Have you ever broken a fan blade of a fan somehow and wondered if you could fix it or replace it after spending all your money on a new build (can happen).
Well it happened to one of my delta fans, one of the 9 blades broke off so there was a unbalanced load (too light on one side and too heavy on the other or example) which made the fan vibrate and reduced airflow.
My fan WAS a 9 blade fan so it was more easier to fix it, from the broken blade skip 2 two blades, break the next blade skip the next 2 blades and cut the next off and you should be left with a 3 blade fan looking fan but with 6 blades instead so you will be left with a 6 blade fan.
(i'll try to post pictures).
Fans with 7 or lower number of blades will be harder to fix, 7 and 5 i will take a look at.
Ones with more than 9 you can try my technique but try to get a equal amount of fan blades.
If you broke more than one then post some pics and i can see what you can do.
Cutting off fan blades is done with cutting pliers or nose pliers, try to cut of the fan not pull it off, you can damage the rotor assembly by trying to pull the fan blades off.