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Inverted Speargun accuracy problem

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Back2Narnia

Member
Jun 9, 2019
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Hi spearfishing community!
I recently returned from my spearfishing trip and had plenty of time in the blue. Unfortunately i had some accuracy problems with my inveted roller speargun.
After reviewing the footage i took i can see why my accuracy was way off sometimes. Sadly i couldnt find a solution for this problem.

The shaft seems to lift in its track what is causing the shaft to fly randomly to the left, right, high and low (may not be a problem with bigger fish as it is not as drastic)
Do you guys have an idea what is causing this problem? I would be happy for any thoughts on this.




1.png
2.png
 
C4 roller-speargun? Nice :)

Is it open or closed muzzle? The spear line looks to be all over the place but perhaps that is normal? Is the spearline loop that is attached to the spear over-large/stiff?

Is the spear, roller muzzle and bands original equipment provided by the manufacturer when you bought it? E.g. any non-originsl equipment? I wondered if the spear might be too slim for the amount of power provided, causing it to flex and buck?


Somebody claimed in a recent thread that rollerguns always shoot a bit low (or was it high?). Not sure if that is true nor why that might be. However the problem you describe sounds different to that, less systemic/more random in direction.
 
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Does not look like a C4 from the top of the mech and the butt. Uneven band pull side to side can move the shaft off line, especially in the lower band battery underneath the gun. Alemanni use those window rollers to wrap one band set top and bottom of the gun to keep their stretch factor down and give them a longer life.
vela 135 3 views XX.jpg

Shooting line snags can cause problems if the line gets caught up on something. However here the spear has not even got out of the gun. No bends in the spear I suppose, but always worth a check.
 
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In fact this is a Alemanni Stilo express Carbon 100 special. The rollers in the front are Alemannis and for the band group i used an Ermes Sub "Bozzello Hard 7"...similar to Alemannis solution.
The muzzle is open and sadly i couldnt think of a different way of rigging the shooting line so it would look any better whilst fired.

My suspicion is also uneven band pull side to side but i cant think of a way to resolve this issue. All the bands are the same length with the inserts beeing also symmetrical. Any ideas how to fix this? It is driving me insane.

Also i noticed that this problem occures more frequent when tracking the fish...so side to side movement of the gun itself. Could this also be the reason for the inconsistent shoot groupings?

I used various shaft diameters ranging from 7mm to 8.5mm and all (more or less) had the same problem.
 
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Are all the pulleys spinning equally freely?

Are you using a Dyneema wishbone? If so are the spear notches (or sharkfin) nice and smooth and polished? Might the Dyneema be a bit thick e.g 2mm rather than 1.9mm, such that it is binding or sticking it the spear's notch

In this case, having an open muzzle at least means the spear line loop is not catching in the muzzle, which happened to me once.
 
You will need a process of elimination to find the causal factor. One way to eliminate the shooting line is to fire the gun without any attached line to the spear. A test shot with no fish involved of course. Side to side band pull unevenness will be revealed by the spear being pulled to one side in the cocked gun before you shoot. Are you using the original bands or a replacement set? As there are holes in the sear box roof then you may be able to see the shaft tail leaning on one side of the sear box. To check the bands remove them and flip them over so that the right hand band becomes the left and vice versa and see if the shot pulls the opposite way.
Alemanni Carbon Stilo Express.jpg
 
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In the Stilo Express the stretch limited front band set are in a sense stretching wishbones which when drawn back for the shot are thin strands on the top deck, as compared with the fatter bands that are always underneath the gun. As side to side the band sets are connected around the rear anchors they need to be able to equalize by the cords/or band slipping on the anchor curves which are drum sections. Theoretically that equalizes the pull.
Alemanni rear anchors.jpg
 
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These look to be carbon wrapped over timber. Its tricky to get the carbon to play nicely over a tight radius & It looks like that track may have been compromised to accomodate the carbon fiber wrap, rather than control the spear in use.
When the spear is loaded it should push slightly down into the track or rail. If it is pushing up or not supported by the rail, this is just as bad as pushing left or right. Before a gun builder thinks about anything else, it is critical in the build that the spear pushes down into the track or rail when loaded & continuing as it is being fired.
Is the spear pushing down into the track when it is loaded? Can you tap down on the spear when it is loaded & hear it tap against the rail? If the spear isnt pushing into the rail it could bend in any of the 360 degrees when fired with the resulting loss of accuracy. If it pushes down on the track, it should do this every time & the track should control this & accuracy is the best. If this isnt the problem then look for something else, but this is a common problem & a good place to start.
 
Theoretically the adjustment of the tapes should work identical to the original solution of Alemanni because the fixing is the same.
The rollers at the front rotate almost identically, only the right one doesn't rotate as smoothly as the left one. That's why I also suspect that the side to side pull is off. Only solution for this that i can think of is buying new bearings.
The shaft in the mechanism is also perfectly straight on top when tension is applied.

Regarding the rail on which the shaft should lie I'm not so sure. the shaft lies on two points and the rest is floating in the air. But I think that this is a desired feature of Alemanni to reduce friction.

I've attached some pictures that clearly show how the setup looks like.
I could add an extra rail or even an enclosed track...but I'm not sure if this would solve my problem 100%.

The setup of the pictures is for a 7,5m shaft...what you can't see on the photos is that there is also an additional kicker band.

20190921_103024.jpg
20190921_103125.jpg
20190921_102855.jpg
20190921_102820.jpg


20190921_102944.jpg
m shaft and
 
Where are your outer rollers?
Stilo Express roller muzzle.jpg

stilo express roller.jpg

I have "added" them here. Looks like you have converted your gun to a band battery inverted rollergun, originally this gun was a double rollergun.
I think that you should recheck your bands as they ain't the original set up even though you have replicated the bands that Alemanni use on their inverted rollerguns.
 
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Yes, i converted it to an inverted roller. I think this system should in theory work better than a normal roller. But thats just my opinion.
I removed the other 2 rollers to attach the "inverter line", with this setup you dont need 4 rollers anyway.

What do you think i should change about the bands?
Also Alemanni is currently working on a hybrid version of this double roller that uses a standard roller plus an inverted setup like my gun.
They also confirmed that my system should in theory work.

I could of course just go back to the og setup with the double roller and Alemanni Bands (200€ for a set though) but i would prefere an inverted setup.
 
Check the bands as I said. It is a couple of minutes work to swap the bands from side to side and see how it then shoots. Everything depends on stretch being equal, i.e. the force on each side, and that may not mean the lengths are equal, although it should. When a spear pulls off line before getting out of the gun the band pull is uneven. I have been there, so I know what I am talking about.
 
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Yes, i converted it to an inverted roller. I think this system should in theory work better than a normal roller. But thats just my opinion.

Just to ask the obvious question & I'm sure many others are thinking the same. Did it shoot ok before you "converted" it?
 
Alright, for my next trip i am goging to buy new bearings and change out the bands. I will change everything step by step so that i can see what change will bring the desired result. Sadly i cant just go and do it now because i dont live near the sea (dont have a pool either)...that is the reason why i started this thread.

Yes the gun did shoot okay as a double roller (as expected from a gun with this pricetag). But i dont really like the cluttered look of all the bands on top of the gun when loaded.
 
Although I don’t think the muzzle rollers shape would have an effect, the Alemanni cord only muzzle rollers are narrower and larger in diameter. You are using the band rollers in the muzzle. If the cable/cord rides up on the rim of that roller it may snag on the nip of the frame, however then it could grab on either side rather than one.
X2 muzzle rollers.jpg
Travel Pro Vela 120 muzzle.jpg
 
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Yes the rollers of the "demultiplied" guns from Alemanni are a bit bigger. I have a bigger pair around that i already tried. Its quit a tight fit though and i dont think the roller line gets stuck on the smaller rollers...i think you would notice this right away if it happend.

Also look at this other screenshot of a spear-nodle. This is a 75cm double rubber speargun with a 7mm shaft tracking a fish right to left.
I still wonder if side to side tracking whilst shooting is leading to this mess.

vlcsnap-2019-09-23-12h08m09s214.png


On the other hand if i shoot my Alemanni stationary without any side to side movement involved it shoots perfectly straight (as it appears)

vlcsnap-2019-09-23-12h19m15s630.png

(Dead center hit on this target)
 
The bend in the spear is more alarming in that top photo. If traversing the gun does that to a gun then I would be surprised as many shots are taken on a swing, although personally I prefer the fish to swim through the shot by anticipating or waiting on its moves. The bunching of the wishbones looks ominous, something seems not right there. These may be artefacts of the image taking process as the gun seems strangely bent.
 
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Funny enough the first picture was actually a hit. I think the spear isnt leaving the gun fast enough to a point where diagonal movement dosnt affect the flight path (like on a handgun i.e.) so any movement whilst the shoot is going off will heavily impact accuracy.

Both of the guns seem to shoot great when you do not track the fish...but thats rather rare with small fish we have in the med. :( skittish little shits.
So the secret is to learn the flightpath of the shaft while tracking and while stationary...
 
Well I have shot plenty of fish for decades and never noticed that effect. Shutter motion can make things appear to bend in still images, but that was on blade shutter film cameras, not digital cameras, although it should depend on the frame rate of the camera.
fish shot adjjpg.jpg

You can see the distortions in this image.
fish shot align.jpg
 
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