Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 31 users online :: 8 registered, 0 hidden and 23 guests


Most users ever online was 101 on Fri Nov 22, 2013 4:13 pm

Registered users: Bernie_McGee, Bing [Bot], Boomer58cal, BowerR64, Google [Bot], Google Adsense [Bot], Majestic-12 [Bot], MSNbot Media based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

Projectile Aerodynamics Research

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
Sponsored 
  • Author
    Message

Projectile Aerodynamics Research

Unread postAuthor: Lentamentalisk » Tue May 11, 2010 6:52 pm

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!
  • 0

Do not look back, and grieve over the past, for it is gone;
Do not be troubled about the future, for it has not yet come;
Live life in the present, and make it so beautiful that it will be worth remembering.
User avatar
Lentamentalisk
Brigadier General
Brigadier General
 
Posts: 1202
Joined: Tue Aug 07, 2007 5:27 pm
Location: Berkeley C.A.
Reputation: 0

Unread postAuthor: JDP12 » Tue May 11, 2010 7:05 pm

Try external-ballistics.com. Good stuff on there
  • 0

User avatar
JDP12
Major General
Major General
 
Posts: 1943
Joined: Fri Mar 30, 2007 8:34 pm
Reputation: 0

Unread postAuthor: Technician1002 » Tue May 11, 2010 7:20 pm

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/

Image

Edit Crazybuilders has some info on their site. Check this page and video.
http://www.crazybuilders.com/item.php?id=000007&type=project_section
  • 0

Last edited by Technician1002 on Tue May 11, 2010 7:26 pm, edited 1 time in total.
User avatar
Technician1002
Chief of Staff
Chief of Staff
 
Posts: 5120
Joined: Sat Apr 04, 2009 11:10 am
Reputation: 8

Unread postAuthor: Lentamentalisk » Tue May 11, 2010 7:23 pm

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.
  • 0

Do not look back, and grieve over the past, for it is gone;
Do not be troubled about the future, for it has not yet come;
Live life in the present, and make it so beautiful that it will be worth remembering.
User avatar
Lentamentalisk
Brigadier General
Brigadier General
 
Posts: 1202
Joined: Tue Aug 07, 2007 5:27 pm
Location: Berkeley C.A.
Reputation: 0

Unread postAuthor: JDP12 » Tue May 11, 2010 7:25 pm

It is but check out the website its actually called external-ballistics.com i believe. Loads of info like whAt you need
  • 0

User avatar
JDP12
Major General
Major General
 
Posts: 1943
Joined: Fri Mar 30, 2007 8:34 pm
Reputation: 0

Unread postAuthor: Lentamentalisk » Wed May 12, 2010 11:44 am

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.
  • 0

Last edited by Lentamentalisk on Wed May 12, 2010 12:09 pm, edited 1 time in total.
Do not look back, and grieve over the past, for it is gone;
Do not be troubled about the future, for it has not yet come;
Live life in the present, and make it so beautiful that it will be worth remembering.
User avatar
Lentamentalisk
Brigadier General
Brigadier General
 
Posts: 1202
Joined: Tue Aug 07, 2007 5:27 pm
Location: Berkeley C.A.
Reputation: 0

Unread postAuthor: JDP12 » Wed May 12, 2010 11:49 am

yeap that's the one. sorry for the confusion.
  • 0

User avatar
JDP12
Major General
Major General
 
Posts: 1943
Joined: Fri Mar 30, 2007 8:34 pm
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: Lentamentalisk » Thu May 13, 2010 3:40 am

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.
  • 0

Do not look back, and grieve over the past, for it is gone;
Do not be troubled about the future, for it has not yet come;
Live life in the present, and make it so beautiful that it will be worth remembering.
User avatar
Lentamentalisk
Brigadier General
Brigadier General
 
Posts: 1202
Joined: Tue Aug 07, 2007 5:27 pm
Location: Berkeley C.A.
Reputation: 0

Unread postAuthor: FighterAce » Thu May 13, 2010 4:02 am

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?
  • 0

User avatar
FighterAce
1st Lieutenant
1st Lieutenant
 
Posts: 282
Joined: Fri Oct 23, 2009 1:28 pm
Location: Croatia/Zagreb
Reputation: 0

Unread postAuthor: Ragnarok » Thu May 13, 2010 7:24 am

Lentamentalisk wrote: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.

FighterAce wrote: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.
  • 0

Does that thing kinda look like a big cat to you?
User avatar
Ragnarok
Chief of Staff
Chief of Staff
 
Posts: 5275
Joined: Tue Dec 19, 2006 8:23 am
Location: The UK
Reputation: 6

Return to Construction Materials/Ammo Discussion

Who is online

Registered users: Bernie_McGee, Bing [Bot], Boomer58cal, BowerR64, Google [Bot], Google Adsense [Bot], Majestic-12 [Bot], MSNbot Media

Reputation System ©'