Selecting Speargun Rubber:
No topic in spearfishing circles creates more controversy and heated debate than speargun rubber. At Sumora, we don’t pretend to have all the answers, but we have scoured the planet to find the best rubber available, and we are on a continual mission to find the best rubber out there. Our search is never ending, so we would like to hear from you if you have come across any special rubber recipes that you can recommend, want us to test, or want us to sell.
Currently we supply our guns with After Burner Rubber, and depending on the muzzle configuration, this rubber comes in with either 16 mm or 20 mm diameters.
Please click on these links to see the correct rubber configurations for your gun length:
Refer to our Tips & Advice section for instructions on how to tie your own bands.
We have selected After Burner Rubber because it offers high tensile strength, high elongation, high modulus, and because it is UV treated reasonable aging endurance, so we are confident that it will give you “good bang for your buck.” If you need to purchase additional rubber bands, you can purchase these here. We also offer pre-made bands that can be easily slipped into Rabitech's new Open Muzzle. Or, Email us and let us know your gun size and we can prepare the appropriate rubbers for you.
Rubber Performance:
There are numerous factors that effect rubber performance, but these can be distilled into two important readings of relevance for Spearfishermen.
Consider the following "testing setup" from the maker of the SuperGun, who clearly takes the science of spearfishing very very seriously.
From the system there are two readings of importance, the first is the length of the rubber, which is the distance it has been stretched, the second is the reading on the scale. From this you will be able to get a force reading for the distance of stretch your gun has. This system enables you to test the strength the rubber at various stretch lengths. You can then determine the poundage or power of the system for your particularly set-up.
So what do these readings tell you?
Initial Tension is the rated power of a band at a certain percentage elongation, and this is usually measured in pounds. So if you take your 20 inch long band, and stretch it to 60 inches, the band will provide a resulting pulling on the spear of approximately 100 pounds. You can then calculate if you have 3 of these bands, that the “power” of your speargun is approximately 300 pounds, for example.
However, initial tension is variable, and changes over time because the rubber loses its ability to contract the longer the time period it is stretched for. So what is done is known as a “soak down” test. In this test, the band is tensioned to a predefined elongation, usually, 200% (3 times its resting length), and then readings are taken on the scale at time intervals. The pressure the rubber exerts on the scale falls off over time, with the result that if you leave the rubber stretched for as long as an hour, the power of the gun will fall off. The greater the elongation, the more rapidly the performance falls off.
The elastic limit is the point at which you can continue to stretch the rubber, but the poundage reading on the scale is not increasing. At this point the elastic limit of the material has been reached and it is close to breaking. Clearly no power is added to the system once the rubber is stretched past this point.
The Perfect Rubber:
The net result of all of this is that the perfect rubber will have the following qualities. It will have a high initial tension, and have a low soak down value, so that it provides repeatable and reliable performance, time and time again.
Sumora does NOT recommend you do your own rubber tests because it can be a dangerous process, particularly when testing the rubber to failure. However, if you are interested in making a setup, the device used to provide the tension to the rubber is a “standard fence strainer,” available at most hardware stores, and you can read additional technical information on speargun rubber on our “An Ode to Speargun Rubber Page.”
