The tiedown tensions for apr13 was examined to see how often the tiedowns were losing tension. The dataset was limited to when the carriage house was at stow. The platform height was not constrained (it could have been at the correct position or out of focus).
There are two factors involved:

• 0 tension. This is when the load cells read 0 tension They do not read negative values
• 0 load: this is when there is no tension left in the cables.
• Because of offsets in the load cell tension measurements, these two do not always agree.
  

The plots show the tiedown tension for apr2013 vs az,za and hour of day (.ps) (.pdf):

• Page 1: td tension vs azimuth:
• black is cable 1 of td, red is cable 2.
• The green solid lines show the azimuth position for each tiedown
• td12: large difference between the 2 cables,. cable 1 hits 0 before all tension gone
• td4: both cables hit no load when the load cells are still reading 5 Kips
• td8: no load looks to be well below the 0 tension value
• Page2: td tension vs dome za.
• Min za for 0 tension:
• td12: za=14.. but this does not look like no load
• td4: za=15 degrees
• td8: za=13 but this doesn't look like no load
• Page 3: td tension vs hour of day:
• hour range where tension goes to 0
• td12:10 - 18
• td4:    9-17
• td8: 8-18 but this is not zero load.
  

summary:

• td 12: the two cable differ by up to 15 kips
• td4: hits 0 load when the tension still reads  5 kips
• td8: hits 0 tension, but the load is still present.
• Looks like we can here zero tension down to za=15
• (need to recalibrate td8 so we can see where it goes to no load)
• 0 tension can be seen from 10 to 18 hours