Entertaining presentation by Steve Marvin of CalAPA member Labelle-Marvin delivered at the CalAPA Southern California Contractors' Dinner Feb. 10, 2015 in Pico Rivera. The presentation draws some intriguing parallels between construction materials testing and acceptance and sports.

1. CAPAPA Technical Tidbit
February 10, 2015

2.  Basketball
 Rim – Standard sec
 Practice Rim – special provisions
 Goal posts
 Football
 Field goal

3.  Variable tolerances
 Football field goal
 Defensive line
 Holder
 Soccer
 Goalie
 Lacrosse
 Goalie
 Hockey
 Goalie
 All
 Wind/rain

4.  Sampling Location and time
 Two hours before game
 Measured by officials
 12.5 to 13.5 psi

5.  No specifics on pressure gage calibration
 Gage manufactures indicate depending upon the quality
of the device it could be from 2% to 5% of full scale
 Pressure gages are 20 psi range
 Therefore good quality device – calibrated to +/- 0.4 psi or
worse case +/- 1.0 psi
 The range measured 2 hours before the game is therefore best
case 12.1 psi to 13.9 psi or worse case 11.5 to 14.5 psi

6.  Example
 Measured ball pressure could be 11.5 psi and measure
12.5 psi before game
 Measure later, same gage? Different gage? 11.5psi could
measure 10.5 to 12.5 psi
 Or Second gage could measure same balls, same time 10.5 to
13.5 psi

7.  Then enter temperature changes
 Assuming dry air, ~ 1 psi per 20 degree change
 Moist air, ~ 1.5 psi per 30 degree change
 Therefore same 12.0 ‘target’ will be at 11.0 with 20 degree
change , +/- 0.4 psi
 Or 10.0 psi with 40 degree change , again +/- 0.4 psi

8. Gage calibration
 Different gages different results?
 90 degree offset
 Input gage bias based on
 Technical experience
 Core correlation
 Maximum density variation (goalie)

9.  ASTM indicates depending upon the use of the device
it could be ½ pound per cubic foot
 Therefore +/- 0.50 pcf
 Similar precision on maximum density
 Worse case +/- 1 pcf swing, or >1/2%, rounded to 1%
 If 95% can be 94%, then you need to be at 96% consistently
to avoid issues
 Add surface texture, thickness variations, etc (more variables
- defensemen)