what size props are yall useing on this motor to get the highest rpm and most power</p>

Peak HP is at about 15,000 rpm, so you would get in that range with a prop that turns 12 to 13K on the ground. I would start with a 13-6 to start with and make that the first data point.

You can choose from:

- Highest RPM
- Most Thrust
- Most Speed

All are somewhat mutually exclusive and require different props.

I'm getting very good speeds on a .50 Bobcat Pusher and that engine using a Graupner 11x8 prop, though overall thrust is not at max and RPM's are not at maximum.

right now i have that motor on a seagull extra 300s and and seagull edge 540... on the extra that motor is brand new and it turns great rpm on a 14x6 but on my edge my .75 has a 14x6 on it and it is turning about 9000 so what prop do you think will get me the most power out of this motor the book that came with the motor said 14x6 but i think something else would be better

How do you want your power?

As Thrust, Flight Speed or RPM's?

Maximum speed or climb comes when you are making the maximum power that the engine is capable. If you are only turning 9,000 static, it is doubtful that you are much over 11,000-12,000 in the air. The diameter and pitch are the two variables, so drop the diameter first by an inch and see where you are. I used to run 13-5's on a ST 75, and it turned a solid 12,000-12,500 depending on the day. It gave me unlimited vertical on a 7 lb. bi-plane, yet enough speed to hold knife edge from horizon to horizon.

Hi,

What prop best suits what motor is largely determined by your flying style and the model you are flying. Even with the same size and pitch you will get differnt results with different brands and materials used in the prop. I started with a 13X6 Master Airscrew on my 75AX powered World Models F3A and ended up with a 13X8 wodden prop (less flex than plastic fantastics), that seems to best suit this model and flying the Sportsman Pattern schedule.

Like HighPlains suggested start with a 13X6 and experiment from there.

Cheers,

Colin

My 75AX on Ultra Sport 60, 8 pounds airplane likes 13x8 the most for the flying I like, I didnt check rpm with it but people ask me if its 120AX in there because of the roar and the pull.
I bet the 13x7 and 13x6 will do well too, you need to try several props it also depends on your specific engine.

I like a Graupner 14x7 or 13.5x8

If you are learning the new plane, it may be a good idea to get hold of a larger prop with lower pitch. I suggest Master Air Screw as they are soft GRP and unlikely to break easily.

In other words, start with 13x8 or 14x6 or 14x7 if you are very comfortable with the airplane or if you are running in the engine. They will give you good speed and decent acceleration but they will keep the speed a little high at landing.

If you are learning the plane or flying 3d or simply like to fly slow (like me), I suggest to get a 14x4 or even 15x4 if your plane has sufficient ground clearance with it. It will give good acceleration but the plane will not have very high top speed and will slow to a crawl at landing (as long as your plane and skills support the crawl without the stall). It means in a new plane if your setup us incorrect and the throttle disconnects, the engine will not rip up the plane through over-speeding, don't ask how I know.

At the end of the day, it is down to personal preference. You have to try both out and see what you are comfortable with

Ameyam

Very happy with an APC 13x6 for general sport flying but definitely experiment with various sizes, designs and manufacturers to find what you like.