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View Full Version : String Beds Have Corners: Lead Placement


TimothyO
02-02-2012, 07:42 AM
After several recent experiments with lead placement I've noticed that it can be far more effective to focus on head lead placement relative to string bed pattern and physical head shape than the traditional clock-based hoop location. The difference is more or less important depending upon the area we're talking about. In other words, 12 is 12 whether were talking about head or string bed.

But for what so many call 2/10 or 5/7 there seems to be more value on focusing on the string bed pattern rather than the head.

For example, it seems that lead placed at the "corners" of the string bed has a more significant effect on feel that what might be the 2/10 clock position. This is more important if you're trying to limit weight and get the most bang for your mass.

Even 3/9 on the head and the string bed are not "co-located". Depending on head shape relative to string pattern the string bed 3/9 can be higher or lower than the head 3/9. And even the head's 3/9 position (as defined as being the vertical center of the head) can be different from the head's widest point which matters since the farther the lead is from the center the greater its effect on stability.

Is there some research or technical document that describes in detail the effects of lead beyond mere clock positions? I'd like to learn more about lead relative to string bed pattern and head shape rather than just "clock position". It really seems that the physics of lead placement is driven by its relationship to the sting pattern and head shape.

corners
02-02-2012, 09:11 AM
After several recent experiments with lead placement I've noticed that it can be far more effective to focus on head lead placement relative to string bed pattern and physical head shape than the traditional clock-based hoop location. The difference is more or less important depending upon the area we're talking about. In other words, 12 is 12 whether were talking about head or string bed.

But for what so many call 2/10 or 5/7 there seems to be more value on focusing on the string bed pattern rather than the head.

For example, it seems that lead placed at the "corners" of the string bed has a more significant effect on feel that what might be the 2/10 clock position. This is more important if you're trying to limit weight and get the most bang for your mass.

Even 3/9 on the head and the string bed are not "co-located". Depending on head shape relative to string pattern the string bed 3/9 can be higher or lower than the head 3/9. And even the head's 3/9 position (as defined as being the vertical center of the head) can be different from the head's widest point which matters since the farther the lead is from the center the greater its effect on stability.

Is there some research or technical document that describes in detail the effects of lead beyond mere clock positions? I'd like to learn more about lead relative to string bed pattern and head shape rather than just "clock position". It really seems that the physics of lead placement is driven by its relationship to the sting pattern and head shape.

I see what you're saying about added mass relative to headshape as those things relate to twistweight. But what does string pattern have to do with it? There is this paper (https://docs.google.com/viewer?a=v&q=cache:bX5KCzbnyX0J:www.physics.usyd.edu.au/~cross/customising.pdf+&hl=en&gl=us&pid=bl&srcid=ADGEEShedJe5YpQxKm7uU2WEPzrAMKKR6LESLaxITuLj VlYFxY0aRV8yck7JCf0u6Dxf2-TWescq6rKyydA2xJFw45OpuPwFjcViHqgMiO3fq0bgQnT7EcHj MvdU-po8sej29sfijKDU&sig=AHIEtbQnKDqkMsslpbimRu0NJMxOFDtN5w), but I'm not sure it offers what you are looking for.

I just think of it in terms of hitting weight. Wherever you add mass to the hoop you are increasing the effective mass at that location and the portion of the stringbed near it. You can think of gradients I suppose, so added mass at 12 will increase ACOR quite a lot near the top of the hoop, to a medium degree below that, etc. Similarly, adding mass only at 3 (these clock positions are perfectly adequate for discussion purposes, IMHO) will increase ACOR close to that location, less so in the middle of the stringbed and not very much at all at 9. Etc., etc. You could draw gradient maps for lead at various locations with dark colors representing high ACOR improvement, then lightening into areas of the stringbed where ACOR improvement would be minimal. Mass at 12 would start with the darkest shade and be the overall darkest map because swingweight, and thus effective hoop mass, increases the most with added lead at that position.

TimothyO
02-02-2012, 01:40 PM
It's not the string pattern per se but the placement of the lead relative to the string pattern.

I noticed it while dorking around with lead near the traditional 2/10 position. It seemd like the effect of the lead was far more pronounced (in a good way) when the lead was placed closer to the "corner" of the string bed as formed by the mains and crosses.

It feels like I get deep ball pocketing and more spin by placing lead at the corners.

I know some folks say lead pulls the sweet spot in the direction of the lead. Maybe by putting lead at the SB corners its mass is working on both the mains and crosses and maybe even magnifying the result.

Again, I don't know why and I don't know if it would work on all frames the same way. It definitely worked on the 300 and a pre-GT Pure Storm 98. It was definitely very dramatic, like flipping a switch. Shift the lead away from the corner and it felt one way. Back to the corner and WOW!!!

You definitely know more the technical details of SB performance than I do. I'm just a duffer playing around with lead but am trying to do so systematically and I'm pretty darn observant/detail oriented. So I'm just reporting how it felt and am curious to know more from those who have deeper technical knowledge of this stuff.

Thanks for the link, I'll have a look this evening!

corners
02-02-2012, 02:56 PM
Hi Tim, I too am fond of lead at 10&2. But these are the reasons why I think I like it:

Prince started their Triple Threat weighting a long while ago now. They looked at the concept of the three swingweights (swingweight, twistweight, recoil weight) and realized they could maximize all of them with the least amount of mass by concentrating that mass at 10 & 2 and in the butt. Mass at 10&2 increases both swingweight (and thus hittingweight and inherent power) and twistweight (and thus inherent power on off-center shots) very efficiently. Mass at 12 is the most efficient for increasing swingweight but doesn't do anything for twistweight. And in terms of the shape of the sweetzone, mass high and wide tends to pull it up and out, which suits modern rotational strokes where the tip is traveling much faster than the bottom of the stringbed. There is a good article, I believe by Cross, on the RSI website called "A Tale of Three Twistweights", or something. It's behind the subscription wall but well worth a read if you have one. If you look at TWUs racquet data you'll see that Prince frames from several generations ago already showed very high twistweight/swingweight ratios and also high recoil weight/static weight ratios (this latter was termed polarization index by Brody, Cross and Lindsey). Babolat's flagships also shared these characteristics. In the past two product cycles I've noticed that a lot more racquets have hit the market with high twistweight/swingweight ratios. Polarization - not so much, probably because a lot of players don't like the way polarized frames swing (they feel sluggish to me but I like serving with them).

I've also noticed that mass at 10&2 seems to sweeten feel while mass at 12 mutes a frame. I've read other posters describe the same effect. I think this is to do with the locations of the vibration nodes on the frame. You can see the nodes in the paper racquet that Cross is vibrating on this page (http://www.physics.usyd.edu.au/~cross/tennis.html) (about halfway down). I'm not going to get into dynamic stiffness and stuff because the topic seems to twist knickers and lead to thread degeneration around here, but I'm sure you've seen the threads where this is discussed.

So that's my take on it. I don't think the corners of the stringbed itself have anything to do with it, but I could be wrong.

TimothyO
02-02-2012, 03:08 PM
I suppose the question then is, how does one define 2/10?

There's the literal 2/10 as if the head were truly a clock. But I'm not sure how useful that is.

There's also a geometric or physical 2/10 that might define some sort of equilibrium in the effect of the lead on twist and plow....moving upe the head acclerates loss in twistweight...moving down the head accelerates loss in plow.

I guess I'm suggesting there's a third 2/10 based on the lead's effect on sweet spot or SB playability and driven by the location of the lead relative to specific groups of strings.

I wonder to what extant the prime physical 2/10 which optimizes TW and Plow is co-located with the prime sweet spot modification. Are they neccessarily the same?

corners
02-02-2012, 04:16 PM
I suppose the question then is, how does one define 2/10?

There's the literal 2/10 as if the head were truly a clock. But I'm not sure how useful that is.

There's also a geometric or physical 2/10 that might define some sort of equilibrium in the effect of the lead on twist and plow....moving upe the head acclerates loss in twistweight...moving down the head accelerates loss in plow.

Well, given that 1 gram of lead 21" from the butt (approx. location of 3&9) bumps swingweight by 2 units and 1 gram at the tip by ~3 units, I wouldn't worry to much about the exact 10&2 - it's gonna be around 2.5 units per gram whether you are a little high or a little low. But twistweight is highly dependent on distance from the long. axis, so to maximize that you want to be a little lower as the curve of the head takes you further away from that axis. (Unless you've got Yonex or some Volkls).

I guess I'm suggesting there's a third 2/10 based on the lead's effect on sweet spot or SB playability and driven by the location of the lead relative to specific groups of strings.

I wonder to what extant the prime physical 2/10 which optimizes TW and Plow is co-located with the prime sweet spot modification. Are they neccessarily the same?

You can locate the node by suspending the frame upside down by your thumb and forefinger at the top of the grip. Then grab a tennis ball and strike the center of the strings with our ear close to the frame. You can hear the frame vibrate (it will be lower pitched than the strings). Strike from the bottom of the stringbed sequentially to the top with your ear open. You'll find a place on the stringbed where you will not hear any vibrations from the frame. That's the node. You can find pictures on the net of how the node is actually a crescent arcing from the center location on the strings that you've found up to 10 on one side and 2 on the other. If you are meticulous you can probably use the tennis ball method to find where the node intersects with the frame. It will be around 10&2 but if you can pinpoint the location you will have a refrerence point for feel experiments. Moving your lead tape up and down you should be able to determine a location that gives you the feel you want and where that location is relative to the node.

Then you'll have to decide if that location is giving you maximal twistweight boost with a ruler, but probably twistweight will be secondary to you at that juncture. Feel seems to end up trumping everything else in the end.

TimothyO
02-02-2012, 05:30 PM
Wow! Great info! I was on the courts today and will be Friday. Sounds like fun experiment for the upcoming rainy weekend. Thx!