I plugged the results of the coastdown test I did this spring on I-26 in the SC coastal plains into the formula (had to convert from my sec per 10mph drop to the spreadsheet's mph drop per 10 secs) and got a Cd of 0.18. I used the air density and Crr values given in the spreadsheet. To fine tune it better, I'll need to calculate my density altitude for 100 ft elevation, 78F, and 75% RH.
|