Golf Balls

[maguromic]

I think why the wording was changed and I am only guessing is that the louvers fit into the rules as well, and lots of classes allowed them. I don’t know about other classes but on fuel/gas roadster you are allowed louvers on the deck lid.  Where you place them will help you in the aero side. My roadster was designed with the help of Stanford University Engineering School and all the aero work was done on the computer and we played around with the louvers on the deck lid till we found the optimal spot to place them.  Paul Vanderley (sp) put his ’33 roadster in a NASCAR wind tunnel and came up with a pattern for the louvers on the deck lid of a ’33.   As mentioned in another thread it’s not the hole you punch in the air that is important, it’s how you exit the hole.

[Blue]

When I was younger and didn't mind the occasional fight, I used to win money in bars on the dimple question.  It took finding an aero professor to arbitrate and beer glasses sometimes flew settling the question, but geeks have to have their fun.

When a golf ball is struck by a driver at a low angle, high velocity, and low spin rate, it pretty much goes straight whether it has dimples or not.  The rotation of the ball drags the boundary layer along with it, more so if the ball is dimpled.  Now, the thicker boundary layer of the dimpled ball causes more drag than the thinner boundary layer of a smooth ball.  But as the dimpled ball slows down relative to its backspin rate, the thick, rotating boundary layer creates lift.  This lift causes the ball's flight path to rise and carries it farther than it would without spin and without dimples.  This is why even a driver has some angle to it.

Higher angle clubs create more spin rate vs. velocity and so the ball gets a greater percentage of its vertical trajectory from spin for the higher numbered clubs.  All of these effects are dependent on velocity and air density.  On the moon, dimples make no difference.

So the dimples create more drag, not less;  and this makes the ball go farther.  Take some Tylenol.

[Dynoroom]

When I was younger and didn't mind the occasional fight, I used to win money in bars on the dimple question.  It took finding an aero professor to arbitrate and beer glasses sometimes flew settling the question, but geeks have to have their fun.

When a golf ball is struck by a driver at a low angle, high velocity, and low spin rate, it pretty much goes straight whether it has dimples or not.  The rotation of the ball drags the boundary layer along with it, more so if the ball is dimpled.  Now, the thicker boundary layer of the dimpled ball causes more drag than the thinner boundary layer of a smooth ball.  But as the dimpled ball slows down relative to its backspin rate, the thick, rotating boundary layer creates lift.  This lift causes the ball's flight path to rise and carries it farther than it would without spin and without dimples.  This is why even a driver has some angle to it.

Higher angle clubs create more spin rate vs. velocity and so the ball gets a greater percentage of its vertical trajectory from spin for the higher numbered clubs.  All of these effects are dependent on velocity and air density.  On the moon, dimples make no difference.

So the dimples create more drag, not less;  and this makes the ball go farther.  Take some Tylenol.

gee...... I thought the dimples in a golf ball were there to help keep it aloft............ so it could fly farther.......... hmmm 

You said it better, thanks

[thundair]

Blue

Is supercavatation possible with a streamliner?...I know it is unacceptable in aircraft as it takes away the control surface action....

[Ratliff]

http://www.aerospaceweb.org/question/aerodynamics/q0215.shtml

The dimples reduce flow separation and thus drag on a sphere.

[Blue]

http://www.aerospaceweb.org/question/aerodynamics/q0215.shtml

The dimples reduce flow separation and thus drag on a sphere.

Sorry, the evidence doesn't support this explanation.  Go out to a golf course, stand behind the tee, watch the ball.  It does not travel in a decaying parabola, it lifts above this path partway through its flight.  This vertical deviation increases with both spin and the sharpness and number of the dimples.

Going through months-old posts looking for ways to post someone else's contrary information is a lot less productive to your education than joining an actual race team.

I read a few of aerospaceweb's other answers, interesting that they couldn't explain how wings work and which of the "theories" presented applied to the various areas of airfoil design.  I could, and did here in a way that even non-aero people can understand.  My professors always said that if you can't explain it to someone outside your field, you really didn't understand what you were talking about.

[Ratliff]

http://www.aerospaceweb.org/question/aerodynamics/q0215.shtml

The dimples reduce flow separation and thus drag on a sphere.

Sorry, the evidence doesn't support this explanation.  Go out to a golf course, stand behind the tee, watch the ball.  It does not travel in a decaying parabola, it lifts above this path partway through its flight.  This vertical deviation increases with both spin and the sharpness and number of the dimples.

Going through months-old posts looking for ways to post someone else's contrary information is a lot less productive to your education than joining an actual race team.

I read a few of aerospaceweb's other answers, interesting that they couldn't explain how wings work and which of the "theories" presented applied to the various areas of airfoil design.  I could, and did here in a way that even non-aero people can understand.  My professors always said that if you can't explain it to someone outside your field, you really didn't understand what you were talking about.

http://www.sciencenetlinks.com/sci_update.cfm?DocID=23

Isn't the golf ball lift just Magnus effect like when someone points a leaf blower straight up and positions a beach ball over it?

http://query.nytimes.com/gst/fullpage.html?res=9C04E6DA143EF934A35752C0A9659C8B63

I have read two theories of lift for wings. One is the classic explanation based on Bernoulli. The other is a Newtonian explanation that lift is an upward thrust resulting from the downward diversion of air.

[oz]

Man I had forgotten about this thread but i am going to take a small ball pein hammer to my helmet now!! Dimples here we come look out avionics the ACNE MAN cometh.

[mtkawboy]

I thought I recalled Mr Dolan saying that the Pettys put the vinyl roof on to cover up an overly acid dipped roof on the car, but I could be wrong

[Blue]

I thought I recalled Mr Dolan saying that the Pettys put the vinyl roof on to cover up an overly acid dipped roof on the car, but I could be wrong

The story is correct from more than one source I have in stock car (NOT nascar) history.

As an aero geek, I have to question how much of the drag reduction came from the turbulent boundary layer staying attached due to the vinyl and how much came from the turbulence from the joints.

[maguromic]

The Penske '69 Trans-Am car also had a vinyl roof.  It was rumored to be because the the roof was too thin from acid dipping the body.  But knowing Penske who knows what they were using it for.  His accomplishments speak for them self!

[mtkawboy]

Penske was know for giving you something to see to keep you from looking somewhere else where he didnt want you to see. When drag racing an NHRA stocker Mustang Cobrajet in the early 70's we would put the wrong dual inlet fuel line on so they could make us change it to the right one, a single inlet. If you didnt give them something to pick on they would keep looking. Once they busted you they were happy

[John Burk]

"The Penske '69 Trans-Am car also had a vinyl roof.  It was rumored to be because the the roof was too thin from acid dipping the body. "

Turning a Javelin that originaly had 70/30 weight distribution into a Trans Am winner must have required quite a bit of acid dipping .

John

[tomsmith]

Let's see...  If you put a lot of dimples on your car, then spin it real fast, you can generate a lot of lift.  If that is what you want, to climb skyward like a golf ball, I would rather not see it in action.  By the way, have you seen the NACA ducts in the rear quarter panel windows of NASCAR cars?  Hopefully, they generate positive pressure to pipe air to the drivers, etc.

[sanger351]

Free dimpling

As some of you know we have been having some pretty wild weather in Iowa this year.  Hail is again predicted for today.  Yesterday tennis ball size (2.5") hail fell about 60 miles from where I live.  Not only will it dimple the shell but it will also probably change the ride height.