Air Pressure and Golf Ball Distance - Page 2

Quote:

Originally Posted by Golfingdad 

 

Umm, this is a forum.  Everybody does that on every thread.  If you want to have a private conversation with David in Florida then start a PM with him.  Several people read these and comment when they feel they have something to add.

 

And since I'm here, I agree with Sacm and David regarding how you calculate percentages, and furthermore, agree with David regarding his hoofbeats parable.  I think you might be waaaaay overthinking this.

You're telling me that everyone thread jacks on every thread. Listen, only A$$ holes posts stupid comments just to pad their thread count or start arguments just to argue; the glass is always half empty with you guys. With 1,800 posts in less than a year, I can see that you've been busy posting a lot about nothing. Where do you find the time to golf, let alone look after your family...my God man!

Now as to your comment about calculating percentages; it has nothing to do with the expression of change in air pressure or drag. Clearly you have not read the entire thread; a 10% change in Air pressure as Sacm is calculating is not physically possible outside of a hurricane, yet he does not dispute the effects of a 10% change on the flight of a golf ball. LOL, I'm glad you agree with him...

Now before you reply, I'm fairly certain the thread jacking rules have not changed in the 5 years I've been a member here, kindly buzz off so that I don't have to get moderators involved. I won't $hit on your threads either...

Quote:

Originally Posted by sacm3bill 

 

I understood what you were saying. That doesn't mean I agreed with it. So I pointed out you were wrong. You then re-explained your thought process, which I understood the first time, hence the "I understood the first time". That was meant to convey that the reason I disagreed with you was not because of a misunderstanding, or because I needed clarification. I disagreed with you because I think you're wrong.

 

Clear now?

Wrong about what? So you are not agreeing with me that it is not possible for barometric pressure to fall from 101.34 (standard) to 91.2, 10% as you would calculate percentages. You are not agreeing with me, even though the lowest non hurricane barometric pressure recorded in the lower 48 is 95.6.

OK, thanks for the arguement.

Since my last post, some people have added to the actual theme of the thread; it was my intention to draw these smart people in. Yes, it's said it went the way it did.

I did not start this thread to Argue, I made it very clear I was no expert from the beginning. Some have also pointed out the rudeness of just a few posters, (they are not referring to me). Please re-read this thread and consider who was actually being the jerk. If the "owner" and "moderator" of this board will not defend those who would try to have civil conversation, then they have no choice but to defend themselves in whatever fashion they feel effective. I'll admit ignored the moronic behavior might have been more effective...these guys are still auguring moot points which have nothing to do with the subject matter.

Mod Edit: Parts where you call other people "jackasses" have been removed. Behave maturely.

Quote:

Originally Posted by sacm3bill 

 

It's irrelevant how much change is "possible".   What you're wrong about is when you speculate that a 2 or 3 Pa change in pressure can result in a 10% change in carry distance, as you did in your first post.  David pointed out that the pressure change from say, 101 to 102 was only 1%. You claimed it was more like 14%. That is where you're wrong.  Please believe me when I tell you that in no scientific community is the "normal range" of a value taken into account when measuring the percentage change of that value.

 

Please prove this. Your stock example was an attempt to make me understand how to calculate percentage, but clearly, even in your example, the math would not be possible. Air Pressure can change 5-10%, the professor of physics I linked to said as much, but if I apply your math to this change, you get a number that isn't even possible. So where my math is clearly not correct and I said it wasn't from the start, your math is absurd and your posts have done absolutely nothing to explain the effects of Air Pressure on golf ball flight.

I fully expect to get an arguement from you without a single attempt to prove your possition...

Quote:

Originally Posted by boogielicious 

It is sad how all these promising threads always down grade into bickering.  I don't know why.  Maybe people just misread the OP or the responses and it just does a death spiral from there.  In the spirit of the holidays (any holiday), let's all try to be a bit more civil.

 

Back to the original subject.  We are discussing three factors that affect air density, temperature, humidity and barometric pressure.  It is a bit of a complicated calculation.  But I will try to put some numbers up for digestion of the nerdy crowd like me.

 

Barometric pressure - a quick calculation of a 994 mbar BP shows this would be equivalent to only 150 meters altitude gain.  994mbar/1.333 = 745.6mmHg  (1mmHg = 1.33322368 mBar).  From the linked chart we get about 150 meters altitude.  

 

source:  http://www.engineeringtoolbox.com/air-altitude-density-volume-d_195.html

 

Humidity - we are stating that humidity is not varying much, but for information, the density can be calculated.

 

source: http://www.engineeringtoolbox.com/density-air-d_680.html

 

Lastly temperature:  We all know cold air is more dense.

 

http://www.engineeringtoolbox.com/air-temperature-pressure-density-d_771.html

 

Putting it all together:  I found this calculator on line;

 

http://www.denysschen.com/catalogue/density.aspx

 

Air density for 46F, 80% humidity normal BP of 760 (sea level) would be 0.0778 lbs-m/ft3

Air density for 46F, 80%, 994mbar (or 150 meters - 492 feet) would be 0.0764 lbs-m/ft3 or about 2% difference.

 

The effect of density on distance is a bit more complicated.  From this source. http://www.golf-simulators.com/physics.htm, and the equations below, it looks like there is a linear relationship.

 

 

where p is the density of air at sea level.  But drag coefficients will also vary with temperature and therefor density.  I couldn't find anything on that.  Both the X and Y components are affected the same.  So we have to make an educated assumption that the distance affect, all things being equal except barometric pressure, would only account for 2% change in distance.

 

None of the equations above have been verified, so we will have to accept them as is.  Feel free to find errors in my assumptions.

 

Unless we are missing a factor, on a 125 yard shot you would only gain about 2.5 yards.  But that may be enough to overshoot the green.

 

BTW, in New England this time of year, if the BP was down at 994, it would be blowing like crazy!  We rarely get low BP and calm weather unless we are in the eye of a N'or Easter.

Wow, awesome info...thanks.

So I played in an event today at Swan-E-Set Golf course just north of Pitt Meadows BC, this is about 30 minutes north east of Vancouver. Even though the course is around a 1 hour drive from the nearest coastline, the area is below sea level. It's a place where golfers now their ball is not going to fly as far, the same goes for Golden Eagle golf course which is 10 minutes from it. I played with 7 cap, an 8 cap and of course I'm a 6 for this course.

Where I was hitting wedge 135 just 2 days ago (10 minutes from the coastline, but a few feet above sea level), today I was lucky to hit a wedge 115 and my playing partners were no different, we were all talking about loss of distance. 160 approach shots required 5 iron; even in the winter, 5 iron goes about 170-175 for me at most Vancouver courses.

The temperature was exactly the same today as Sunday. The humidity was roughly the same, 93% in the nearest town, 10 minutes away. Sunday it was 88-90% in North Vancouver. I don't know what the barometric pressure was, since I was not carrying a barometer, but in the nearest town it was 100.2 today, which is lower than normal, we are in the middle of a low pressure system which started Sunday. Since the course is below sea level and sea level pressure in 101.34, I can only imagine the pressure was higher, perhaps 2 points higher than Sunday's 99.4.

For those who have participated in this thread, and those who will. It's a fact that air pressure fluctuate greatly in some areas of the planet and very little in others. If you don't see a significant change in golf ball distance from one week to the next, it's very likely the air pressure in your area does not change much. If on the other hand, you wonder why the ball just doesn't fly sometimes, it may be the air pressure, but as others have already said, temperature and humidity can be influencers. I'm more interested in ball flight distance changes when the temp and humidity are constant

Quote:

Originally Posted by Paradox 

all I know is that a pressure change from 101 to 102 would result in a percentage change of .9%  

 

(new value - old value)/ old value = n x 100 = % change.

It might very well, but I would be very surprised if the effect on air density was just 0.9% and that's what this thread is about.

The physics professor in the link I posted previously made reference to a 10% change in air pressure and the influence on golf ball distance (a 240 yard drive would be 267). He also made references to change in air pressure not being more than 5-10% usually. Since it is impossible for the air pressure to drop 10% by the way you are calculating it, he must be talking about a different unit of measure. The lowest recorded non-hurricane barometric pressure in the lower 48 is 95.6 and it most certainly did not get to that value overnight.

Quote:

Originally Posted by sacm3bill 

 

Agreed, the units matter, especially when the systems define different points as zero, and the percentages will change depending on that. I'm just saying that the observed normal range ("from 98 to 105... for 98% of the inhabited areas of the planet", as limoric put it), does not come into play when figuring percentage change.

 

 

The percentage change doesn't matter and I don't care what it is. I'm after the percentage change in air density or the percentage change that an object is affected by when passing through that air density. It's the point of the whole thread, you could have chosen to look at it a different way, despite how you understood my description..