Round Ball in shotgun question

[piwo]

You learned gentlemen are far advanced in your understanding of aerodynamics then I will ever hope to attain. There is one facet of the golf ball analogy that I'm a little unclear on its appropriateness in this discussion. Be nice, this is outside my area of expertise

When a golf ball is struck with a club, its shape RADICALLY changes. A super slow motion /still photograph of a ball being struck shows the ball smashed to almost flat: it literally covers the entire face of the club and the "grooves" of the club "bite" the soft cover (thus the "square groove controversy in golf: too much spin). Upon release, a great deal of spin in imparted on the ball.

When shooting a patched roundball I do not know if the ball is deforming in the barrel on the way out, but there is certainly nothing imparting spin that these dimples will interact with while flying as with a golf ball spinning in the air. It's essentially a knuckleball coming out, and in my simple mindedness, I'd think that it would fly much truer without the dimples to "catch the wind", which is exactly what a knuckleball pitcher is doing with the seams of the baseball, and why the sprue should either be up or down... but not to the side?

Yes, no ??

[floodgate]

Geoff:

Yes, I well remember the Canberra/B57; one of our colleagues used it for high-altitude weather reconaissance. We referred to it as "The Batplane". Very handsome!

Doug

[grumpy one]

Doug, I don't know when they were last used operationally - the Australian ones seemed pretty old when they were used for low-altitude missions in Vietnam.

piwo, the aerodynamic effects of the dimples on golf balls are intended to have their effect while the ball is in free flight, not when it is still being accelerated by the club. Hence the ball is spherical when they are doing their job. Also, the aerodynamic advantage created by the dimples is not their only effect, it is just one that has been documented. Incidentally the advantage that has been demonstrated supposedly is comparable with what happens when it is hit with a driver, with a near-vertical front face. This would impart relatively little spin.

Considering a round rifle bullet, it would be rotating at very high speed due to the rifling as well as travelling at high linear speed. Both speeds are likely to be way too high for boundary layer effects near the separation point to be of any importance. A musket ball probably wouldn't be rotating much, but I think would still be travelling too fast linearly.

[floodgate]

Geoff:

This would have been around 1964-67, and they were being retired from front-line service before that. But DAMN! - they were beautiful birds!. The crew coming down to our staging station on Puerto Rico said that - nemmine that clouds aren't supposed to grow above about 45,000-50,000 feet, they were looking UP at them cruising at 55,000. As a chemist friend said - and shut down a fomal debate on the spot - "Science is full of things that ain't so!"

Doug

[grumpy one]

It wasn't just that they were pretty, Doug, it was the long technological half-life. The first flight was in 1949, after the project started in 1944 - in British service it replaced a piston-engined wood-and-fabric WW II light bomber called Mosquito. The British finally took the last Canberra out of reconnaisance service last June, so it had an awfully long run as an active warbird - 55 years or so.

Having said all that, I agree with you - it certainly was pretty.