Making a 1 band gun better

I think that a tab midway along the length of the shaft should work, as many people already have a rest tab set up like that. I think that a notch, however would not be a good idea. You would significantly weaken the shaft. Shaft whip could be a problem with open tracks and thin shafts. Even on thicker shafts, the mid-span notch would make the shaft much more likely to bend on a holed up fish, I think.

I have no problem with the conventional multi band set up. I agree with everything Jeff said. There's not much sideways force acting on the back of the shaft where the notches normally are. The middle of the shaft is another story. You'd have to go with tabs. Rest tabs have been done before. Not a big deal doing this to a stainless steel shaft. Also possible on an RA shaft. See this thread http://spearfishing.world/spea…e-with-american-guns.html

You cant calculate it by inches because the band length is a factor. Pulling 4 inches on a 20inch band is not the same as pulling 4 inches on a 5 inch band.

Say one side of 20mm band is 12 inches and you pull 24 inches past that, that equals 200%, ~130lbs and a total length from tab to band hole of 36 inches. Add 4 inches to next tab that equals 28/12= 233%, ~140lbs and so on.

We usually load bands to 250% elongation.
Elongation is deformation / original length. Deformation =stretched length - original length.

This chart is provided by primeline industries rubber. I modified it to suit speargun rubber which has 2 sides. Different manufacturers will vary.

The energy of the cocked band, if I remember correctly, is directly proportional to length (given equal %elongation)..

Quote from hau

Is it possible for a spearo to cock say 1 bigger band to equal the power of 2 smaller bands?

How about a Roller Gun?

hau, the first thought is that the more rubber is being stretched the more power you get. So you measure how much rubber is in a 20mm rubber section and compare it to the amount of rubber in two 16mm sections. Obviously two 16mm sections have more rubber material than a 20mm but it doesn't end there IMO. I believe that at a certain point another effect comes into play but I don't know how to explain it. When I shot a 20mm band together with a 16mm band I felt the 20mm to have too much pop. The cloud of bubbles was bigger and the gun jumped more. I get this idea that at a certain point the bigger the band is the more it negates some of its own power, maybe due to more surface area and more water resistance? IDK but it just didn't feel right.

I came away with the conclusion that whenever possible it's better to use multiple bands to achieve the required power. Never mind that two 16mm bands obviously have more power than one 20mm. Later there was a post on SB where the matter was approached scientifically and it was demonstrated that the power increase of the 20mm was less than what would be expected solely based on the increase in rubber material. There was a sliding scale where another factor came into play and negated the advantage of the bigger rubber. Sorry I can't be more specific. All I know is that I don't like those bands and sold all the bulk 20mm rubber I had.

There is a limit of the power you´ll get stretching a band. The top is around 3 or 3.5 X the lenght of the band, any less and is underpowered, any more and the band will not have any more power and will be stressed. I would prefer 1 thick band instead of two in an euro gun. Cause having too much power in a light rig kindda defeat the very porpuse of the Euros, accuracy and simplicity. If you want to go multiband, then a wooden-heavier gun is a must.