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Punted Football
5

Punted Football

Punted Football

(OP)
Yesterday I took a tour of the new Dallas Cowboy stadium and it is an engineering marvel.  Above the field is a mammoth 4 sided scoreboard/screen, the bottom of which is 90 feet off the playing field.  (Its length extends from 20 yard line to 20 yard line)

There is debate as to whether that is too low and may be hit by punts.  I've read that the average hang time for an NFL punt is 4.6 seconds.  To calculate the height I used the following reasoning, does this seem sound?

Discounting aerodynamics, a punted football will follow a parabolic arc, with exactly half it's time traveling upwards, and the other half downward.  That's 2.3 seconds going up and 2.3 seconds going down.

Using the formula y= (0.5)(32.2 ft/s sq)(time squared).  I calculate the average height based on average hang time is 85.2 feet.  A hang time of 4.73 seconds and above translates toa punt 90 feet and higher height.

Does this seem correct?
 

RE: Punted Football

launch angle and punting distance will certainly affect the height. It seems like you have ignored both. In addition, wind can change the flight path to something other than a parabola.

RE: Punted Football

GoldDredger seems to have calculated the worst of all possible punts - straight up and straight down - no gain in yardage - fire the punter.  Go Cowboys!!!

RE: Punted Football

As cvg mentioned launch angle will affect the height dramatically.  I'd try to model it as a ballistic trajectory and make some assumptions on the launch angle.  You should be able to use the hang time to estimate an inital velocity.

I know it neglects friction and the aerodynamics of the football, but it would probably be a reasonable estimate of the flight path.   

RE: Punted Football

Take an long punt length, say 60 yards, and given the hang time as a trajectory as bpattengale noted, you should be able to get the height.  

RE: Punted Football

GoldDredger's calculation are exactly correct (for a vacuum, with an acceleration of 1 G). The X and Y components of motion are independent. The distance traveled will depend on the initial angle and velocity, but the altitude reached will be 85.2 feet for a hang time of 4.6 seconds.

www.SlideRuleEra.net idea
www.VacuumTubeEra.net r2d2

RE: Punted Football

it is clear that drag and wind forces are a major component and especially on longer, lower launch angle kicks will result in less height.  You simply cannot discount aerodynamics and get a reasonable accurate answer.

http://en.wikipedia.org/wiki/Trajectory_of_a_projectile

RE: Punted Football

3
When any free ball strikes an object above the field of play, including lighting, sound equipment, wires, etc. the down is replayed under rule. This rule was added to the rulebook years ago when punter Ray Guy hit the sound and scoreboard gondola on the ceiling of the Superdome. Guy became the only man to hit it with a punt that traveled roughly 180 feet in the air.

Initial velocity and launch angle determine the horizontal range and hang time of a punt, with a significant dependence on air resistance resulting from various spins on the ball. Air resistance reduced distances of punts by 24-33% and had a nearly negligible effect on hang times estimated from simple equations for projectile motion. The equations of motion provide a reasonable approximation for hang times, but need to include air drag factors to accurately model distances.

http://www.wooster.edu/physics/jrIS/Files/Ryan.pdf

RE: Punted Football

Hire a punter and a surveyor and make some tests??

RE: Punted Football

Gold Dredger -

Your assumption is a classic mistake made by engineers to make the calculations easier and eliminate the real world. Assumptions may lead you to the calculated result you expect.

Neglecting aerodynamics for an object traveling through the air is wrong, but it makes it fit idealized engineering formula if nothing else is considered. That is if the temperature is neglected.

It may be close for a round baseball (neglecting similitude and shape factors).

A football is a different shape and has different properties when propelled. The spin is one of the aerodynamic properties neglected in the interest of simplicity.

A football does not always travel in a smooth predictable path (according to equations) and it may even go end-over-end. Have you ever observed a punt "turning over" in its arc as its speed, orientation and aerodynamic properties change in an attempt to control the impact angle and the following roll.

A satellite is easy to predict because there is in an essential vacuum and only momentum and the gravity of surrounding masses.

For a football, you need a bigger computer and a more realistic parameters or just hire a punter to do everything he can do to provide some of the practical outer limits.

RE: Punted Football

Sounds like a fun way to for ESPN the the Discovery Channel to chew up half an hour =)

RE: Punted Football

(OP)
Thanks for the posts guys.  

bimr above found an actual study of punts, comparing equation predictions to real world results.  They found that HORIZONTAL distances are 20-30% less than calculated, however the hang time values were not significantly affected.  Presumably because drag affecting the accent would similarly act on the ball during decent, a wash if you will.  

In the horizontal, drag affects the net flight entirely in the opposite direction of the flight, which may explain the reduced distances but not the hang times.

An important point is that hang times are real world results; ACTUAL recorded times from professional punts over many seasons of play.  The study shows that hang time isn't affected as much by drag. I would speculate then that neither is vertical height of the punt.

The average professional punt hangtime of 4.6 seconds I believe results in height of around 85 feet, irregardless of velocity, angle or horizontal distance. Once punts pass the threshold of 4.73 seconds, we start seeing heights above 90 feet.

I am looking forward to football season this year.  I guess we will see if punts regularly hit this thing or not.  Remember that if this does become an issue, you heard it hear first, lol.



  

    

RE: Punted Football

(OP)
* here first

RE: Punted Football

I drove by the construction site about a a year and half ago and remember actually stopping to admire and take a few pictures. Leave it to an engineer to stop by a site and do this.

I will certainly watch for this during football season. I hate the cold and dry desertlike feeling of the off-season. Lol. I really like footbal even though my team hasn't done that great in a while.

RE: Punted Football

CPNG -

When you watch make sure you have your stop watch and a way to accurately determine the height. - The refs will take care of the distance.

RE: Punted Football


Ya might wanna consider using an average of the ten longest punts of record-----------

At 74th year working on IR-One2 PhD from UHK  - - -

RE: Punted Football

bimr - as a punter (and place-kicker) I can say that no human can punt a ball 180 feet high on earth and in the atmosphere.  The Superdome's board used to be at 90', but they raised it (to over 180') after Guy hit it.

 


If you "heard" it on the internet, it's guilty until proven innocent. - DCS

http://www.eng-tips.com/supportus.cfm

RE: Punted Football

swearingen, you took the words out of my mouth.  Living in N.O., I remember Ray Guy hitting the dome screen multiple times. (He was one the the best at what he does.) I think the Saints punter at the time hit it once.

Regardless of the math involved, if this screen is as low as the one in the Superdome used to be, then someone aught to be repremanded for not doing his homework.  I hope this doesn't happen.

RE: Punted Football

The post actually said "traveled roughly 180 feet in the air". Should have stated the vertical distance as well.

The screens were dropped from 100 feet above the field to 90. Then Oakland's Ray Guy hit the gondola with a punt during the Pro Bowl game.

RE: Punted Football

http://myespn.go.com/blogs/nflnation/0-10-255/Titans-punter-hits-Jerry-s-video-board.html

Quote:

Titans punter hits Jerry's video board

August 21, 2009 10:35 PM

Posted by ESPN.com's Matt Mosley

ARLINGTON, Texas -- It's already happened! In the inaugural preseason game at Cowboys Stadium, Titans punter A.J. Trapasso boomed a punt that deflected off the bottom of an enormous video board that stretches from one 20-yard line to the other.

Titans coach Jeff Fisher immediately threw his red challenge flag onto the field as Trapasso pointed to the board. Cowboys coach Wade Phillips had a smirk on his face while players and coaches behind him chuckled.

According to the officials, the play is blown dead as soon as the ball makes contact with the video board and the down is repeated. And that's the exact same thing that will happen in a regular-season game. We've asked Jerry Jones and Wade Phillips about this very thing, but they both thought it wouldn't happen.

I'm not sure if there's a way the video board can be lifted any higher. I'm looking up there right now and it's not like there's much room. I'll ask Jerry Jones about the play after the game. Fisher's the co-chair of the competition committee, but I don't think this is something they've spent much time discussing. My guess is that Fisher instructed Trapasso to kick the ball as high as he could to see what would happen.

Trapasso hit the board three times in pre-game warmups. So far, Cowboys punter Mat McBriar hasn't come close to making contact. I'm sure he's a little embarrassed to be overshadowed by the little-known Trapasso.

AFC South blogger Paul Kuharsky is now trying to find out what would happen if one of Vince Young's passes floated into the video board.

RE: Punted Football

GoldDredger -There's your answer.  Just saw it on TV.  

Yeah, it's too low!  There's no good excuse for that happening.

RE: Punted Football

your a beast i first did read this a work heck of board, i calculated 88 ft, toooooo low dang jerry pay me a million ill consult with you and tell you its tooooo low lol!!!!1 nice screeeen!!!!

RE: Punted Football

4.6 sec!

RE: Punted Football

all those nerds nit picking at drag...get a life, issac newton said 88 feet if you want to say 86.9 you be correct but im an engineer and i put a factor of safety in everything so go ahead and argue about tenths of a feet nerds!

RE: Punted Football

(OP)
Well well well.  Seems that it is all over the news now, check this out.

Dallas Stadium has a design flaw with the screen, funny thing is there is PLENTY of room to raise it.   Just 15 more feet and only the most extraordinary punts could hit it.

Sure wish Jerry Jones would put me on the payroll, I'm right here in town and predicted it weeks ago.

Just remember where you heard it first guys.




 

RE: Punted Football

GoldDredger,
You most definetely called it and I think that pretty much gives your the right to tell Jerry, "I told you so". Unfortunately I missed the game so I didn't get a chance to watch it live but we all read about it before opeening day. Cool stuff, now if we can somehow send our posts to Jerry because based on the article I read, it doesn't sound like he wants to raise it.  

RE: Punted Football

GoldDredger,

I'm not going to argue over a few tenths.  I'll give you props for this one.

Did you hear Jerry Jones actually blame the punter???  Punters only kick that high in order to hit screens.

Looks like that screen is going to stay for now.

RE: Punted Football

Quote:

"concretemasonry" said: Your assumption is a classic mistake made by engineers to make the calculations easier and eliminate the real world. Assumptions may lead you to the calculated result you expect.

It is more accurate is to say this is a classic mistake made by mathematicians, who have the luxury of ignoring anything based in reality should they choose.

As a double-doctorate mathematician once said to me: "The difference between an engineer and a mathematician is that mathematicians make assumptions."

p.s. holy cow this forum software is horrific. Please stop using frames...my eyes, burning.....noooooooo....

 

RE: Punted Football

Engineers should stick to what they know and design the structures. The use and criteria for objects in the area should be in the expected requirements for the use. Any college student can calculate the theoretical track of a an object under the ASSUMED conditions, but real life facts are the most important factors in the real world design of functional fixtures.

I remember years ago when a high hit went into the 4" ventilation hole in between the layers of of the Minnesota Metrodome that was an the air supported dome (now about 30 years old). This was years after the roof successfully sustained a collapse from a snow fall/snow removal and structurally survived. Provisions were made for very unusual high high hits that hit speakers or the guy wires in many indoor and outdoor parks were incorporated into the ground rules that are common and acceptable. The ball went in and was not found until much later. The design criteria should have been based on the criteria and if other items were installed that is the responsibility of the owner/architect/interior designer. Obviously the engineer should not be responsible for the structure built low enough for the undesigned scoreboard assembly and the installed height. It is possible that a 2 1/2 " baseball could go through a 4" hole widely spaced that is 200 feet high. Mesh may have been installed and a few more holes used to make up for the minor air flow, but someone designed and approved the roof structure for all uses and cite some paragraph in the criteria intially if it was described.

The scoreboard in the new Dallas football stadium was was scheduled for a temporary removal for a short term rental for a rock concert (about $1-2 million cost).

It is just an ego situation between a football god and the real world god. Now, punters may be aiming for the known target when necessary and the length is not necessary.
Either the roof height was set out too low in the criteria or the scoreboard was installed too low.

Dick

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