DL9999 said:I think the classic example of a dimpled surface being used to reduce form drag is that of a golf ball.
The fact that dimples work with a golf ball doesn't necessarily mean that any rough surface will always reduce drag for any object though.
DL9999 said:As far as I remember, everything I have ever read on the subject mentioned reduction in drag as the main purpose of the dimples on a golf ball.
I can't see how dimples would make the ball spin correctly. Spin is imparted as the ball is struck.
bladerunner said:Recent pictures of Bradley Wiggins show that he was wearing Bont shoes at the Tour - although the Bont logos were masked out. So, it must mean that he liked the shoes a lot more than the ones his sponsor [Adidas??] could supply!
runninboy said:At the moment of impact the ball is not spinning it is stationary, spin will occur after the impact, some of it due to the ball encountering wind resistance.
DL9999 said:Once a golf ball is in the air, the only only forces acting on it are gravity and aerodynamic forces, and I can't see that they are going to make it spin.
A golf ball has a regular, spherical surface. This means that, unless the ball is already spinning, the air flow is going to be pretty much symmetrical around an axis passing through the centre of the ball, parallel to the direction of travel through the air, and the only aerodynamic force will be drag, which won't make the ball spin.
If there is spin on the ball, there will be some circulation in the air flow around the ball, resulting in lift; however, the air flow will cause any spin to decrease over time, not increase.
runninboy said:EVENTUALLY the air flow will cause the spin to lessen as the ball is further from impact but initially i believe it would be a contributing factor...