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#### Re: New WGT Calculator in Progress

Sun, Aug 2 2020 12:55 AM by ichott. 53 replies.
•  Redmonod 15 Posts Wed, Apr 15 2020 1:06 PM

There are a number of sources online and in books with equations that describe the lift and drag forces on a golf ball. It’s a very deep rabbit hole if you have the time to pursue it. But, if you’re like me and enjoy that sort of thing, it can be great fun. Just don’t expect miracles in the end. I’ve built a number of spreadsheet-based trajectory models over the last few years and given enough time and patience  it is possible to approximate what each of your clubs is doing (using club mapping to adjust the models). For example, I use one to determine the correction to apply for elevation, since it depends on what club is being used, what spin is being used, and how hard the ball is hit. Which is to say it’s not a simple divide by 3 or whatever (although that’s often a close approximation). That spreadsheet calculates a trajectory (with lift and drag) for a given club to determine the yardage where the ball would land in the absence of wind. The biggest unknown is how WGT treats wind. For example, how does the engine model the wind velocity vs. height above the ground (linear equation or something else)? And how do the wind parameters change from course to course and day to day? As best I can tell, WGT wind is really not like real world wind. So I rely on estimations for wind effect as I haven’t yet been able to get a model to work consistently (but I keep working at it).

The best players that play by feel will always have an advantage over people like me that rely on spreadsheets. With time and experience they just take a lot more factors into account. I just enjoy the challenge of building models and I hope you will too.

•  BaggerPantz 55 Posts Wed, Apr 15 2020 5:42 PM

Half the fun for me is trying to replicate their physics by tweaking my spreadsheet.

The fact you can hook up a Trackman to this and play it as a simulator means their engine must roughly approximate those used by club fitters.  That’s the direction I’m heading in now... (although it sounds like you went there and it wasn’t any more accurate than my if/then statements).

So, one thing I did to test this theory — I tried to figure out what WGT must think my swing speed, backspin and launch angle must be — by mapping the WGT driver carry and apex totals and then getting flightscopes trajectory optimizer to match the result.

Result: 167mph swing, 12degree launch, 1800 rpm backspin, gets me roughly the same result on WGT Kiawah #1 and Flight scope.  So maybe there is potential using this approach.

Ill keep tinkering with it.

redmonod, Check your WGT profile wall for message.

•  Tony08888 269 Posts Thu, Apr 16 2020 4:12 AM

BaggerPantz:

I’ve spent some time and looked into the WGT engine.  It’s actually pretty sophisticated.  My simple algebra and calculus math is never going to “solve” it, and here’s the reason; MAGNUS FORCE.

Pausing here.  Curious if others have tackled Magnus force and how they overcame it.

Bagger - check out "WGT Tips" on mistresscossete's blog. She deals with a lot of those variables. It's a long read, but if you're good with math this may help you overcome some of these math problems.

~ Tony

•  ichott 7 Posts Sun, Aug 2 2020 12:55 AM
Hi bagger, love your methodology and spirit (ignore the naysayers!) , I agree and it’s part of the ‘fun’ of fine tuning within WGT, just like real golf, it’s “not a game of perfect” it’s a game of minimising errors/mistakes and spreadsheets are a way to help those interested in that, and count me in! Would appreciate seeing your ss please in return for mine, which is pretty good I 🤔