Hello,
"F" speed is the minimum maneuvre speed for the flap setting. It is generated by the FMC depending on the ZFW, fuel and the cg. Practically, it means 25 degree bank is allowed with further 15 degree protection (1.3 g capability).
Without FMC, no "F" is generated, so to maneuvre, we have to back to V2+15 for takeoff flaps and fixed speed based on weight eg 190kts for flaps 1 weight below 53070kg fo B737-400.
I stand corrected...