What's better for spin: stiff or soft?

[marosmith]

I know we aren't talking scientifically, but if we were the soft racket when hit in the sweet spot imparts more spin.

Of course a larger racket that is stiff will be much more forgiving especially with fast swings and that's why I think it's considered the norm for many "spin players". Of course Fed has a mild/soft racket with a small head size so....

[Anton]

Originally Posted by marosmith

I know we aren't talking scientifically, but if we were the soft racket when hit in the sweet spot imparts more spin.

is there some actual science behind your claim of speaking scientifically?

There is nothing in racket flexing more that adds spin on the ball, if anything it causes less spin because there is less pressure on the strings.

You may swing harder with softer racket because you may not be as concerned with sending the ball too deep, that probably will add spin.

[mxmx]

To me, thickness of beam also has an influence and should be considered. Thinner beams feel faster through the air...my success with spin on the k-blade98 and tour 100, were at least partially due to the thinner beams feeling faster through the air at the swing angle needed in your swing...

[cork_screw]

Generally soft, but that's the least common indicator of what enhances spin.

String pattern, strings, tension, and head shape say more about spin than softness or stiffness.

[travlerajm]

Originally Posted by Anton

is there some actual science behind your claim of speaking scientifically?

There is nothing in racket flexing more that adds spin on the ball, if anything it causes less spin because there is less pressure on the strings.

You may swing harder with softer racket because you may not be as concerned with sending the ball too deep, that probably will add spin.

A flexier frame does have more spin potential for the same swingpath than a stiffer frame.
When the frame flexes in the direction normal (perpendicular) to the stringbed upon impact of the ball with the stringbed, the strings are not stretched as much in the normal direction as they are with a stiffer frame.
With less normal stretch of the stringbed, the strings are freer to stretch more in the downward direction (assuming upward swingpath). The increased downward stretch of the stringbed means that more energy is available to be transferred into tangential force on the surface of the ball (upon upward stringbed snapback). Most of this extra tangential force manifests as increased rpm - the rest goes into increased launch angle, requiring the user to close the face more, which in turn further increases rpm.

[D-money]

I've always felt that I get better spin with softer flex all other things being equal. I don't like the feel of flexible rackets though so it doesn't matter.

[Anton]

Originally Posted by travlerajm

A flexier frame does have more spin potential for the same swingpath than a stiffer frame.
When the frame flexes in the direction normal (perpendicular) to the stringbed upon impact of the ball with the stringbed, the strings are not stretched as much in the normal direction as they are with a stiffer frame.
With less normal stretch of the stringbed, the strings are freer to stretch more in the downward direction (assuming upward swingpath). The increased downward stretch of the stringbed means that more energy is available to be transferred into tangential force on the surface of the ball (upon upward stringbed snapback). Most of this extra tangential force manifests as increased rpm - the rest goes into increased launch angle, requiring the user to close the face more, which in turn further increases rpm.

The pressure would be lessened in both directions - normal AND downward, right? They maybe are freer to move downward, but now there is also less force pushing down.

Is there any any actual experimentation on this?

[travlerajm]

Originally Posted by Anton

The pressure would be lessened in both directions - normal AND downward, right? They maybe are freer to move downward, but now there is also less force pushing down.

The pressure on the stringbed is only lessened in the normal direction (assuming that the racquet has the same stiffness in the plane of the stringbed).

But this touches on an important point - the bending stiffness of racquets varies not only the plane perpendicular to the stringbed, but also in the plane of the stringbed.

Racquets that are stiffenend in the plane of the stringbed tend to be more spin-friendly than you might expect. Examples include the AeroPro Drive, the Prince More Technology frames (like NXG), the Prince O-ports frames, and some of the higher end Wilson's (like K6.1 95, which is highly reinforced in that plane in the throat).

The most spin friendly frames (not accounting for string pattern) are those where the ratio of bending stiffness in the plane of the stringbed to the bending stiffness in the plane perpendicular to the stringbed is very high.

Originally Posted by Anton

Is there any any actual experimentation on this?

I did my own careful experimentation on this subject 8 years ago, when I first discovered how much differences in stiffness could affect spin.

I demo'd about 20 different racquets of various designs (several at a time) to collect data. I then clamped the handle rigidly to my kitchen countertop, and suspended a 2kg weight from the center of the stringbed (I used a full half-gallon plastic orange juice container with a loop handle).

I measured the distance in mm that the tip of the racquet would deflect due to the suspended weight. Then I rotated the grip 90 degrees, and measured the same deflection in the other plane too. The 2kg weight was selected so that the deflections would approximately match up with Wilson's old si index scale - 2-3mm deflection for a Wilson Profile in the plane perpendicular to the stringbed.

The stiffness highest ratio I measured was for the K6.195 16x18. Not coincidently, this frame had the highest TW review rating for spin of any racquet tested at that time. The AeroPro drive was quite stiff in the plane of the stringbed, but since it was also stiff in the perpendicular plane, it's ratio was not as high as for the K6.195. The Wilson Profile had the lowest ratio of any frame I tested (not surprisingly, with 38mm beam). The Profile is by far the least spin-friendly frame I've ever used.

The bottom line is that for maximum spin, you want a thin-beam frame that is highly reinforced in the plane of the stringbed. These types of frames generally work best with tight string patterns to compensate for the extra spin potential from the stiffness ratio. On the other hand, frames with low stiffness ratios (really wide beams) will tend to require open patterns (or spin-friendly string setups) to compensate for the lack of inherent spin potential.

[Anton]

Originally Posted by travlerajm

The pressure on the stringbed is only lessened in the normal direction (assuming that the racquet has the same stiffness in the plane of the stringbed).

But this touches on an important point - the bending stiffness of racquets varies not only the plane perpendicular to the stringbed, but also in the plane of the stringbed.

Racquets that are stiffenend in the plane of the stringbed tend to be more spin-friendly than you might expect. Examples include the AeroPro Drive, the Prince More Technology frames (like NXG), the Prince O-ports frames, and some of the higher end Wilson's (like K6.1 95, which is highly reinforced in that plane in the throat).

The most spin friendly frames (not accounting for string pattern) are those where the ratio of bending stiffness in the plane of the stringbed to the bending stiffness in the plane perpendicular to the stringbed is very high.

I did my own careful experimentation on this subject 8 years ago, when I first discovered how much differences in stiffness could affect spin.

I demo'd about 20 different racquets of various designs (several at a time) to collect data. I then clamped the handle rigidly to my kitchen countertop, and suspended a 2kg weight from the center of the stringbed (I used a full half-gallon plastic orange juice container with a loop handle).

I measured the distance in mm that the tip of the racquet would deflect due to the suspended weight. Then I rotated the grip 90 degrees, and measured the same deflection in the other plane too. The 2kg weight was selected so that the deflections would approximately match up with Wilson's old si index scale - 2-3mm deflection for a Wilson Profile in the plane perpendicular to the stringbed.

The stiffness highest ratio I measured was for the K6.195 16x18. Not coincidently, this frame had the highest TW review rating for spin of any racquet tested at that time. The AeroPro drive was quite stiff in the plane of the stringbed, but since it was also stiff in the perpendicular plane, it's ratio was not as high as for the K6.195. The Wilson Profile had the lowest ratio of any frame I tested (not surprisingly, with 38mm beam). The Profile is by far the least spin-friendly frame I've ever used.

The bottom line is that for maximum spin, you want a thin-beam frame that is highly reinforced in the plane of the stringbed. These types of frames generally work best with tight string patterns to compensate for the extra spin potential from the stiffness ratio. On the other hand, frames with low stiffness ratios (really wide beams) will tend to require open patterns (or spin-friendly string setups) to compensate for the lack of inherent spin potential.

Interesting theory, but even without questioning methodology there is clearly a problem:

stiffness of a racket is not tested in stringbed plane, it is tested in normal to stringbed plane ONLY.

From your examples - Super spiny K 6.1 95 has flex rating of 69!

From your earlier comments one would draw conclusion that because k 6.1 95 is stiff, then therefore it is not as spin friendly as something similar specs but softer, for example Yonex RQiS 1 Tour, which is btw has quite low rebound angle (and I assume spin)

[travlerajm]

Originally Posted by Anton

Interesting theory, but even without questioning methodology there is clearly a problem:

stiffness of a racket is not tested in stringbed plane, it is tested in normal to stringbed plane ONLY.

From your examples - Super spiny K 6.1 95 has flex rating of 69!

From your earlier comments one would draw conclusion that because k 6.1 95 is stiff, then therefore it is not as spin friendly as something similar specs but softer, for example Yonex RQiS 1 Tour, which is btw has quite low rebound angle (and I assume spin)

I misrecalled the model. It was another red-and-white wilson with similar name that scored 86 for topspin. Don't think it was the ncode either. But I did measure the stiffness in both directions and I recall it only deflected 4 mm in plane, and 7mm in perp plane. 7mm was typical for a frame with mid 60s flex, but 4mm in plane was the stiffness I measured.

[travlerajm]

Originally Posted by Anton

Interesting theory, but even without questioning methodology there is clearly a problem:

stiffness of a racket is not tested in stringbed plane, it is tested in normal to stringbed plane ONLY.

From your examples - Super spiny K 6.1 95 has flex rating of 69!

From your earlier comments one would draw conclusion that because k 6.1 95 is stiff, then therefore it is not as spin friendly as something similar specs but softer, for example Yonex RQiS 1 Tour, which is btw has quite low rebound angle (and I assume spin)

I misrecalled the model. It was another red-and-white wilson with similar name that scored 86 for topspin. Don't think it was the ncode either. But I did measure the stiffness in both directions and I recall it only deflected 4 mm in plane, and 7mm in perp plane. 7mm in perp plane was typical for a frame with mid 60s flex, but 4mm in plane was the stiffest value I measured. I will try to dig up my spreadsheet.

[travlerajm]

I looked back and dug up some of the stiffness measurements I had entered 5 years ago (I measured others but, apparently these are the only ones I recorded and saved):

Racquets, in order from highest (most spin-friendly) stiffness ratio to lowest:
Yonex RDX500mp - dx: 7.1mm, dy: 5.2mm, ratio: 1.37
Wilson nSix-One 95 - dx: 7.2mm, dy: 5.3mm, ratio: 1.36
O3 Blue - dx: 11.3mm, dy: 9.0mm, ratio: 1.26
POG OS - dx: 4.9mm, dy: 4.6mm, ratio: 1.07
Aeropro Drive plus - dx: 5.5mm, dy: 5.3mm, ratio: 1.04
O3 tour mp - dx: 6.2mm, dy: 6.1mm, ratio: 1.02
Flexpoint radical OS: dx: 7.2mm, dy: 7.3mm: ratio: 0.99
Wilson Hyper Hammer Titanium 5.0 OS - dx: 4.6mm, dy: 7.0mm, ratio: 0.66

Some notes:
dy = deflection in plane of stringbed
The Hammer Titanium 5.0 is indeed extremely UNspin-friendly, even though the string pattern is extremely open.
It's interesting to see that the POG's cross-bar appears to have a measurable stiffening effect in plane.
The deflections are high for the O3 Blue because it had a soft rubberized pallet that was not rigid, but I don't the ratio was affected much.

[kaiser]

Trav, interesting stuff. What exactly do you mean by stiffness in the string bed plane and how did you measure it?

And did I understand correctly that you measured the stiffnes in the perpendicular plane by fixing the handle and suspending a weight from the middle of the stringbed? If so, how did you control for differences in strinbed stiffness between the various rackets?

[travlerajm]

Originally Posted by kaiser

Trav, interesting stuff. What exactly do you mean by stiffness in the string bed plane and how did you measure it?

And did I understand correctly that you measured the stiffnes in the perpendicular plane by fixing the handle and suspending a weight from the middle of the stringbed? If so, how did you control for differences in strinbed stiffness between the various rackets?

The racquet handle is clamped on the countertop, and the rest of the frame cantilevered out. I then hang the weight from the center of the stringbed (modeling the point of impact). I measure the deflection of the tip (difference in height when weight is applied to center of stringbed).

I take the measurement with the racquetface directed upward (dx), and then also take the measurement with the racquetface facing to the side (dy).

The deflection of the tip is, for all practical purposes, independent of the deflection of the stringbed when weight is applied to the stringbed.

One other thing I forgot to mention, the stiffness ratios correlate extremely well with TW topspin ratings. The correlation becomes almost linear if the weighted ratio dx/(dy)^2 (or other higher power of dy) is used (the O3 Blue omitted from analysis due to soft pallet).
In other words, dy is a bigger factor than dx in determining spin potential. I have also found that dx and dy are both more important factors than string pattern.

[ChicagoJack]

Trav -

You've been posting about this subject for many years, big thanks. Would it be a gross oversimplification to say that with regards to spin enhancement, you advocate:

1. Thinner beams with flexibility in the throat. (Increased dwell time -> Promotes downward string bed deformation -> loads the string slide and snap back mechanism.)

2. Stiffer string beds (increased ball deformation -> additional spin as the ball returns to a round shape, similar to the overspin present in super balls, I think you sent me a paper on this back in 2006)

3. Stiffer hoops. ( dont understand what the deal is here)

Like Kaiser, I too am puzzling over what you mean by "stiffness in the string plane" perhaps you are advocating for stiffer hoops, to accompany the flexible throat? And if that's correct, could you elaborate on that particular concept? Im kinda fuzzy on that.

Thanks

Jack

[Anton]

Originally Posted by travlerajm

I looked back and dug up some of the stiffness measurements I had entered 5 years ago (I measured others but, apparently these are the only ones I recorded and saved):

Racquets, in order from highest (most spin-friendly) stiffness ratio to lowest:
Yonex RDX500mp - dx: 7.1mm, dy: 5.2mm, ratio: 1.37
Wilson nSix-One 95 - dx: 7.2mm, dy: 5.3mm, ratio: 1.36
O3 Blue - dx: 11.3mm, dy: 9.0mm, ratio: 1.26
POG OS - dx: 4.9mm, dy: 4.6mm, ratio: 1.07
Aeropro Drive plus - dx: 5.5mm, dy: 5.3mm, ratio: 1.04
O3 tour mp - dx: 6.2mm, dy: 6.1mm, ratio: 1.02
Flexpoint radical OS: dx: 7.2mm, dy: 7.3mm: ratio: 0.99
Wilson Hyper Hammer Titanium 5.0 OS - dx: 4.6mm, dy: 7.0mm, ratio: 0.66

Some notes:
dy = deflection in plane of stringbed
The Hammer Titanium 5.0 is indeed extremely UNspin-friendly, even though the string pattern is extremely open.
It's interesting to see that the POG's cross-bar appears to have a measurable stiffening effect in plane.
The deflections are high for the O3 Blue because it had a soft rubberized pallet that was not rigid, but I don't the ratio was affected much.

Problem remains - Wilson nSix-One 95 also had a very high stiffness rating (and feel) as well and produced more spin than a softer racket witha similar spec, but considerably softer Yonex I mentioned. 500mp btw had more open pattern then the n95.

Basically the problem is that there is no ratio data, there is only data for stiffens in normal to string bed plane. I can't look at the racket stats on tennis warehouse and conclude how good a racket would be for spin.

Jack - when RDC machine tests stiffness it applies pressure to racket at 90 degrees to racket as it lays flat. 90 degrees angle is called "normal to". So RDC machine tests stiffness in a plane normal to stringbed plane

===----==
^

If you were to apply pressure to a racket that lays on it's side that would be testing stiffness in the plane of stringbed plane:

O----==
^

[travlerajm]

Originally Posted by ChicagoJack

Trav -

You've been posting about this subject for many years, big thanks. Would it be a gross oversimplification to say that with regards to spin enhancement, you advocate:

1. Thinner beams with flexibility in the throat. (Increased dwell time -> Promotes downward string bed deformation -> loads the string slide and snap back mechanism.)

Yes - this is generally true.

Originally Posted by ChicagoJack

2. Stiffer string beds (increased ball deformation -> additional spin as the ball returns to a round shape, similar to the overspin present in super balls, I think you sent me a paper on this back in 2006)

The effect of sringbed stiffness on spin is complex. Yes, increased ball deformation leads to more spin. But it may be at a cost of less string stretching. So in some cases stiffening a stringbed will increase spin, but in many cases it will actually reduce spin.

After much experimentation with a variety of string types and patterns, I currently advocate using a stringbed that is dense and stiff in the center, but open and deformable at the periphery. I skip the top and bottom cross and the outer mains on my current racquet to turn an 18x20 into a 16x18 that is dense in the center. The stiffness in the center where the ball meets the strings is important for control - if the center of the stringbed is soft, the ball will dent into it, causing launch angle to be more dependent on swingpath and incoming spin. You don't want that - if the stringbed does not dent, the launch angle is more independent of the incoming spin and swingpath, so the launch angle is determined mostly by racquetface angle, giving optimal control. Having a more open periphery lets the center of the stringbed deflect more to increase spin and power.

The type of spin matters. Spin is less useful if the added bit gives high launch angle. It's much better to have high rpm with low launch angle. As a rule of thumb, the "good" type of spin is easiest to get with a really dense stringbed strung really loose with strings that slide against each other well. The "bad" type of spin tends to be produced in very open patterns unless they are strung very tight.

Originally Posted by ChicagoJack

3. Stiffer hoops. ( dont understand what the deal is here)

Like Kaiser, I too am puzzling over what you mean by "stiffness in the string plane" perhaps you are advocating for stiffer hoops, to accompany the flexible throat? And if that's correct, could you elaborate on that particular concept? Im kinda fuzzy on that.

Stiffness in the stringplane means resistance to bending when you clamp the handle and pull the racquet toward the 3 or 9 edge of the hoop. An Aeropro Drive, for example, is widened in the throat to counter this type of bending, making the frame more spin-friendly. The POG and NXG frames too, are reinforced in this direction with the cross-bar, making them more spin-friendly.

[fuzz nation]

Funky business...

My NXG mids took my assumptions regarding racquet types, string patterns, and spin production and planted them all firmly on their ear. While those have probably the most dense pattern in any graphite frame I've owned, they probably also rank among the greatest spin-factories I've ever used.

[Anton]

Originally Posted by travlerajm

The type of spin matters. Spin is less useful if the added bit gives high launch angle. It's much better to have high rpm with low launch angle. As a rule of thumb, the "good" type of spin is easiest to get with a really dense stringbed strung really loose with strings that slide against each other well. The "bad" type of spin tends to be produced in very open patterns unless they are strung very tight.

Yep that's ideally what I'm after - more spin but at the same time keep the launch angle low.

[travlerajm]

Originally Posted by Anton

Yep that's ideally what I'm after - more spin but at the same time keep the launch angle low.

The racquet that gave me the most amazing spin while still having low launch angle was the BLX Pro Tour. I had it strung with kevlar/poly in the low 40s.
It has just about the densest patterned you can buy. Unfortunately, I had to return the one I bought from TW because it had a misaligned pallet, and they had no more in stock to replace it.

On the other end of the spectrum, I had to move on from the O3 Red because the extremely open pattern was not a good match for the extremely spin-friendly stiffness ratio. The launch angle was just too extreme, especially with spin-friendly string setups. That's why I'm not really tempted by the Steam 99s at all.

I just ordered a BLX Blade to replace my BLX Pro Tour to have something similar to play around with, but I don't think the Blade has as dense a pattern as the Pro Tour though.