!in1.uu.net!CS.Arizona.EDU!uncial.CS.Arizona.EDU!ho
Subject: rec.sport.disc FAQ (1/5) General Information
Date: 4 Jan 1996 22:20:01 GMT

Rec-sport-disc-archive-name: faq-part1
Posting-Frequency: monthly

rec.sport.disc FAQ (1/5) General Information

===================================================================

Table of Contents:

   1)   What is Ultimate?
        -   Organizations supporting Ultimate competition?
   2)   What is Disc Golf?
   3)   Am I eligible for Collegiate Disc?
   4)   How is the UPA Top 25 Computed?
   5)   What's a MAC, and how do I do it?
        a)   What's a hammer?
        b)   What are other kinds of throws?
   6)   How do discs fly? [ for the physicist ]
        -    Are there books about discs and Ultimate?
   7)   Glossary
   admin)   FAQ information and administrative swill 

   more faqs)  FAQ Part 2 Contacts and Records
   more faqs)  FAQ Part 3 On-line Info Guide
   more faqs)  FAQ Part 4 Cleats and medical info
   more faqs)  FAQ Part 5 Disc Golf

[ I think there should be a separate posting on gloves - if anyone
wants to contribute the glove FAQ, please post a request for info to be mailed
to you.  -HKO]
===================================================================

 1)  What is Ultimate?

     Ultimate is a fabulous, high-energy sport that can be enjoyed by
     people of all ages and disc-skills who don't mind a little
     running and a lot of fun.  The description below applies to the
     outdoor version of the game.  The indoor version, being on a
     smaller field, is somewhat modified (a slightly smaller field and
     fewer players) but mostly similar.

     Picture, if you will, a playing field (usually grass, but
     desperate teams will play on almost any surface) as follows:


     <- 25 yds -> <--------------- 70 yds --------------> <- 25 yds ->
   ^ +-----------+---------------------------------------+-----------+
   | |           |                                       |           |
   | |           |                                       |           |
   | |           |                                       |           |
   | |   End     |                                       |   End     |
  40 |           |                                       |           |
  yds|   Zone    |                                       |   Zone    |
   | |           |                                       |           |
   | |           |                                       |           |
   | |           |                                       |           |
   | |           |                                       |           |
   v +-----------+---------------------------------------+-----------+


     On this playing field are two teams of seven players each.  The
     object of the game is for a team to pass the disc from player to
     player, all the way up the field, and catch the disc in their end-
     zone, which scores a point.  Players cannot run with the disc, but
     must plant a pivot foot (as in basketball) and throw the disc to
     a teammate.  When holding the disc, a player gets ten seconds to
     throw it to a teammate (five or seven seconds indoors), which is
     counted off by the defender guarding the offensive player (known
     as "marking" the thrower.)  If the disc isn't thrown in time, it's
     called a "stall" and the defense takes over.

     If the offensive team drops the disc, catches it out of bounds, or
     failes to complete a pass because a defender somehow blocks the 
     pass, the other team picks up the disc where it lands and works to
     score in the other direction.  Defenders gnerally play either a
     man-to-man or zone defense in their attempt to block a throw.

     The game is non-contact - it's a foul to hit the other player, or
     to hit the disc while it's being held.  (Blocking the disc right
     after it's thrown, known as a "point-block", is a very hot play!)
     Nor can a defender be "picked" off the player being guarded.  Any
     play carried out with the main intent to prevent another player
     from having a fair chance at catching the disc or making a defense
     is considered a foul; in other words, you have to "play the disc,
     not the person!"

     Probably the most important part of Ultimate is known as "The
     Spirit of the Game".  This catch-phrase is used to describe the
     respect that every player in the game has for his fellow players.
     No referees are used in the game.  Instead, each player does his
     best to make an honest call if necessary, and trust the calls of
     his fellow players, with the implicit assumption that nobody in
     Ultimate would try to cheat.

     This principle is what makes Ultimate special to so many people,
     and all Ultimate players try to keep the Spirit alive by
     maintaining this high level of trust, no matter how competitive
     the game gets.  If people cannot resolve their differences, people
     usually say "back to the thrower", which allows play to continue
     on without forcing the issue one way or another.

     The best way to see how Ultimate is played is to go watch a local
     tournament.  Ultimate players share a great comraderie, and LOVE
     to introduce new players to the sport.  So come on out and watch!


     Organizations supporting Ultimate competition are the 
     Ultimate Players Assocation (UPA) and the World Flying Disc
     Federation (WFDF ).  The UPA is a United States organization
     which sponsors a club competition series in the fall and a
     college competition series in the spring.

     The WFDF runs their championships in even numbered years.  Each country
     gets to send one team - and it can be a club team (e.g., the US sends its 
     champion), or an all-star/select team (which almost every other country 
     does).

     In odd numbered years, they run the WUCC - the World Ultimate Club 
     Championships, where each country is allowed to send a specified number 
     of existing club teams.  So, many "real" teams from countries, versus a 
     single select or put together team for the WFDF championships.



===================================================================

 2)  What is Disc Golf?

     Disc golf is a great sport for everybody that relies on one's
     ability to throw a disc with power and accuracy.  People of any
     age, ability, and gender can excel and enjoy disc golf immensely.

     The object of the game is to traverse a course from beginning to
     end in the fewest total number of throws of a golf disc.  Similar
     to the traditional golf game, a course is composed of a number of
     holes, in which each player begins by throwing from the tee, and
     completes the hole by landing in or striking the target.

     The total score for a course is determined by totaling the
     number of throws made on each hole. The winner is the player who
     completes the course in the fewest number of throws...or whoever
     has the most fun!

     Disc golf courses exist in many different terrains.  Often they
     are laid out among wooden areas, with water hazards, large
     elevation changes, and difficult throws.  Other courses are
     mostly flat, with few natural obstacles.  The obstacles should be
     considered part of the course, and not tampered with (even when a
     tree eats your disc!)

     The average course is 18 holes, but 9 hole and 27 hole courses
     exist as well.  The average hole is around 425 ft (130m), but
     some are as short as 150 ft (45m) or as long as 1000 ft (300m).
     Courses usually have a listed par, for pro or amateur players.
     Of course, people practice disc golf all the time by just aiming
     for an object a hundred yards away, which is the kind of disc
     golf one will often see being played on university campuses or
     urban parks.

     Terms:
     Tee - this the area where the player starts each hole. Some
        courses have multiple tees for each hole. The material on the
        tee surface varies from concrete, asphalt, dirt, crushed
        stone, or wood chips.  In general, any flat non-slippery
        surface is good.

     Target - The target is where the disc must land in in order to
        complete the hole.  The target is usually a "pole hole" which
        is specially made to catch the golf disc. Courses that do not
        use pole holes are usually known as object courses. A typical
        "object target" is a tree trunk, 4x4 or pipe.

     Golf disc - a "golf disc" is a flying disc made especially for
        the sport of disc golf, although some players use Wham-O type
        frisbees.  Golf discs vary in weight and size. They are
        usually harder and denser than Wham-O type frisbees.  Special
        models exist for driving, putting and "up shots" (not as far
        as a drive, but more than a putt) much like different golf
        clubs exist in ball golf.  However, players are not required
        to use a "driver" as a driver or a "putter" as a putter.  Some
        players throw a putter as their first shot from the tee.  A
        golf disc generally costs anywhere from US $5-7, depending on
        how many are bought.


     A professional PDGA tour exists, currently has about 5000-7000
     active members, some of whom play on a professional level for
     money, and some play on a amateur level for non cash prizes.  The
     top money winner last year won over US $16,000.



===================================================================

 3)  Am I eligible for Collegiate Ultimate under the UPA?

   See http://www.upa.org/~upa/upa/admin/collelg.html for the full description.

     [ The original version of the following was written by Frank Revi on 
     August 29, 1992 when he was UPA National College Director.  The 
     current director is 74404.753@compuserve.com (Jay Cohen), who 
     added a few changes.]

     The following is a SUMMARY of UPA college eligibility
     requirements.  It is intended to give an overview of the
     requirements.  It is not the full text, and therefore DOES NOT
     give definitive information for all cases.  The official text as
     published in the UPA newsetter pertaining to the season in
     question is the only source of official documentation of the
     eligibility rules for that season.

     All questions on eligibility should be addressed to the National
     College Director.  "Rulings" from other coordinators and UPA
     headquarters staff are not final.

     UPA college eligibility is a 5-year window during which a player
     may participate in the series.  The window runs continuously from
     the player's first participation in a UPA sanctioned event or
     first UPA membership, whichever comes first; but no earlier than
     the date of high school graduation (i.e. UPA events/membership
     while in high school don't count).  The window closes annually on
     1 June.  The intent of this rule is to only allow players with less 
     than five years of experience to compete at college level.  The 
     player must further meet the following requirements:

     *  Be registered and enrolled in a regularly matriculated degree
        program at the institution for which s/he is eligible to play

     *  Be taking a minimum of two full-time classes during the academic
        period(s) containing both March 1st and May 1st of the current
        year (must be at least a half time student).

        [The above requirement is waived for students taking the
        minimum required academic load required to graduate at the end
        of the academic period containing May 1st.  Research and
        thesis work may be counted towards the required courseload IF
        it is officially recognized as equivalent by the institution
        (e.g. if you register for research in the equivalent of course
        hours, that counts).  Any questionable situations require a
        clarification request (see below).]

     *  Be a member of the UPA in good standing

     The UPA does not grant exemptions to the eligibility rules.

     In cases where the rules are not clear, a clarification request
     may be made in writing by returning an official form by the
     deadline published in the newsletter.  Forms must be requested in
     writing from UPA HQ; directions are printed on the form.
     Requests are reviewed by the Coordinating Committee and responses
     are mailed.

     The eligibility of all players on a given team must apply at the
     same branch or location of that school.

     Teams must submit completed rosters signed and sealed by the
     registrar before playing in any series event.

===================================================================

 4)  How is the UPA Top 25 List Computed?

     The UPA Top 25 is calculated by Eric Simon and distrbuted weekly.
     However, the Top 25 isn't accurate unless college tournaments
     call in their scores!  So, please, all college teams and
     tournament directors should send in their scores to Eric or the
     UPA (see FAQ.2 for a contact list.)

     The most basic explanation of the Top 25 rating system is this:
     for each game a team plays, the team gets rating points.  These
     rating points are then averaged.

     The next level of complexity is how to compute the points for a
     given game, and how to avereage them.  The points for a given
     game is given by this formula:


        pts = opp_rate + (400 / x)                           (1)


     where opp_rate is the rating of the opponent, and x is a factor
     that depends upon the score.  The formula for x is:


        x = max(.66,(2.5*(losing score/winning score)^2))    (2)


     Rather than explain it, let me give an example.  Suppose team A
     beats team B 15-11.  According to the formula, take the fraction
     11/15, square it, and multiply by 2.5.  This gives us 1.34.
     Suppose, further, that team B has a rating of 1000.  According to
     formula (1), we simply compute 1000 + 400/1.34 and get 1298.  The
     "max" that's used for formula (2) makes it so that the smallest
     that x can equal is .66, which means that the best (or worst) a
     team can do in a specific game is to perform at 600 points better
     (or worse) than their opponent.  (A score of 13-5 will get you
     600 points).

     So, suppose team A has played in 4 games, and each individual
     game rating is 1298, 913, 1410, and 1103.  Well, we simply
     average them together, and team A has a rating of
     (1298+913+1410+1103)/4 which is 1181.  But, actually, the
     averaging isn't quite that simple, either.  We actually take a
     weighted average.  In the above example, each game had a weight
     of 1, in actuality, the weight depends upon how recently the game
     was played.  This formula is:


        wt = min(1,1/(((today-gamedate+4)/7).4))            (3)


     Suppose games were played on four consecutive Saturdays.  Since
     the ratings are done on Mondays, this would mean that the games
     were played 2, 9, 16, and 23 days ago.  Well, by formula (3), any
     game played within 3 days of the rating gets a weight of 1.
     Games played the week before, or 9 days ago, get a weight of
     1/((9/7)^.4) which is about .9.  The games 16 days ago are
     weighted at about .72, etc.  This is called a decay function,
     and, basically, it means that the more recent the game is, the
     more heavily it is weighted.

     Finally, whatever the weight it, it is doubled for games at
     Regionals, and tripled for games at Nationals.  After all, teams
     are usually at full strength during those tourneys, and the games
     are more important.  Finally, it is hoped that the winner of
     Nationals will come out as number one in the rankings.  Luckily
     this has always happenned, although one year a team that lost in
     the semifinals almost finished first.

     But that's not all!  Suppose the ratings of the teams you play
     change.  An underated team you lost to in the first round ends up
     winning the tournament.  Should your rating reflect that teams'
     victories, in other words trying to take into account that the
     other team was a really good team.  Of course it should.  Suppose
     your team's rating went up during the course of the tourney, too;
     shouldn't other teams, in turn, get the benefit of that?

     This is done in an interative process.  On Monday, every team
     gets re-rated.  That is, we recompute every individual game
     rating, based on the previous week's ratings, and the new date.
     Then, each team gets a new rating for the current week.  Then, we
     re-rate every team again, using this week's ratings, to get a new
     set of ratings.  We do this 20 times (this is why a computer is
     indispensable).  Eventually (usually after only about 8
     interations) the ratings reach some sort of equilibrium.  It's
     kind of a neat process to watch.  If some team does really well,
     and the rating goes up 250 points, then, on the second iteration,
     all teams that have played the first team goes up by a smaller
     amount, and on the third iteration, all the teams that have
     played the teams that played the first team will go up by a small
     amount, and so on.

     The biggest problem with the system is that in some areas of the
     country not everyone is calling in scores.  Let me give a classic
     example of how an entire region can be adversely effected by
     this.

     Suppose the best team in Region X always calls in their games
     (and, in fact, more winners than losers call games in).  So,
     suppose this team "State U." calls in 13 games of theirs, all
     victories.  None of the other teams had called in any scores.
     This team beat, say, team B in the finals of two other
     tournaments.  Obviously, team B must've been pretty good to make
     it to the finals, but to the computer, team B was simply 0-2.  In
     fact, to the computer, it looked like the 13-0 team was playing a
     really wimpy schedule because every team that had played was
     winless!  So what happens?  State U doesn't get a very high
     ranking.  Now, weeks later, the other scores are called in.  It's
     too late, State U is already ranked lower than they should be,
     and all these other schools are, correctly, ranked lower than
     State U is.  So, the whole region gets ranked lower than they
     should be.



===================================================================

 5)  What's a MAC, and how do I do it?

     A MAC, also known as a "mack", actually stands for Midflight
     Attitude Correction.  In the sport of Ultimate, it usually
     happens by mistake, but here's how to do it on purpose.

     To MAC a disc effectively, one needs to be aware of the direction
     of spin the disc has.  The two possibilities are clockwise
     (originating from a standard backhand throw from a right-handed
     player) and counterclockwise (a sidearm throw from a right-handed
     player).

     The best throws to MAC are hard with lots of Zs (spin).  The
     technique is to allow the disc to be throw at you very hard,
     allow the disc to pass you, the MACer, on one side of your body
     or another, and just as the disc is perpendicular to the throw
     line, touch the side of the disc very briefly.

     If the throw is clockwise, allow the disc to pass your right side
     (as you are looking at the thrower) and tap the top of the disc's
     platter, near the outside of the disc at the point closests to
     you.  The disc will then take a MAC, climbing upward.  If the
     clockwise throw passes on your left, that tap will send it
     straight into the ground.

     Switch everything around for a counterclockwise throw.  Disc
     passes you on the left, tap the side of the disc, it takes a MAC
     and climbs up.  Disc passes on your right, tap it on the side,
     the disc dives down into the ground.

     There are some neat variations of the MAC, like the foot MAC,
     which takes some extra practice.  Hitting the disc on the outside
     edge from the thrower is also harder.  If you want to see one of
     the best MACers alive, watch Dan (Stork) Roddick sometime.  He is
     amazing!  (he is also the Sports Director for Wham-O).  And no
     place is better to MAC than on a California beach somewhere.

   a)  What's a hammer?
       See http://www.upa.org/~upa/faq/hammer.html

   b)  What are other kinds of throws?
       See http://www.upa.org/~upa/upa/throws.html
.(also in the FTP area).

===================================================================

 6)  How do discs fly?  How can I find out more?

     This is a partial listing of articles and research done by various people
     around the world on how discs fly.  The result of a full bibliographic
     search on disc activities is available at http://www.upa.org/~upa/faq/bib.html.


     Harrison Ka., "Flippin Frisbee", New Scientist, 1990 Aug 11, v127
       n1729:67-67.
     Horowitz, Judy and Bloom, Billy, "Frisbee, More Than a Game of Catch
       and Throw", Leisure Press, New York, 1984, ISBN 0-88011-105-4.
     Johnson, Stancil E.D., "Frisbee: A practitioner's manual and
       definitive treatise", New York: Workman Publishing Company,
       1975, ISBN: 0-911104-53-4.
     Kalb, Irv and Kennedy, Tom, "Ultimate, Fundamentals of the Sport",
       Revolutionary Publications, P.O. Box 4787, Santa Barbara, CA,
       1982, ISBN 0-942156-00-5.
     Katz, Paul, "The free flight of a rotating disc", Israel Journal of
       Technology, vol. 6, nos. 1--2, pp. 150--155.
     Nakamura Y, Fukamachi, "Visualization of the Flow Past a Frisbee",
       Fluid Dynamics Research, 1991 Jan, v7 n1:31-35.
     Schuurmans, Mac'e, "Flight of the Frisbee", New Scientist, 1990 Jul
       28, v127 n1727:37-40.
     Schuurmans, Mac'e, "Frisbee: History and aerodynamics", Basel,
       Switzerland, February 1985 (in German, 51 pages).
     Simon, Craig, "Frisbee: Beyond catch and throw", 1982 (65 pages).
       Out of print.  Craig Simon's email address is 72210.3613@compuserve.com.


     Some work has been done on converting discs into interesting
     weapons, by using the disc to launch either a flare or a hand
     grenade; these are discussed in some of the above messages.

     Apparently, the patent applications from Wham-O in the late
     1950's are interesting reading material.  See the patent section
     of any well-stocked university library for references in this
     area.

     frevi@athena.mit.edu did work as an undergrad (MIT) involving the
     visualization of flow around a rotating frisbee using dry ice
     vapor as the tracer aerosol and stroboscopic and conventional
     photography.  In particular, a number of photos were taken of
     vapor flowing around a disc mounted on a motor in various
     orientations, the trajectory of a frisbee throw through a sort-of
     stationary flow field stopped stroboscopically, and various
     multiple exposures of throw/release motions.  The results of the
     flow studies seemed to indicate that a rotating frisbee induces
     lift independent of a trajectory vector; i.e. the disc doesn't
     have to be going someplace to generate lift, just spinning.

     medf214@chpc.utexas.edu (Aaron Altman) did some interesting work
     analyzing the behavior of a disc in a wind tunnel, with specific
     regards to the so-called airbounce.  He examined the effects of
     windspeed and angle of attack [alpha] on a disc.  From his
     messages, slightly edited:

       After performing many wind tunnel tests on an old, wasted
       Wham-O, I measured the effects of varying angle of attack and
       windspeed.  It was difficult to determine the rate at which an
       average disc is spun, so this part of the experiment is very
       much "up in the air".  There was also no way to simulate the
       initial "throw", or accelleration of the disc, so all of these
       results examine the disc under a constant windspeed, which
       ignores all of the interesting things which happen to the
       airflow around a disc as it is thrown.

       The simplest visualization for the results is to draw the
       analogy between an airplane on approach to landing, and a disc
       at high alpha.  Increasing the angle of attack increases the
       induced drag (or resulting drag force), but enables the disc to
       fly slower while still flying in the same flight path.  The
       airflow on the top of the disc is usually not "attached" fully,
       inplying a turbulent, vortical, unsteady, non-laminar flow.
       The same is true for an airplane on approach to landing.  The
       airplane reduces its speed, but the flight path is maintained
       (within a certain range) by increasing the alpha of the plane.
       In an airbounce, some extra lift is generated from the
       so-called "ground effect" as well.

       This experiment gave no data on the limits of the ground
       effect.  However, the limits are determined by the amount of
       wing loading, so one can guess from experience with other
       flying objects.  For example, the ground effect for a Cessna
       172 tends to be approximately 1/2 the span the wing, which is s
       approximately 20 ft.  This causes the airplane to float above
       the runway at speeds lower than would normally be possible for
       this airplane.  From discussions of the ground effect with
       pilots of larger airplanes, such as the Boeing 727, this
       equation (1/2 span) doesn't hold as well, and the ground effect
       tends to be between 1/2 and 1/3 span.  At any rate, that brings
       us back to the disc...If we took 1/2 the span of the disc, this
       would place us somewhere about 6 inches off the ground.

       So, what does this all mean? In terms of flight dynamics, the
       small displacement given to the disc by the thumb at the last
       second causes the leading edge to rise.  This, in combination
       with the large, instantaneous, simultaneous forward force of
       the throw, (called the impulse,) creates a high angle of attack
       flight regime, with the possibility of an increase in altitude,
       depending on the actual angle of release from the hand (angle
       the arm makes with horizontal upon release of the disc, not the
       same as displacement given by the thumb.

       Of course, if all of this is true [and it may not be!] it
       should be possible to throw a disc at high alpha, without the
       angle imparted to the horizon by the arm, and still have an
       airbounce.  This would result in a disc flying without a change
       in height, but with a large angle of attack.  This would imply
       that, not only is it necessary to apply thumb pressure, but the
       angle of release is also quite important in establishing a true
       airbounce.

       Given all of this, one can describe the physics required to
       throw a disc that goes down and then up.  The follow-through on
       the throw would be downward, but the force applied to the disc
       in that instance is applied just below the horizontal (say,
       between -3 to -8 degrees).  This force will cause the initial
       trajectory of the disc to be slightly downward.  After some
       distance, the component of lift generated by the forward motion
       of disc (at alpha) overcomes the initial slight downward
       component given in the initial release of the disc.  In
       studying the problem as a thin airfoil (using thin airfoil
       theory) this can be shown to be possible quite trivially.

       When a disc is thrown, it undergoes an initial acceleration
       that is quite large.  Once released, the speed decreases as a
       result of viscous losses due to the friction of air.  This
       change in speed results in a highly unsteady problem (which
       changes as a function of time).  By analyzing the lift force
       and drag force (Cl, Cd respectively) at many different
       windspeeds and alphas, a profile of the behavior of the disc as
       its thrown can be examined, with Cd and Cl increasing
       essentially linearly with alpha.

       In addition, I would like to comment on some info included in
       the most recent version of the FAQ.  As determined by my
       experimentation, the component of lift generated by a
       stationary disc, spinning, is extraordinarily small when
       compared to the component of lift generated by the forward
       motion of the disc.

       This is with reference to the work done by frevi@athena.mit.edu.
       The information that he obtained was strictly qualitative, and
       the quantitative data that I obtained tells me that a spinning
       disc (without a directional component) generates very little
       lift.  A good physical analogy would be to say that if this
       were true, than this aspect of lift would be exploited in
       modern lifting bodies, lending creedence to the possibility of
       flying saucers!

     * Whew *  People interested in more detail, or interested in
     using this as a "grossly understudied...killer thesis topic" are
     encouraged to contact Aaron directly.



===================================================================

  8) GLOSSARY
     Here are a few terms used to describe disc behavior:

     Overstable - a disc that turns left when thrown flat with a right
         handed backhand throw


     Stable - a disc that goes straight when thrown flat with a right
         handed backhand throw.


     Instable  -    a disc that turns right when thrown flat with a right
         (understable)    handed backhand throw.


     Hyzer - The disc is tilted towards the ground to make the disc turn
          left when thrown with a right handed backhand throw.


     Anhyzer -  The disc is tilted to produce a curve from left to right
          when thrown with a right handed backhand throw.

    The Greatest -  Shortening of the phrase "The Greatest Play 
    in Ultimate".  I.e., When a player on the offensive team jumps from
    in bounds to catch a disc, going out of bounds, and before he contacts out
    of bounds he throws to a team-mate in bounds. Bonus points if it is also
    thrown for a goal.

===================================================================

 a)  FAQ information and administrative swill

     This is part one of the rec.sport.disc FAQ [Frequently Asked
     Questions list].  This file, and its companion files, are posted
     bi-weekly to rec.sport.disc, news.answers and rec.answers.  The posting
     is designed to answer questions which are commonly asked by new
     readers of the group, as well as to provide a reliable source of
     information for regular readers.

.
     Please send updates, additions, and corrections to Hilarie Orman,
     ho@cs.arizona.edu
.
     
     No guarantee as to the accuracy of this information implied or
     expressed.  But I hope it's right....  Thanks to all the people
     who've helped contribute to this FAQ, especially David Birnbaum, the
     original maintainer of this FAQ, and Loring Holden, the previous
     maintainer..


