Sir, lower rubber should be stretched ( pretensioned ) to certain lenght ( depending on thickness and length of upper rubber ) and then you should tie dyneema on it ... in perfect circumstances , when gun is loaded both rubbers should be extended to their optimal lenght ( in most cases it"s around 3x ( or 300%) of the original lenght ) ... The most simple setup is with two same rubbers ( same type and thickness ) , then you cut them to the same length (slightly less than 1/3 of the gun length from arrow pin to gun muzzle) then pretension lower rubber at (let's say) 2x ( or 200%) and then tie dyneema ! This way when gun is loaded you will have both rubbers stretched to the optimal length (300%) through the whole length of speargun, and you will have almost no recoil !
![Presentazione Shark System [RoiSub]](http://i.ytimg.com/vi/o6hiL03vmeU/mqdefault.jpg)
Sir, lower rubber should be stretched ( pretensioned ) to certain lenght ( depending on thickness and length of upper rubber ) and then you should tie dyneema on it ... in perfect circumstances , when gun is loaded both rubbers should be extended to their optimal lenght ( in most cases it"s around 3x ( or 300%) of the original lenght ) ... The most simple setup is with two same rubbers ( same type and thickness ) , then you cut them to the same length (slightly less than 1/3 of the gun length from arrow pin to gun muzzle) then pretension lower rubber at (let's say) 2x ( or 200%) and then tie dyneema ! This way when gun is loaded you will have both rubbers stretched to the optimal length (300%) through the whole length of speargun, and you will have almost no recoil !
Exactly, very good remark ,and what about the shorter upper rubbers , how long they should be compared to the lower ones ?
Scusa il pretenzionamento non lo calcoli???????????
Scusa il pretenzionamento?????????
Dyneema 2mm !!