Parabolic Drag

[epoletna]

I think there might be a little confusion of terms here. As any pilot or engineer should be able to tell you (I'm an FAA certificated flight instructor) any aircraft moving through the air is affected by two types of drag: parasite drag and induced drag. Parasite drag is caused by anything sticking out into the airflow, like rivets above the skin, antennas, etc.

Induced drag is caused as a function of the lift caused by the wings, because the wings are redirecting the airflow, and the faster the airplane is flying, the greater the induced drag.

I do not see how a bullet would have differing induced drag, because it is not creating lift by redirecting airflow. In other words, I think the induced drag for a bullet would be fairly constant.

I suppose a Hammer bullet, with the grooves, would experience parasite drag, just as I suspect a bullet with a cannelure would experience parasite drag.

I wonder if people are confusing the word parasite with the word parabolic? A parabola is a type of curve, and I suppose the shape of the grooves on the Hammer bullet could be parabolic, although that is unclear to me and it would take careful measurement to establish that.

A parabolic curve would probably be a fair description for the curve described by a bullet fired nearly level -- the more it slows, the steeper the curve toward the earth when graphed against its speed. I'd have to look at that to determine if that is a true parabola.

The statement "parabolic drag" implies that the curve described by the bullet (presumably a parabola) somehow influences drag. I would need an explanation of how that works.

I'd also need an explanation of how a monometal bullet has different drag. I'm still pondering that. Gravity should affect both equally.

 

[Mikecr]

Wouldn't it be a waste of forum energy, if this entire thread was fuddled up with the term parabolic -instead of parasitic!

 

[59FLH]

Both terms fuddle it up until one separates technical terms from catch phrases.

 

[tt35]

I have a headache.

 

[tim_w]

If we are going to be computing the effects of drive bands then the same goes for the engraving of the barrel lands on the bullets body. To compute the effects of bands accurately would require it with the engravings from the rifling and that would be different for various barrels. I know Brain has discussed the land engraving variations effects at ELR ranges. It was yrs ago. Can not recall where I read or heard it.

 

[Hugnot]

My thinking is for airfoils a composite drag chart would look like a parabola should the parasitic drag increase with speed and the lift drag decrease with speed, The X axis being speed, the Y axis being drag. Sort of like 2 sloping curved lines having a parabolic shaped composite line above.

For spinning bullets subject to slowing down and yawing and precession effects. As the velocity decreases the parasitic drag would decrease but the effects of spinning causing yawing and precession would remain constant or greater making the 2nd drag effect greater.. Sort of like 2 sloping curved lines one being curved down as the parasitic drag decreased but the other line would sloping up as yawiing or precession increased. A composite graph of both would look like a parabola.

This assumes bullet yaw or precession effects would increase??

Some think anular bullet grooves reduce flying bullet skin friction. Land engraving might also affect skin friction. Math/physics guys get into boundary layers & Reynold's numbers to describe this stuff.

 

[Zen Archery]

Thank you sir. The reason that I posed the question was because another member here stated that parabolic drag was induced by mono bullets due to their lower material density. I had never heard of such a thing and when I asked for clarification in the thread I was being told that I was out of line, for lack of better terms,

Way to be out of line Steve.

Arguing two different drags(not they/them drags) but physical drags. Hammer bullet design reduces bearing surface drag created by contact with the barrel which is very simple physics and I doubt Mr. Steve was thinking about air drag once it leaves the barrel;

I'm totally with bluegrass on this one. First time I heard, read the phrase I thought of internal ballistics not external.

From my understanding the Hammer Bullet Bands are designed on a "parabolic" curve. The bands contact to the rifling is minimal compared to traditional CC bullet that bullet "drag" was "reduced" significantly.

It would be worth measuring how much bearing surface material from a common CC bullet in the same caliber and weight class as a Hammer bullet would differ.

Sorry late to the conversation just my .02

 

[RidgeTop]

Well if you don't put wings on your bullets, I believe everything will be just fine.

You would think the fast rotation of the spiral rifling groves would lessen drag.

 

[Bob Wright]

Howard Hughes spent a whole bunch of money using a flush rivet vs a convex rivet because of "parasitic drag reduction" on aircraft. Bullet grooves, no idea....@Bryan Litz might know.

 

[Mikecr]

The bands contact to the rifling is minimal compared to traditional CC bullet that bullet "drag" was "reduced" significantly.

Friction is reduced,, not drag.
There is no drag in internal ballistics