it for nuking the slugs down around the rigs. 'Course they've got serious problems even before they shoot being at 200' and inbred and all...


Thanks Sven,
Yea there's some pretty good things in The Book.
Hows the halibut shooting out there. I love to stick flounder out here, a 10#er gets me going. I can imagine what a 100-200# would do. My dad caught some in Alaska(rod/reel) and from the pics I could only imagine what something like that would look like U/W. Take care.
Yeah Jay, I'd love to stick a 200 pounder also, (now THERE'S a trigger for Anderson..rofl )but those are a different halibut altogether. Shooting something like that would be like pissing off a dinosaur. The halibut here, also Pacific halibut will run to 20-30 lbs and unless you nuke 'em in the head, be prepared for a real tussle and more often than not a tweaked shaft. But damn, talk about good eats!:t

Sven , when I am in need of cheering, I can always count on you to make me laugh! Thanks,
Erik Y.:)
no gracias neccesary

Abalone-solutely my pleasure, Eric. A little mature levity is a neccesary thing, no?

That, a little agreement with a Higher Power and some humility, and my day is off and running. I just wish it paid better. :confused: