A typo was reported in this thread on the Keel Section Offsets table. The Chord Length is listed as .75x and should be listed as .075x The web page has been updated to correct the typo. The source document in the pdf file and attached Excel spreadsheet will be corrected and uploaded this weekend.
The documents available to download on the J/30 Class Rules web page have all been updated with the correction. The change is annotated in red print so it is clearly visible.