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 36 users online :: 4 registered, 0 hidden and 32 guests


Most users ever online was 218 on Wed Dec 07, 2016 6:58 pm

Registered users: Bing [Bot], Google [Bot], MSNbot Media, Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

Most Efficient Projectile Shape

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

Unread postAuthor: jimmy101 » Fri Dec 05, 2008 1:00 pm

Ragnarok wrote:The interesting part is that the water's surface tension exceeds the forces on it from drag.

Yep, the terminal velocity is so slow that friction between the air and the surface of the drop is nearly zero. The terminal velocity of a 1.5mm raindrop is only 20~25 FPS (~7m/s).
  • 0

Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3130
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Unread postAuthor: psycix » Sat Dec 06, 2008 3:10 pm

Ragnarok wrote:
psycix wrote:They are all very amusing, but they dont have much to do with aerodynamic shapes do they?

Actually, it does. The important point is that water drops in free fall are not the "teardrop shape" they're often assumed to be.

Which I already posted earlier in this thread. :D

jimmy101 wrote:Yep, the terminal velocity is so slow that friction between the air and the surface of the drop is nearly zero. The terminal velocity of a 1.5mm raindrop is only 20~25 FPS (~7m/s).

Which is probably due to the low sectional density.
  • 0

Till the day I'm dieing, I'll keep them spuddies flying, 'cause I can!

Spudfiles steam group, join!
User avatar
psycix
Donating Member
Donating Member
 
Posts: 3684
Joined: Mon Jun 25, 2007 7:12 am
Location: The Netherlands
Reputation: 0

Unread postAuthor: jimmy101 » Sat Dec 06, 2008 5:57 pm

psycix wrote:
jimmy101 wrote:Yep, the terminal velocity is so slow that friction between the air and the surface of the drop is nearly zero. The terminal velocity of a 1.5mm raindrop is only 20~25 FPS (~7m/s).

Which is probably due to the low sectional density.

Yep, with a density of just 1g/cc water makes a pretty crap "shell". Lead is 11.3g/cc. 11.3 times as much mass, 11.3x the sectional density for a sphere, basically the same Cd. Water would make a pretty crappy bullet.
  • 0

Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3130
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Unread postAuthor: Ragnarok » Sat Dec 06, 2008 6:50 pm

jimmy101 wrote:Water would make a pretty crappy bullet.

It would... but that does bring up the question of ice bullets. Clearly ballistically and terminally poor with a density of even less than water, but very hard to trace forensically, as they would quickly melt away.

I know the Mythbusters got bad results with making and firing them, but that is in a rifle with very high pressure, high temperature gases - but what about in a reasonably high pressure, low-ish calibre pneumatic spudgun?

Obviously, I'm not suggesting the use of it, but it is an interesting question.

I reckon that with a decent mould, you could make a hollow tailed projectile that would exhibit good stability and passable accuracy - and you could make up for the low density by making a fairly long projectile to improve the sectional density.

Might be interesting to look into.
  • 0

Does that thing kinda look like a big cat to you?
User avatar
Ragnarok
Chief of Staff
Chief of Staff
 
Posts: 5339
Joined: Tue Dec 19, 2006 8:23 am
Location: The UK
Reputation: 8

Unread postAuthor: jackssmirkingrevenge » Sat Dec 06, 2008 7:34 pm

Ragnarok wrote:I reckon that with a decent mould, you could make a hollow tailed projectile that would exhibit good stability and passable accuracy - and you could make up for the low density by making a fairly long projectile to improve the sectional density.


The hollow tail would probably shatter on firing. I think that - speaking theoretically, of course - you'd have to be at a few yards range anyway, close enough for stability not to matter. There's definitely no question of having any significant accuracy beyond a target that's in the same room.
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: Ragnarok » Sat Dec 06, 2008 8:42 pm

jackssmirkingrevenge wrote:The hollow tail would probably shatter on firing.

Depends on how hollow. I think that if the outer diameter matched the diameter of the pipe it was being fired from closely enough, the gases in the tail would force it against the walls not unlike an airgun pellet's skirt does

With something like my porting muzzle attachment, you could then kill the barrel pressure at the muzzle end very quickly so that once the support of the walls was lost, there was no pressure on the inside either.

I'll add it to my list of "Things to try sometime", see what kind of results I can get at range. Obviously in practical terms, an untraceable ice bullet is no use unless you're at least far enough from your target that you can't be identified yourself.
  • 0

Does that thing kinda look like a big cat to you?
User avatar
Ragnarok
Chief of Staff
Chief of Staff
 
Posts: 5339
Joined: Tue Dec 19, 2006 8:23 am
Location: The UK
Reputation: 8

Unread postAuthor: inonickname » Sun Dec 07, 2008 7:29 pm

http://ourworld.compuserve.com/homepage ... lemods.htm

I'd say 1 is your best bet, so golf balls are good..
  • 0

User avatar
inonickname
Lieutenant General
Lieutenant General
 
Posts: 2606
Joined: Sun Dec 07, 2008 3:27 am
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: jimmy101 » Sun Dec 07, 2008 8:56 pm

I don't think it would be difficult to get an ice slug up to lethal KE's with sufficient accuracy at say a 100 foot range.

Heck a basic cylinder from a rifled barrel, or even a sphere from a rifled barrel should do the trick. Perhaps not the most elegantor efficient round but certainly should be possible to get enough accuracy and KE to do "significant damage".
  • 0

Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3130
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Unread postAuthor: Ragnarok » Sun Dec 07, 2008 9:18 pm

jimmy101 wrote:I don't think it would be difficult to get an ice slug up to lethal KE's with sufficient accuracy at say a 100 foot range.

Yeah, but 100 feet is still close enough that it's kind of pointless trying to hide the ballistics or evidence by using an ice bullet - you're close enough to be traced, unless of course you have a compact and near silent launcher which can generate a reasonable KE, and that's no mean feat.

I was thinking out beyond at least 100 yards myself, far enough that you're far enough away that it will be starting to get hard to spot or identify where you shot from.
  • 0

Does that thing kinda look like a big cat to you?
User avatar
Ragnarok
Chief of Staff
Chief of Staff
 
Posts: 5339
Joined: Tue Dec 19, 2006 8:23 am
Location: The UK
Reputation: 8

Unread postAuthor: psycix » Mon Dec 08, 2008 11:02 am

Or let the slugs rain down from the sky by firing them upwards like long range artillery.
Could fire it over a few houses, so you are not in the line of sight.
  • 0

Till the day I'm dieing, I'll keep them spuddies flying, 'cause I can!

Spudfiles steam group, join!
User avatar
psycix
Donating Member
Donating Member
 
Posts: 3684
Joined: Mon Jun 25, 2007 7:12 am
Location: The Netherlands
Reputation: 0

Unread postAuthor: jimmy101 » Mon Dec 08, 2008 12:18 pm

Ragnarok wrote:Yeah, but 100 feet is still close enough that it's kind of pointless trying to hide the ballistics or evidence by using an ice bullet - you're close enough to be traced, unless of course you have a compact and near silent launcher which can generate a reasonable KE, and that's no mean feat.

Kennedy was shot from a range of about 180 feet. People in the area could not localize the shooter. 40+ years later it still can not be proven where the shooter(s) was(were) based on the audio recordings of the event.

100' is probably far enough. As long as there is no one close to the muzzle and it is a complex accoustic location (i.e., around buildings).

The human ability to localize a sound is really pretty poor. Especially when the sound was unexpected and there is an echo. People are so bad at it that the military uses accoustic devices to localize enemy shooters.
  • 0

Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3130
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Unread postAuthor: Lentamentalisk » Mon Dec 08, 2008 4:34 pm

jimmy101 wrote:The human ability to localize a sound is really pretty poor. Especially when the sound was unexpected and there is an echo. People are so bad at it that the military uses accoustic devices to localize enemy shooters.

It should be noted that mainly these are used on Humvees, because they are too loud inside to have the slightest clue where shots are coming from.
  • 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: Floyd » Tue Dec 16, 2008 3:57 pm

Whoa, I haven't checked this thread for a while until I saw it on this wiki page. I thought why would that be on the wiki page and then I looked here and saw all of the replies. Thanks a lot for the discussion, I learned a lot from reading it. I am going to do the fair, but I don't plan on going any higher than the school level.
  • 0

User avatar
Floyd
Sergeant
Sergeant
 
Posts: 86
Joined: Thu Jul 10, 2008 6:42 pm
Reputation: 0

Unread postAuthor: Ragnarok » Tue Dec 16, 2008 4:14 pm

Floyd wrote:I thought why would that be on the wiki page and then I looked here and saw all of the replies.

It would be on the Wiki Page because I thought it contained some good information.
  • 0

Does that thing kinda look like a big cat to you?
User avatar
Ragnarok
Chief of Staff
Chief of Staff
 
Posts: 5339
Joined: Tue Dec 19, 2006 8:23 am
Location: The UK
Reputation: 8

Unread postAuthor: raptorforce » Tue Dec 16, 2008 11:46 pm

wow not fun reading 6 pages of comments to catach up i ve made some projectiles like its a spitzer design with a steel tip but is surrounded by wood. i am going to try fill it with lead solder and put a steel tip on top of that as i cannot find any harder material that i can get but i do have my eye carbide for some reason i cant upload a picture
  • 0


raptorforce
Sergeant First Class
Sergeant First Class
 
Posts: 137
Joined: Wed Nov 26, 2008 2:18 am
Reputation: 0

PreviousNext

Return to Construction Materials/Ammo Discussion

Who is online

Registered users: Bing [Bot], Google [Bot], MSNbot Media, Yahoo [Bot]

cron
Reputation System ©'