The present rules for F4 scale are available at
https://www.fai.org/sites/default/files/sc4_vol_f4_scale_22.pdf Note that this is the 2022 Edition, effective 1st January 2022.
At the April 9, 2022 CIAM Plenary F4 meeting, revisions were approved for the F4 Sporting Code. The control line related changes had been in the works for many years and would have originally been approved in 2020, but COVID pandemic restrictions kept postponing the meetings (the F4 committee was unable to meet in 2020 and 2021). I want to thank the folks who had been pushing the control line changes for many years - they were finally approved at the plenary meeting and will be posted/effective 1st January 2023.
There were two (2) primary changes for control line:
1) Secondary Control Functions (including but not limited to control of engine/s, landing gear, landing flaps) can be controlled using 2.4GHz radio control equipment with the transmitter under the sole control of the pilot in the center of the circle during the flight.
2) F4B models shall be static judged to the same rules set at F4H static judging (where all static judging is carried out at a distance of 5 meters).
For the 2022 NATS, we will be using the F4 2022 edition with the two additional approved changes listed above. The 2022 NATS is our first opportunity in many years to fly F4 and we want to use this as preparation for team selection in 2023.
You also stated "I see the new weight limit is now 7 kg but I don't see any flying line diameter specs or any reference to AMA line size requirements."
- The 7 kg weight limit is not new - I verified this is the same as the 2010 version (sorry I do not have older versions).
- The F4 rules never included flying line diameter specs, just need to pass the pull test - I verified this is the same as the 2010 version (sorry I do not have older versions).
PM me with your phone number if you would like to discuss further. We are hoping to welcome many new entrants at the NATS this year with F4B.
Pete