How to Calculate Band Length

With the shaft in the speargun, measure the distance from the front notch or fin to the rear of the band eye as illustrated below.


Multiply this dimension by 2/3 (0.66). The result is the band length that will yield an optimum 200% stretch to 3 times it's starting length.

You may encounter differing opinions about the exact ratio to use. Some people prefer a shorter band/higher ratio. This results in more power and a slightly longer stroke but also shortens band life and may make the bands difficult to reach on longer spearguns. On the other hand a smaller Spearo may opt for a longer band of greater diameter to make the bands easier to reach. The 3 to 1 ratio we use approximates that of bands specified by most OEM's. We prefer adjusting power by changing the number and diameter of bands while maintaining the 3 to 1 length.

If you would like more technical information on the power of different band diameters, take a look at the Band Power page in the Reference section of our site.

Back to blog

Leave a comment

Please note, comments need to be approved before they are published.