| philfree |
10-01-2015 09:09 PM |
So I read this and cyphered out that for 1000 ft of elevation change there is about 1.5% difference in how the far the golf ball travels. So if I hit a 9 iron 150 yards in Springfield, MO at about 1200 ft elevation that same shot will only go 147 yards on Hilton Head Island. All other things remaining then same of course. That could be significant. Drop the temp to in the 50's and that's another half of club.
http://www.usgtf.com/articles/summer12/page33.html
Quote:
Most of us have heard that you gain around 15% in distance when you go from playing at sea level to playing about a mile above sea level (5,280 feet, 1,760 yards, or 1,609 meters). How accurate is this long-held belief?
First, in researching the matter, we found that you cannot use a simple linear equation that works for all clubs. Each club has a different percentage, because they are not all launched at the same angle. What is true is that, at elevation given the same temperature, air pressure, and humidity, the ball faces less air density and thus will travel farther horizontally. What is also true that the ball will not stay in the air as long, because the lift provided by the backspin is also lessened.
Does anyone remember their physics from school? A projectile that does not create its own lift will travel farthest when launched at a 45° angle. This can be seen with someone shooting a basketball or throwing a rock. Golf balls create their own additional lift due to backspin and dimples.
A projectile that does not create its own lift will begin to decrease its angle of ascent the moment it is launched. A golf ball does not do that, because it creates its own additional lift. This additional lift will do one of the following: 1) Slow the reduction of the angle of ascent; 2) Keep a constant angle of ascent for a period of time; 3) Increase the ball’s angle of ascent for a period of time. As a result, launching a golf ball with a driver at 45° will not produce maximum distance.
If you’ve attended a professional baseball game, you might have noticed that pop-ups in the infield behave differently than what would be considered normal with regular projectiles. This is because the baseball, like the golf ball, has backspin. Illustration A demonstrates what a regular projectile’s trajectory would be, known as a parabola, while Illustration B illustrates a typical baseball popup’s trajectory:
In both illustrations, we are assuming the projectile is launched at the same initial velocity and angle. You can see that the baseball in Illustration B travels higher and shorter than the projectile in Illustration A, which is not creating any additional lift. Okay, so what does this have to do with golf and altitude?
It means that a ball hit with a driver at altitude will not realize the same distance gains, percentagewise, as will a ball hit with a shorter iron. Because of the lower air density at altitude, the ball’s backspin doesn’t create as much lift as it would at sea level. As a result, balls hit with a driver won’t stay in the air as long proportionally as compared with a 9-iron, and thus won’t realize the distance gains percentage-wise as would the shorter iron.
Another factor to consider is the air temperature, which plays a larger role in air density than most people think. The Winter 2011 edition of Golf Teaching Pro addressed this, but here we will add a little more detail. Shelquist Engineering has an air density calculator at http://wahiduddin.net/calc/calc_ da_rh.htm, which is where we obtained the following information.
At sea level, assuming 90° air temperature, 50% humidity, and 29.00 inches of barometric pressure (typical of a summer day), the air density is .069 lbs. per cubic foot. Reduce the air temperature to 50° with all the other factors being the same and the air density increases to .075 lbs. per cubic foot – an 8.7% increase in air density.
Experimenting with the calculator at 50° with all other factors being equal, we found you have to get to an altitude of 2,250 feet to get to the same air density as a typical Florida summer day. You can see that air temperature does indeed have a dramatic effect on the air density, just as elevation does.
Let’s go to altitude at one mile high. At 90° with the other factors the same as described previously, the air density decreases to .057 lbs. per cubic foot. As an interesting aside, the air density at 0° at mile high elevation is the same as the air density at 90° at sea level.
To sum it up, it’s not so easy to figure distance gains based purely upon altitude alone. We must also largely take into account air temperature, and to a lesser extent barometric pressure. A one-inch drop in barometric pressure is roughly equivalent to going up 1,000 feet in elevation. Humidity’s effect on distance is negligible. Percentage-wise, based upon our experiences playing at mile-high altitude as opposed to sea level, we believe you can figure on roughly a 10% increase with your shorter clubs and a 5% increase with your longer clubs. As the old disclaimer goes, your individual results may vary.
As golf gets more into the scientific age, science gets more into golf. If you are interested in experimenting with the Shelquist Engineering air density calculator, we have provided the QR code for your smartphone.
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