hydrodynamic shaft principle

[fishimani]

I was walking around at work today and had a thought.... since rifles have increased range and accuracy by means of a rifled barrel which spins the bullet, can the same principle be applied to a pneumatic gun? I am aware that it seems unlikely to "spin" a floppered shaft out of a band powered gun and you wouldn't want to because i am guessing that good accuracy would be impossible. Has this thought been brought up yet? Has anyone tried a fully (and i mean fully) enclosed rifled track? I hope i don't sound to idiotic to bring this up. I was under the assumption that aerodynamic and hydrodynamic principles are similar.... any thoughts????

-Pete

 

[DivingDane]

how would you propel a spear in a rubber gun with a fully enclosed, rifled track? no way to attach the rubbers to the shaft.

Second issue i could see is that when a shaft is spinning the centrifical force would cause the flopper to spin open placing uneven wait in different direction which i think would cause the shaft to go topsy tervy. kinda like throughing a football with weight on one side.

like your thinking and if shafts did not have floppers as in target shooting speargun this could work very well.

other issue i just though of would be that if the line is attached to the end of the spear the line would coil up and also cause accuracy issues. of course using a line slide should remedy this issue.

havent really come to a conclusion as far as target shooting is concerned but will have to think about it some more, interesting idea though.... have some rep!

DD

 

[alexrom1207]

A bullet because it is so short, really needs that spin to it in order to maintain a consistent trajectory and prevent it from tumbling. A spear, unlike a bullet, does not suffer from this same problem. It is more akin to an arrow, which benefits more from being stabilized by "fins" than it would be by being propelled in a spiraling motion. Considering the distances at which the spear will have enough force to penetrate, I don't think that a spiraling affect would be very useful. The bigger the gun, the longer the spear, and the more accurate it will be over distance....so the only guns that have the ability to shoot far enough to benefit from the spiraling are already relatively accurate. If you had a 50cm gun at 60 bars of pressure and were trying to get 15-20 feet out of it, the boring might help (the flopper issue being ignored).

 

[foxfish]

Very interesting idea - I would suggest a line slider that has some form of flight, like a dart. It would have to lock in place & might make a big hole in a fish but would make a good experiment?

 

[Salehthefish]

Interesting idea as foxfish says, but medium of water is heavier than air this means it needs more power than that used in riffles. Can we consider that the power produced in rubber bands or air gun is more powerful than the power of riffle? Maybe there is a way to use normal riffle under water if it is evacuated (So that no water touch there) and it should be experimented for working in water... Difficult question but it can make good thoughts maybe something new can come out of this question!!!

 

[Old Man Dave]

In Terry Maas's book Bluewater Hunting there is some very interesting info an big gun design and testing. He says these guns can see the spear rotate up to 5 times over their 20 foot range. So it would seem that spears do spin at least in some cases.

Dave.

 

[foxfish]

I just have spent the last twenty mins searching for a vid that has been posted on db but just cant find it at the moment - it shows a automatic Russian made made underwater fire arm, I seem to remember the bullets spinning thought the water?

 

[shrek]

the whole point of spinning rifle bullets is so that any unevenness is constantly being shifted and providing acuracy i think for the purposes of spearfishing you should look more to archery , here there are 2 ways of making arrows fly staight one involves the fletching layed in a spiral patern to spin the arrow like a bullet the other is layed staight and just creates drag
this i think would be more usable to spear shafts .
where i think the most gains made would be in penertration as anything that reduces yaw and keeps the shaft staight helps emencly with arrows so it only stands to reason that a shaft kept as straight as posible in a medium as dence as water has got to make a diference the drag created by a shaft not flying true is huge just imagine trying topoke a shaft straight as opposed to waving it sideways your having to move a lot off water i think that a lot of attention needs to be paid to the shooting line and release as any disturbance will upset the shaft, likewise overpowering shafts will cause exsessive whip or yawing and anybody whos been fishing for a while will tell you thats what makes guns shoot like shit.
so as someone else already said there could be some fun had having a play with this one but i think a camera capable of slowmotion might be quite revealing?