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Old 02-27-2013, 07:51 AM   #60
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Join Date: Mar 2006
Posts: 4,342

I just found this thread. It’s an interesting topic.

I discovered 5-6 years ago an interesting phenomenon, and I confess that I still cannot fully explain the physics of it.

If you start with a stock racquet (doesn’t really matter what the starting specs are, it could be a light tweener, or it could be a players racquet, as long the swingweight is in the typical range), and then proceed to add mass gradually to the upper hoop, it will tend to become more powerful and less spin-friendly.

But as you continue to add mass, eventually you reach a “tipping point”, where further additions of mass start to have the opposite effect on spin and power level a groundstroke. Continued addition of mass beyond this tipping point result in a heavier, spinnier response from the stringbed (I had previously termed this zone beyond the tipping point as “SW2”).

I found it uncanny that the tipping point almost always occurs at a swingweight near 360 (but it can vary, depending on the starting specs of the frame). It seems to be at least in part a swingweight effect, because the “spin reversal” (that is, the increased spin with further mass increase) happens regardless of whether I place the extra lead at 3-&-9 or at 12. But I have also noticed that the heavy ball effect (seemingly effortless natural spin) is most pronounced when a significant fraction of the added mass is at 3 and 9.

I had presumed in the past that this “spin reversal” effect must be somehow related to the effects of ball flattening. But now I’m not so sure – I think ball flattening is part of the story, but these other effects discussed by TW professor (rotation effect, shortside effect, could also be contributing to this phenomenon).

The TW Professor’s experiment looked at what happens when you add 100g, which pushes you far past the tipping point, into the realm of very spin-friendly racquets. But I think the experiment is jumping over the more interesting question of what is happening in between. In my experience, it doesn’t take 100g addition to enjoy these heavy-spin effects – all it takes is pushing the swingweight of your racquet up to around 370 SW.

Doing the experiment on court (or even against a wall) is fun and easy to do. Just grab a roll of lead tape, and start adding a couple grams at a time, and observe the difference in ball response. When you finally get past the tipping point, and the ball starts to really dip after it leaves your stringbed, it is a strange sensation.

As for creating more consistent spin across the face from 3 to 9, I have never specifically tried to optimize that. However, I can tell you that whenever I try to play with a frame of stock swingweight (325 or so), I am never completely comfortable with the predictability of spin and launch angle. For me, the difference in control (with ‘control’ defined here as predictability of ball response) between 325 SW and swingweight in high 360s is night and day. Maybe part of the reason is that the high 360s swingweight range is where spin rate is nearly equalized across the face from 3 to 9?

Once you combine predictability of ball response (which for me comes with combining high enough swingweight and stiff enough stringbed) with the ability to control the racquetface through the contact point (which for me can be achieved by carefully tuning the MgR/I parameter), tennis becomes a lot easier.
BLX Blade 98. 26.75". 13.195 oz., 12.55", 357 SW. 16x20 (outer mains skipped)
Pre-Stretched Ashaway Kevlar 16g/ZX Monogut Natural 16g, 90/40 lbs

Last edited by travlerajm : 02-27-2013 at 07:54 AM.
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