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Old 09-04-2019, 05:12 AM   #16
kavachi
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Re: Doggies - can an inverted roller really cut the mustard??

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Originally Posted by popgun pete View Post
Shaft energy is ˝ mass of projectile x velocity squared when the shaft hits the fish. Longer shaft has a greater surface area and more drag from “skin friction”, but not a lot in it. Mass increase is proportional to shaft length.
So given identical material and same tip, 150 x 9.5mm should provide a tad more penetration at the fish than a 170 x 8.5mm?
Albeit with some additional recoil in the bargain
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Old 09-04-2019, 05:36 AM   #17
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Re: Doggies - can an inverted roller really cut the mustard??

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Originally Posted by kavachi View Post
So given identical material and same tip, 150 x 9.5mm should provide a tad more penetration at the fish than a 170 x 8.5mm?
Albeit with some additional recoil in the bargain
Yeah, in your example I think the shorter shaft actually weighs just short of 10% more than the longer, thinner one. So, if we don't look at drag and if we make an allowance to say the speed would be the same, your shorter shaft would punch 10% harder.
Then again, I don't know how to calculate the difference in speed if the energy input is the same (same rubbers) while the shaft mass changes.

But I think what is also important in the formula Pete quoted is that speed matters more than mass (if I understand it correctly). If you can increase the speed by, say 20%, you gain more energy (impact punch) than if you increase the mass of the shaft by 20%. Maybe this can help explain why airguns and reverse guns still carry ooomp (if they indeed do shoot faster).

(I could be totally mistaken in all this...)
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Old 09-04-2019, 05:43 AM   #18
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Re: Doggies - can an inverted roller really cut the mustard??

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Originally Posted by Diving Gecko View Post
Yeah, in your example I think the shorter shaft actually weighs just short of 10% more than the longer, thinner one. So, if we don't look at drag and if we make an allowance to say the speed would be the same, your shorter shaft would punch 10% harder.
Then again, I don't know how to calculate the difference in speed if the energy input is the same (same rubbers) while the shaft mass changes.
But I think what is also important in the formula Pete quoted is that speed matters more than mass (if I understand it correctly). If you can increase the speed by, say 20%, you gain more energy (impact punch) than if you increase the mass of the shaft by 20%. Maybe this can help explain why airguns and reverse guns still carry ooomp (if they indeed do shoot faster).
(I could be totally mistaken in all this...)
Thanks DG!
I need to get hold of some of that thick foam Majd uses, and compare the two shafts
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Old 09-04-2019, 08:28 AM   #19
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Re: Doggies - can an inverted roller really cut the mustard??

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Originally Posted by kavachi View Post
So given identical material and same tip, 150 x 9.5mm should provide a tad more penetration at the fish than a 170 x 8.5mm?
Albeit with some additional recoil in the bargain
That calculation was easy for a longer shaft versus a shorter shaft of the same diameter. You can work it out for different diameters, but then you calculate the shaft volumes which we did not have to do before as the length was the only variable between them. The ratio of the diameters squared tells you how much heavier shafts of the same lengths are at different diameters. Hence a 9.5 mm is (9.5/8.5)^2 = 1.249 or 25% heavier than an 8.5 mm shaft.

150/170 is 0.882 so we multiply 1.249 x 0.882 =1.102 and that means there is about 10% difference in the shaft masses. Using the equation we had before v2 = v1 x sqrt 1.10 = v1 x 1.049 or 5% extra speed on the longer, but smaller diameter shaft for the same impact. Remember v is the downrange velocity, not the launch velocity. Tests have shown that heavy shafts hold speed better at longer distances and maintain more destructive capability while lighter shafts fly faster initially until they are overhauled by heavier shafts, provided the guns have the power to get them up to velocity initially. That is why many spearoes have used 3/8” shafts for decades, but it was either that or 5/16” as there was not much else to choose from.
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Old 09-04-2019, 11:10 PM   #20
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Re: Doggies - can an inverted roller really cut the mustard??

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Originally Posted by popgun pete View Post
That calculation was easy for a longer shaft versus a shorter shaft of the same diameter. You can work it out for different diameters, but then you calculate the shaft volumes which we did not have to do before as the length was the only variable between them. The ratio of the diameters squared tells you how much heavier shafts of the same lengths are at different diameters. Hence a 9.5 mm is (9.5/8.5)^2 = 1.249 or 25% heavier than an 8.5 mm shaft.
150/170 is 0.882 so we multiply 1.249 x 0.882 =1.102 and that means there is about 10% difference in the shaft masses. Using the equation we had before v2 = v1 x sqrt 1.10 = v1 x 1.049 or 5% extra speed on the longer, but smaller diameter shaft for the same impact. Remember v is the downrange velocity, not the launch velocity. Tests have shown that heavy shafts hold speed better at longer distances and maintain more destructive capability while lighter shafts fly faster initially until they are overhauled by heavier shafts, provided the guns have the power to get them up to velocity initially. That is why many spearoes have used 3/8” shafts for decades, but it was either that or 5/16” as there was not much else to choose from.
Thanks Pete!
Look forward to testing them out side by side, see if can retain that punch with the much shorter shaft.
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Old 10-08-2019, 03:26 PM   #21
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Re: Doggies - can an inverted roller really cut the mustard??

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Originally Posted by 2fishin2 View Post
I agree with everything Gecko said. Deeper dives in current. Not great places for large guns. Although I did shoot my largest DT 75kg with a 140

Although I do still have an Albacore 130, I have since "learned" to enjoy the benefits of the shorter inverted guns. I have a Roisub 115, Alemani 120 and Carbonia 115. Notice the shorter sizes I shoot 8.5 shafts on all of them and they can be configured with 9mm shafts.

These short guns have more stopping power and NO recoil. A real pleasure to shoot for sure. After shooting them, Ill never go back to long guns.
Not to derail this doggy thread, but how do you like the Carbonia 115?

I'm thinking about replacing one or both of my Bleutec Oceanborn's (125 and 145) with a roller. I have a Seal 80 double roller and love it for the reef. The more I shoot the standard guns I keep wishing I had a larger roller. I'm looking at Petar Pan, Alemanni, Carbonia, and Briante. They all have their pros and cons, so I'm trying to find guys with each to get their thoughts.

Thanks!
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Old 10-09-2019, 07:52 AM   #22
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Re: Doggies - can an inverted roller really cut the mustard??

Doggies - can inverter roller really cut the mustard?

According to my friend Paul, yes it can. This is 'just' 110 invert roller.
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Old 10-09-2019, 04:57 PM   #23
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Re: Doggies - can an inverted roller really cut the mustard??

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Originally Posted by gspearguns View Post
Doggies - can inverter roller really cut the mustard?

According to my friend Paul, yes it can. This is 'just' 110 invert roller.
They say the "proof is in the eating" and the guns can certainly deliver as shown here. Pity that the Doggies themselves are not better eating.

Here is a pretty good guide to Tuna with someone who thinks they are good to eat. Nice drawing!
https://www.sportfishingmag.com/tuna...strated-guide/

Last edited by popgun pete; 10-09-2019 at 10:55 PM.
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Old 12-09-2019, 08:06 AM   #24
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Re: Doggies - can an inverted roller really cut the mustard??

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Originally Posted by kavachi View Post
For me the double-offset-flopper shafts are just so much better for dogtooth

Having the whole shaft in the fish rather than just a slip tip makes a big difference in slowing that insane swimming power doggies possess.

I work bloody hard to get good holding shots on big dogs - have missed so many opportunities cos just wasnt quite close enough or couldnt see the head and shoulders and didnt take the shot. But inevitably I do end up with body shots sometimes, and the double offset floppers hold even when the doggie hits the end of the tuna board line and god knows how much shock load is on the gear. Have had sliptips rip thru doggies.

With a tuned-up Albacore and a close shot you can end up stringing a big dog, and in that case the whole shaft toggles like a giant sliptip, no way that is going to rip out. Downside is the shaft is going get seriously bent ; )

Lastly, no dicking around with setting sliptips whilst getting thrown around in rough weather
Sorry for still being daft on this matter
But I have been thinking about the double offset flopper shafts and still can't understand exactly why they are better?
The way I see it (right now) is that if the shaft penetrates far enough so that rear barb engages, then the front barb is not doing any work. And if only the front barb engages, having the rear barb does nothing at all.

I get the part about keeping the shaft full bore and not having recessed floppers, but is the only real advantage of double offset floppers, that you can rip off the rear barb and still have a chance of holding the fish with the front one - so, is it only about insurance...?

EDIT: Kept thinking about it and maybe it has to do with where on the shaft, the fish is held. If at the front flopper, the shaft works like any other good, single barb shaft, but if the fish is behind the rear barb, perhaps the fact that you have more shaft stickout in front of the barb makes it hold better?

Last edited by Diving Gecko; 12-09-2019 at 08:17 AM.
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Old 12-09-2019, 02:34 PM   #25
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Re: Doggies - can an inverted roller really cut the mustard??

If the barbs are opened as they pull back through the fish body without the tip going right through then they will hold over a greater area. Same as double flopper tips that swivel on the same pin, which is what I use. The kicked up ends on the barbs or floppers travel rearwards through the meat and spread like a grappling hook, although against bone it is not so easy to open up, but then the other side flopper can open. Some tips have three floppers, such as the Sampson tip.
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Old 12-13-2019, 01:11 AM   #26
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Re: Doggies - can an inverted roller really cut the mustard??

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Originally Posted by Diving Gecko View Post
Sorry for still being daft on this matter
But I have been thinking about the double offset flopper shafts and still can't understand exactly why they are better?
The way I see it (right now) is that if the shaft penetrates far enough so that rear barb engages, then the front barb is not doing any work. And if only the front barb engages, having the rear barb does nothing at all.

I get the part about keeping the shaft full bore and not having recessed floppers, but is the only real advantage of double offset floppers, that you can rip off the rear barb and still have a chance of holding the fish with the front one - so, is it only about insurance...?

EDIT: Kept thinking about it and maybe it has to do with where on the shaft, the fish is held. If at the front flopper, the shaft works like any other good, single barb shaft, but if the fish is behind the rear barb, perhaps the fact that you have more shaft stickout in front of the barb makes it hold better?

I think the idea of a second flopper is simply to add insurance. A large Dogtooth Tuna WILL break any flopper. I know this was a big problem and and Hunt tried many changes to deal with this issue. With normal SS hammered pins, the pins would shear off. They then tried welding the pins and the welding process would somehow harden the pin and they would break off. The best system now is a combination of using the correct pin (which does not get brittle with welding) and use both welding and hammering. Also using a cone placed correctly can support the flopper when it opens 90 degrees as the cone acts like a buttress for the flopper and dramatically strengthens it.

Using a conventional double flopper means you have to reduce the thickness of the tip of the shaft ... so basically after one fish the shaft is toast. Even smallish fish or a hit on a reef can bend those thin tips ... so not a good idea. With staggered floppers you have a full bore shaft with an extra flopper in case the first one breaks. Big dogtooth are incredibly strong fish ... and if you don't stone them they really will push your gear to breaking point. Also the fact that they like to go deep into a reef where sharks will shred them or they can get tangled deep where it is impossible to get them untangled without scuba gear. Usually you try and force them in shallow water to avoid them going deep by using a big shallow first float, or just man handling them ... this puts tremendous stess on your gear. I can't think of another fish that puts that much stress on your terminal tackle ... not only strength wise ... but also due to its habitat and how you have to use force to keep it from going deep. By far the most effective way to catch and land big dogtooth is to get a good first shot and try and stone it.
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Old 12-13-2019, 01:56 AM   #27
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Re: Doggies - can an inverted roller really cut the mustard??

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Originally Posted by spearq8 View Post
Using a conventional double flopper means you have to reduce the thickness of the tip of the shaft ... so basically after one fish the shaft is toast. Even smallish fish or a hit on a reef can bend those thin tips ... so not a good idea. With staggered floppers you have a full bore shaft with an extra flopper in case the first one breaks.
Not if you are using screw on tips with say a four blade head where the twin floppers ride in the wake or slipstream shadow of the head, such as the old "Mako" heads from Undersee. The problem with screw on tips was that they often did not screw on straight with respect to the shaft axis, but this was the consequence of when to cheapen their manufacture the aligning step was left out. Originally you had a step on the shaft, then another step to the base of the male screw thread which is the thread peak diameter. When the tip screwed on a matching step inside it contacted the aligning step and the tip was on axis with the shaft even if the connecting thread had been slightly out of alignment when it was cut. You sometimes had shafts with 1/4" N.F. thread, a 5/16" aligning step and the shaft diameter at 3/8". In fact I have still got one, but later threads were cut at 5/16" on the 3/8" shafts, thus only one step.
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Old 12-13-2019, 03:04 AM   #28
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Doggies - can an inverted roller really cut the mustard??

Quote:
Originally Posted by spearq8 View Post
I think the idea of a second flopper is simply to add insurance. A large Dogtooth Tuna WILL break any flopper. I know this was a big problem and and Hunt tried many changes to deal with this issue. With normal SS hammered pins, the pins would shear off. They then tried welding the pins and the welding process would somehow harden the pin and they would break off. The best system now is a combination of using the correct pin (which does not get brittle with welding) and use both welding and hammering. Also using a cone placed correctly can support the flopper when it opens 90 degrees as the cone acts like a buttress for the flopper and dramatically strengthens it.

Using a conventional double flopper means you have to reduce the thickness of the tip of the shaft ... so basically after one fish the shaft is toast. Even smallish fish or a hit on a reef can bend those thin tips ... so not a good idea. With staggered floppers you have a full bore shaft with an extra flopper in case the first one breaks. Big dogtooth are incredibly strong fish ... and if you don't stone them they really will push your gear to breaking point. Also the fact that they like to go deep into a reef where sharks will shred them or they can get tangled deep where it is impossible to get them untangled without scuba gear. Usually you try and force them in shallow water to avoid them going deep by using a big shallow first float, or just man handling them ... this puts tremendous stess on your gear. I can't think of another fish that puts that much stress on your terminal tackle ... not only strength wise ... but also due to its habitat and how you have to use force to keep it from going deep. By far the most effective way to catch and land big dogtooth is to get a good first shot and try and stone it.


Thanks for weighing in:-)
I am thinking there might be small advantage in having the fish behind the rear barb - you’ll have the tip of the shaft further out on the “other side” so it can’t cut up the fish and enlarge the exit hole. (Though I don’t know if that’s a real risk on single barb shafts).

In regards to the flopper resting against the rear flange of the cone, I guess thats why Hunt are tack welding the cones in place now.

As for the man-handling, on our latest trip we had a freediver with us who was still new to spearing so while she was confident pulling the trigger on smaller guns on smaller fish in the shallows, she understandably was not yet confident doing the same on a doggie. But she was in the water with us and my friend and her developed a really interesting system where she would stay at the float and if he took a shot she would put pressure on the fish immediately. Then when he surfaced, they would both fight the floatline together. I think this is the main reason he didn’t loose his shaft as he was rigged with mono (I’ll hook him up with stiff dyneema for our upcoming trip). But I think this could be a good thing to incorporate between buddies. It was easy for her as she didn’t have a loaded gun with her when we dove the doggie spots, though.
I’m sure others are doing this already but jut wanted to float the idea here, too:-)


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Last edited by Diving Gecko; 12-13-2019 at 10:34 AM.
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