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Cone Drag

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Cone Drag

Unread postAuthor: skyjive » Mon Sep 01, 2008 11:42 am

Is there any way of theoretically determining the drag coefficient of a cone with the airflow directed from the point to the base, 1/2" across at the base and 3" long?
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Unread postAuthor: rp181 » Mon Sep 01, 2008 11:59 am

it is, just to complicated to worry about in general spudding. The longer the cone the less drag. It also helps to make the cone really smooth (if its wood, coat it)
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Unread postAuthor: jimmy101 » Mon Sep 01, 2008 7:04 pm

Googling "coefficient of drag cone length diameter" gives this page as the first hit.

(sure would be nice if people would at least try to find an answer before asking the forum)

BTW, a cone is unstable in flight (if made from a constant density material) so the Cd is really pretty irrelevent.
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Unread postAuthor: skyjive » Mon Sep 01, 2008 10:32 pm

I actually am using a 1/4" carriage bolt with a conic paper tail to make blunt dart ammo for my 1/2" gun, and it is quite stable in flight.

And thanks for the link, its much better than what I usually expect from google searches for stuff like that
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Unread postAuthor: rp181 » Mon Sep 01, 2008 10:44 pm

unless you have a highspeed camera, your not gonna know.
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Unread postAuthor: jimmy101 » Tue Sep 02, 2008 12:44 pm

rp181 wrote:unless you have a highspeed camera, your not gonna know.

Not really. It is usually pretty easy to tell if a projectile is tumbling in flight. Just blast it through pieces of cardboard at a couple different ranges. If the hole is circular (but the ammo isn't a sphere) at several different ranges then it is reasonable to conclude that the round is stable in flight.
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Unread postAuthor: jackssmirkingrevenge » Tue Sep 02, 2008 2:13 pm

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sorry, mind tired from work, not reading titles well :roll:
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Unread postAuthor: POLAND_SPUD » Tue Sep 02, 2008 5:58 pm

lol JSR are they your relatives ? :wink:
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Unread postAuthor: jackssmirkingrevenge » Wed Sep 03, 2008 12:08 am

POLAND_SPUD wrote:lol JSR are they your relatives ?


Yes, I have distant cousins in Poland :P :D
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Unread postAuthor: POLAND_SPUD » Wed Sep 03, 2008 2:30 pm

nice try...but they can't be polish.... there are no all orange road cones in poland.. they have to have 2 white stripes :D
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Re: Cone Drag

Unread postAuthor: Antonio » Thu Sep 04, 2008 10:58 am

skyjive wrote:Is there any way of theoretically determining the drag coefficient of a cone with the airflow directed from the point to the base, 1/2" across at the base and 3" long?


I would use the link that jimmy sent and just use a general cd coefficient. It is possible to find out the cd coefficient but only with experimentation. Like that I found the cd of 0.2g bb balls. I did this shooting a target at different ranges and plotting how long it takes to get there. Like this u can c how much the airfriction breaksdown the bb ball. It is a bit complex as the velocity changes during the flight. But if you are interested I could give u the method.. I think i posted it somewhere. The main importance for a flying rocket shape object is that the center of mass is supposed to be far forward and the center of pressure (airdrag) further back. For a stable rocket object the distance between the cg and cp should be twice the radius I think (it could be 3).
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Unread postAuthor: jackssmirkingrevenge » Thu Sep 04, 2008 2:35 pm

POLAND_SPUD wrote:nice try...but they can't be polish.... there are no all orange road cones in poland.. they have to have 2 white stripes :D


It was an international party ;p
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