Do shaped polys slide offer lower friction than smooth polys?

[Maui19]

After spending a lot of time looking at string friction and spin, and I wondering if we are missing something. I see people talking about how smooth polys offer lower friction (string against string), and I think that may be incorrect. For starters, TW's string friction rankings (http://twu.tennis-warehouse.com/learning_center/COFreporter.php) seems to indicate that a lot of shaped polys show low sliding friction. That got me thinking about the interaction between two strings, and how there are several factors determining how easily one string will slide against another: coefficient of static friction, coefficient of dynamic friction, and contact area. It's that last one that may the key. In a stringbed, a shaped string is going to have a smaller contact area than a smooth string. (Think about tires--all things being equal, a wide tire is going to provide higher friction with the road than a narrow one).

So maybe the "slipperiest" strings are going to be the shaped strings rather than the smooth ones.

 

[thebeast73]

this would make sense unless the cross string was softer. if the cross was softer then the main would dig into the cross and increase the force needed to get it moving

 

[Steve Huff]

I theory you would think so, but I imagine the thinner edges notch more easily too.

 

[share1law]

Slipperiest between the strings will help, but not between the ball and string. The string has two contact surfaces, one contacts the ball and the other contacts other strings.

The shaped string gives more spin because it increases the friction between string and ball while it does not change the friction between the strings. But the edges will be rounded quickly.

We beat this topic to death in the following post, check it out:
http://tt.tennis-warehouse.com/showthread.php?t=361507

 

[MuscleWeave]

I think slickness of the surface of the cross string is a greater factor than shape.

MW

 

[ethebull]

there are several factors determining how easily one string will slide against another: coefficient of static friction, coefficient of dynamic friction, and contact area. It's that last one that may the key. In a stringbed, a shaped string is going to have a smaller contact area than a smooth string. (Think about tires--all things being equal, a wide tire is going to provide higher friction with the road than a narrow one).

So maybe the "slipperiest" strings are going to be the shaped strings rather than the smooth ones.

Contact area is determined by pressure and the stiffness of the materials. I doubt shaped strings have the nessessary surface hardness to effect contact area. I am also skeptical about shaped strings changing the friction on the ball.

People are often taken in by over simplified, seemingly logical but mostly marketing driven, design elements. We are also vulnerable to being confused by our own perceptions.

Take bicycle tires for road riding; how they are marketed, sold, and perceived. The fact is, the fastest (lowest rolling resistance) tires are treadless (slick) tires, about 25-27mm wide, pumped to right around 100 psi. Slick tires actually grip better in corners than treaded tires, even in wet conditions. However the most popular tires are 23mm wide, pumped to 110-120 psi, and have some fine tread on them. The narrower harder tires feel faster, and the tread is believed to increase traction in the corners, but this is not the case.

 

[MuscleWeave]

Contact area is determined by pressure and the stiffness of the materials. I doubt shaped strings have the nessessary surface hardness to effect contact area. I am also skeptical about shaped strings changing the friction on the ball.

People are often taken in by over simplified, seemingly logical but mostly marketing driven, design elements. We are also vulnerable to being confused by our own perceptions.

Take bicycle tires for road riding; how they are marketed, sold, and perceived. The fact is, the fastest (lowest rolling resistance) tires are treadless (slick) tires, about 25-27mm wide, pumped to right around 100 psi. Slick tires actually grip better in corners than treaded tires, even in wet conditions. However the most popular tires are 23mm wide, pumped to 110-120 psi, and have some fine tread on them. The narrower harder tires feel faster, and the tread is believed to increase traction in the corners, but this is not the case.

So is this to say that a smooth cross will impart spin to the ball better, but a shaped cross will have lower friction with the mains? My thinking is that for a cross, it would be more important that it move freely with the mains, and leave it to the mains to make contact with the ball to produce spin.

Winner: Shaped Cross - I can't wait to try this out.

MW

 

[nvottennis]

After spending a lot of time looking at string friction and spin, and I wondering if we are missing something. I see people talking about how smooth polys offer lower friction (string against string), and I think that may be incorrect. For starters, TW's string friction rankings (http://twu.tennis-warehouse.com/learning_center/COFreporter.php) seems to indicate that a lot of shaped polys show low sliding friction. That got me thinking about the interaction between two strings, and how there are several factors determining how easily one string will slide against another: coefficient of static friction, coefficient of dynamic friction, and contact area. It's that last one that may the key. In a stringbed, a shaped string is going to have a smaller contact area than a smooth string. (Think about tires--all things being equal, a wide tire is going to provide higher friction with the road than a narrow one).

So maybe the "slipperiest" strings are going to be the shaped strings rather than the smooth ones.

Don't even worry about friction when it comes to spin. Just do what experience dictates.