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# Downhill vs Uphill Putts

June 1 2015 at 5:12 PM

Hi All,

Curious if anyone has collected empirical or bothered to calculate the relative increase and decrease in distance a putt needs to be hit to stop at the hole. For example, a downhill 10' putt on a 1% slope would need to be hit like a XX foot level putt on the same stimped green? While a uphill 10' putt on a 1% slope would need to be hit like a XX foot level putt on the same stimped green? Would then be curious how these values change for 2% and 3% slopes.

Thanks

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Geoff Mangum
Owner
71.54.49.31

# Uphill / Downhill and Level-Equivalent Putts

June 4 2015, 11:48 PM

Sure! I've been teaching this for years.

The basic conversion is roughly (rule of thumb) each 1" of elevation difference between ball and hole requires 1 foot of level putting added for uphill or subtracted for downhill.

For example, if a putt involves 6" of net uphill elevation change from the ball to the higher hole, the player can add 6 feet past the hole to locate a "virtual hole" and then, pretending that the putt is no longer uphill but now level, the player putts all the way to the virtual hole, and this "extra" energy is what it takes to move the ball 6" vertically in gravity. The ball actually stops at the real hole.

This "rule of thumb" derives from the fact that a Stimpmeter translates 10.34" of potential energy from the vertical release height of the ball into about 10 feet of lateral / horizontal roll across the green. So, roughly, as a rule of thumb, this is "about" 1" of vertical elevation corresponds to 1 foot of horizontal roll.

This has nothing to do with slope, but with NET elevation difference between ball and hole.

There is no real point in calculating a more exact conversion factor for different Stimp speeds. And it really only applies to substantial elevation changes, as on long putts over significant slope and up or down steep tiers involving substantial vertical elevation change over a short horizontal span.

Cheers!

Geoff Mangum
Putting Coach and Theorist

PuttingZone.com -- over 200 Certified PuttingZone Coaches teaching in 21 Countries Worldwide and growing strong!
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 This message has been edited by aceputt from IP address 71.54.49.31 on Jun 4, 2015 11:49 PM

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sammy
184.147.205.127

# More putting variables....

June 6 2015, 4:46 PM
 Geoff... have you ever encountered and even recognized a green with a variable stimp .... perhaps due to different water saturation, grain directions, brown patches and even mowing irregularities? Can you account for all the variables from your vast putting experience and depth of knowledge when you read a green?
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Geoff Mangum
Owner
71.70.255.203

# Green Speed variation

June 21 2015, 11:46 AM

Sure! I have been a greenskeeper mowing greens daily and setting pins and concerning myself with problems on the greens from abusive use, excessive heat, excessive water, pests, disease, and weeds.

Green speed over the entire surface of EVERY green is never perfectly uniform. But it's a question of degree and significance to humans playing the game of golf.

First, the grass coverage is not perfectly uniform, some areas more sparse, some diseased, some weakened by heat, some "hydrophobic" and won't accept water for the roots, some covered with poa annua seed heads, etc. So there is always SOME variability of green speed across the entire contour surface.

Second, technically speaking as a matter of the physics of grass friction that determines green speed, the exact same surface coverage -- perfectly uniform grass -- presents different green speed depending upon whether the surface area is level or sloped. Tilting the surface out of gravity level reduces how gravity holds the mass of the ball into the surface, and this affects the friction.

Third, the speed of the ball affects the green speed. Even if the surface is perfectly level and the grass perfectly uniform, a ball experiences differences in green friction depending upon the ball's speed. A slower ball experiences more friction than a faster ball.

Fourth, the "launch conditions" of the putt at the beginning affect the green speed at least in the beginning segment of the putt until this initial conditions are washed out of the putt. For example, a ball that hops off the face (such as one that makes a dotted pattern on a dew-covered green instead of a uniformly continuous track thru the dew) experiences less friction: balls in the air do not get retarded by the grass friction. But, cutting the other way, balls with energy getting consumed in hopping up and down instead of moving laterally towards the target go shorter along the surface than otherwise, so this is sort of a pseudo-friction that makes up for the Swiss-cheesing of actual friction due to hopping, and the net effect is nearly a wash. A different hopping effect is that balls in the air don't "take the break" while in the air, as only the lean of the slope directs the ball "downhill" according to the slope -- consequently, hopping balls don't break as much as expected, which is sort of like the green speed being a bit slower (more friction) than usual, as slow greens break less than faster greens.

All that being said, it is still a matter of degree and significance.

And my testimony from 25 years direct experience is that the degree of difference in green speed, and the frequency and significance of the differences, are "nugatory".

Your approach to the issue -- finding problems everywhere when there really are no real problems of practical significance, reminds me of Zeno and his claim that because walking to a wall always first requires walking halfway from wherever you currently stand, no one could possibly ever actually walk all the way to a wall. Which, of course, is utter nonsense.

Cheers!

Geoff

 This message has been edited by aceputt from IP address 71.70.255.203 on Jun 21, 2015 11:48 AM

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sammy