I'm pretty convinced it's called the F chord for a reason.And no, 'F' does not stand for that other word.
I can now make a nice clean F chord almost every single time. But I can not change to it fast enough to use it while playing.
I think my D chord is getting worse in the process.
Which F are you referring too? The big bar F, or the little F? Changing to C from little F is very easy if you think of it in the correct way. All you're doing is moving middle and ring fingers up 1 string each and rolling your index finger up a little to expose the 1st string. You don't even need to lift the index finger off the board to make the change and the middle and ring fingers shouldn't come more than a hairs width off the strings to make the move.
Changing to C from Big F is not too hard either as long as you think about the change before you make it. If you make your Big F with your 3rd finger (ring finger) on the 5th string then it doesn't need to move at all to change to C. Finger 2 (middle) only comes up 1 string and finger 1 (index) just slides down to string 2 without lifting it off the fret board. The key is not lifting the fingers too far off the fret board. I still haven't mastered the switch from big F to C even though I can visualize it and explain it. My problem is that my pinky keeps wanting to do something instead of just coming off the string and it messes with my head.
Not quite sure your D is suffering in the change though.
Now if only I could play as well as I can visualize it. Congrats on mastering a clean F and good luck with that clean transition.