Really silly inquiry regarding the barrier in a 50m pool.

Because the barrier (usually called a bulkhead technically) was already in at one end of the pool when it was 50m. And some pools (Federal Way is an example) have two bulkheads installed. That way the pool can be used as a single 50 meter course, two 25 yard courses, or two 25 meter courses. Maximum versatility!

To all, Calvin is correct that a new measurement must take place every time the bulkhead is moved. Additionally, the pool must be measured before the meet and after each session(s) of the meet. Personally, USA-S local meets should be more stringent, but the likelihood of national records is far less in local meets, so they don't go to the trouble. In Masters, you never know who is going to show up. I see alot of pool measurement forms because my wife approves all national records. Many Meet directors or meet referees just do not understand the rules and assume the pool will be set properly and the paperwork will be completed accurately. They are not. Another example of the swimmers need to ensure the bulkhead pools are legal before the meet. The reason for before and after sessions is because some pools will measure with the lane lines loose and then crank them tight. if the pool was just legal with lane lines loose, some (or all) lanes can become too short after tightening. It is a game some hosts play. This usually (but not always) benefits the middle lanes more than the outside ones. Just a little more to the story.... Paul

For a long time I've been wondering why the necessity for so much measuring in pools where the docking stations for the bulkheads are static. But the tightness of the lane lines is something I'd never thought of. Interesting. But really, why is constant measuring required in pools that don't have moveable bulkheads, and touch pads aren't used? Once a static pool like that is measured it seems like that should be the end of measuring. Is there something I'm not seeing? Dan

we had our Illinois state meet at the pool in Munster ,ind. and the bridges were set so as to run 2 25 S C Y pools at the same time. Both pools are measured to maintain the proper distance to allow records to be set.

ForceDJ, Pools or courses that do not include moveable bulkheads only need to be measured once (each lane of the course) or after a renovation that includes the tank or gutter systems. Another problem with moveable bulkheads is the "pinning" mechanism. Over time, the holes where the pins fit do wear and get bigger. These pools are built to be as close to the minimum legal length as possible, so even a small amount of wear can be a problem. And, there are other systems that do not include pins - sometimes just the weight of the bulkhead itself resting on the bottom or on the gutters. These are subject to stressors that move the bulkhead thereby affecting the length of the course. Lots and lots of variables which makes the measurements important. And, finally, a masters national or world record can be set almost anywhere and at any time of the year. I set my SCM world record in a little meet in the middle of May - only 2 people in the event. Luckily, the pool did not have a bulkhead and had been measured. BUT, it would be very sad if record swim was done and the pool was too short. because someone decided not to measure. Windrath

Let us consider a swimmer doing the 100 freestyle in a pool that is exactly 25 yards. For purposes of simplifying the math, let us say he or she does a time of exactly 50.00 seconds. At this rate of speed, the swimmer is traveling at 2 yards per second, or 72 inches per second. Let us now consider that the swim takes place in a bulkhead pool that, for whatever reason (poor design, overly tight lane lines, deteriorating pins) is a quarter inch short. The swimmer now benefits from swimming instead of 100 yards, 99 yards and 35 inches. Assuming he or she holds the same rate of speed as before, they will benefit by 1/72 seconds, or .013888 seconds. Instead of a 50.00, their time will be 49.98611112. Leaving aside that any 49 seems a lot faster than any 50 (and any food item priced at $2.99 seems a lot cheaper than one priced at $3.00), the difference in times really is close to negligible. Timing systems can go to the thousandth of a second but such times are not factored in to settle ties because of the inherent inaccuracy when you get to such tiny slivers of time. (I know, I know, even nanoseconds matter--but we aren't talking Fermi Lab here.) Put me down in the camp that considers the USMS measurement requirements ludicrous, especially since "hand timing" is still legal, and it's virtually certain that there is much, much more room for error in hand timing than there is from pools that are an inch or so off absolute kosher length status. Until USMS decides to only count times with electronic timing systems, I say forget about the minutiae of pool measurement differences. Any pool that is minutely under (or over, for that matter) length was no doubt built so long ago that there are likely to be all sorts of design features that slow down performance well beyond what putative benefit swimming an inch short per 100 provides.

Hi Jim, I am not necessarily against what you are suggesting, but the devil is in the details. Yes, over a 100 yard race, the shortness might be negligible, but by the time you get to a 1650, what was negligible is now measurable. One question to you - define "minutely?" Best, Paul

Put me down in the camp that considers the USMS measurement requirements ludicrous, especially since "hand timing" is still legal, and it's virtually certain that there is much, much more room for error in hand timing than there is from pools that are an inch or so off absolute kosher length status. Wow. I didn't realize that, either. The allowance of hand timing does make the strict adherence to length seem hypocritical. I was considering what Windrath suggested about that fraction of time over the length of a 1650. That comes out to 0.230 second (less than one-quarter second) per 1650 (Well, at least at the 100y pace suggested above). Obviously it is "measurable." But handheld/manual timing can error that much. Ridiculous! Something else I was just thinking about bulkheads, and how the tightness of lane lines causes them to bow, and creates inaccurate measurements in the center lanes. My question is...if that is caused by the bowing of the bulkhead which is placed in the center of the pool...can't it be corrected by tightening the lane lines in the 'other' pool to take the bow out of the bulkhead? Instead of just mooring the bulkhead at the sides of the pool...seems like there should be a mooring, or two, to the bottom of the pool so that it can't bow when lane lines are tightened. Dan

Let us consider a swimmer doing the 100 freestyle in a pool that is exactly 25 yards. For purposes of simplifying the math, let us say he or she does a time of exactly 50.00 seconds. At this rate of speed, the swimmer is traveling at 2 yards per second, or 72 inches per second. Let us now consider that the swim takes place in a bulkhead pool that, for whatever reason (poor design, overly tight lane lines, deteriorating pins) is a quarter inch short. The swimmer now benefits from swimming instead of 100 yards, 99 yards and 35 inches. Assuming he or she holds the same rate of speed as before, they will benefit by 1/72 seconds, or .013888 seconds. Instead of a 50.00, their time will be 49.98611112. Leaving aside that any 49 seems a lot faster than any 50 (and any food item priced at $2.99 seems a lot cheaper than one priced at $3.00), the difference in times really is close to negligible. Timing systems can go to the thousandth of a second but such times are not factored in to settle ties because of the inherent inaccuracy when you get to such tiny slivers of time. (I know, I know, even nanoseconds matter--but we aren't talking Fermi Lab here.) Put me down in the camp that considers the USMS measurement requirements ludicrous, especially since "hand timing" is still legal, and it's virtually certain that there is much, much more room for error in hand timing than there is from pools that are an inch or so off absolute kosher length status. Until USMS decides to only count times with electronic timing systems, I say forget about the minutiae of pool measurement differences. Any pool that is minutely under (or over, for that matter) length was no doubt built so long ago that there are likely to be all sorts of design features that slow down performance well beyond what putative benefit swimming an inch short per 100 provides. But stop watches don't round up so 49.986 is 49.98. If you swam in the legal pool at 49.99, you got beat by .01 by someone who swam 50.00.

I also believe that the pool does not have to be “exactly” 25 yards or meters. I know there is a +/- factor (what that is I couldn’t say). But I also realize Jim might have just been saying exactly 25 yards for the sake of argument. Not sure that a quarter inch is outside the margin of errors not.