My question regards 3 blade props if you are using a 18x6 on 25cc gas what 3 blade would you use and how do you figure out with out spending $20 a prop to find out.I'm going to use this prop on my T-28 1/5 scale plane.Thank you

Normaly it's safe to go down one size and you'll be OK. 18/6 X 2 = 14/6 X 3. I run a 26/10 two blade on my ZDZ 80 and a 24/10 three blade. Alittle less power, but a lot less noise.

I usually try to go down one size in diameter and up one in pitch.....or as close as possible to that

Bob,

Try it the way JB is doing it by dropping an inch in dismeter and adding an inch in pich and you will get that lost power back and still keep the noise low.