rof and accuracy

[Minimag4me]

so probably the distancy and velocity is increased by this drafting but by how much? is it enough to be measureable?

[Vegeta]

AGD has already done some about this in testing. They supposedly used a Cinipex (?) camera, which runs at a high framerate, soemthing to the effect of 1200 frames/sec. to photograph a ball leavign hte barrel. They flowed grren smoke over the ball to study how it went around it. Spent big bucks. At least that is how I heard it. Tom, if you could confirm this and tell us more about your research, we'd love to know.

[Gup44]

Chk6... As far as how long the trails are I keep thinking about canoing. If you have ever paddled in a canoe, then you have watched the water swirl behind your paddle and continue to swirl for some time even after the paddle is out of the water. I would venture to say sometimes up to 15 or 20 seconds or possibly more.

I don't know the math and the differences between water and air, but I would guess that the "trails" behind a paintball could last some time... Definately long enough to effect a the next few paintballs in a sting at 10bps.

I don't know if this makes sense. But it was my own mind's eye.

-Gup44

[AGD]

Deep Blue is really coming along nicely here, I am enjoying the high level conversation.

The aviation term is "Wake Turbulence". It's generated by the wings in the form of vortexes on liftoff by large airplanes. The swirling air can persist for quite a while and can cause accidents.

We have not specifically studied the effect of turbulence and it's effect on the ball following but there are some tantilizing clues. There have been reports of bench mounted guns shooting tighter groups at higher speeds. There is no known explanation for this (or if it is in fact true). Paintballs positively generate wake turbulence because you can hear them buzz by you out in the field. This is an understudied area worthy of some effort.

Water is commonly used to study aerodynamic forces. It is not a direct one to one comparison because water has more mass and viscosity. In order to match flow effects between such diverse mediums as water and air you have to use some fancy mathematics. The math forumulas generate Reynolds Numbers which are used to match the different flow characteristics. In general if you have a sphere about 1 foot wide at 150 mph and want to test it in water you would use one about 1 inch wide with a water flow of a few miles per hour. This is a ballpark from work we did in the 80's on cooling drag in motorcycles and airplanes.

The airflow around a sphere is a classic study for first time aerodynamicists. It's is well understood (and it sucks). The notable points are the fact that laminar flow exists around the front of the ball and the laminar layer stays attached for some distance past the mid point. Just past the midpoint it detaches and becomes turbulent in unpredictable and random ways. A boundary layer exists near the surface where the air transistions from high speed to virtually not moving on the surface of the ball. The thickness of the boundary layer is one of the determining factors of how long the laminar flow stays attached. The longer it stays attached the more aero the body. Golf ball dimples try to influence the boundary layer.

There are several cool experiments you could do and be the first ones to reveal these secrets. Find a room you can fire paint in an created a cloud of smoke that hovers in mid air. Fire a paintball through it while video taping and you should be able to time how long the turbulence effect lasts. Make sure you fire from far enough away that the gun blast does not affect it.

Another thing you could do is get your fishing pole and glue a nylon ball to the fishing line and drag it through the water like a lure. The movement of the ball would demonstrate how the ball flies through the air. We know for a fact that paintballs "wobble" back and forth in flight and that this is the major contributor to accuracy reduction.

Keep up the good conversation guys this is really interesting.

AGD

[clockworkmiller]

Im am so doing that experiment with the smoke. Im no numbers wiz, but i'll get the data down and find a physics professor who would help with calculations. We have the basement in the frat house that is never used, and has very stagnant air, which would be perfect for this experiment.

Thank you tom very much for the information. If you have any other ideas on experiments, just post them, and Im sure I, or someone else would be more than willing to help out. See you in march.

[media]

Dimples. OMG, don't throw away that old dimpled paint! I wonder if anyone has tried to make a paintball with a surface simular to a golf ball. It'd probably shoot fine since proper paint to barrel match only requires the paintball to just skim the barrel. I'd assume it would be to expensive to manufacture though.

[Wat]

Fuids = Death...

Gawd...fluids...i had a fluids lab at MIT where i had make a velocity flow meter out of a ping pong ball suspended on a string. Four weeks of collecting data, writing ugly equations and a Mountain Dew drip and i had a flow meter that was 5% accurate.

Anyways...the thing with fluids, is that the equations involved are whats called non-linear. Otherwise known as pains in the buttocks. These equations cannot be solved and the only way to find the answer is through actual experiments or massive computer number crunching.

In solids, the equations are mostly linear and we can do pencil, paper and brain analysis and come up with a reasonable answer without ever getting our hands dirty. But in fluids, we can't. We can't say with much certainty without running experiments, computer models or looking up numbers in those big books of data, which is really just someone else's experiments.

I applaud AGD for actually getting in the lab and running tests instead of just spewing marketing myths. If anyone can program, someone should write up one of those SETI like screen savers/distributed number crunching programs and we could use every pballers computer to model the flow around a paintball.

[Minimag4me]

i believe the golf ball dimple thing was tried but it didnt work or at least not well enough(little gain) to be manufactured.

I wish i had a place to do that smoke/room thing. That would be interesting.

[PBpunk]

my friend has a fog machine but i dont think my mom would like me shooting paint down the hallway