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Discussion Starter · #1 ·
Ok, so I thought of a potential flaw with certain attachment methods for latex tubes. When drawn back I think that extra air will accumulate in the tubes. You can tell that extra air is held in the tubes if you put your thumbs over both ends of a tube and stretch it. You will feel suction. If the wrong tying method is used, the tubes will have to force the air out as they retract back. I would think that this would slow the tubes down quite a bit, which would also slow down the projectile.

I think that the worst design is probably the commonly used (commercial) "fist" tying method. I think it is the worst because it allows the air to be drawn in slowly through the openings near the pouch, but does not allow a quick "exhale" of the air. This means that air pressure would build quickly in the tube as it retracts.

I think the best possible design are ones that completely seal off the tubes by tying. When you retract the tubes no new air would be pulled in. Another good method could be slipping the tubes over a small open ended metal pipe that could "breathe" freely.

I also suspect that this effect may be what caused many people to notice that their commercial slingshots seemed to shoot faster if they released immediately after drawing, instead of waiting and aiming.
 

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Well, I think that if you use the constriction knot, that is a pretty airtight binding. But I may be wrong here!

I think an underwater test is in order to see if indeed air is pressed out of te tubes when you release. If that should be the case, then indeed Aaron is right, the shot would be slower.
 

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I've considered that about tubes before too and that is why I decided to attach them like flat bands and getting rid of the factory "slip-through" knot at the pouch.
 

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Discussion Starter · #4 ·
I thought about this some more, and I think you would have to tie the pouch on AFTER the band is in place. If you don't you will pressurize the tubes as you slide them over the fork prongs. I did this last night on my Marksman/Kent combo and I wonder if that contributed to its power.
 

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I doubt it. When tubes are stretched the inner diameter usually shrinks as the tube elongates. Meaning the volume of air in the tube will be roughly the same. I would venture that the volume of space decreases more rapidly as the tube is stretched, and air is pressed out creating a slight vacuum as the bands contract when being fired.

I have yet to see a tube that does not shrink it's radius while being pulled.

Also, with underwater tests, be aware of cavitation creating false bubbles when you fire it. leading to incorrect speculation.
 

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Also you could try to remove the air inside the tube like a collapsed plastic straw if both ends are sealed off. But don't equate any extra gains on the removal of the air, you also change the structural geometry of the tube making it flatter. So any gains you might see are from the structural change and not the removal of the air. As the tube contracts it can fold easier.
 
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