Can someone tell me the impact of hitting down on putts?

[Slab]

What I mean is with the putter having about 3 degrees of loft what is the impact (physics) to the spin/distance/roll characteristics etc, of a ball much further back in the stance (off right toe) so when struck the loft is zero or even a negative loft

thanks in advance

 

[JT77]

Not 100% sure but if u hit into the ball with negative loft it would force the ball into the turf first causing a poor roll of the ball. I think the idea is to get the ball rolling a smooth as poss as quick as poss

 

[the_coach]

negative attack, negative loft at impact, will cause the ball to travel in a 'bounce' type pattern often times a strike delivering this pattern (ie negative AoA so neg loft) the second & third 'bounces' are bigger than the initial one.

(as the ball is initially driven downwards into it's resting spot {a ball has always eventually come to rest in an indentation on the green even though it's imperceptible} on the green so with this there is an element of trapping the ball - even though the ball is in contact with the face for little ways less than half a millisecond)

there will also be a repeated bunch of bounce motions at some distances through the balls travel (usually around 2", 4" & 7") until the ball speed falls off & backspin dissipates to reach zero skid to allow a momentum of 'true roll'.

- object of a solid putt is to get the ball into a roll pattern of motion as soon as possible.
you want the time taken to 'zero skid' to be as short as possible only after the zero skid point will the ball roll, earliest the ball reaches 'zero skid' the more consistent then the ball is at holding it's intended path.
approx guide the optimum zero skid number is around 10%-15% the overall distance of the putt (variable due to speed of green)

so negative strike won't give the optimum conditions for the ball to roll to hold it's line, also won't be a consistent strike contact so there can be a large variable in pace putt to putt - particularly the longer the putt & the more 'force' to the strike can also affect the starting direction

ideally the putter folks use along with their stroke mechanics should be looking to achieve zero skid at the earliest point in the ball travel
- bearing in mind the 10% to 15% ratio to overall distance (% difference due to green speed)
so in a 10 ft putt optimum zero skid through optimum strike would happen approx 1.5ft in the balls travel

things to consider as to why there maybes both negative AoA/loft at strike would be - not enough dynamic loft at impact - hitting down on the ball with the putting stroke - having the ball to far back in the stance - the putter not having enough static loft

 

[Slab]

Thanks guys

Coach I appreciate the time taken for your reply, its pretty much what I was looking for and while I don't understand some of the terminology, it does make sense

I'm a tinkerer (even when somethings not broken) and recent changes to ball position etc have given mixed putting results so I wanted to understand the effect on the ball, its easy to see what the ball does differently when you have a driver in hand but not so easy to spot it when the putts only 10ft

 

[the_coach]

optimum ball position is going to be one that at contact is at the bottom of the swing arc which then will have the AoA between 0º & 1º. at contact the putter head ideally will be at a constant speed - no acceleration or decel. putter shaft at strike optimum angle is very near to vertical.

for most folks with a good set up posture & the right length putter this puts the ball position a fraction ahead of center sternum, weight pretty even through stance, but slightly favoring the lead leg.

any solid putt the ball leaves the ground from the get go (mostly you can't see this but it happens) with decent strike loft will impart little backspin. for the short time the ball is airborne it does not lose any ball speed at first ground it starts to both lose ball speed & scrub off the backspin by skidding.

then you reach zero skid {zero skid is the point where all skid has been eliminated from the golf ball's roll. This happens when the golf ball rotates 360 degrees every 5.25 inches (the circumference of the golf ball)} - then the ball is on ground with true roll but will be continuing to lose ball speed, but not at a constant rate, initial velocity, slope, moisture, direction of roll to grain all has a bearing.

 

[Slab]

Thanks for the additional info Coach, much appreciated