Originally posted by MrRob
I have the option of a 2.1 gear box and I have noticed a few racers running 2.1 so can someone please explain the pros & cons of runnning a 2.1.
Its because there is an optimum pitch prop which I think it 27",
For example every time a prop completes 1 full rotatation you loose X amount of speed/engine rpm from the drag of the blades and weight of spinning prop etc.
So the smaller 25" prop turning faster on a 1.87 ratio is less efficient then a 27" on 2:1 ration
so even if the engine with the faster turning 25" prop travles the same distance as the slower turning 27" prop it will be a quicker combination because yoiu are not loosing as much of the engines power through drag.