Stiffness? What exactly it is ...

Discussion in 'Racquets' started by racquet88, Mar 20, 2012.

  1. racquet88

    racquet88 New User

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    Does the stiffness has something to do with the weight of the racquet or is something totally aside from weight or swingweight of the racquet.

    I am asking bc i like light frames. I was realizing some of the frames i had demoed have a very high stiffness level.
     
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  2. LeeD

    LeeD Bionic Poster

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    Not directly connected but...
    If you make a really lightweight racket soft, it bends all the time losing power and causing stress fractures. All rackets already bend lots, so making it soft makes it bend more and more often at a higher amplitude, breaking down the materials it's made with.
     
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  3. insiderman

    insiderman Rookie

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    Best if you go to the USRSA website or also here on TW's homepage (University) area for better answering your question - as the (sorry, no harm no foul~!) above reply is not valid. Also search for articles from Howard Brady...

    Light frames are Mfg'd to be with a higher stiffness as to return more energy to the ball - as the frame has less Mass (weight) so the power output can be optimized by being stiffer - as for lower flex frames, then typically are heavier - meaning more Mass contacting the ball, etc.
    As for "stress" on a lighter vs. heavier frame, there is no relevance here - as they are designed equally to withstand WAY more then hitting a 'yellow-ball'....
     
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  4. LeeD

    LeeD Bionic Poster

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    We just go into the same subject from opposite approaches.
    Both a valid.
    I've seen plenty of rackets broken by big servers hitting mishit overheads. Few rackets are really all that strong, as they get more flexible or dead within mostly about a year of amateur play.
    As for studies, they can be manipulated any way you want, by the author, using selected certain information, glossing over the rest.
    I've had a history of building with fiberglass and carbon fiber, kevlar, and lots of composite exotics. I've made surfboards, motorcycle fairings, seats, race car parts, and sailboat fiberglass parts. I do have a little knowledge on the subject of composite building.
    Notice most top pros, not all, get multiple SETS of rackets each season. What, you think the rackets play the same after THEY hit with them?
    Notice F-117 body parts get changed out after less than 20 flights. They are not broken, they are FATIQUED.
     
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  5. jnd28

    jnd28 Rookie

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    Interesting. I always thought that frames must wear out. But many play with the same frame for years and years. Based on your experience how long should a frame "last"? And how long do you think it takes to "break-in" a frame? Im sure it depends on a lot of things such as how hard someone hits a ball and the makeup of the frame.

    Any thoughts would be welcome.

    Thanks
    JND28
     
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  6. kaiser

    kaiser Semi-Pro

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    If that were true, I suppose I would have to replace my $4000 full carbon fiber bike every year...?
     
    Last edited: Mar 21, 2012
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  7. rich s

    rich s Hall of Fame

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    Stiffness is the ability of an object to resist deformation under load/stress..... (the opposite of flexibility...)

    Material properties and object geometry influence the object's stiffness....

    A racquet that is stiff will return more energy to a ball than a racquet that is flexible..... all other things being equal.

    A light racquet will transfer less energy to a ball than a heavier one.... all other things being equal....

    For these reasons racquet manufacturers will make lighter frames stiffer so as to maximize energy transferred to the ball/minimize energy lost due to racquet deflection.....
     
    Last edited: Mar 21, 2012
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  8. rich s

    rich s Hall of Fame

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    what "parts" would that be?
     
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  9. LeeD

    LeeD Bionic Poster

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    EVERY single exterior body part of a F-117, B-1, B-2, and now the YF-22-23 needs to be replaced before it's 24th flight. That is the nature of carbon fiber. Fatique is the problem. Symptoms are lessened rebound ability, and softer initial stiffness. Carbon fiber is going waaay up in price, because the defense industry demands sooo much, and they pay more than the average wholesale customers.
    Carbon frames. My g/f has two Treks, both high end maybe 8 years ago, over $4,000, all DuraAce, one with SuperRecord shifting parts, and both don't feel, TO HER, like they did when new. Wheels and tires are full aero style money no object, in good condition, so not the culprit. Forks and stays look undamaged.
    She get's on a Cannondale SuperSix and goes WOW!
    Fairings for road racing bikes get changed out every 6 or so races, and practice fairings are put on when the bike is not in the actual race course.
    Windsurfing carbon fiber fins get delaminations within a year, by hard riders.
    Think! How can you make sometime super light, super stiff, and super resilent, and pair it to parts that don't have nearly it's characteristics?
     
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  10. kaiser

    kaiser Semi-Pro

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    The amount wear and strain a tennis racket must endure is infinitisemal compared from jet or bomber wings, and I'm pretty sure the 1 kg frame of my Cervelo RS takes a much bigger beating from my 100kg frame than my 4D200 Tours from a 56g tennis ball. The early carbon bike frames of 8 years ago are noodles compared to current frames, the technology has improved vastly since. And personally, I've never ever seen a racket broken simply from serving or smashing. Broke a couple myself while serving, but that was because they slipped out of my hand and launched themselves head-on into the court... :(

    Aren't you exaggerating things a teeny weeny bit?
     
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  11. LeeD

    LeeD Bionic Poster

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    Kaiser...
    When I was playing, it was A/Open class back in the late '70's. Some really big strong guys crushing the ball then.
    More recently, maybe earliest 2000's, at HarborPointTennis, saw a well struck overhead crack the racket across it's widest point, middle of crosses.
    I cracked TWO PrinceChang's just below middle of strings, and I don't have a specially big serve, but was hitting some Open level overheads then.
    Anyways, your experience is a tiny slice of the pie.
    Even the lowest touring pros get a couple SETS of rackets every season. The top guys like the top 10 probably go thru over 40 rackets each season, and the picky ones more.
    Yes, JamesBlake is reputed to use 2 year old rackets, but it's the exception, not the rule.
    Why do you think pro bike riders get new frames a couple of times a year? Carbon wears out, loses it's springback, elasticity, and initial hardness.
    Just because YOU cannot feel it, it appears most other tennis players feel a frame going dead within 5 or so stringjobs if they are hard hitters and good players.
     
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  12. LeeD

    LeeD Bionic Poster

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    Oh, Kaiser, you are absurd in your statement that 2004 carbon fiber bikes are all flexy flyers. If anything, they rode STIFFER than the modern bikes, as the modern bikes focus on COMFORT thru flexing forks, downtubes, and chainstays.
    Some of the stiffest bikes ever made were late '80's Cannondale aluminum bikes. All the effort since then was to make them ride SOFTER and with more resilience.
    Are you saying LanceArmstrong's Tour bike, which he rode for ONE race..the Tour, is a flexy flyer compared to the new bikes? You are waaaay off base.
     
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  13. kaiser

    kaiser Semi-Pro

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    Yeah, yeah... :)
     
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  14. LeeD

    LeeD Bionic Poster

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    :):)
    Just kidding....
    Truth hurts.
    Truth backed with facts and a little experience hurts also.
    Just kidding...
    But I've been working with carbon fiber since the mid '70's, first with surfboard construction, then road racing fairings and seats, on to car fairings, spoilers, and ground effect covers.
    Worse, I still get to ride my old 1989 CannondaleR-500, and have a 2011 CannondaleCaad8-6. Night and day, the new bike is much softer, compliant, and comfortable.
     
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  15. rich s

    rich s Hall of Fame

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    WADR...... you have no clue what you are talking about....
     
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  16. sureshs

    sureshs Bionic Poster

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    No it doesn't
     
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  17. LeeD

    LeeD Bionic Poster

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    Love the last two posts. Care to elaborate? No? Of course not.
     
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  18. SFrazeur

    SFrazeur Legend

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    Racquets will soften from use and restringings. However, most players will not notice. Most 4.5s would not notice nor be concerned.

    -SF
     
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  19. LeeD

    LeeD Bionic Poster

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    I respectfully disagree.
    As a 4.0.
    I had 3 PrinceChangs for about 2 years, bought 2 more from the local rep, and the last two, thos seemingly identical in paint, color, shape, and weight, felt much livelier, the ball coming off the strings much quicker. Same strings, I strung with PrinceTourneyNylon15 thosedays.
    In the older days, I'd retire my WilsonKramerProStaffs after every 3 string jobs, the racket feeling dead after a couple, but I was too cheap to switch, especially with VS 16.
    Most of the college team members I practiced with got 2 or 3 sets of rackets a year. They sold the old ones for their costs, getting a livelier and stiffer racket in the process.
    My two relatively new LMRadMids feel much livelier than my buds 5 of the same. He's 6' and 220, smacking the heck out of the rackets for 5 years.
    In motorcycle, cars, and aero industries, and including windsurfing and surfing, carbon fiber tends to break down much quicker than most would believe.
     
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  20. SFrazeur

    SFrazeur Legend

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    You know carbon fiber should break down. You are expecting it. Also, you may be a 4.0 now, but it sounds like you were a higher level player "back in the day" as it were. Perhaps you are a 5.0 in a 4.0s body. ;) Ah Time. You harsh mistress. And by that I mean *****. It seems that you would be more sensitive to racquet softening than most at 4.0

    Wood laminates would break down a lot faster than carbon fiber/resin epoxy. You say you'd retire after 3 string jobs, roughly how long was that? And do you mean full string jobs or did you doing any patching?

    -SF
     
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  21. LeeD

    LeeD Bionic Poster

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    Wilson made me pay for 3 rackets, and then sent me 3 more every 3 months for almost a year. Switched to YonexOPSGreens.
    Each string job maybe lasted a week or so, never used patches, as I was a stringer at a tennis shop.
    Less than 4 months ago, I cracked my friend's LMRadMid practicing overheads, right across the center crosses. I was showing off how hard an overhead should be hit if the ball bounces within 6' of the service line. I did miss a few, both long and into the net. That particular racket was maybe 3 years old, one of 5 my friend rotates thru.
     
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  22. LeeD

    LeeD Bionic Poster

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    Oh, I doubt I would hit 40 overheads as hard as I could with my own rackets. My friend kept saying I could never crack a racket, him 75lbs heavier than me. My serve is maybe 20 mph faster than either of his.
     
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  23. SFrazeur

    SFrazeur Legend

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    Did you notice change or softening with metal racquets?

    -SF
     
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  24. LeeD

    LeeD Bionic Poster

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    OPS seemed to hit every groundstroke and serve about 5 mph faster, without really losing control. I could use the GoldOPS for a softer feel, but the Green felt like a real weapon. Those aluminum rackets got softer after about 3-4 string jobs, usually about 3 months, for a set of three. The welds seem to fail first, then the pallet of the handle came unglued. I had to pay wholesale - something for every one of them, but it was worth the money for the knowledge of having the biggest weapon at the time.
    I always thought the KramerProStaff was a bad match for my game, but it was the only company who'd help me out, and straight Kramer's and Smiths were too heavy for my skinny style of play.
    Wilson never did offer me any help with the 2000 or 3000 steel rackets, but I couldn't serve well with them anyways.
     
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  25. rich s

    rich s Hall of Fame

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    I have a Bachelor of Science in Aerospace Engineering ....I work in the aircraft industry....I have done so since 1988..... I work with (design, test, build with, etc) the materials we are discussing day in and day out.......

    to make a blanket statement about 4 different aircraft (that are nothing alike) having to have "every single exterior body part replaced before its 24th flight"....... ( I like the "body part" phrase there.....)...alone and by itself speaks volumes about you having no knowledge about what you are saying and that you aren't even aware that you know not way you say......

    furthermore.... the F-117 has be retired for several years and the YF- 22/23 were prototypes for downselection..... not aircraft that were/are in the the Air Force's active inventory of aircraft. The 22 and 23 were only designed for a few hundred flight hours and the B-1 and F-117 have/had more metallic structure than composite structure......

    do you need more elaboration or can I rest on my original statement?!?!?...
     
    Last edited: Mar 21, 2012
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  26. LeeD

    LeeD Bionic Poster

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    See, you ignore the facts, rambling on and on.
    You do agree the F-117, retired or not, needed body panels on a regular app. 20 flight schedule, right?
    Why do you think B-1 and B-2 used some metal body panel parts? And you mentioned the LATER models of F-117 used more metal, less composite body panel parts, didn't you? WHY do you think that is?
    As for the F22, we will know soon enough. The protos used the same thickness and grade of carbon as will the early production series. Once the flaw is discovered, it will be changed, for sure. ONCE THE FLAW, which is carbon fiber in a thin stiff laminate, is discovered.
    YOU, as an engineer KNOW that nobody would use thinner weaker materials to make the prototypes! They use what they can procure!
    And currently, the USAF is the biggest user of carbon fiber in the world.
     
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  27. kaiser

    kaiser Semi-Pro

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    Rambling??? I've just been reading about a psychology paper titled The Pot Calling the Kettle Black...
     
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  28. rich s

    rich s Hall of Fame

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    Lee.... give it a rest....

    I have worked on one of the projects you refer to and I have friends and colleagues who have worked on other projects on your list too..... you have no idea what you are talking about......
     
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  29. lbjames23

    lbjames23 Banned

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    okay, calm down guys. I see the reasons behind both of your theories. So take a K90 for eg, the "braided" carbon fiber will be wore out say 200 hr s of hitting ? and the frame becomes flexible ? is that it ?
     
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  30. lbjames23

    lbjames23 Banned

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    and FYI , the carbon fibers used in those PS frames do increase their weight by a lot.
     
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  31. TaihtDuhShaat

    TaihtDuhShaat Semi-Pro

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    So frames get more spin friendly over time? Cool.
     
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