ORIGINAL: winglift
When and why would you want to use a 3-bladed prop? Is it better than a 2-bladed prop? What is the rule of thumb in choosing which one to use?
If noise is an issue a 3 blade does tend to be quieter and as stated ground clearance is also improved .
Two blade props are more efficient as a rule but they also require more right thrust and have a larger prop wash .
This can be good or bad just depends on the airframe .
As for sizing a three blade the larger the engine the greater the difference in diam .
eg 23cc = 1 inch decrease in diam
30 cc = 2 inch decrease in diam
50 cc = 2 inch decrease in diam
100cc= 3 inch decrease in diam
150cc= 3 inch decrease in diam
200cc = 3 to 4 inch decrease in diam
Pitch is another story but that relates more to
airframe + usage = required pitch
Stu