I have a 140L which I'm going to fit in a 1/4 scale Super Cub.

I'll be running it on 20/20 and sometimes using it as a glider tug.

Scale prop dia is around 19" (so 18"-20" would be good) and when not using it as a tug I'd like to be able to fly it at a scale speed.

What size/s shall I go for?

you can try lots of differnt props. You should run a prop that turns about 8400-8800rpm. I know that a 16-10 on the fuel you are using will work in that rpm range.


I don't think you are going to get a prop that runs well enough that is 18-19" diameter....in the right rpm range.

The main reason is props get heavier with larger diameter and that will add additional load to the engine. SO you will have to go to a very flat pitch prop and it will rev up higher but its addition weight will add load and the engine will not like it.

To get scale flight performance I suggest using the throttle to reduce power.

Try some props but I think your engine will be happy with the 16-10 or 17-8 props. Given your 20/20 fuel mix. Even going to higher nitro like a 30% fuel you are only going to get one prop size and usually its a pitch size and not a diamter.

We are currently running 170DZ's on 17 and 18" props. The 170DZ has a ton more HP than a 140L



Troy Newman
Team YS

Thanks for the info Troy,
What about a carbon 18x6?