Rubber band set-up on 75cm speargun

[Wisamz]

Hello spearos
I need your expertise with my gun setup, i got a 75cm yuma cressi speargun , brought a 6.5 shaft 105cm and am planning to use two 14mm rubber band, i just need your advice on the length of the band that i should get.
And how does this setup sounds to you ?

 

[Commander Coo1]

I would probably start with 19" and if its too easy to load/not enough power, cut an inch off one side and re-tie them.

 

[Brochman]

As above but it also depends on whether the band's you are using are progressive or reactive. Also using two 14mm might be too much power for a 75cm gun causing the gun to recoil more so you will miss your target. A singular 16mm band is the norm for a 75cm speargun helping for a smoother shot with less recoil so more accuracy.

 

[Wisamz]

As above but it also depends on whether the band's you are using are progressive or reactive. Also using two 14mm might be too much power for a 75cm gun causing the gun to recoil more so you will miss your target. A singular 16mm band is the norm for a 75cm speargun helping for a smoother shot with less recoil so more accuracy.

So how about a singular 18.5 mm ,
and what would be the ideal length for a 16mm or 18mm or 14mm ?
Could you tell me how is it calculated does the thickness of the rubber make a difference in the rubber length ?

 

[Brochman]

Here are the stats of the Cressi Yuma from the Cressi website https://cressi.es/en/2_fusil_yuma
Also here is a video explaining about different types of bands, band stretch and how to calculate the length of bands for a speargun

 

[Mr. X]

I have a 65cm speargun with 2x14mm and a 75cm speargun on which I've used various single rubbers. I think it has 16mm bulk rubber currently although most often it had 18-20mm bulk rubber; it came with 18 or 18.5mm screw in rubbers.

If you are new to spearing or the speargun, bulk 16mm is probably a good option to start with. As somebody else already suggested above. Going up to 18 or. 18.5 later if you feel the need and don't suffer loading.

A 75cm speargun is intended for fairly close range shots. If you need more range, consider a longer speargun. (I often switch between my 75 and my 90 these days).

 

[hteas]

The 105cm shaft may cause problems no matter which rubber you choose. I have a 60cm gun with a 90 cm shaft gun that shoots accurately, and a 90cm gun that needed a 130cm shaft. The 90cm gun was very noisy and inaccurate with a 120cm shaft. Changing to the longer shaft made an amazing difference. Your gun may need a 110 to 115cm shaft to keep away from the harmonic.
A 16mm band with a stretch ratio of 3.5 to 1 should be plenty for the gun. Measure the distance from the muzzle to the rear notch. Double that number because the band goes along both sides of the barrel. Divide that number by 3.5 to get the length of the unstretched band (knot to knot).