Projectile Aerodynamics Research

[Lentamentalisk]

Hey everyone,
For my end of year Stat project, I am going to measure spread, and energy loss over distance, for various different shaped projectiles. That all is easy, and I have it totally covered.
The tricky part is that my teacher is requiring us to reference at least two studies/experiments on the subject matter. I know I have seen discussion as to projectile shape and form here, and I am pretty sure I have seen actual data from actual research, but I can't seem to find the right search terms. There seems to be much more on the internet about maximizing damage on impact, and less on getting it to fly straight, or without losing speed.

Any and all links or papers welcome.
Thanks so much!

[JDP12]

Try external-ballistics.com. Good stuff on there

[Technician1002]

There is a ballistics tool in GGDT.

http://www.spudfiles.com/spud_wiki/index.php?title=GGDT

More info on the ballistics tool is here;

http://thehalls-in-bfe.com/GGDT/



Edit Crazybuilders has some info on their site. Check this page and video.
http://www.crazybuilders.com/item.php?i ... ct_section

[Lentamentalisk]

Yeah. I understand the whole trajectory thing.
However, I am more concerned about how different shaped bullets effect drag and stability, than calculating their range, depending on an angle.

external ballistics does seem to be a useful term.

[JDP12]

It is but check out the website its actually called external-ballistics.com i believe. Loads of info like whAt you need

[Lentamentalisk]

http://www.external-ballistics.com/ does not exist.
http://www.exteriorballistics.com/ does, and it seems to have some good stuff on it.

edit:
Still, I haven't found anything on projectile shape. Yes, they have drag equations and all, but noting on the shape of bullets. They focus on once you have already bought your premade bullets, rather than on the design of each one.

Specifically, I am looking for something about how a boat tail, or a hollow tail, or a rounded nose vs a pointed nose, will change its stability or drag.

[JDP12]

yeap that's the one. sorry for the confusion.

[Lentamentalisk]

At last! I finally found what I had been searching for!

http://www.frfrogspad.com/drgshape.htm
http://www.frfrogspad.com/coefdrag.gif


I'll let you all know what we find out, though it may not be too unobvious. Pointy things go farther, straighter, faster. As you get farther from the target, your aim is worse and your bullets go slower. We are hoping to be able to pin some numbers on those trends though. Maybe even calculate and sketch a Cd curve... that would be pretty cool.

[FighterAce]

Do you know whats the drag coef of cones with different angles?
I use nail darts with cone angle of 9°. I know that drag coef for 60° cones is 0.5 and 30° is 0.34 but not sure on diameter and length of those... Any ideas what would be for 9° or how to calculate it involving length and diameter of the projectile?

[Ragnarok]

Maybe even calculate and sketch a Cd curve... that would be pretty cool.

Don't expect that to be easy. Most of the time, they're calculated using Doppler radar chronograph data.

There are a set of equations which can estimate Cd curves, but there is no damn way I can recall those off the top of my head.

Do you know whats the drag coef of cones with different angles?

An estimation of the Cd of a simple cone shape with its point into the flow is Cd = 0.0056*Angle of point in degrees + 0.162

but not sure on diameter and length of those

Cross sectional area does not factor in Cd, which is a dimensionless variable.

Diameter does factor in drag calculations (or ballistic coefficient), but the drag coefficient is expressly free of any such dimensions.