The reason is Herb Jenks the inventor of Sky poles, Cata-poles, and Pacers knew that the measurement was about stiffness and the need to only measure the sail of the pole that provided the stiffness difference between poles.
SO the unit measured 6 inches up from the butt of the pole and right at the tip of the top of the sail piece.
This gave him a relative stiffness measurable between pole.
The unit did have frictionless bearing on their supports and a 50 lb weight was suspended in the middle of the sail.
The more the weight de-flexes the pole the lighter the pole and the stiffer the pole the less the weight de-flexes the pole.
SO this unit measures deflection of the pole and the dynamic tester to see if the pole is structurally sound is called a FLEX Machine!
So if you measure 6 inches up from the butt and find the sail you will get a similar number and you will now know the span that could be used to get a similar number.
Please do not lose any sleep over being a perfectionist, as you will never get an exact number ok
(PLEASE NOTE: Don't sweat the little stuff! The difference between 21.0 and 21.3 is 9/10th of lbs softer and a 21.0 to a 21.6 is almost 2 lbs)
HERE ARE OTHER REASONS WHY:
1. I moved my Deflex machine from California to Mexico then back to California and now in Texas. Every time I moved it! It was not exactly calibrated due to humidity, temperature, altitude, and many other variables too precise to mention here!
2. Bearings are different and provide a variable frictionless surface on each machine!
3.Some manufacturers use a laser light for precise measure in units of .00001 and some use a light bulb and view the shadow on the measuring stick in units of .01. ( If the bulb moves with the weight you can get the most accurate measurement as the shadow will stay parallel. We use a electrical strip with a sliding rod placed on the pole to zero and them measure .0001 de-flection electronically! It does not need to be electrical and Here is one you can buy for $32.00 that will work!
http://www.valleyvet.com/ct_detail.html?pgguid=30E071E6-7B6A-11D5-A192-00B0D0204AE5&ccd=IYA001&utm_source=yahoo_store&utm_medium=cpc&utm_content=23942
SPIRIT POLES:
Keep in mind that Spirit uses 14' sail spans for 13'6" poles, 15' sail spans for 14'6" poles and 16' sail spans for 15'6" poles
This will allow one on a 13'6" to use flex number to move to the 14' with a number that is comparable to the next length. Good idea but then you change scales when you go from 14' to 14'6"
Other than this their spans and system matches ESSX.
EARL BELL FLEX NUMBER:
The Earl Bell Flex System is 12" from each end as the span and his supports are on ropes hanging from the ceiling!
His number is usually between the other brands and is close to work with. Earl Bells System is very close to ESSX Flex system
GILL POLES:
Gill has made a few changes over the years and the Best flex was changed once since it was made in 1996. THE spans are wider measuring more of the pole. They feel this is the most accurate measure as the number they get is encompasses more of the fiberglass rod whither you bend the pole there or not!
My opinion is if you measure more of the pole you will get a bigger number than the rest of the brands and you are measuring more of the pole and not just the sail. You stiffness number now is measuring not he sail but the pole it self and areas of the pole that do not bend or are relative to the stiffness of the pole that you use in the vault. Just my thoughts on the matter
With carbon weave they get a stiffness number that fits their scale and gives them data on the stiffness above the sail and for that reason alone the number does not equate to other brands. ( Example the span of 16'5" poles is 175 inches we use 169 inches)
As you can see 6" more of the glass is a part of their number and will not match other brands! Gill flex system is close in some 13' and 14' poles but on shorter length and longer length they have re designed the system for their needs. When they purchased and moved the Pacer plant over to Gill in Illinois it was mentioned by the owner, that they may of not gotten the exact spans and weights used in Nevada when setting up their flex system especially on the short length poles. And for the very old smaller pole they were stiffer. this was corrected in 1996 with eh Best flex system.
ALTIUS POLES:
You will need to convert inches to metric to match other brands and we have found them to use a very close system to our ESSX poles and they are similar also to Spirit. ( Example; 7.4 Inches x 2.54=18.796 metric)
THE BOTTOM LINE
ALL POLE BRANDS LINED UP WITH THE PROPER WEIGHT RATINGS AND WERE SAFE!
For safety sake I have tested and compared all poles using different spans and will say that all the pole manufactures are aligned on the weights to flex number.
Example; All these poles measured the same flex number on my machine and the ratings matched while they each had a totally different flex number spirit and Altius were within .2 of my number and Gill was well a bigger number and could not be compared unless I was able to obtain a flex number on my machine. a 14'3 Altius-160 is equal to an ESSX CARBON 14'1-162.4 they both are equal to a 13'11" pacer -160 and a 14'1-160 spirit. ( Make note that a Nordic 14'1-155 with a slightly stiffer flex number was equal to all the other brands. I would of rated it a 160.0)
WANT MORE INFO?
http://officialessx.com/forum/index.php?showtopic=16