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All About Guns What's your weapon of choice, and why? Discuss the beloved speargun here!

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Old 03-25-2016, 02:56 AM   #1
spearq8
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Optimal band choices for different shafts

More band power does not always translate to better shaft performance. I mentioned this many times but here you can see it in action. Light shafts will perform much better if you mate them to thinner bands and will have worse performance if you over power a setup already at terminal velocity. You can see that as you get more shaft mass, the shaft is able to absorb more band energy and will benefit from bigger band loads. So before loading your 7mm @ 150cm shaft with 3 x 16mm small ID bands thinking you have the ultimate power load ... take a look at this video.

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Old 03-25-2016, 07:20 AM   #2
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Re: Optimal band choices for different shafts

OK, OK, I'm listening; all 14.5 Primeline 1/16th.

http://spearboard.com/attachment.php...d=1458908378mm
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Old 03-25-2016, 12:23 PM   #3
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Re: Optimal band choices for different shafts

You should caliper check your bands to see what is your actual diameter. Primeline bands can really vary quite a bit. For light shaft I like the 13.6mm to 14.2mm and for middle mass shafts the stuff around 14.2 to 14.5 is great ... for heavy mass shafts ... the upper range of 14.5 to 15mm is great. Not everyone selling bands will throw a caliper on the batch and let you know the exact diameter. I like to keep batches in the lower end for light shaft and batches in the higher end heavier shafts. Jon Bailey from Spearitco will caliper the batch before sending it and I think he just got a big batch of new amber colored small ID 14mm selling for quite cheap. He did mention he would not carry the blue colored small ID bands as they cost a lot more and he did not think they are worth the extra cost.
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Old 03-25-2016, 01:40 PM   #4
brandon cadalzo
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Re: Optimal band choices for different shafts

What diameter shafts are we talking about here when you say light, middle and heavy mass shafts? Are both length and diameter a factor?
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Old 03-26-2016, 04:25 AM   #5
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Re: Optimal band choices for different shafts

I consider light shafts as being up to 7mm diameter @ 150cm and medium shafts at up 7.5mm @ 150cm and heavy shafts as being 8mm @ 160cm or heavier. Obviously this is just a ball park figure, but I find it very useful in choosing what band diameter would work best. I specifically look for batches of rubber at 13.6mm to 14.1mm for lighter shafts (6.5mm and 6.75mm). As you can see the 14mm bands work fantastic with the lighter shafts and is probably something that very few people know. In Europe 6mm and 6.5mm shafts are very popular and yet I always see those setup with a single 20mm band or double 17.5mm bands. No wonder a roller will outperform that setup. Put two 14mm bands and they will easily outperform the 17.5mm bands with those light shafts. My guess is that with 6.5mm shaft you should even drop to 13.5mm bands for better performance (although I have never tried it yet). This is the setup I used for the Sporasub 105 gun and if you look a that video you can see that it dramatically improves on a single 20mm band. Even Sporasub engineers where shocked when I sent them that video. Also the Pathos guns I bought came with 7mm shafts and 2 x 17.5mm bands ... you can easily improve performance by using the 14mm bands. 14mm bands are not a cure all though ... and once you get into heavier shafts you need to increase band diameter. Another thing is that the thinner bands don't handle high stretch very well and should be kept at 360% or 370% max ... thicker bands can use higher stretch.
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Old 03-26-2016, 05:25 AM   #6
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Re: Optimal band choices for different shafts

Cool to see proven in video, what many are doing already.
I have always wondered why many euro companies pair thin spears with those thick bands. Pathos and omer seem to be especially bad. I once had an omer with 6mm spear and 20mm screw-in band, that was terrible.
The south afrikaans have long learned to use 14mm bands with shafts up to 7.0 and 16mm with 7.5mm. More recently even 2x14mm rubbers with 7.5mm shafts on long bluewater guns.

Imho the first step in designing or setting up a speargun should be the choice of shaft diam and length, then maximize the band stretch for that shaft and choose number and diam of bands matching that shaft.
Then the rest just follows that setup.

Madj, jugding from the video it is hard to say, was there a big improvement from 7.0mm & 14mm compared to 8.0&14.5mm?
It almost seems that the thin shaft performs nearly as good as the thick one?
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Old 03-26-2016, 07:53 AM   #7
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Re: Optimal band choices for different shafts

how much overhang y used ?doescutting band at 380% is reducing the life of the band and difficult for loading ?

Last edited by doyenofcastle; 03-26-2016 at 08:07 AM.
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Old 03-26-2016, 11:41 AM   #8
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Re: Optimal band choices for different shafts

Quote:
Originally Posted by schwaman View Post
Cool to see proven in video, what many are doing already.
I have always wondered why many euro companies pair thin spears with those thick bands. Pathos and omer seem to be especially bad. I once had an omer with 6mm spear and 20mm screw-in band, that was terrible.
The south afrikaans have long learned to use 14mm bands with shafts up to 7.0 and 16mm with 7.5mm. More recently even 2x14mm rubbers with 7.5mm shafts on long bluewater guns.

Imho the first step in designing or setting up a speargun should be the choice of shaft diam and length, then maximize the band stretch for that shaft and choose number and diam of bands matching that shaft.
Then the rest just follows that setup.

Madj, jugding from the video it is hard to say, was there a big improvement from 7.0mm & 14mm compared to 8.0&14.5mm?
It almost seems that the thin shaft performs nearly as good as the thick one?

The 8mm @ 14.5mm is for sure a much more powerful setup. But 121cm of band stretch is 121cm of band stretch ... not really enough to give you large tuna power. I think you need a good 130cm of band stretch for 2 bands to give you tuna power. If you get the same penetration with both shafts, you have to realize that with the thicker shaft there is a lot more energy going into the fish. Also the Devotosub shafts are not recessed ... and while this makes the tip stronger, it also gives it a larger cross section which makes penetration more difficult. The Devotosub 8mm shaft has a cross section of about 12.5mm ... compared to the Hunt 8mm shaft which has a recessed flopper and only has a cross section of about 9.5mm.
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Old 03-26-2016, 02:01 PM   #9
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Re: Optimal band choices for different shafts

Spearq8 I would love to see you test a pathos 100
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Old 03-26-2016, 03:26 PM   #10
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Re: Optimal band choices for different shafts

Unfortunately I don't have a Pathos 100 ... but it should perform very close to how the Sporasub 105 performed. With 2 x 14mm @ 360% and a 7mm shaft ... would be an awesome setup up to 5 meters. Of course I would change out the sears and customize the handle.

As for 380% hurting the bands ... I don't think so. Some 14.5mm bands I can barely stretch them to 360% while others are easy to push to 380%. You sort of have to feel how it goes and then adjust accordingly.
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Old 03-27-2016, 03:46 AM   #11
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Re: Optimal band choices for different shafts

I just did some calculation you can check if their is a mistake ,but it seem 14.5 small Id/16mm regular Id have similar power,
I used 315% of 16.5 mm rubber more power and less effort to load ,I just order some 14.5mm small Id yesterday and I ll try them to my new build roller
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Old 03-27-2016, 04:26 AM   #12
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Re: Optimal band choices for different shafts

Quote:
Originally Posted by doyenofcastle View Post
I just did some calculation you can check if their is a mistake ,but it seem 14.5 small Id/16mm regular Id have similar power
This is all very general as 14mm small ID bands can vary from 13.6mm to 15.1mm. The tolerances when making bands are quite high and the only way to really measure what diameter bands you have is to hit a caliper on it.
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Old 03-27-2016, 04:33 AM   #13
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Re: Optimal band choices for different shafts

I always measure them but can't measure the shore unless I got one instrument to check the ductility
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Old 03-27-2016, 04:40 AM   #14
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Re: Optimal band choices for different shafts

http://www.aliexpress.com/item/Shore...5-07c4519164d9



if really interested to check accurately your rubber
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Old 03-27-2016, 11:23 AM   #15
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Re: Optimal band choices for different shafts

Quote:
Originally Posted by doyenofcastle View Post
http://www.aliexpress.com/item/Shore...5-07c4519164d9



if really interested to check accurately your rubber
I think it's imperative to always accurately check your rubber. You don't want problems on the fishing grounds
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