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Mixing different band thickness on the same gun.

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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Kodama

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Jun 20, 2016
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On several occasions, especially on the Italian forums i have read about spearos combining different band thickness on the same gun.
Especially with carbon guns like those of C4 this seems fashionable.

Does anyone have experience with this? I am interested in the philosophy behind it and even more so in any number if they are available.

For example i see 16 and 14mm bands combined on a 94cm gun.

Your thoughts?
 
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Leander

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Oct 17, 2017
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fashionable
This.

Every manufacturer boasts about the 'research' going into their guns/fins/suits/etc, but in reality there's not really much research being done except for the few cracks on the different forums who like tinker with their stuff.

Perhaps by 'research' they mean using Google. :)
 

mariusshobo

Well-Known Member
Sep 22, 2013
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I see no problem doing that.
But keep the thicker band closer to the shaft - if you are using dyneema wishbones; if using steel ones with different sizes that arranges bands parallel, does not matter).

As for theory (mine, at least, form the depths of my economist brain :))), there is an example:
- a pipe speargun with a single hole to insert the two bands, so the bands rubs against each other when loaded;
- dyneema wishbones;
- two bands from the same range / manufacturer : 16mm and 14mm (the 16mm one is obviously thicker and stronger);
- same stretch factor for both bands;
- loading the bands on the same shark fin;

If the 14mm is closer to the shaft, the 16mm will push against the 14mm and tend to raise it, inducing an upward force that can ruin accuracy.
When the gun is fired; the 16mil will push against the 14mil band and tend to crush it against the shaft. Not good.

Any other thoughts?
 
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Leander

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Oct 17, 2017
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But why would you mix them? The most valid reason I see is if you need to rig a gun double banded, but only have a little of both diameters left, and the stores are closed because of corona.

Of course you could mix them to go inbetween double-14 and double-16, but keep-it-simple gets you more fish.
 

mariusshobo

Well-Known Member
Sep 22, 2013
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What do you mean by "closer to the shaft"? Do you mean to keep the thicker band closer to the tube and the thinner band furthest out on the muzzle?
I mean the first band that is loaded.
bands.jpg
 

Kodama

Well-Known Member
Jun 20, 2016
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I see no problem doing that.
But keep the thicker band closer to the shaft - if you are using dyneema wishbones; if using steel ones with different sizes that arranges bands parallel, does not matter).

As for theory (mine, at least, form the depths of my economist brain :))), there is an example:
- a pipe speargun with a single hole to insert the two bands, so the bands rubs against each other when loaded;
- dyneema wishbones;
- two bands from the same range / manufacturer : 16mm and 14mm (the 16mm one is obviously thicker and stronger);
- same stretch factor for both bands;
- loading the bands on the same shark fin;

If the 14mm is closer to the shaft, the 16mm will push against the 14mm and tend to raise it, inducing an upward force that can ruin accuracy.
When the gun is fired; the 16mil will push against the 14mil band and tend to crush it against the shaft. Not good.

Any other thoughts?

That is an interesting line of thought.
Anyway it has to do with performance in That some users seem to prefer such a setup.

2c0551950835ae0e4582c18d25ce78ed.jpg
 

popgun pete

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Jul 30, 2008
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Planet Dive Store has the new 105 - 110 cm C4 Carbon "Gladius" models with 6.75 mm tabbed shafts and a 16 mm and a 14 mm band. The 85 - 95 models have a 6.5 mm tabbed shaft and one 16 mm band.
 
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Kodama

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Jun 20, 2016
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Planet Dive Store has the new 105 - 110 cm C4 Carbon "Gladius" models with 6.75 mm tabbed shafts and a 16 mm and a 14 mm band. The 85 - 95 models have a 6.5 mm tabbed shaft and one 16 mm band.

I first noticed this setup on the spec sheets and afterwards learned more spearos do so on older models too.

My main concern would be a potential difference in retracting ratio causing the setup to be inefficient where one band is doing all the work and the other Almost nothing.
There must be a rational (and hopefully some sound physics) behind it that i would love to understand.
And only having access to a pool for test shooting once in a while i don’t feel like doing time consuming experiments.
 
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mariusshobo

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Sep 22, 2013
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1 band 16mil + 1 band 14mil will pull harder then a single 16mil band. So the theory that the 16mil band will do all the work do not stand IMO.
 

popgun pete

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Jul 30, 2008
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The effect of bands is cumulative, if you want to test this then try pulling both bands back at once. The use of different band diameters is to provide more energy without going as far as 2 times the larger size band.
 
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Kodama

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Jun 20, 2016
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The effect of bands is cumulative, if you want to test this then try pulling both bands back at once. The use of different band diameters is to provide more energy without going as far as 2 times the larger size band.

So then one band just provides less force. If it is that simple why not adjust the bandstretch instead?
Use the same band thickness set one on 320% and the other on 280% and call it a day. There must be more to it i would think.
 
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popgun pete

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Jul 30, 2008
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So then one band just provides less force. If it is that simple why not adjust the bandstretch instead?
Use the same band thickness set one on 320% and the other on 280% and call it a day. There must be more to it i would think.
No, there isn't.
 

mariusshobo

Well-Known Member
Sep 22, 2013
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set one on 320% and the other on 280% and call it a day.
There is this factor - 3.4 I think, no 100% sure - and stretching bands after that will not translate in increased shaft velocity anymore.
So, if you need faster shaft, stretch the bands more. But once both bands hit the stretch factor, it is senseless to do it over that.
You need more power, that means another band or a thicker band.
 

Kodama

Well-Known Member
Jun 20, 2016
436
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Check at 7:25.
“C4 decided to do this must have a good reason for it”......

Do they?


 

Kodama

Well-Known Member
Jun 20, 2016
436
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There is this factor - 3.4 I think, no 100% sure - and stretching bands after that will not translate in increased shaft velocity anymore.
So, if you need faster shaft, stretch the bands more. But once both bands hit the stretch factor, it is senseless to do it over that.
You need more power, that means another band or a thicker band.

You could stretch bands further. However it is rather a question off wether you can somehow comfortably load them.
At a certain point you need to increase the diameter of the shaft to handle the increased force applied.
 

mariusshobo

Well-Known Member
Sep 22, 2013
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If the 14mm is closer to the shaft, the 16mm will push against the 14mm and tend to raise it, inducing an upward force that can ruin accuracy.
When the gun is fired; the 16mil will push against the 14mil band and tend to crush it against the shaft. Not good.

I've quote myself and challenge my theory.
Here is a screen shot with ARCUS G speargun, where the bands are stashed in top of one another. The fisherman is George Vasiliou (World Champion 2016).
And the way he twist his wrist during shot is in total contradiction with what I know and do, but he is doing just fine.
arcus g.jpg


full vid here
 
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popgun pete

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Jul 30, 2008
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Good shooting at around 40 m down, all fish hit in about the same place, just back of the head as they turn. Curiosity is their undoing. Knowing exactly how your shaft flies lets you pull off the same shot time after time.
 
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