Have any of you measured your spearguns 'stretch ratio', and how did you do it.?
I came up with a method but don't know if it is the same as used by others. The type of gun which was measured uses a continuous loop, not screw in plugs.
I measured the overall length of the loop and subtracted the wishbone length. IOW, the length of the rubber between tie-offs was measured. Thus, a rubber band which has 26" overall length has an effective length of 24". I measured the length of pull on the gun less the wishbone length. Thus, a gun with 42 inch nominal pull has an actual pull of 39 inches when the pull is measured between the muzzle and the rubber's tie offs. This number, 39 inches, was multiplied by two. One inch was added to account for muzzle width. The resulting number, 79 inches, was divided by 24, the effective rubber length. The quotient was 3.3 which looks to be the correct number for the stretch ratio.
The gun is the Biller 'Carribean' mentioned in the previous thread. The bands are Riffe rubber, 5/8.
I came up with a method but don't know if it is the same as used by others. The type of gun which was measured uses a continuous loop, not screw in plugs.
I measured the overall length of the loop and subtracted the wishbone length. IOW, the length of the rubber between tie-offs was measured. Thus, a rubber band which has 26" overall length has an effective length of 24". I measured the length of pull on the gun less the wishbone length. Thus, a gun with 42 inch nominal pull has an actual pull of 39 inches when the pull is measured between the muzzle and the rubber's tie offs. This number, 39 inches, was multiplied by two. One inch was added to account for muzzle width. The resulting number, 79 inches, was divided by 24, the effective rubber length. The quotient was 3.3 which looks to be the correct number for the stretch ratio.
The gun is the Biller 'Carribean' mentioned in the previous thread. The bands are Riffe rubber, 5/8.
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